# Wireshark Developer’s Guide

## Version 3.1.0

List of Figures

6.1. Wireshark function blocks

List of Tables

1. Typographic Conventions
3.1. Commit message tags
8.1. Control packet:
8.2. Commands and application for controls

List of Examples

9.1. Dissector Initialisation.
9.2. Dissector Handoff.
9.3. Dissection.
9.4. Plugin Packet Dissection.
9.5. Registering data structures.
9.6. Dissector data structure globals.
9.7. Dissector starting to dissect the packets.
9.8. Wrapping up the packet dissection.
9.9. Naming the packet types.
9.10. Adding Names to the protocol.
9.11. Adding Flags to the protocol.
9.12. Enhancing the display.
9.13. Decompressing data packets for dissection.
9.14. Reassembling fragments - Part 1
9.15. Reassembling fragments part 2
9.16. Reassembling fragments - Initialisation
9.17. Reassembling fragments - Data
9.18. Reassembling TCP fragments
9.19. Initialising a tap
9.20. Calling a protocol tap
9.21. Initialising a stats interface
9.22. Initialising a stats session
9.23. Generating the stats

# Preface

## 1. Foreword

This book tries to give you a guide to start your own experiments into the wonderful world of Wireshark development.

Developers who are new to Wireshark often have a hard time getting their development environment up and running. This is especially true for Win32 developers, as a lot of the tools and methods used when building Wireshark are much more common in the UNIX world than on Win32.

The first part of this book will describe how to set up the environment needed to develop Wireshark.

The second part of this book will describe how to change the Wireshark source code.

We hope that you find this book useful, and look forward to your comments.

## 2. Who should read this document?

The intended audience of this book is anyone going into the development of Wireshark.

This book is not intended to explain the usage of Wireshark in general. Please refer the Wireshark User’s Guide about Wireshark usage.

By reading this book, you will learn how to develop Wireshark. It will hopefully guide you around some common problems that frequently appear for new (and sometimes even advanced) developers of Wireshark.

## 3. Acknowledgements

The authors would like to thank the whole Wireshark team for their assistance. In particular, the authors would like to thank:

The authors would also like to thank the following people for their helpful feedback on this document:

• XXX - Please give feedback :-)

And of course a big thank you to the many, many contributors of the Wireshark development community!

This book was developed by Ulf Lamping and updated for VS2013 by Graham Bloice

It is written in AsciiDoc.

## 5. Where to get the latest copy of this document?

The latest copy of this documentation can always be found at: https://www.wireshark.org/docs/ in A4 PDF, US letter PDF, single HTML, and chunked HTML.

## 7. Typographic Conventions

The following table shows the typographic conventions that are used in this guide.

Table 1. Typographic Conventions

Style Description Example

Italic

File names, folder names, and extensions

C:\Development\wireshark.

Monospace

Commands, flags, and environment variables

CMake’s -G option.

Bold Monospace

Commands that should be run by the user

Run cmake -G Ninja ...

Dialog and window buttons

Press to go to the Moon.

Key

Keyboard shortcut

Press Ctrl+Down to move to the next packet.

Select GoNext Packet to move to the next packet.

Important and notable items are marked as follows:

This is a warning You should pay attention to a warning, otherwise data loss might occur.
This is a note A note will point you to common mistakes and things that might not be obvious.
This is a tip Tips are helpful for your everyday work using Wireshark.

### 7.2. Shell Prompt and Source Code Examples

Bourne shell, normal user.

$# This is a comment$ git config --global log.abbrevcommit true

Bourne shell, root user.

# # This is a comment
# ninja install

Command Prompt (cmd.exe).

>rem This is a comment
>cd C:\Development

PowerShell.

PS$># This is a comment PS$>choco list -l

C Source Code.

#include "config.h"

/* This method dissects foos */
static int
dissect_foo_message(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree _U_, void *data _U_)
{
/* TODO: implement your dissecting code */
return tvb_captured_length(tvb);
}

# Part I. Wireshark Build Environment

## 1.1. Introduction

This chapter will provide you with information about Wireshark development in general.

## 1.2. What is Wireshark?

Well, if you want to start Wireshark development, you might already know what Wireshark is doing. If not, please have a look at the Wireshark User’s Guide, which will provide a lot of general information about it.

## 1.3. Supported Platforms

Wireshark currently runs on most UNIX-like platforms and various Windows platforms. It requires Qt, GLib, libpcap and some other libraries in order to run.

As Wireshark is developed in a platform independent way and uses libraries (such as the Qt GUI library) which are available for many different platforms, it’s thus available on a wide variety of platforms.

Binary packages are available for the following platforms along with many others:

### 1.3.1. Unix and Unix-like platforms

• Apple macOS
• FreeBSD
• HP-UX
• IBM AIX
• NetBSD
• OpenBSD
• Oracle Solaris

#### 1.3.1.1. Linux

• Debian GNU/Linux
• Ubuntu
• Fedora
• Gentoo Linux
• IBM S/390 Linux (Red Hat)
• Mandrake Linux
• PLD Linux
• Red Hat Linux
• Rock Linux
• Slackware Linux
• Suse Linux

### 1.3.2. Microsoft Windows

Wireshark supports Windows natively via the Windows API. Note that in this documentation and elsewhere we tend to use the terms “Win32”, “Win”, and “Windows” interchangeably to refer to the Windows API. Wireshark runs on and can be compiled on the following platforms:

• Windows 10 / Windows Server 2016
• Windows 8.1 / Windows Server 2012 R2
• Windows 8 / Windows Server 2012
• Windows 7 / Windows Server 2008 R2

Development on Windows Vista, Server 2008, and older versions may be possible but is not supported.

## 1.4. Development and maintenance of Wireshark

Wireshark was initially developed by Gerald Combs. Ongoing development and maintenance of Wireshark is handled by the Wireshark core developers, a loose group of individuals who fix bugs and provide new functionality.

There have also been a large number of people who have contributed protocol dissectors and other improvements to Wireshark, and it is expected that this will continue. You can find a list of the people who have contributed code to Wireshark by checking the About dialog box of Wireshark, or have a look at the https://www.wireshark.org/about.html#authors page on the Wireshark web site.

The communication between the developers is usually done through the developer mailing list, which can be joined by anyone interested in the development activities. At the time this document was written, more than 500 persons were subscribed to this mailing list!

It is strongly recommended to join the developer mailing list, if you are going to do any Wireshark development. See Section 1.7.6, “Mailing Lists” about the different Wireshark mailing lists available.

### 1.4.1. Programming languages used

Most of Wireshark is implemented in plain ANSI C. A notable exception is the code in ui/qt, which is written in C++.

The typical task for a new Wireshark developer is to extend an existing, or write a new dissector for a specific network protocol. As (almost) any dissector is written in plain old ANSI C, a good knowledge about ANSI C will be sufficient for Wireshark development in almost any case.

So unless you are going to change the build process of Wireshark itself, you won’t come in touch with any other programming language than ANSI C (such as Perl or Python, which are used only in the Wireshark build process).

Beside the usual tools for developing a program in C (compiler, make, …​), the build process uses some additional helper tools (Perl, Python, Sed, …​), which are needed for the build process when Wireshark is to be build and installed from the released source packages. If Wireshark is installed from a binary package, none of these helper tools are needed on the target system.

### 1.4.2. Open Source Software

Wireshark is an open source software (OSS) project, and is released under the GNU General Public License (GPL). You can freely use Wireshark on any number of computers you like, without worrying about license keys or fees or such. In addition, all source code is freely available under the GPL. Because of that, it is very easy for people to add new protocols to Wireshark, either as plugins, or built into the source, and they often do!

You are welcome to modify Wireshark to suit your own needs, and it would be appreciated if you contribute your improvements back to the Wireshark community.

You gain three benefits by contributing your improvements back to the community:

• Other people who find your contributions useful will appreciate them, and you will know that you have helped people in the same way that the developers of Wireshark have helped you and other people.
• The developers of Wireshark might improve your changes even more, as there’s always room for improvement. Or they may implement some advanced things on top of your code, which can be useful for yourself too.
• The maintainers and developers of Wireshark will maintain your code as well, fixing it when API changes or other changes are made, and generally keeping it in tune with what is happening with Wireshark. So if Wireshark is updated (which is done often), you can get a new Wireshark version from the website and your changes will already be included without any effort for you.

## 1.5. Releases and distributions

The officially released files can be found at https://www.wireshark.org/download.html. A new Wireshark version is released after significant changes compared to the last release are completed or a serious security issue is encountered. The typical release schedule is about every 4-8 weeks (although this may vary). There are two kinds of distributions: binary and source; both have their advantages and disadvantages.

### 1.5.1. Binary distributions

Binary distributions are usually easy to install (as simply starting the appropriate file is usually the only thing to do). They are available for the following systems:

• Windows (.exe file). The typical Windows end user is used to getting a setup.exe file which will install all the required things for him.
• Win32 PAF (.paf.exe file). Another Windows end user method is to get a portable application file which will install all the required things for him.
• Debian (.deb file). A user of a Debian Package Manager (DPKG) based system obtains a .deb file from which the package manager checks the dependencies and installs the software.
• Red Hat (.rpm file). A user of a RPM Package Manager (RPM) based system obtains an .rpm file from which the package manager checks the dependencies and installs the software.
• macOS (.dmg file). The typical macOS end user is used to getting a .dmg file which will install all the required things for him.
• Solaris. A Solaris user obtains a file from which the package manager (PKG) checks the dependencies and installs the software.

However, if you want to start developing with Wireshark, the binary distributions won’t be too helpful, as you need the source files, of course.

For details about how to build these binary distributions yourself, e.g. if you need a distribution for a special audience, see Section 3.11, “Binary Packaging”.

### 1.5.2. Source code distributions

It’s still common for developers for UNIX-like platforms to give the end user a source tarball and let the user compile it on their target machine (configure make make install). However, for different UNIX and UNIX-like systems, such as Linux distributions, it’s becoming more common to release binary packages (e.g., .deb or .rpm files) these days.

You should use the released sources if you want to build Wireshark from source on your platform for productive use. However, if you going to develop changes to the Wireshark sources, it might be better to use the latest Git sources. For details about the different ways to get the Wireshark source code see Section 3.3, “Obtain the Wireshark sources”.

Before building Wireshark from a source distribution, make sure you have all the tools and libraries required to build. The following chapters will describe the required tools and libraries in detail.

## 1.6. Automated Builds (Buildbot)

The Wireshark Buildbot automatically rebuilds Wireshark on every change of the source code repository and indicates problematic changes. This frees the developers from repeating (and annoying) work, so time can be spent on more interesting tasks.

• Recognizing (cross platform) build problems - early. Compilation problems can be narrowed down to a few commits, making a fix much easier.
• "Health status" overview of the sources. A quick look at: https://buildbot.wireshark.org/wireshark-master/ gives a good "feeling" if the sources are currently "well". On the other hand, if all is "red", an update of a personal source tree might better be done later …​
• "Up to date" binary packages are available. After a change was committed to the repository, a binary package / installer is usually available within a few hours at: https://www.wireshark.org/download/automated/. This can be quite helpful, e.g. a bug reporter can easily verify a bugfix by installing a recent build.
• Automated regression tests. In particular, the fuzz tests often indicate "real life" problems that are otherwise hard to find.

### 1.6.2. What does the Buildbot do?

The Buildbot will do the following (to a different degree on the different platforms):

• Check out from the source repository
• Build
• Create binary packages and installers
• Create source packages and run distribution checks
• Run regression tests

Each step is represented at the status page by a rectangle, green if it succeeded or red if it failed. Most steps provide a link to the corresponding console logfile, to get additional information.

The Buildbot runs on a platform collection that represents the different "platform specialties" quite well:

• Windows 8.1 x86 (Win32, little endian, Visual Studio 2013)
• Windows Server 2012 R2 x86-64 (Win64, little endian, Visual Studio 2013)
• Ubuntu x86-64 (Linux, little endian, gcc, Clang)
• macOS x86-64 (BSD, little endian, Clang)

and two buildslaves that run static code analysis to help spot coding issues:

• Visual Studio Code Analysis (Win64, little endian, VS 2013)
• Clang Code Analysis (Linux, little endian, Clang)

Each platform is represented at the status page by a single column, the most recent entries are at the top.

## 1.7. Reporting problems and getting help

If you have problems, or need help with Wireshark, there are several places that may be of interest to you (well, beside this guide of course).

### 1.7.1. Website

You will find lots of useful information on the Wireshark homepage at https://www.wireshark.org/.

### 1.7.2. Wiki

The Wireshark Wiki at https://wiki.wireshark.org/ provides a wide range of information related to Wireshark and packet capturing in general. You will find a lot of information not part of this developer’s guide. For example, there is an explanation how to capture on a switched network, an ongoing effort to build a protocol reference and a lot more.

And best of all, if you would like to contribute your knowledge on a specific topic (maybe a network protocol you know well), you can edit the Wiki pages by simply using your webbrowser.

### 1.7.3. FAQ

Before sending any mail to the mailing lists below, be sure to read the FAQ, as it will often answer any questions you might have. This will save yourself and others a lot of time. Keep in mind that a lot of people are subscribed to the mailing lists.

You will find the FAQ inside Wireshark by clicking the menu item Help/Contents and selecting the FAQ page in the upcoming dialog.

An online version is available at the Wireshark website: https://www.wireshark.org/faq.html. You might prefer this online version as it’s typically more up to date and the HTML format is easier to use.

### 1.7.4. Other sources

If you don’t find the information you need inside this book, there are various other sources of information:

• The file doc/README.developer and all the other README.xxx files in the source code. These are various documentation files on different topics
Read the README README.developer is packed full with all kinds of details relevant to the developer of Wireshark source code. Its companion file README.dissector advises you around common pitfalls, shows you basic layout of dissector code, shows details of the APIs available to the dissector developer, etc.
• The Wireshark source code
• Tool documentation of the various tools used (e.g. manpages of sed, gcc, etc.)
• The different mailing lists. See Section 1.7.6, “Mailing Lists”

### 1.7.5. Q&A Site

The Wireshark Q&A site at https://ask.wireshark.org/ offers a resource where questions and answers come together. You have the option to search what questions were asked before and what answers were given by people who knew about the issue. Answers are graded, so you can pick out the best ones easily. If your issue isn’t discussed before you can post one yourself.

### 1.7.6. Mailing Lists

There are several mailing lists available on specific Wireshark topics:

wireshark-announce
This mailing list will inform you about new program releases, which usually appear about every 4-8 weeks.
wireshark-users
This list is for users of Wireshark. People post questions about building and using Wireshark, others (hopefully) provide answers.
wireshark-dev
This list is for Wireshark developers. People post questions about the development of Wireshark, others (hopefully) provide answers. If you want to start developing a protocol dissector, join this list.
wireshark-bugs
This list is for Wireshark developers. Every time a change to the bug database occurs, a mail to this mailing list is generated. If you want to be notified about all the changes to the bug database, join this list. Details about the bug database can be found in Section 1.7.7, “Bug database (Bugzilla)”.
wireshark-commits
This list is for Wireshark developers. Every time a change to the Git repository is checked in, a mail to this mailing list is generated. If you want to be notified about all the changes to the Git repository, join this list. Details about the Git repository can be found in Section 3.2, “The Wireshark Git repository”.

You can subscribe to each of these lists from the Wireshark web site: https://www.wireshark.org/lists/. From there, you can choose which mailing list you want to subscribe to by clicking on the Subscribe/Unsubscribe/Options button under the title of the relevant list. The links to the archives are included on that page as well.

The archives are searchable You can search in the list archives to see if someone previously asked the same question and maybe already got an answer. That way you don’t have to wait until someone answers your question.

### 1.7.7. Bug database (Bugzilla)

The Wireshark community collects bug reports in a Bugzilla database at https://bugs.wireshark.org/. This database is filled with manually filed bug reports, usually after some discussion on wireshark-dev, and automatic bug reports from the Buildbot tools.

### 1.7.8. Reporting Problems

If you report problems, provide as much information as possible. In general, just think about what you would need to find that problem, if someone else sends you such a problem report. Also keep in mind that people compile/run Wireshark on a lot of different platforms.

When reporting problems with Wireshark, it is helpful if you supply the following information:

1. The version number of Wireshark and the dependent libraries linked with it, e.g. Qt, GLib, etc. You can obtain this with the command wireshark -v.
2. Information about the platform you run Wireshark on.
3. A detailed description of your problem.
4. If you get an error/warning message, copy the text of that message (and also a few lines before and after it, if there are some), so others may find the build step where things go wrong. Please don’t give something like: "I get a warning when compiling x" as this won’t give any direction to look at.
Don’t send large files Do not send large files (>100KB) to the mailing lists, just place a note that further data is available on request. Large files will only annoy a lot of people on the list who are not interested in your specific problem. If required, you will be asked for further data by the persons who really can help you.
Don’t send confidential information If you send captured data to the mailing lists, or add it to your bug report, be sure it doesn’t contain any sensitive or confidential information, such as passwords. Visibility of such files can be limited to certain groups in the Bugzilla database though.

### 1.7.9. Reporting Crashes on UNIX-like platforms

When reporting crashes with Wireshark, it is helpful if you supply the traceback information (besides the information mentioned in Section 1.7.8, “Reporting Problems”).

You can obtain this traceback information with the following commands:

$gdb whereis wireshark | cut -f2 -d: | cut -d' ' -f2 core >& bt.txt backtrace ^D$
Using GDB Type the characters in the first line verbatim. Those are back-tics there. backtrace is a gdb command. You should enter it verbatim after the first line shown above, but it will not be echoed. The ^D (Control-D, that is, press the Control key and the D key together) will cause gdb to exit. This will leave you with a file called bt.txt in the current directory. Include the file with your bug report. If you do not have gdb available, you will have to check out your operating system’s debugger.

You should mail the traceback to wireshark-dev[AT]wireshark.org or attach it to your bug report.

### 1.7.10. Reporting Crashes on Windows platforms

You can download Windows debugging symbol files (.pdb) from the following locations:

Files are named "Wireshark-pdb-winbits-x.y.z.zip" to match their corresponding "Wireshark-winbits-x.y.z.exe" installer packages.

## 2.1. UNIX: Installation

All the tools required are usually installed on a UNIX developer machine.

If a tool is not already installed on your system, you can usually install it using the package in your distribution: aptitude, yum, Synaptic, etc.

If an install package is not available or you have a reason not to use it (maybe because it’s simply too old), you can install that tool from source code. The following sections will provide you with the webpage addresses where you can get these sources.

## 2.2. Win32/64: Step-by-Step Guide

A quick setup guide for Win32 and Win64 with recommended configuration.

Warning Unless you know exactly what you are doing, you should strictly follow the recommendations below. They are known to work and if the build breaks, please re-read this guide carefully. Known traps are: Not using the correct (x86 or x64) version of the Visual Studio command prompt. Not copying/downloading the correct version of vcredist_xYY.exe.

### 2.2.1. Install Microsoft C compiler and SDK

You need to install, in exactly this order:

Check the checkbox for “Desktop development with C++” and then uncheck all the optional components other than the “VC++ 2017” item with the “latest …​ tools”, the “Windows 10 SDK”, and the “Visual C++ tools for CMake” (unless you want to use them for purposes other than Wireshark).

You can use Chocolatey to install Visual Studio, to correctly configure the installation, copy the deployment XML file msvc2015AdminDeployment.xml from the source code tools directory and pass the path the file to the chocolatey install command:

PS$>choco install -y VisualStudio2015Community --timeout 0 -package-parameters "--AdminFile path\to\msvc2015AdminDeployment.xml" You can use other Microsoft C compiler variants, but VS2017 is used to build the development releases and is the preferred option. It’s possible to compile Wireshark with a wide range of Microsoft C compiler variants. For details see Section 4.5, “Microsoft compiler toolchain (Windows native)”. You may have to do this as Administrator. Compiling with gcc or Clang is not recommended and will certainly not work (at least not without a lot of advanced tweaking). For further details on this topic, see Section 4.4, “GNU Compiler Toolchain (UNIX And UNIX-like Platforms)”. This may change in future as releases of Visual Studio add more cross-platform support. Why is this recommended? While this is a huge download, Visual Studio 2017 Community Edition is the only free (as in beer) versions that includes the Visual Studio integrated debugger. Visual Studio 2017 is also used to create official Wireshark builds, so it will likely have fewer development-related problems. ### 2.2.2. Install Qt The main Wireshark application uses the Qt windowing toolkit. To install Qt, go to the “Download Qt” page, select “Go open source”, download the Qt Online Installer for Windows from the Qt Project and select, for the desired Qt version, a component that matches your target system and compiler. For example, at the time of this writing the Qt 5.12.1 “msvc2017 64-bit” component is used to build the official 64-bit packages. The “Qt Debug Information Files” component contains PDB files which can be used for debugging. You can deselect all of the other the components such as “Qt Charts” or “Android xxxx” as they aren’t required. Note that installation of separate Qt components are required for 32 bit and 64 bit builds, e.g. “msvc2017 32-bit” and “msvc2017 64-bit”. The environment variable QT5_BASE_DIR should be set as appropriate for your environment and should point to the Qt directory that contains the bin directory, e.g. C:\Qt\5.12.5\msvc2017_64 The Qt maintenance tool (C:\Qt\MaintenanceTool.exe) can be used to upgrade Qt to newer versions. ### 2.2.3. Recommended: Install Chocolatey Chocolatey is a native package manager for Windows. There are packages for most of the software listed below. Along with traditional Windows packages it supports the Python Package Index. Chocolatey tends to install packages into its own path (%ChocolateyInstall%), although packages are free to use their own preferences (Python for example is installed to C:\Python37). You can install Chocolatey packages using the command choco install (or its shorthand, cinst). > rem Flex and Bison are required. > choco install -y winflexbison > rem Git, CMake, Perl, Python, etc are also required, but can be installed > rem via their respective installation packages. > choco install -y git cmake strawberryperl python3 ### 2.2.4. Install Python Get a Python 3.x installer from https://python.org/download/ and install Python into the default location (C:\Python37). Alternatively you can install Python using Chocolatey: PS$>choco install -y python3

Chocolatey installs Python in C:\Python37 by default.

### 2.2.5. Install Perl

Get a Perl installer from http://strawberryperl.com/ http://www.ActiveState.com/ and install Perl into the default location.

Alternatively you can install Perl using Chocolatey:

PS$>choco install -y strawberryperl # ...or... PS$>choco install -y activeperl

### 2.2.6. Install Git

Please note that the following is not required to build Wireshark but can be quite helpful when working with the sources.

Working with the Git source repositories is highly recommended, as described in Section 3.3, “Obtain the Wireshark sources”. It is much easier to update a personal source tree (local repository) with Git rather than downloading a zip file and merging new sources into a personal source tree by hand. It also makes first-time setup easy and enables the Wireshark build process to determine your current source code revision.

There are several ways in which Git can be installed. Most packages are available at the URLs below or via Chocolatey. Note that many of the GUI interfaces depend on the command line version.

If installing the Windows version of git select the Use Git from the Windows Command Prompt (in chocolatey the /GitOnlyOnPath option). Do not select the Use Git and optional Unix tools from the Windows Command Prompt option (in chocolatey the /GitAndUnixToolsOnPath option).

#### 2.2.6.2. Git Extensions

Git Extensions is a native Windows graphical Git client for Windows. You can download the installer from https://github.com/gitextensions/gitextensions/releases/latest.

#### 2.2.6.4. Command Line client via Chocolatey

The command line client can be installed (and updated) using Chocolatey:

PS$> choco install -y git #### 2.2.6.5. Others A list of other GUI interfaces for Git can be found at https://git-scm.com/downloads/guis ### 2.2.7. Install CMake Get the CMake installer from https://cmake.org/download/ and install CMake into the default location. Ensure the directory containing cmake.exe is added to your path. Alternatively you can install CMake using Chocolatey: PS$>choco install -y cmake

Chocolatey ensures cmake.exe is on your path.

### 2.2.8. Install Asciidoctor, Xsltproc, And DocBook

Asciidoctor can be run directly as a Ruby script or via a Java wrapper (AsciidoctorJ). It is used in conjunction with Xsltproc and DocBook to generate the documenation you’re reading and the User’s Guide.

The easiest way to install them on Windows is via Chocolatey:

PS$>choco install -y asciidoctorj xsltproc docbook-bundle Chocolatey ensures that asciidoctorj.exe and xsltproc.exe is on your path and that xsltproc uses the DocBook catalog. ### 2.2.9. Install and Prepare Sources Make sure everything works It’s a good idea to make sure Wireshark compiles and runs at least once before you start hacking the Wireshark sources for your own project. This example uses Git Extensions but any other Git client should work as well. Download sources Download Wireshark sources into C:\Development\wireshark using either the command line or Git Extensions: Using the command line: >cd C:\Development >git clone https://code.wireshark.org/review/wireshark Using Git extensions: 1. Open the Git Extensions application. By default Git Extensions will show a validation checklist at startup. If anything needs to be fixed do so now. You can bring up the checklist at any time via ToolsSettings. 2. In the main screen select Clone repository. Fill in the following: Repository to clone: https://code.wireshark.org/review/wireshark Destination: Your top-level development directory, e.g. C:\Development. Subdirectory to create: Anything you’d like. Usually wireshark. Check your paths Make sure your repository path doesn’t contain spaces. 3. Click the button. Git Extensions should start cloning the Wireshark repository. ### 2.2.10. Open a Visual Studio Command Prompt From the Start Menu (or Start Screen), navigate to the “Visual Studio 2017” folder and choose the Command Prompt appropriate for the build you wish to make, e.g. “x64 Native Tools Command Prompt for VS 2017” for a 64-bit version or “x86 Native Tools Command Prompt for VS 2017” for a 32-bit version. Depending on your version of Windows the Command Prompt list might be directly under “Visual Studio 2017” or you might have to dig for it under multiple folders, e.g. Visual Studio 2017Visual Studio ToolsWindows Desktop Command Prompts. Pin the items to the Task Bar Pin the Command Prompt you use to the Task Bar for easy access. All subsequent operations take place in this Command Prompt window. 1. Set environment variables to control the build. Set the following environment variables, using paths and values suitable for your installation: > rem Let CMake determine the library download directory name under > rem WIRESHARK_BASE_DIR or set it explicitly by using WIRESHARK_LIB_DIR. > rem Set *one* of these. > set WIRESHARK_BASE_DIR=C:\Development > rem set WIRESHARK_LIB_DIR=c:\wireshark-win64-libs > rem Set the Qt installation directory > set QT5_BASE_DIR=C:\Qt\5.12.5\msvc2017_64 > rem Append a custom string to the package version. Optional. > set WIRESHARK_VERSION_EXTRA=-YourExtraVersionInfo If you are using a version of Visual Studio earlier than VS2017 then you must set an additional env var, e.g. for VS2019 set the following: > set VisualStudioVersion=10.0 Setting these variables could be added to a batch file to be run after you open the Visual Studio Tools Command Prompt. Use Qt’s LTS branch We recommend using the most recent “long term support” branch of Qt5 to compile Wireshark on Windows. At the time of writing this is Qt 5.12. 2. Create and change to the correct build directory. CMake is best used in an out-of-tree build configuration where the build is done in a separate directory to the source tree, leaving the source tree in a pristine state. 32 and 64 bit builds require a separate build directory. Create (if required) and change to the appropriate build directory. > mkdir C:\Development\wsbuild32 > cd C:\Development\wsbuild32 to create and jump into the build directory. The build directory can be deleted at any time and the build files regenerated as detailed in Section 2.2.11, “Generate the build files”. ### 2.2.11. Generate the build files CMake is used to process the CMakeLists.txt files in the source tree and produce build files appropriate for your system. You can generate Visual Studio solution files to build either from within Visual Studio, or from the command line with MSBuild. CMake can also generate other build types but they aren’t supported. The initial generation step is only required the first time a build directory is created. Subsequent builds will regenerate the build files as required. If you’ve closed the Visual Studio Command Prompt prepare it again. To generate the build files enter the following at the Visual Studio command prompt: > cmake -G "Visual Studio 15 2017" ..\wireshark Adjusting the paths as required to Python and the wireshark source tree. To use a different generator modify the -G parameter. cmake -G lists all the CMake supported generators, but only Visual Studio is supported for Wireshark builds. To build an x64 version, the -G parameter must have a Win64 suffix, e.g. -G "Visual Studio 15 2017 Win64": > cmake -G "Visual Studio 15 2017 Win64" ..\wireshark The CMake generation process will download the required 3rd party libraries (apart from Qt) as required, then test each library for usability before generating the build files. At the end of the CMake generation process the following should be displayed: -- Configuring done -- Generating done -- Build files have been written to: C:/Development/wsbuild32 If you get any other output, there is an issue in your envirnment that must be rectified before building. Check the parameters passed to CMake, especially the -G option and the path to the Wireshark sources and the environment variables WIRESHARK_BASE_DIR and QT5_BASE_DIR. ### 2.2.12. Build Wireshark Now it’s time to build Wireshark! 1. If you’ve closed the Visual Studio Command Prompt prepare it again. 2. Run > msbuild /m /p:Configuration=RelWithDebInfo Wireshark.sln to build Wireshark. 3. Wait for Wireshark to compile. This will take a while, and there will be a lot of text output in the command prompt window 4. Run C:\Development\wsbuild32\run\RelWithDebInfo\Wireshark.exe and make sure it starts. 5. Open HelpAbout. If it shows your "private" program version, e.g.: Version 3.1.0-myprotocol123 congratulations! You have compiled your own version of Wireshark! You may also open the Wireshark solution file (Wireshark.sln) in the Visual Studio IDE and build there. Tip If compilation fails for suspicious reasons after you changed some source files try to clean the build files by running msbuild /m /p:Configuration=RelWithDebInfo Wireshark.sln /t:Clean and then building the solution again. The build files produced by CMake will regenerate themselves if required by changes in the source tree. ### 2.2.13. Debug Environment Setup You can debug using the Visual Studio Debugger or WinDbg. See the section on using the Debugger Tools. ### 2.2.14. Optional: Create User’s and Developer’s Guide Detailed information to build these guides can be found in the file docbook\README.adoc in the Wireshark sources. ### 2.2.15. Optional: Create a Wireshark Installer Note: You should have successfully built Wireshark before doing the following. If you want to build your own Wireshark-win32-3.1.0-myprotocol123.exe, you’ll need NSIS. You can download it from http://nsis.sourceforge.net. Note that the 32-bit version of NSIS will work for both 32-bit and 64-bit versions of Wireshark. NSIS v3 is required. Note: For Visual Studio 2015 and earlier, if you do not yet have a copy of vcredist_x86.exe or vcredist_x64.exe in ./wireshark-winXX-libs (where XX is 32 or 64) you will need to download the appropriate file and place it in ./wireshark-winXX-libs before starting this step. If building an x86 version using a Visual Studio 2015 or earlier “Express” edition or an x64 version with any edi of Visual Studio 2015 or earlier, then you must have the appropriate vcredist file for your compiler in the support libraries directory (vcredist_x86.exe in wireshark-32-libs or vcredist_x64.exe in wireshark-win64-libs). The files can be located in the Visual Studio install directory for non-Express edition builds, or downloaded from Microsoft at https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads for Express edition builds. Note you must use the correct version of vcredist for your compiler, unfortunately they all have the same name (vcredist_x86.exe or vcredist_x64.exe). You can use Windows Explorer and examine the “Properties → Details” tab for a vcredist file to determine which compiler version the file is for use with. For Visual Studio 2017 and later, all editions include the redistributables, so you do not need to download them. If you’ve closed the Visual Studio Command Prompt prepare it again. Run > msbuild /m /p:Configuration=RelWithDebInfo nsis_package_prep.vcxproj > msbuild /m /p:Configuration=RelWithDebInfo nsis_package.vcxproj to build a Wireshark installer. If you sign your executables you should do so between the “nsis_package_prep” and “nsis_package” steps. Run > packaging\nsis\wireshark-win64-{wireshark-version}-myprotocol123.exe to test your new installer. It’s a good idea to test on a different machine than the developer machine. Note that if you’ve built an x86 version, the installer name will contain “win32”. ## Chapter 3. Work with the Wireshark sources ## 3.1. Introduction This chapter will explain how to work with the Wireshark source code. It will show you how to: • Get the source • Compile it on your machine • Submit changes for inclusion in the official release This chapter will not explain the source file contents in detail, such as where to find specific functionality. This is done in Section 7.1, “Source overview”. ## 3.2. The Wireshark Git repository Git is used to keep track of the changes made to the Wireshark source code. The code is stored inside Wireshark project’s Git repository located at a server at the wireshark.org domain. Changes to the official repository are managed using the Gerrit code review system. Gerrit makes it easy to test and discuss changes before they are pushed to the main repository. For an overview of Gerrit see the Quick Introduction. Why Git? Git is a fast, flexible way of managing source code. It allows large scale distributed development and ensures data integrity. Why Gerrit? Gerrit makes it easy to contribute. You can sign in with any OpenID provider and push your changes. It’s usable from both the web and command line and is integrated with many popular tools. Git is our third revision control system Wireshark originally used Concurrent Versions System (CVS) and migrated to Subversion in July 2004. The Subversion repository was subsequently migrated to Git in January 2014. Using Wireshark’s Git repository you can: • Keep your private sources up to date with very little effort • Get a mail notification when the official source code changes • Get the source files from any previous release (or any other point in time) • Have a quick look at the sources using a web interface • See which person changed a specific piece of code • and much more ### 3.2.1. The web interface to the Git repository If you need a quick look at the Wireshark source code you can browse the most recent file versions in the master branch using Gitweb: https://code.wireshark.org/review/gitweb?p=wireshark.git;a=tree You can also view commit logs, branches, tags, and past revisions: https://code.wireshark.org/review/gitweb?p=wireshark.git ### 3.2.2. Git Naming Conventions Like most revision control systems, Git uses branching to manage different copies of the source code and allow parallel development. Wireshark uses the following branch naming conventions: • master: Main feature development and odd-numbered “development” releases. • master-x.y: Stable release maintenance. For example, master-3.0 is used to manage the 3.0.x official releases. Tags for major releases and release candidates consist of a “v” followed by a version number such as “v3.0.1” or “v3.0.3rc0”. Major releases additionally have a tag prefixed with “wireshark-” followed by a version number, such as “wireshark-3.0.0”. ## 3.3. Obtain the Wireshark sources There are several ways to obtain the sources from Wireshark’s Git repository. Check out from the master branch using Git. Using Git is much easier than synchronizing your source tree by hand using any of the snapshot methods mentioned below. Git merges changes into your personal source tree in a very comfortable and quick way. So you can update your source tree several times a day without much effort. Keep your sources up to date The following ways to retrieve the Wireshark sources are sorted in decreasing source timeliness. If you plan to commit changes you’ve made to the sources, it’s a good idea to keep your private source tree as current as possible. The age mentioned in the following sections indicates the age of the most recent change in that set of the sources. ### 3.3.1. Git over SSH or HTTPS Recommended for development purposes. Age: a few minutes. You can use a Git client to download the source code from Wireshark’s code review system. Anyone can clone from the anonymous git URL: If you create a Gerrit account you can clone from an authenticated URL: SSH lets you use Gerrit on the command line. HTTP lets you access the repository in environments that block the Gerrit SSH port (29418). At the time of this writing (early 2014) we recommend that you use the SSH interface. However, this may change as more tools take advantage of Gerrit’s HTTP REST API. The following example shows how to get up and running on the command line. See Section 4.12, “Git client” for information on installing and configuring graphical Git and Gerrit clients. 1. Sign in to https://code.wireshark.org/review using OpenID (click Register or Sign In in the upper right corner of the web page). Follow the login instructions. 2. In the upper right corner of the web page, click on your account name and select Settings. 3. Under Profile set a username. This will be the username that you use for SSH access. For the steps below we’ll assume that your username is henry.perry. 4. Select SSH Public Keys and add one or more keys. You will typically upload a key for each computer that you use. 5. Install git-review. This is an installable package in many Linux distributions. You can also install it as a Python package. (This step isn’t strictly necessary but it makes working with Gerrit much easier.) To install it from Chocolatey run # If you have not already, install Python 3 first and then *restart* the shell. PS$>choco install -y python3
PS$>choco install -y git-review -source python # Make sure that "git-review" is present in our path (edit the version as needed). PS$>$userpath = [Environment]::GetEnvironmentVariable("Path", [EnvironmentVariableTarget]::User) PS$>$userpath += ";C:\Python37\Scripts" PS$>[Environment]::SetEnvironmentVariable("Path", $userpath, [EnvironmentVariableTarget]::User) PS$>RefreshEnv
6. Now on to the command line. First, make sure git works:

$git --version 7. If this is your first time using Git, make sure your username and email address are configured. This is particularly important if you plan on uploading changes. $ git config --global user.name "Henry Perry"
$git config --global user.email [email protected] 8. Next, clone the Wireshark master: $ git clone ssh://[email protected]:29418/wireshark

The checkout only has to be done once. This will copy all the sources of the latest version (including directories) from the server to your machine. This may take some time depending on the speed of your internet connection.

9. Then set up the git pre-commit hook and the push address:

$cd wireshark$ cp tools/pre-commit .git/hooks/
$git config --add remote.origin.push HEAD:refs/for/master This will run a few basic checks on commit to make sure that the code does not contain trivial errors. It will also warn if it is out of sync with its master copy in the tools/ directory. The change in the push address is necessary: We have an asymmetric process for pulling and pushing because of gerrit. 10. Initialize git-review. $ git review -s

This prepares your local repository for use with Gerrit, including installing the commit-msg hook script.

### 3.3.2. Git web interface

Recommended for informational purposes only, as only individual files can be downloaded.

Age: a few minutes (same as anonymous Git access).

The entire source tree of the Git repository is available via a web interface at https://code.wireshark.org/review/gitweb?p=wireshark.git. You can view each revision of a particular file, as well as diffs between different revisions. You can also download individual files but not entire directories.

### 3.3.3. Buildbot Snapshots

Recommended for development purposes, if direct Git access isn’t possible (e.g. because of a restrictive firewall).

Age: some number of minutes (a bit older than the Git access).

The Buildbot server will automatically start to generate a snapshot of Wireshark’s source tree after a source code change is committed. These snapshots can be found at https://www.wireshark.org/download/automated/src/.

If Git access isn’t possible, e.g. if the connection to the server isn’t possible because of a corporate firewall, the sources can be obtained by downloading the Buildbot snapshots. However, if you are going to maintain your sources in parallel to the "official" sources for some time, it’s recommended to use the anonymous (or authenticated) Git access if possible (believe it, it will save you a lot of time).

### 3.3.4. Released sources

Recommended for building pristine packages.

Age: from days to weeks.

The official source releases can be found at https://www.wireshark.org/download.html. You should use these sources if you want to build Wireshark on your platform for with minimal or no changes, such Linux distribution packages.

The differences between the released sources and the sources in the Git repository will keep on growing until the next release is made. (At the release time, the released and latest Git repository versions are identical again :-).

## 3.4. Update the Wireshark sources

After you’ve obtained the Wireshark sources for the first time, you might want to keep them in sync with the sources at the upstream Git repository.

Take a look at the Buildbot first As development evolves, the Wireshark sources are compilable most of the time — but not always. You should take a look at https://buildbot.wireshark.org/wireshark-master/waterfall before fetching or pulling to make sure the builds are in good shape.

### 3.4.1. Update Using Git

After you clone Wireshark’s Git repository you can update by running

$git status$ git pull

Depending on your preferences and work habits you might want to run git pull --rebase or git checkout -b my-topic-branch origin/master instead.

Fetching should only take a few seconds, even on a slow internet connection. It will update your local repository history with changes from the official repository. If you and someone else have changed the same file since the last update, Git will try to merge the changes into your private file (this works remarkably well).

### 3.4.2. Update Using Source Archives

There are several ways to download the Wireshark source code (as described in Section 3.3, “Obtain the Wireshark sources”), but bringing the changes from the official sources into your personal source tree is identical.

First of all, you will download the new .tar.xz file of the official sources the way you did it the first time.

If you haven’t changed anything in the sources, you could simply throw away your old sources and reinstall everything just like the first time. But be sure, that you really haven’t changed anything. It might be a good idea to simply rename the "old" dir to have it around, just in case you remember later that you really did change something before.

If you have changed your source tree, you have to merge the official changes since the last update into your source tree. You will install the content of the .tar.xz file into a new directory and use a good merge tool (e.g. http://winmerge.sourceforge.net/for Windows) to bring your personal source tree in sync with the official sources again.

This method can be problematic and can be much more difficult and error-prone than using Git.

## 3.5. Build Wireshark

The sources contain several documentation files. It’s a good idea to read these files first. After obtaining the sources, tools and libraries, the first place to look at is doc/README.developer. Inside you will find the latest information for Wireshark development for all supported platforms.

Build Wireshark before changing anything It is a very good idea to first test your complete build environment (including running and debugging Wireshark) before making any changes to the source code (unless otherwise noted).

Building Wireshark for the first time depends on your platform.

### 3.5.1. Building on Unix

The recommended (and fastest) way to build Wireshark is with CMake and Ninja:

# Starting from your Wireshark source directory, create a build directory
# alongside it.
$cd ..$ mkdir wireshark-ninja
$cd wireshark-ninja # Assumes your source directory is named "wireshark".$ cmake -G Ninja ../wireshark
$ninja (or cmake --build .) If you need to build with a non-standard configuration, you can run $ cmake -LH ../wireshark

to see what options you have.

### 3.5.2. Windows native

Follow the build procedure in Section 2.2.12, “Build Wireshark” to build Wireshark.

After the build process has successfully finished, you should find a Wireshark.exe and some other files in the run\RelWithDebInfo directory.

## 3.6. Run generated Wireshark

Beware of multiple Wiresharks An already installed Wireshark may interfere with your newly generated version in various ways. If you have any problems getting your Wireshark running the first time, it might be a good idea to remove the previously installed version first.

### 3.6.1. Unix-like platforms

After a successful build you can run Wireshark right from the build directory. Still the program would need to know that it’s being run from the build directory and not from its install location. This has an impact on the directories where the program can find the other parts and relevant data files.

In order to run the Wireshark from the build directory set the environment variable WIRESHARK_RUN_FROM_BUILD_DIRECTORY and run Wireshark. If your platform is properly setup, your build directory and current working directory are not in your PATH, so the command line to launch Wireshark would be:

### 3.7.2. Windows native

You can debug using the Visual Studio Debugger or WinDbg. See the section on using the Debugger Tools.

## 3.8. Make changes to the Wireshark sources

As the Wireshark developers are working on many different platforms, a lot of editors are used to develop Wireshark (emacs, vi, Microsoft Visual Studio and many, many others). There’s no "standard" or "default" development environment.

There are several reasons why you might want to change the Wireshark sources:

• Add support for a new protocol (a new dissector)
• Change or extend an existing dissector
• Fix a bug
• Implement a glorious new feature

The internal structure of the Wireshark sources will be described in Part II, “Wireshark Development”.

Ask the wireshark-dev mailing list before you start a new development task. If you have an idea what you want to add or change it’s a good idea to contact the developer mailing list (see Section 1.7.6, “Mailing Lists”) and explain your idea. Someone else might already be working on the same topic, so a duplicated effort can be reduced. Someone might also give you tips that should be thought about (like side effects that are sometimes very hard to see).

If you have finished changing the Wireshark sources to suit your needs, you might want to contribute your changes back to the Wireshark community. You gain the following benefits by contributing your improvements:

• It’s the right thing to do. Other people who find your contributions useful will appreciate them, and you will know that you have helped people in the same way that the developers of Wireshark have helped you.
• You get free enhancements. By making your code public, other developers have a chance to make improvements, as there’s always room for improvements. In addition someone may implement advanced features on top of your code, which can be useful for yourself too.
• You save time and effort. The maintainers and developers of Wireshark will maintain your code as well, updating it when API changes or other changes are made, and generally keeping it in tune with what is happening with Wireshark. So if Wireshark is updated (which is done often), you can get a new Wireshark version from the website and your changes will already be included without any effort for you.

There’s no direct way to push changes to the Git repository. Only a few people are authorised to actually make changes to the source code (check-in changed files). If you want to submit your changes, you should upload them to the code review system at https://code.wireshark.org/review. This requires you to set up git as described at Section 3.3.1, “Git over SSH or HTTPS”.

### 3.9.1. Some Tips For A Good Patch

Some tips that will make the merging of your changes into Git much more likely (and you want exactly that, don’t you?):

• Use the latest Git sources. It’s a good idea to work with the same sources that are used by the other developers. This usually makes it much easier to apply your patch. For information about the different ways to get the sources, see Section 3.3, “Obtain the Wireshark sources”.
• Update your sources just before making a patch. For the same reasons as the previous point.
• Inspect your patch carefully. Run git diff and make sure you aren’t adding, removing, or omitting anything you shouldn’t.
• Find a good descriptive topic name for your patch. Short, specific names are preferred. snowcone-machine-protocol is good, your name or your company name isn’t.
• Don’t put unrelated things into one large patch. A few smaller patches are usually easier to apply (but also don’t put every changed line into a separate patch).

In general, making it easier to understand and apply your patch by one of the maintainers will make it much more likely (and faster) that it will actually be applied.

Please remember Wireshark is a volunteer effort. You aren’t paying to have your code reviewed and integrated.

### 3.9.2. Writing a Good Commit Message

When running git commit, you will be prompted to describe the change. Here are some guidelines on how to make that message actually useful to other people (and to scripts that may try to parse it):

• Provide a very brief description (under 60 characters) of the change in the first line. If the change is specific to a single protocol, start this line with the abbreviated name of the protocol and a colon. If the change is not complete yet prefix the line with [WIP] to inform this change not to be submitted yet. This can later be removed.
• Insert a single blank line after the first line.
• Provide a detailed description of the change in the following lines, breaking paragraphs where needed. Limit each line to 80 characters. You can also add metadata at the bottom of the commit message which will be used by Gerrit for searching and triggering Bugzilla integration. Each line of the footer is of the form Label: value. There can be no extra line-breaks between footer lines.

Wireshark currently supports the following metadata tags:

Table 3.1. Commit message tags

Tag Meaning

Change-id

A unique hash describing the change, which is generated automatically by the git commit-msg hook which you installed during setup. This should not be changed, even when rebasing or amending a commit following code review. If you pass --no-verify to git commit you will have to add this line yourself.

Bug

Make Gerrit automatically add a comment and close the given bug number when the commit is merged. For use when the change does fully fix the issue.

Ping-Bug

Make Gerrit just add a comment to the referenced bug. For use when the change is related but does not fully fix the issue.

Note The Bug and Ping-Bug tags are particularly useful if a capture file has been provided via a Bugzilla entry in parallel with the change. All non-trivial fixes to dissectors should try to do this.

Putting all that together, we get the following example:

MIPv6: fix dissection of Service Selection Identifier

APN field is not encoded as a dotted string so the first character is not a length

Bug: 10323
Change-Id: Ia62137c785d505e9d0f1536a333b421a85480741

### 3.9.3. Code Requirements

The core maintainers have done a lot of work fixing bugs and making code compile on the various platforms Wireshark supports.

To ensure Wireshark’s source code quality, and to reduce the workload of the core maintainers, there are some things you should think about before submitting a patch.

Pay attention to the coding guidelines Ignoring the code requirements will make it very likely that your patch will be rejected.
• Follow the Wireshark source code style guide. Just because something compiles on your platform, that doesn’t mean it’ll compile on all of the other platforms for which Wireshark is built. Wireshark runs on many platforms, and can be compiled with a number of different compilers. See Section 7.2, “Coding Style”for details.
• Submit dissectors as built-in whenever possible. Developing a new dissector as a plugin is a good idea because compiling and testing is quicker, but it’s best to convert dissectors to the built-in style before submitting for check in. This reduces the number of files that must be installed with Wireshark and ensures your dissector will be available on all platforms.

This is no hard-and-fast rule though. Many dissectors are straightforward so they can easily be put into "the big pile", while some are ASN.1 based which takes a different approach, and some multiple source file dissectors are more suitable to be placed separately as plugins.

• Ensure Wireshark Git Pre-Commit Hook is in the repository. In your local repository directory, there will be a .git/hooks/ directory, with sample git hooks for running automatic actions before and after git commands. You can also optionally install other hooks that you find useful.

In particular, the pre-commit hook will run every time you commit a change and can be used to automatically check for various errors in your code. The sample git pre-commit hook simply detects whitespace errors such as mixed tabs and spaces; to install it just remove the .sample suffice from the existing pre-commit.sample file.

Wireshark provides a custom pre-commit hook which does additional Wireshark-specific API and formatting checks, but it might return false positives. If you want to install it, copy the pre-commit file from the tools directory (cp ./tools/pre-commit .git/hooks/) and make sure it is executable or it will not be run.

If the pre-commit hook is preventing you from committing what you believe is a valid change, you can run git commit --no-verify to skip running the hooks. Warning: using --no-verify avoids the commit-msg hook, and thus will not automatically add the required Change-ID to your commit. In case you are not updating an existing patch you may generate a Change-ID by running git review -i (or git commit --amend if don’t use git review).

Additionally, if your system supports symbolic links, as all UNIX-like platforms do, you can use them instead of copying files. Running ln -s ./tools/pre-commit .git/hooks creates a symbolic link that will make the hook to be up-to-date with the current master. The same can be done for commit-msg script.

• Fuzz test your changes! Fuzz testing is a very effective way to automatically find a lot of dissector related bugs. You’ll take a capture file containing packets affecting your dissector and the fuzz test will randomly change bytes in this file, so that unusual code paths in your dissector are checked. There are tools available to automatically do this on any number of input files, see: https://wiki.wireshark.org/FuzzTesting for details.

When you’re satisfied with your changes (and obtained any necessary approval from your organization) you can upload them for review at https://code.wireshark.org/review. This requires a Gerrit Code Review account as described at Section 3.2, “The Wireshark Git repository”.

Changes should be pushed to a magical "refs/for" branch in Gerrit. For example, to upload your new Snowcone Machine Protocol dissector you could push to refs/for/master with the topic "snowcone-machine":

$git push ssh://[email protected]:29418/wireshark HEAD:refs/for/master/snowcone-machine The username my.username is the one which was given during registration with the review system. If you have git-review installed you can upload the change with a lot less typing: # Note: The "-f" flag deletes your current branch.$ git review -f

You can push using any Git client. Many clients have support for Gerrit, either built in or via an additional module.

You might get one of the following responses to your patch request:

• Your patch is checked into the repository. Congratulations!
• You are asked to provide additional information, capture files, or other material. If you haven’t fuzzed your code, you may be asked to do so.
• Your patch is rejected. You should get a response with the reason for rejection. Common reasons include not following the style guide, buggy or insecure code, and code that won’t compile on other platforms. In each case you’ll have to fix each problem and upload another patch.
• You don’t get any response to your patch. Possible reason: All the core developers are busy (e.g., with their day jobs or family or other commitments) and haven’t had time to look at your patch. Don’t worry, if your patch is in the review system it won’t get lost.

If you’re concerned, feel free to add a comment to the patch or send an email to the developer’s list asking for status. But please be patient: most if not all of us do this in our spare time.

### 3.9.5. Backporting a change

When a bug is fixed in the master branch it might be desirable or necessary to backport the fix to a stable branch. You can do this in Git by cherry-picking the change from one branch to another. Suppose you want to backport change 1ab2c3d4 from the master branch to master-1.10. Using "pure Git" commands you would do the following:

# Create a new topic branch for the backport.
$git checkout -b backport-g1ab2c3d4 origin/master-1.10 # Cherry-pick the change. Include a "cherry picked from..." line.$ git cherry-pick -x 1ab2c3d4

# If there are conflicts, fix them.

# Compile and test the change.
$make$ ...

EDITOR docbook/release-notes.adoc

$git commit --amend -a # Upload the change to Gerrit$ git push ssh://[email protected]:29418/wireshark HEAD:refs/for/master-1.10/backport-g1ab2c3d4

If you want to cherry-pick a Gerrit change ID (e.g. I5e6f7890) you can use git review -X I5e6f7890 instead of git cherry-pick and git review instead of git push as described in the previous chapter.

## 3.10. Apply a patch from someone else

Sometimes you need to apply a patch to your private source tree. Maybe because you want to try a patch from someone on the developer mailing list, or you want to check your own patch before submitting.

Beware line endings If you have problems applying a patch, make sure the line endings (CR/LF) of the patch and your source files match.

### 3.10.1. Using patch

Given the file new.diff containing a unified diff, the right way to call the patch tool depends on what the pathnames in new.diff look like. If they’re relative to the top-level source directory (for example, if a patch to prefs.c just has prefs.c as the file name) you’d run it as:

$patch -p0 < new.diff If they’re relative to a higher-level directory, you’d replace 0 with the number of higher-level directories in the path, e.g. if the names are wireshark.orig/prefs.c and wireshark.mine/prefs.c, you’d run it with: $ patch -p1 < new.diff

If they’re relative to a subdirectory of the top-level directory, you’d run patch in that directory and run it with -p0.

If you run it without -pat all, the patch tool flattens path names, so that if you have a patch file with patches to CMakeLists.txt and wiretap/CMakeLists.txt, it’ll try to apply the first patch to the top-level CMakeLists.txt and then apply the wiretap/CMakeLists.txt patch to the top-level CMakeLists.txt as well.

At which position in the filesystem should the patch tool be called?

If the pathnames are relative to the top-level source directory, or to a directory above that directory, you’d run it in the top-level source directory.

If they’re relative to a subdirectory — for example, if somebody did a patch to packet-ip.c and ran diff or git diff in the epan/dissectors directory — you’d run it in that subdirectory. It is preferred that people not submit patches like that, especially if they’re only patching files that exist in multiple directories such as CMakeLists.txt.

## 3.11. Binary Packaging

Delivering binary packages makes it much easier for the end-users to install Wireshark on their target system. This section will explain how the binary packages are made.

### 3.11.1. Packaging Guidelines

The following guidelines should be followed by anyone creating and distributing third-party Wireshark packages or redistributing official Wireshark packages.

##### Spelling And Capitalization

Wireshark is spelled with a capital “W”, and with everything else lower case. “WireShark” in particular is incorrect.

##### Main URL

The official Wireshark project URL is https://www.wireshark.org/.

Official packages are distributed on the main web server (www.wireshark.org) and a number of download mirrors. The canonical locations for packages are in the all_versions subdirectories on each server.

##### Artwork

Logo and icon artwork can be found in the image directory in the distribution. This is available online at

##### Licensing

Wireshark is released under the GNU General Public License version 2 or later. Make sure you and your package comply with this license.

Wireshark and the “fin” logo are registered trademarks of the Wireshark Foundation. Make sure you and your package comply with trademark law.

##### Privileges

All function calls that require elevated privileges are in dumpcap.

WIRESHARK CONTAINS OVER THREE MILLION LINES OF SOURCE CODE. DO NOT RUN THEM AS ROOT.

Warnings are displayed when Wireshark and TShark are run as root.

There are two configure-time options on non-Windows systems that affect the privileges a normal user needs to capture traffic and list interfaces:

-DDUMPCAP_INSTALL_OPTION=capabilities
Install dumpcap with cap_net_admin and cap_net_raw capabilities. Linux only.
-DDUMPCAP_INSTALL_OPTION=suid
Install dumpcap setuid root.

These are necessary for non-root users to be able to capture on most systems, e.g. on Linux or FreeBSD if the user doesn’t have permissions to access /dev/bpf*. Setcap installation is preferred over setuid on Linux. If -DDUMPCAP_INSTALL_OPTION=capabilities is used it will override any setuid settings.

The -DENABLE_CAP option is only useful when dumpcap is installed setuid. If it is enabled dumpcap will try to drop any setuid privileges it may have while retaining the CAP_NET_ADMIN and CAP_NET_RAW capabilities. It is enabled by default, if the Linux capabilities library (on which it depends) is found.

Note that enabling setcap or setuid installation allows packet capture for ALL users on your system. If this is not desired, you can restrict dumpcap execution to a specific group or user. The following two examples show how to restrict access using setcap and setuid respectively:

# groupadd -g packetcapture
# chmod 750 /usr/bin/dumpcap
# chgrp packetcapture /usr/bin/dumpcap

# chgrp packetcapture /usr/bin/dumpcap
# chmod 4750 /usr/bin/dumpcap
##### Customization

Custom version information can be added by running tools/make-version.pl. If your package contains significant changes we recommend that you use this to differentiate it from official Wireshark releases.

$tools/make-version.pl --set-release --untagged-version-extra=-{vcsinfo}-FooCorp --tagged-version-extra=-FooCorp See tools/make-version.pl for details. The Git version corresponding to each release is in version.h. It’s defined as a string. If you need a numeric definition, let us know. If you have a question not addressed here, please contact wireshark-dev[AT]wireshark.org. ### 3.11.2. Debian: .deb Packages The Debian Package is built using dpkg-buildpackage, based on information found in the source tree under debian. See http://www.debian-administration.org/articles/336 for a more in-depth discussion of the build process. In the wireshark directory, type: $ dpkg-buildpackage -rfakeroot -us -uc

to build the Debian Package.

### 3.11.3. Red Hat: .rpm Packages

You can build an RPM package using the rpm-package target. The package version is derived from the current git HEAD, so you must build from a git checkout.

The package is built using rpmbuild, which comes as standard on many flavours of Linux, including Red Hat, Fedora, and openSUSE. The process creates a clean build environment in ${CMAKE_BINARY_DIR}/packaging/rpm/BUILD each time the RPM is built. The settings that control the build are in${CMAKE_SOURCE_DIR}/packaging/rpm/wireshark.spec.in. The generated SPEC file contains CMake flags and other settings for the RPM build environment. Many of these come from the parent CMake environment. Notable ones are:

• \_prefix is set to CMAKE_INSTALL_PREFIX. By default this is /usr/local. Pass -DCMAKE_INSTALL_PREFIX=/usr to create a package that installs into /usr.
• Whether or not to create the “wireshark-qt” package (-DBUILD_wireshark).
• Lua, c-ares, nghttp2, and other library support (-DENABLE_…​).
• Building with Ninja (-G Ninja).

$ninja rpm-package # ...or, if you're using GNU make...$ make rpm-package

to build the binary and source RPMs. When it is finished there will be a message stating where the built RPM can be found.

This might take a while This creates a tarball, extracts it, compiles Wireshark, and constructs a package. This can take quite a long time. You can speed up the process by using Ninja. If you’re using GNU make you can add the following to your ~/.rpmmacros file to enable parallel builds: %_smp_mflags -j %(grep -c processor /proc/cpuinfo)

Building the RPM package requires quite a few packages and libraries including GLib, gcc, bison, flex, Asciidoctor, and Qt development tools such as uic and moc. The required Qt packages can usually be obtained by installing the qt5-devel package. For a complete list of build requirements, look for the “BuildRequires” lines in packaging/rpm/wireshark.spec.in.

### 3.11.4. macOS: .dmg Packages

The macOS Package is built using macOS packaging tools, based on information found in the source tree under packaging/macosx. It must be built using CMake. In your build directory, type:

$make dmg_package to build the macOS Package. ### 3.11.5. Windows: NSIS .exe Installer The Nullsoft Install System is a free installer generator for Windows systems. Instructions on installing it can be found in Section 4.16, “Windows: NSIS (Optional)”. NSIS is script based. You can find the main Wireshark installer generation script at packaging/nsis/wireshark.nsi. When building with CMake you must first build the nsis_package_prep target, followed by the nsis_package target, e.g. > msbuild /m /p:Configuration=RelWithDebInfo nsis_package_prep.vcxproj > msbuild /m /p:Configuration=RelWithDebInfo nsis_package.vcxproj Splitting the packaging projects in this way allows for code signing. This might take a while Please be patient while the package is compressed. It might take some time, even on fast machines. If everything went well, you will now find something like: wireshark-setup-3.1.0.exe in the packaging/nsis directory in your build directory. ### 3.11.6. Windows: PortableApps .paf.exe Package PortableApps.com is an environment that lets users run popular applications from portable media such as flash drives and cloud drive services. Install the PortableApps.com Platform. Install for “all users”, which will place it in C:\PortableApps. Add the following apps: • NSIS Portable (Unicode) • PortableApps.com Installer • PortableApps.com Launcher • PortableApps.com AppCompactor When building with CMake you must first build the nsis_package_prep target (which takes care of general packaging dependencies), followed by the portableapps_package target, e.g. > msbuild /m /p:Configuration=RelWithDebInfo nsis_package_prep.vcxproj > msbuild /m /p:Configuration=RelWithDebInfo portableapps_package.vcxproj This might take a while Please be patient while the package is compressed. It might take some time, even on fast machines. If everything went well, you will now find something like: WiresharkPortable3.1.0.paf.exe_ in the packaging/portableapps directory. ## Chapter 4. Tool Reference ## 4.1. Introduction This chapter will provide you with information about the various tools needed for Wireshark development. None of the tools mentioned in this chapter are needed to run Wireshark. They are only needed to build it. Most of these tools have their roots on UNIX or UNIX-like platforms such as Linux, but Windows ports are also available. Therefore the tools are available in different "flavours": • UNIX and UNIX-like platforms: The tools should be commonly available on the supported UNIX and UNIX-like platforms. Cygwin is unsupported. • Windows native: Some tools are available as native Windows tools, no special emulation is required. Many of these tools can be installed (and updated) using Chocolatey, a Windows package manager similar to the Linux package managers apt-get or yum. Follow the directions Unless you know exactly what you are doing, you should strictly follow the recommendations given in Chapter 2, Quick Setup. The following sections give a very brief description of what a particular tool is doing, how it is used in the Wireshark project and how it can be installed and tested. Documentation for these tools is outside the scope of this document. If you need further information on using a specific tool you should find lots of useful information on the web, as these tools are commonly used. You can also get help for the UNIX based tools with toolname --help or the man page via man toolname. You will find explanations of the tool usage for some of the specific development tasks in Chapter 3, Work with the Wireshark sources. ## 4.2. Chocolatey Chocolatey is a Windows package manager that can be used to install (and update) many of the packages required for Wireshark development. Chocolatey can be obtained from the website or from a Command Prompt: C:\>@powershell -NoProfile -ExecutionPolicy unrestricted -Command "iex ((new-object net.webclient).DownloadString(_https://chocolatey.org/install.ps1_))" && SET PATH=%PATH%;%ALLUSERSPROFILE%\chocolatey\bin or a Powershell prompt: PS:\>iex ((new-object net.webclient).DownloadString(_https://chocolatey.org/install.ps1_)) Chocolatey sometimes installs packages in unexpected locations. Python is a notable example. While it’s typically installed in a top-level directory, e.g. C:\Python37 or in %PROGRAMFILES%, e.g. C:\Program Files\Python37, Chocolatey tends to install it under C:\ProgramData\chocolatey or C:\Tools. If you want to avoid this behavior you’ll probabaly want to install Python using the packages from python.org. ## 4.3. CMake Wireshark’s build environment can be configured using CMake on various UNIX-like platforms, including Linux, macOS, and *BSD, and on Windows. CMake is designed to support out-of-tree builds - so much so that in-tree builds do not work properly in all cases. Along with being cross-platform, CMake supports many build tools and environments including traditional make, Ninja, and MSBuild. Our Buildbot runs CMake steps on Ubuntu, Win32, Win64, and macOS. In particular, the macOS and Windows packages are built using CMake. Building with CMake typically includes creating a build directory and specifying a generator, aka a build tool. For example, to build Wireshark using Ninja in the directory wireshark-ninja you might run the following commands: # Starting from your Wireshark source directory, create a build directory # alongside it.$ cd ..
$mkdir wireshark-ninja$ cd wireshark-ninja
# Assumes your source directory is named "wireshark".
$cmake -G Ninja ../wireshark$ ninja (or cmake --build .)

Using CMake on Windows is described further in Section 2.2.11, “Generate the build files”.

Along with specifying a generator with the -G flag you can set variables using the -D flag. Useful variables and generators include the following:

-DBUILD_wireshark=OFF
Don’t build the Wireshark GUI application. Each command line utility has its own BUILD_xxx flag as well. For example, you can use -DBUILD_mmdbresolve=OFF to disable mmdbresolve.
-DENABLE_CAP=OFF
Disable the POSIX capabilities check
-DCMAKE_BUILD_TYPE=Debug
Enable debugging symbols
-DCARES_INCLUDE_DIR=/your/custom/cares/include, -DCARES_LIBRARY=/your/custom/cares/lib/libcares.so
Let you set the path to a locally-compiled version of c-ares. Most optional libraries have xxx_INCLUDE_DIR and xxx_LIB flags that let you control their discovery.
-DENABLE_APPLICATION_BUNDLE=OFF
Disable building an application bundle (Wireshark.app) on macOS

You can list all build variables (with help) by running cmake -LH [options] ../<Name_of_WS_source_dir>. This lists the cache of build variables after the cmake run. To only view the current cache, add option -N.

After running cmake, you can always run make help to see a list of all possible make targets.

Note that CMake honors user umask for creating directories as of now. You should set the umask explicitly before running the install target.

Official documentation: https://cmake.org/documentation/

About CMake in general and why KDE4 uses it: http://lwn.net/Articles/188693/

Introductory tutorial/presentation: http://ait.web.psi.ch/services/linux/hpc/hpc_user_cookbook/tools/cmake/docs/Cmake_VM_2007.pdf

Introductory article in the Linux Journal: http://www.linuxjournal.com/node/6700/print

Useful variables: http://www.cmake.org/Wiki/CMake_Useful_Variables

## 4.4. GNU Compiler Toolchain (UNIX And UNIX-like Platforms)

### 4.4.1. gcc (GNU Compiler Collection)

The GCC C compiler is available for most UNIX and UNIX-like operating systems.

If GCC isn’t already installed or available as a package for your platform, you can get it at: http://gcc.gnu.org/.

After correct installation, typing at the bash command line prompt:

$gcc --version should result in something like gcc (Ubuntu 4.9.1-16ubuntu6) 4.9.1 Copyright (C) 2014 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Your version string may vary, of course. ### 4.4.2. gdb (GNU Project Debugger) GDB is the debugger for the GCC compiler. It is available for many (if not all) UNIX-like platforms. If you don’t like debugging using the command line, many GUI frontends for it available, including Qt Creator, CLion, and Eclipse. If gdb isn’t already installed or available as a package for your platform, you can get it at: http://www.gnu.org/software/gdb/gdb.html. After correct installation: $ gdb --version

should result in something like:

GNU gdb (Ubuntu 7.8-1ubuntu4) 7.8.0.20141001-cvs
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".

Your version string may vary, of course.

### 4.4.3. make (GNU Make)

GNU make isn’t supported either for Windows GNU Make is available for most of the UNIX-like platforms.

If GNU Make isn’t already installed or available as a package for your platform, you can get it at: http://www.gnu.org/software/make/.

After correct installation:

$make --version should result in something like: GNU Make 4.0 Built for x86_64-pc-linux-gnu Copyright (C) 1988-2013 Free Software Foundation, Inc. Licence GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Your version string may vary, of course. ### 4.4.4. Ninja Ninja is an alternative to make, and is available for many of the UNIX-like platforms. It runs builds faster than make does. It is designed to have its build files generated by tools such as CMake; to generate build files for Ninja, run CMake with the -G Ninja flag. If Ninja isn’t already installed, see the list of suggestions for Ninja packages at: https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages. If Ninja isn’t already installed and isn’t available as a package for your platform, you can get it from: https://ninja-build.org. You can download the source code or binaries for Linux, macOS, and Windows (we have not tested Ninja on Windows). ## 4.5. Microsoft compiler toolchain (Windows native) To compile Wireshark on Windows using the Microsoft C/C++ compiler, you’ll need: 1. C compiler (cl.exe) 2. Assembler (ml.exe for 32-bit targets and ml64.exe for 64-bit targets) 3. Linker (link.exe) 4. Resource Compiler (rc.exe) 5. C runtime headers and libraries (e.g. stdio.h, vcruntime140.lib) 6. Windows platform headers and libraries (e.g. windows.h, WS2_32.lib) 7. HTML help headers and libraries (htmlhelp.h, htmlhelp.lib) ### 4.5.1. Official Toolchain Packages And Alternatives Official releases are or were built with the following Visual C++ versions: • Wireshark 3.0.x: Microsoft Visual C++ 2017. • Wireshark 2.6.x: Microsoft Visual C++ 2017. • Wireshark 2.4.x: Microsoft Visual C++ 2015. • Wireshark 2.2.x: Microsoft Visual C++ 2013. • Wireshark 2.0.x: Microsoft Visual C++ 2013. • Wireshark 1.12.x: Microsoft Visual C++ 2010 SP1. • Wireshark 1.10.x: Microsoft Visual C++ 2010 SP1. • Wireshark 1.8.x: Microsoft Visual C++ 2010 SP1. • Wireshark 1.6.x: Microsoft Visual C++ 2008 SP1. • Wireshark 1.4.x: Microsoft Visual C++ 2008 SP1. • Wireshark 1.2.x: Microsoft Visual C++ 2008 SP1. • Wireshark 1.0.x and earlier: Microsoft Visual C++ 6.0. Using the release compilers is recommended for Wireshark development work. “Community” editions of Visual Studio such as “Visual Studio Community 2017” can be used to compile Wireshark but any PortableApps packages you create with them might require the installation of a separate Visual C++ Redistributable package on any machine on which the PortableApps package is to be used. See Section 4.5.4, “Visual C++ Runtime “Redistributable” Files” below for more details. However, you might already have a different Microsoft C++ compiler installed. It should be possible to use any of the following with the considerations listed. You will need to sign up for a Visual Studio Dev Essentials account if you don’t have a Visual Studio (MSDN) subscription. The older versions can be downloaded from https://visualstudio.microsoft.com/vs/older-downloads/. Visual C++ 2015 Community Edition IDE + Debugger? Yes SDK required for 64-bit builds? No CMake Generator: Visual Studio 14 You can use Chocolatey to install Visual Studio, e.g: PS:\> choco install VisualStudioCommunity2015 ### 4.5.2. cl.exe (C Compiler) The following table gives an overview of the possible Microsoft toolchain variants and their specific C compiler versions ordered by release date.  Compiler Package cl.exe _MSC_VER CRT DLL Visual Studio 2015 14.0 1900 msvcr140.dll After correct installation of the toolchain, typing at the Visual Studio Command line prompt (cmd.exe): > cl should result in something like: Microsoft (R) C/{cpp} Optimizing Compiler Version 18.00.31101 for x86 Copyright (C) Microsoft Corporation. All rights reserved. usage: cl [ option... ] filename... [ /link linkoption... However, the version string may vary. Documentation on the compiler can be found at Microsoft Docs ### 4.5.3. link.exe (Linker) After correct installation, typing at the Visual Studio Command line prompt (cmd.exe): > link should result in something like: Microsoft (R) Incremental Linker Version 12.00.31101.0 Copyright (C) Microsoft Corporation. All rights reserved. usage: LINK [options] [files] [@commandfile] ... However, the version string may vary. Documentation on the linker can be found at Microsoft Docs ### 4.5.4. Visual C++ Runtime “Redistributable” Files Please note: The following is not legal advice. Ask your preferred lawyer instead. It’s the authors view and this view might be wrong. Wireshark and its libraries depend on POSIX functions such as fopen() and malloc(). On Windows, these functions are provided by the Microsoft Visual C++ Runtime. There are many different versions of the CRT and Visual C++ 2015 and later use the Universal CRT. The Universal CRT comes standard with Windows 10 and is installed as part of Windows Update on earlier versions of Windows. The Wireshark .exe installers include redistributables (vcredist_x86.exe or vcredist_x64.exe) which ensure that the Universal CRT is installed and up to date. Make sure you’re allowed to distribute this file The files to redistribute must be mentioned in the redist.txt file of the compiler package. Otherwise it can’t be legally redistributed by third parties like us. The following Microsoft Docs link is recommended for the interested reader: Redistributing Visual C++ Files In all cases where vcredist_x86.exe or vcredist_x64.exe is downloaded it should be downloaded to the directory into which the support libraries for Wireshark have been downloaded and installed. This directory is specified by the WIRESHARK_BASE_DIR or WIRESHARK_LIB_DIR environment variables. It need not, and should not, be run after being downloaded. ### 4.5.5. Windows Platform SDK The Windows Platform SDK (PSDK) or Windows SDK is a free (as in beer) download and contains platform specific headers and libraries (e.g. windows.h, WSock32.lib, etc.). As new Windows features evolve in time, updated SDKs become available that include new and updated APIs. When you purchase a commercial Visual Studio or use the Community Edition, it will include an SDK. ## 4.6. Documentation Toolchain Wireshark’s documentation is split across two directories. The doc directory contains man pages written in Perl’s POD (Plain Old Documentation) format. The docbook directory contains the User’s Guide, Developer’s Guide, and the release notes, which are written in Asciidoctor markup. Our various output formats are generated using the following tools. Intermediate formats are in italics. Guide HTML Asciidoctor → DocBook XML → xsltproc + DocBook XSL Guide PDF Asciidoctor Guide HTML Help Asciidoctor → DocBook XML → xsltproc + DocBook XSL → HHC Release notes HTML Asciidoctor Release notes text Asciidoctor → HTML → html2text.py ### 4.6.1. Asciidoctor Asciidoctor comes in several flavors: a Ruby gem (Asciidoctor), a Java bundle (AsciidoctorJ), and transpiled JavaScript (Asciidoctor.js). Only the Asciidoctor and AsciidoctorJ flavors are supported for building the Wireshark documentation and AsciidoctorJ is recommended. The guides and release notes were originally written in DocBook (hence the directory name). They were later converted to AsciiDoc and then migrated to Asciidoctor. compat-mode is currently enabled for the guides, but we are steadily migrating to Asciidoctor’s modern (>= 1.5.0) syntax. PDF output requires Asciidoctor PDF. It is included with AsciidoctorJ but not with Asciidoctor. ### 4.6.2. Xsltproc And DocBook The single HTML, chunked HTML, and HTML Help guides are generated using DocBook XSL stylesheets. They in turn require an XSLT processor. We use xsltproc. ### 4.6.3. HTML Help HTML Help is used to create the User’s and Developer’s Guide in .chm format. The User’s Guide .chm file is included with the NSIS and WiX installers and is used as Wireshark’s built-in help on Windows. This compiler is used to generate a .chm file from a bunch of HTML files — in our case to generate the User’s and Developer’s Guide in .chm format. The compiler is only available as the free (as in beer) "HTML Help Workshop" download. If you want to compile the guides yourself, you need to download and install this. If you don’t install it into the default directory, you may also have a look at the HHC_DIR setting in the file docbook/Makefile. The files htmlhelp.c and htmlhelp.lib are required to be able to open .chm files from Wireshark and show the online help. Both files are part of the SDK (standalone (P)SDK or MSVC since 2002). ### 4.6.4. Debugger Using a good debugger can save you a lot of development time. The debugger you use must match the C compiler Wireshark was compiled with, otherwise the debugger will simply fail or you will only see a lot of garbage. #### 4.6.4.1. Visual Studio Integrated Debugger You can use the integrated debugger of Visual Studio if your toolchain includes it. Open the solution in your build directory and build and debug as normal with a Visual Studio solution. To set the correct paths for Visual Studio when running Wireshark under the debugger, add the build output directory to the path before opening Visual Studio from the same command prompt, e.g. C:\Development\wsbuild32>set PATH="%PATH%;C:\Development\wsbuild32\run\RelwithDebInfo" C:\Development\wsbuild32>wireshark.sln for PowerShell use PS C:\Development\wsbuild32>$env:PATH += ";$(Convert-Path run\RelWithDebInfo)" PS C:\Development\wsbuild32>wireshark.sln When Visual Studio has finished loading the solution, set the executable to be run in the debugger, e.g. Executables\Wireshark, by right clicking it in the Solution Explorer window and selecting "Set as StartUp Project". Also set the Solution Configuration (usually RelWithDebInfo) from the droplist on the toolbar. Note Currently Visual Studio regards a command line build as incomplete, so will report that some items need to be built when starting the debugger. These can either be rebuilt or ignored as you wish. The normal build is an optimised release version so debugging can be a bit difficult as variables are optimised out into registers and the execution order of statements can jump around. If you require a non-optimised version, then build using a debug configuration. #### 4.6.4.2. Debugging Tools For Windows You can also use the Microsoft Debugging Tools for Windows toolkit, which is a standalone GUI debugger. Although it’s not that comfortable compared to debugging with the Visual Studio integrated debugger it can be helpful if you have to debug on a machine where an integrated debugger is not available. You can get it free of charge from Microsoft in several ways, see the Debugging tools for Windows page. You can also use Chocolatey to install WinDbg: PS:\> choco install windbg To debug Wireshark using WinDbg, open the built copy of Wireshark using the File → Open Executable…​ menu, i.e. C:\Development\wsbuild32\run\RelWithDebInfo\Wireshark.exe. To set a breakpoint open the required source file using the File → Open Source File…​ menu and then click on the required line and press F9. To run the program, press F5. If you require a non-optimised version, then build using a debug configuration, e.g. msbuild /m /p:Configuration=Debug Wireshark.sln. The build products will be found in C:\Development\wsbuild32\run\Debug\. ## 4.7. bash The bash shell is needed to run several shell scripts. #### Unix Bash (the GNU Bourne-Again SHell) is available for most UNIX and UNIX-like platforms. If it isn’t already installed or available as a package for your platform, you can get it at http://www.gnu.org/software/bash/bash.html. After correct installation, typing at the bash command line prompt: $ bash --version

should result in something like:

GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2016 Free Software Foundation, Inc.

Your version string will likely vary.

## 4.8. Python

Python is an interpreted programming language. It is used to generate some source files, documentation, testing and other tasks. Python 3.4 and later is required. Python 2.7 is no longer supported.

Python is either included or available as a package on most UNIX-like platforms. Windows packages and source are available at https://python.org/download/.

You can also use Chocolatey to install Python:

PS:\> choco install Python3

Chocolatey installs Python into C:\Python37 by default. You can verify your Python version by running

$python3 --version on UNIX-like platforms and rem Official package C:> cd python35 C:Python35> python --version rem Chocolatey C:> cd \tools\python3 C:\tools\python3> python --version on Windows. You should see something like Python 3.5.1 Your version string may vary of course. ## 4.9. Perl Perl is an interpreted programming language. The homepage of the Perl project is http://www.perl.com. Perl is used to convert various text files into usable source code. Perl version 5.6 and above should work fine. #### Unix Perl is available for most UNIX and UNIX-like platforms. If perl isn’t already installed or available as a package for your platform, you can get it at http://www.perl.com/. After correct installation, typing at the bash command line prompt: $ perl --version

should result in something like:

This is perl 5, version 26, subversion 0 (v5.26.0) built for x86_64-linux-gnu-thread-multi
(with 62 registered patches, see perl -V for more detail)

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl".  If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.

However, the version string may vary.

#### Windows

A native Windows Perl package can be obtained from Strawberry Perl or Active State. The installation should be straightforward.

You may also use Chocolatey to install either package:

PS:\> choco install StrawberryPerl

or

PS:\> choco install ActivePerl

After correct installation, typing at the command line prompt (cmd.exe):

> perl -v

should result in something like:

This is perl, v5.8.0 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Binary build 805 provided by ActiveState Corp. http://www.ActiveState.com
Built 18:08:02 Feb  4 2003
...

However, the version string may vary.

## 4.10. Bison

Bison is a parser generator used for some of Wireshark’s file format support.

#### Unix

Bison is available for most UNIX and UNIX-like platforms. See the next section for native Windows options.

If GNU Bison isn’t already installed or available as a package for your platform you can get it at: http://www.gnu.org/software/bison/bison.html.

After correct installation running the following

$bison --version should result in something like: bison (GNU Bison) 2.3 Written by Robert Corbett and Richard Stallman. Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Your version string may vary. #### Windows A native Windows version of bison is available in the winflexbison Chocolatey package. Note that the executable is named win_bison. Native packages are available from other sources such as GnuWin. They aren’t officially supported but should work. ## 4.11. Flex Flex is a lexical analyzer generator used for Wireshark’s display filters, some file formats, and other features. #### Unix Flex is available for most UNIX and UNIX-like platforms. See the next section for native Windows options. If GNU flex isn’t already installed or available as a package for your platform you can get it at http://www.gnu.org/software/flex/. After correct installation running the following $ flex --version

should result in something like:

flex version 2.5.4

#### Windows

A native Windows version of flex is available in the winflexbison Chocolatey package. Note that the executable is named win_flex.

PS:\>choco install winflexbison

Native packages are available from other sources such as GnuWin. They aren’t officially supported but should work.

## 4.12. Git client

The Wireshark project uses its own Git repository to keep track of all the changes done to the source code. Details about the usage of Git in the Wireshark project can be found in Section 3.2, “The Wireshark Git repository”.

If you want to work with the source code and are planning to commit your changes back to the Wireshark community, it is recommended to use a Git client to get the latest source files. For detailed information about the different ways to obtain the Wireshark sources, see Section 3.3, “Obtain the Wireshark sources”.

You will find more instructions in Section 3.3.1, “Git over SSH or HTTPS” on how to use the Git client.

#### Unix

Git is available for most UNIX and UNIX-like platforms. If Git isn’t already installed or available as a package for your platform, you can get it at: http://git-scm.com/.

After correct installation, typing at the bash command line prompt:

$git --version should result in something like: git version 2.14.1 Your version will likely be different. #### Windows The Git command line tools for Windows can be found at http://git-scm.com/download/win and can also be installed using Chocolatey: PS:\> choco install git After correct installation, typing at the command line prompt (cmd.exe): > git --version should result in something like: git version 2.16.1.windows.1 However, the version string may vary. ## 4.13. Git Powershell Extensions (Optional) A useful tool for command line git on Windows is PoshGit. Poshgit provides git command completion and alters the prompt to indicate the local working copy status. You can install it using Chocolatey: PS:\>choco install poshgit ## 4.14. Git GUI Client (Optional) Along with the traditional command-line client, several GUI clients are available for a number of platforms. See http://git-scm.com/downloads/guis for details. ## 4.15. patch (Optional) The patch utility is used to merge a diff file into your own source tree. This tool is only needed, if you want to apply a patch (diff file) from someone else (probably from the developer mailing list) to try out in your own private source tree. It most cases you may not need the patch tool installed. Git and Gerrit should handle patches for you. You will find more instructions in Section 3.10, “Apply a patch from someone else”on how to use the patch tool. #### Unix Patch is available for most UNIX and UNIX-like platforms. If GNU patch isn’t already installed or available as a package for your platform, you can get it at http://www.gnu.org/software/patch/patch.html. After correct installation, typing at the bash command line prompt: $ patch --version

should result in something like:

patch 2.5.8
Copyright (C) 2002 Free Software Foundation, Inc.

This program comes with NO WARRANTY, to the extent permitted by law.
You may redistribute copies of this program
under the terms of the GNU General Public License.

written by Larry Wall and Paul Eggert

However, the version string may vary.

#### Windows

The Windows native Git tools provide patch. A native Windows patch package can be obtained from http://gnuwin32.sourceforge.net/. The installation should be straightforward.

## 4.16. Windows: NSIS (Optional)

The NSIS (Nullsoft Scriptable Install System) is used to generate Wireshark-win32-3.1.0.exe from all the files needed to be installed, including all required DLLs, plugins, and supporting files.

To install it, download the latest released version from https://nsis.sourceforge.net. NSIS v3 is required. You can also install it using Chocolatey:

PS$> choco install nsis You can find more instructions on using NSIS in Section 3.11.5, “Windows: NSIS .exe Installer”. ## 4.17. Windows: WiX Toolset (Optional) The Wix Toolset can be used to generate Windows Installer (.msi) packages. You can download it from the WiX web site or install it using Chocolatey: PS$> choco install wixtoolset

Wireshark’s .msi packaging is currently experimental and the generated packages may be incomplete.

## 4.18. Windows: PortableApps (Optional)

The PortableApps.com Installer is used to generate WiresharkPortable-3.1.0.paf.exe from all the files needed to be installed, including all required DLLs, plugins, and supporting files.

To install it, do the following:

• Install the following applications in the PortableApps.com environment:

• PortableApps.com Installer
• PortableApps.com Launcher
• NSIS Portable (Unicode)
• PortableApps.com AppCompactor

You can find more instructions on using the PortableApps.com Installer in Section 3.11.6, “Windows: PortableApps .paf.exe Package”.

## 5.1. Introduction

Several libraries are needed to build and run Wireshark. Most of them are split into three packages:

1. Runtime. System and third party libraries such as vcruntime140.dll and libglib-2.0-0.dll.
2. Developer. Documentation, header files, import libraries, and other files needed for compilation.
3. Source. Library sources, which are usually not required to build Wireshark.
Our libraries are freely available All libraries required to build Wireshark on Windows are available for download at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/ and https://anonsvn.wireshark.org/wireshark-win64-libs/trunk/packages/. See Section 5.3, “Windows Automated Library Download” for an easier way to install them.

## 5.2. Binary Library Formats

Binary libraries are available in different formats, depending on the C compiler used to build it and of course the platform they were built for.

#### Unix

If you have installed unix binary libraries on your system, they will match the C compiler. If not already installed, the libraries should be available as a package from the platform installer, or you can download and compile the source and then install the binaries.

#### Windows

Most of the Win32 binary libraries you will find on the web are in this format. You will recognize MSVC libraries by the .lib/.dll file extension.

The required libraries (apart from Qt) are automatically downloaded as part of the CMake generation step, and subsequently as required when libraries are updated.

The libraries are downloaded into the directory indicated by the environment variable WIRESHARK_BASE_DIR, this must be set appropriately for your environment. The libraries are downloaded and extracted into WIRESHARK_BASE_DIR\wireshark-win32-libs and WIRESHARK_BASE_DIR\wireshark-win64-libs for 32 and 64 bit builds respectively.

You may also directly set the library directory with the environment variable WIRESHARK_LIB_DIR, but if you switch between 32 bit and 64 bit builds, the value of this must be set appropriately.

## 5.4. Qt

The Qt library is used to build the UI for Wireshark and is used to provide a platform independent UI. Wireshark can be built with Qt 5.2 or later.

For more information on the Qt libraries, see Section 12.2, “The Qt Application Framework”.

#### Unix

Most Linux distributions provide Qt and its development libraries as standard packages. The required libraries and tools will likely be split across several packages. For example, building on Ubuntu requires qttools5-dev, qttools5-dev-tools, libqt5svg5-dev, qtmultimedia5-dev, and possibly others.

The Qt Project provides an installation tool for macOS, similar to Windows. It is available at https://www.qt.io/download-open-source/#section-2.

#### Windows

Qt5 must be installed manually from the Qt installers page https://www.qt.io/download-open-source/#section-2 using the version of Qt appropriate for your compiler. Note that separate installations (into different directories) of Qt are required for 32 bit and 64 bit builds. The environment variable QT5_BASE_DIR should be set as appropriate for your environment and should point to the Qt directory that contains the bin directory, e.g. C:\Qt\5.9.5\msvc2017_64.

## 5.5. GLib And Supporting Libraries

The GLib library is used as a basic platform abstraction library and can be used in both CLI and GUI applications. For a detailed description about GLib see Section 7.3, “The GLib library”.

GLib depends on GNU libiconv, GNU gettext, and other libraries. You will typically not come into contact with these while doing Wireshark development. Wireshark’s build system check for and require both GLib and its dependencies.

#### Unix

The GLib library is available for most Linux distributions and UNIX flavors. If it isn’t already installed and isn’t available as a package for your platform, you can get it at http://www.gtk.org.

## 5.6. SMI (Optional)

LibSMI is used for MIB and PIB parsing and for OID resolution.

#### Unix

If this library isn’t already installed or available as a package for your platform, you can get it at http://www.ibr.cs.tu-bs.de/projects/libsmi/.

#### Windows

Wireshark uses the source libSMI distribution at http://www.ibr.cs.tu-bs.de/projects/libsmi/. LibSMI is cross-compiled using MinGW32. It’s stored in the libsmi zip archive at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.7. c-ares (Optional)

C-Ares is used for asynchronous DNS resolution. This is the primary name resolution library in Wireshark.

#### Unix

If this library isn’t already installed or available as a package for your platform, you can get it at http://c-ares.haxx.se/.

#### Windows

C-Ares is cross-compiled using MinGW32 and is available at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.8. zlib (Optional)

 zlib is designed to be a free, general-purpose, legally unencumbered — that is, not covered by any patents — lossless data-compression library for use on virtually any computer hardware and operating system. -- The zlib web site http://www.zlib.net/

#### Unix

This library is almost certain to be installed on your system. If it isn’t or you don’t want to use the default library you can download it from http://www.zlib.net/.

## 5.9. libpcap or Npcap (Optional, But Strongly Recommended)

Libpcap and Npcap provide that packet capture capabilities that are central to Wireshark’s core functionality.

#### Unix: libpcap

If this library isn’t already installed or available as a package for your platform, you can get it at http://www.tcpdump.org/.

#### Windows: Npcap

The Windows build environment compiles and links against the WinPcap SDK (WpdPack) and includes the Npcap packet capture driver with the .exe installer. Both are automatically downloaded by CMake.

You can download the Npcap Windows packet capture library manually from https://nmap.org/npcap/.

Npcap has its own license with its own restrictions Insecure.Com LLC, aka “The Nmap Project” has granted the Wireshark Foundation the right to include Npcap with the installers that we distribute from wireshark.org. If you wish to distribute your own Wireshark installer or any other package that includes Npcap you must comply with the Npcap license and may be required to purchase a redistribution license. Please see https://nmap.org/npcap/ for more details.

## 5.10. GnuTLS (Optional)

The GNU Transport Layer Security Library is used to enable TLS decryption using an RSA private key.

#### Unix

If this library isn’t already installed or available as a package for your platform, you can get it at https://gnutls.org/.

#### Windows

We provide a package cross-compiled using MinGW32 at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.11. Gcrypt

The Gcrypt Library is a low-level cryptographic library that provides support for many ciphers and message authentication codes, such as DES, 3DES, AES, Blowfish, SHA-1, SHA-256, and others.

#### Unix

If this library isn’t already installed or available as a package for your platform, you can get it at https://directory.fsf.org/wiki/Libgcrypt.

#### Windows

Part of our GnuTLS package.

## 5.12. Kerberos (Optional)

The Kerberos library is used to dissect Kerberos, sealed DCERPC and secureLDAP protocols.

#### Unix

If this library isn’t already installed or available as a package for your platform, you can get it at http://web.mit.edu/Kerberos/dist/.

#### Windows

We provide a package at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.13. LUA (Optional)

The LUA library is used to add scripting support to Wireshark.

#### Windows

We provide a copy of the official package at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.14. MaxMindDB (Optional)

MaxMind Inc. publishes a set of IP geolocation databases and related open source libraries. They can be used to map IP addresses to geographical locations and other information.

If libmaxminddb library isn’t already installed or available as a package for your platform, you can get it at https://github.com/maxmind/libmaxminddb.

We provide a package for Windows at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

## 5.15. WinSparkle (Optional)

WinSparkle is an easy-to-use software update library for Windows developers.

#### Windows

We provide a copy of the WinSparkle package at https://anonsvn.wireshark.org/wireshark-win32-libs/trunk/packages/.

# Part II. Wireshark Development

## 6.1. Introduction

This chapter will give you a short overview of how Wireshark works.

## 6.2. Overview

The following will give you a simplified overview of Wireshark’s function blocks:

The function blocks in more detail:

GUI
Handling of all user input/output (all windows, dialogs and such). Source code can be found in the ui/qt directory.
Core
Main "glue code" that holds the other blocks together. Source code can be found in the root directory.
Epan

Enhanced Packet ANalyzer — the packet analyzing engine. Source code can be found in the epan directory. Epan provides the following APIs:

• Protocol Tree. Dissection information for an individual packet.
• Dissectors. The various protocol dissectors in epan/dissectors.
• Dissector Plugins - Support for implementing dissectors as separate modules. Source code can be found in plugins.
• Display Filters - The display filter engine at epan/dfilter.
Wiretap
The wiretap library is used to read and write capture files in libpcap, pcapng, and many other file formats. Source code is in the wiretap directory.
Capture
The interface with the capture engine. Source code is in the root directory.
Dumpcap
The capture engine itself. This is the only part that is to execute with elevated privileges. Source code is in the root directory.
Npcap and libpcap
These are separate libraries that provide packet capture and filtering support on different platforms. The filtering in Npcap and libpcap works at a much lower level than Wireshark’s display filters and uses a significantly different mechanism. That’s why we have different display and capture filter syntaxes.

## 6.3. Capturing packets

Capturing takes packets from a network adapter and saves them to a file on your hard disk.

Since raw network adapter access requires elevated privileges these functions are isolated into the dumpcap program. It’s only this program that needs these privileges, allowing the main part of the code (dissectors, user interface, etc) to run with normal user privileges.

To hide all the low-level machine dependent details from Wireshark, the libpcap and Npcap (see Section 5.9, “libpcap or Npcap (Optional, But Strongly Recommended)”) libraries are used. These libraries provide a general purpose interface to capture packets and are used by a wide variety of applications.

## 6.4. Capture Files

Wireshark can read and write capture files in its natural file formats, pcapng and pcap, which are used by many other network capturing tools, such as tcpdump. In addition to this, as one of its strengths, Wireshark can read and write files in many different file formats of other network capturing tools. The wiretap library, developed together with Wireshark, provides a general purpose interface to read and write all the file formats. If you need to add support for another capture file format this is the place to start.

## 6.5. Dissect packets

While Wireshark is loading packets from a file each packet is dissected. Wireshark tries to detect the packet type and gets as much information from the packet as possible. In this run though, only the information shown in the packet list pane is needed.

As the user selects a specific packet in the packet list pane this packet will be dissected again. This time, Wireshark tries to get every single piece of information and put it into the packet details pane.

## 7.1. Source overview

Wireshark consists of the following major parts:

• Packet dissection - in the /epan/dissectors and /plugins/epan/* directories
• Capture file I/O - using Wireshark’s own wiretap library
• Capture - using the libpcap and Npcap libraries, in dumpcap.c and the /capchild and _/caputils directories
• User interface - using Qt and associated libraries
• Utilities - miscellaneous helper code
• Help - using an external web browser and text output

## 7.2. Coding Style

The coding style guides for Wireshark can be found in the "Code style" section of the file doc/README.developer.

## 7.3. The GLib library

GLib is used as a basic platform abstraction library. It doesn’t provide any direct GUI functionality.

To quote the GLib Reference Manual:

GLib provides the core application building blocks for libraries and applications written in C. It provides the core object system used in GNOME, the main loop implementation, and a large set of utility functions for strings and common data structures.

GLib contains lots of useful things for platform independent development. See https://developer.gnome.org/glib/ for details about GLib.

## 8.1. How To Add A New Capture Type To Libpcap

For this discussion, I’ll assume you’re working with libpcap 1.0 or later. You probably don’t want to work with a version older than 1.0, even if whatever OS you’re using happens to include libpcap - older versions are not as friendly towards adding support for devices other than standard network interfaces.

(It’s currently incomplete, but I’ll be finishing it up over time. If you have contributions, feel free to submit pull requests for it.)

If you had to introduce one or more new DLT_* values, you will also have to add support in Wireshark for those DLT_* values to wiretap/pcap-common.c, which might mean adding one or more WTAP_ENCAP types to wtap.h and to the encap_table[] table in wiretap/wtap.c. You’d then have to write a dissector or dissectors for the link-layer protocols or protocols and have them register themselves with the wtap_encap dissector table, with the appropriate WTAP_ENCAP values by calling dissector_add_uint().

## 8.2. Extcap: Developer Guide

The extcap interface is a versatile plugin interface that allows external binaries to act as capture interfaces directly in Wireshark. It is used in scenarios, where the source of the capture is not a traditional capture model (live capture from an interface, from a pipe, from a file, etc). The typical example is connecting esoteric hardware of some kind to the main Wireshark app.

Without extcap, a capture can always be achieved by directly writing to a capture file:

Bash example for traditional capture with a capture file.

$the-esoteric-binary --the-strange-flag --interface=stream1 --file dumpfile.pcap &$ wireshark dumpfile.pcap

but the extcap interface allows for such a connection to be easily established and configured using the Wireshark GUI.

The extcap subsystem is made of multiple extcap binaries that are automatically called by the GUI in a row. In the following chapters we will refer to them as "the extcaps".

Extcaps may be any binary or script within the extcap directory. Please note, that scripts need to be executable without prefacing a script interpreter before the call.

Important Windows Users Because of restrictions directly calling the script may not always work. In such a case, a batch file may be provided, which then in turn executes the script. Please refer to Section 8.2.1.4.1, “Execute a script-based extcap on Windows” for more information.

### 8.2.1. Extcap command line interface

The actual capture is run after a setup process that can be made manually by the user or automatically by the GUI. All the steps performed are done for every extcap.

Let’s go through those steps.

#### 8.2.1.1. Query for available interfaces

In the first step the extcap is queried for its interfaces.

$extcapbin --extcap-interfaces This call must print the existing interfaces for this extcap and must return 0. The output must conform to the grammar specified for extcap, and it is specified in the doc/extcap.4 generated man page (in the build dir). Since Wireshark 2.9 this call is extended with --extcap-version=x.x, which will always represent the calling Wireshark’s version information. This can be used to change behavior depending on the Wireshark version in question. Example call for interface query. $ extcap_example.py --extcap-interfaces --extcap-version=3.0
extcap {version=1.0}{help=Some help url}
interface {value=example1}{display=Example interface 1 for extcap}
interface {value=example2}{display=Example interface 2 for extcap}

The version for the extcap sentence (which may exist as many times as is needed, but only the last one will be used) will be used for displaying the version information of the extcap interface in the about dialog of Wireshark.

The value for each interface will be used in subsequent calls as the interface name IFACE.

Using the help argument, an interface may provide a generic help URL for the extcap utility.

#### 8.2.1.2. Ask for DLT’s to each interface

The extcap binary is queried for all valid DLTs for all the interfaces returned by step 1.

$extcap_example.py --extcap-dlts --extcap-interface IFACE This call must print the valid DLTs for the interface specified. This call is made for all the interfaces and must return 0. Example for the DLT query. $ extcap_example.py --extcap-interface IFACE --extcap-dlts
dlt {number=147}{name=USER1}{display=Demo Implementation for Extcap}

A binary or script, which neither provides an interface list or a DLT list will not show up in the extcap interfaces list.

#### 8.2.1.3. The extcap configuration interface

The extcap binary is asked for the configuration of a specific interface

$extcap_example.py --extcap-interface IFACE --extcap-config Each interface can have custom options that are valid for this interface only. Those config options are specified on the command line when running the actual capture. To allow an end-user to specify certain options, such options may be provided using the extcap config argument. To share which options are available for an interface, the extcap responds to the command --extcap-config, that shows all the available options (aka additional command line options). Those options are automatically presented via a dialog to the user for the individual interface. Example for interface options. $ extcap_example.py --extcap-interface IFACE --extcap-config
arg {number=0}{call=--delay}{display=Time delay}{tooltip=Time delay between packages}{type=integer}{range=1,15}{required=true}
arg {number=1}{call=--message}{display=Message}{tooltip=Package message content}{placeholder=Please enter a message here ...}{type=string}
arg {number=2}{call=--verify}{display=Verify}{tooltip=Verify package content}{type=boolflag}
arg {number=3}{call=--remote}{display=Remote Channel}{tooltip=Remote Channel Selector}{type=selector}
arg {number=4}{call=--server}{display=IP address for log server}{type=string}{validation=\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b}
value {arg=3}{value=if1}{display=Remote1}{default=true}
value {arg=3}{value=if2}{display=Remote2}{default=false}

Now the user can click on the options and change them. They are sent to the extcap when the capture is launched.

There are three kind of options available:

 Flag boolflag for instance expects the option to be present resulting in the corresponding entry set to true, false otherwise Value are value based options and each expect a single value via the command-line call Selection are selections and can be presented multiple times in the command line. Both expect subsequent "value" items in the config list, with the corresponding argument selected via arg

#### 8.2.1.4. The capture process

Once the interfaces are listed and configuration is customized by the user the capture is started.

$extcap_example.py --extcap-interface IFACE [params] --capture [--extcap-capture-filter CFILTER] --fifo FIFO To run the capture, the extcap must implement the --capture, --extcap-capture-filter and --fifo option. They are automatically added by Wireshark that opens the fifo for reading. All the other options are automatically added to run the capture. The extcap interface is used like all other interfaces (meaning that capture on multiple interfaces, as well as stopping and restarting the capture is supported). ##### 8.2.1.4.1. Execute a script-based extcap on Windows To use scripts on Windows, please generate an <scriptname>.bat inside the extcap folder, with the following content (in this case for a Python-based extcap utility): @echo off <Path to python interpreter> <Path to script file> %* Windows is not able to execute most scripts directly (Powershell being an exception), which also goes for all other script-based formats besides VBScript and PowerShell ### 8.2.2. Extcap Arguments The extcap interface provides the possibility for generating a GUI dialog to set and adapt settings for the extcap binary. All options must provide a number, by which they are identified. No NUMBER may be provided twice. Also all options must present the elements CALL and DISPLAY, where call provides the arguments name on the command-line and display the name in the GUI. Additionally TOOLTIP and PLACEHOLDER may be provided, which will give the user an explanation within the GUI, about what to enter into this field. These options do have types, for which the following types are being supported:  INTEGER, UNSIGNED, LONG, DOUBLE This provides a field for entering a numeric value of the given data type. A DEFAULT value may be provided, as well as a RANGE arg {number=0}{call=--delay}{display=Time delay}{tooltip=Time delay between packages}{type=integer}{range=1,15}{default=0} STRING Let the user provide a string to the capture arg {number=1}{call=--server}{display=IP Address}{tooltip=IP Address for log server}{type=string}{validation=\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b} validation allows to provide a regular expression string, which is used to check the user input for validity beyond normal data type or range checks. Back-slashes must be escaped (as in \\b for \b) PASSWORD Let the user provide a masked string to the capture. Password strings are not saved, when the extcap configuration is being saved arg {number=0}{call=--password}{display=The user password}{tooltip=The password for the connection}{type=password} BOOLEAN, BOOLFLAG This provides the possibility to set a true/false value. BOOLFLAG values will only appear in the command-line if set to true, otherwise they will not be added to the command-line call for the extcap interface arg {number=2}{call=--verify}{display=Verify}{tooltip=Verify package content}{type=boolflag} FILESELECT Let the user provide a filepath to the capture. If MUSTEXIST is being provided, the GUI checks if the file exists. arg {number=3}{call=--logfile}{display=Logfile}{tooltip=A file for log messages}{type=fileselect}{mustexist=false} SELECTOR, RADIO, MULTICHECK Optionfields, where the user may choose one or more options from. If PARENT is provided for the value items, the option fields for MULTICHECK and SELECTOR are being presented in a tree-like structure. SELECTOR and RADIO values must present a default value, which will be the value provided to the extcap binary for this argument arg {number=3}{call=--remote}{display=Remote Channel}{tooltip=Remote Channel Selector}{type=selector} value {arg=3}{value=if1}{display=Remote1}{default=true} value {arg=3}{value=if2}{display=Remote2}{default=false} #### 8.2.2.1. Reload a selector A selector may be reloaded from the configuration dialog of the extcap application within Wireshark. With the reload argument (defaults to false), the entry can be marked as reloadable. arg {number=3}{call=--remote}{display=Remote Channel}{tooltip=Remote Channel Selector}{type=selector}{reload=true}{placeholder=Load interfaces...} After this has been defined, the user will get a button displayed in the configuration dialog for this extcap application, with the text "Load interfaces…​" in this case, and a generic "Reload" text if no text has been provided. The extcap utility is then called again with all filled out arguments and the additional parameter --extcap-reload-option <option_name>. It is expected to return a value section for this option, as it would during normal configuration. The provided option list is then presented as the selection, a previous selected option will be reselected if applicable. #### 8.2.2.2. Validation of arguments Arguments may be set with {required=true} which enforces a value being provided, before a capture can be started using the extcap options dialog. This is not being checked, if the extcap is started via a simple double-click. The necessary fields are marked for the customer, to ensure a visibility for the end customer of the required argument. Additionally text and number arguments may also be checked using a regular expression, which is provided using the validation attribute (see example above). The syntax for such a check is the same as for Qt RegExp classes. This feature is only active in the Qt version of Wireshark. ### 8.2.3. Toolbar Controls An extcap utility can provide configuration for controls to use in an interface toolbar. These controls are bidirectional and can be used to control the extcap utility while capturing. This is useful in scenarios where configuration can be done based on findings in the capture process, setting temporary values or give other inputs without restarting the current capture. Example of interface definition with toolbar controls. $ extcap_example.py --extcap-interfaces
extcap {version=1.0}{display=Example extcap interface}
interface {value=example1}{display=Example interface 1 for extcap}
interface {value=example2}{display=Example interface 2 for extcap}
control {number=1}{type=selector}{display=Time delay}{tooltip=Time delay between packages}
control {number=2}{type=boolean}{display=Verify}{default=true}{tooltip=Verify package content}
control {number=3}{type=button}{display=Turn on}{tooltip=Turn on or off}
control {number=4}{type=button}{role=logger}{display=Log}{tooltip=Show capture log}
value {control=1}{value=1}{display=1 sec}
value {control=1}{value=2}{display=2 sec}{default=true}

All controls will be presented as GUI elements in a toolbar specific to the extcap utility. The extcap must not rely on using those controls (they are optional) because of other capturing tools not using GUI (e.g. tshark, tfshark).

#### 8.2.3.1. Controls

The controls are similar to the ARGUMENTS, but without the CALL element. All controls may be given a default value at startup and most can be changed during capture, both by the extcap and the user (depending on the type of control).

All controls must provide a NUMBER, by which they are identified. No NUMBER may be provided twice. Also all options must present the elements TYPE and DISPLAY, where TYPE provides the type of control to add to the toolbar and DISPLAY the name in the GUI.

Additionally TOOLTIP and PLACEHOLDER may be provided, which will give the user an explanation within the GUI.

All controls, except from the logger, help and restore buttons, may be disabled (and enabled) in GUI by the extcap during capture. This can be because of set-once operations, or operations which takes some time to complete.

All control values which are changed by the user (not equal to the default value) will be sent to the extcap utility when starting a capture. The extcap utility may choose to discard initial values and set new values, depending on implementation.

These TYPEs are defined as controls:

 BOOLEAN This provides a checkbox with the possibility to set a true/false value. The extcap utility can set a default value at startup, and can change (set) and receive value changes while capturing. When starting a capture the GUI will send the value if different from the default value. The payload is one byte with binary value 0 or 1. Valid Commands: Set value, Enable, Disable. BUTTON This provides a button with different ROLEs: CONTROL This button will send a signal when pressed. This is the default if no role is configured. The button is only enabled when capturing. The extcap utility can set the button text at startup, and can change (set) the button text and receive button press signals while capturing. The button is disabled and the button text is restored to the default text when not capturing. The payload is either the button text or empty (signal). Valid Commands: Set value, Enable, Disable. LOGGER This provides a logger mechanism where the extcap utility can send log entries to be presented in a log window. This communication is unidirectional. The payload is the log entry, and should be ended with a newline. Maximum length is 65535 bytes. Valid Commands: Set log entry, Add log entry. The Set command will clear the log before adding the entry. HELP This button opens the help page, if configured. This role has no controls and will not be used in communication. Valid Commands: NONE. RESTORE This button will restore all control values to default. This role has no controls and will not be used in communication. The button is only enabled when not capturing. Valid Commands: NONE. SELECTOR This provides a combo box with fixed values which can be selected. The extcap utility can set default values at startup, and add and remove values and receive change in value selection while capturing. When starting a capture the GUI will send the value if different from the default value. The payload is a string with the value, and optionally a string with a display value if this is different from the value. This two string values are separated by a null character. Valid Commands: Set selected value, Add value, Remove value, Enable, Disable. If value is empty the Remove command will remove all entries. STRING This provides a text edit line with the possibility to set a string or any value which can be represented in a string (integer, float, date, etc.). The extcap utility can set a default string value at startup, and can change (set) and receive value changes while capturing. When starting a capture the GUI will send the value if different from the default value. The payload is a string with the value. Maximum length is 32767 bytes. Valid Commands for control: Set value, Enable, Disable. The element VALIDATION allows to provide a regular expression string, which is used to check the user input for validity beyond normal data type or range checks. Back-slashes must be escaped (as in \\b for \b).

#### 8.2.3.2. Messages

In addition to the controls it’s possible to send a single message from the extcap utility to the user. This message can be put in the status bar or displayed in a information, warning or error dialog which must be accepted by the user. This message does not use the NUMBER argument so this can have any value.

##### 8.2.3.2.1. Control Protocol

The protocol used to communicate over the control pipes has a fixed size header of 6 bytes and a payload with 0 - 65535 bytes.

Table 8.1. Control packet:

 Sync Pipe Indication (1 byte) Message Length (3 bytes network order) Control Number (1 byte) Command (1 byte) Payload (0 - 65535 bytes)

Sync Pipe Indication:

The common sync pipe indication. This protocol uses the value “T”.

Message Length:

Payload length + 2 bytes for control number and command.

Control Number:

Unique number to identify the control. This number also gives the order of the controls in the interface toolbar.

Table 8.2. Commands and application for controls

Command Byte Command Name Control type

0

Initialized

none

1

Set

boolean / button / logger / selector / string

2

logger / selector

3

Remove

selector

4

Enable

boolean / button / selector / string

5

Disable

boolean / button / selector / string

6

Statusbar message

none

7

Information message

none

8

Warning message

none

9

Error message

none

The Initialized command will be sent from the GUI to the extcap utility when all user changed control values are sent after starting a capture. This is an indication that the GUI is ready to receive control values.

The GUI will only send Initialized and Set commands. The extcap utility shall not send the Initialized command.

Messages with unknown control number or command will be silently ignored.

## 9.1. How it works

Each dissector decodes its part of the protocol, and then hands off decoding to subsequent dissectors for an encapsulated protocol.

Every dissection starts with the Frame dissector which dissects the packet details of the capture file itself (e.g. timestamps). From there it passes the data on to the lowest-level data dissector, e.g. the Ethernet dissector for the Ethernet header. The payload is then passed on to the next dissector (e.g. IP) and so on. At each stage, details of the packet will be decoded and displayed.

Dissection can be implemented in two possible ways. One is to have a dissector module compiled into the main program, which means it’s always available. Another way is to make a plugin (a shared library or DLL) that registers itself to handle dissection.

There is little difference in having your dissector as either a plugin or built-in. On the Windows platform you have limited function access through the ABI exposed by functions declared as WS_DLL_PUBLIC.

The big plus is that your rebuild cycle for a plugin is much shorter than for a built-in one. So starting with a plugin makes initial development simpler, while the finished code may make more sense as a built-in dissector.

Read README.dissector The file doc/README.dissector contains detailed information about implementing a dissector. In many cases it is more up to date than this document.

## 9.2. Adding a basic dissector

• A packet type - 8 bits, possible values: 1 - initialisation, 2 - terminate, 3 - data.
• A set of flags stored in 8 bits, 0x01 - start packet, 0x02 - end packet, 0x04 - priority packet.
• A sequence number - 16 bits.

### 9.2.1. Setting up the dissector

The first decision you need to make is if this dissector will be a built-in dissector, included in the main program, or a plugin.

Plugins are the easiest to write initially, so let’s start with that. With a little care, the plugin can be made to run as a built-in easily too so we haven’t lost anything.

Example 9.1. Dissector Initialisation.

#include "config.h"

#include <epan/packet.h>

#define FOO_PORT 1234

static int proto_foo = -1;

void
proto_register_foo(void)
{
proto_foo = proto_register_protocol (
"FOO Protocol", /* name       */
"FOO",      /* short name */
"foo"       /* abbrev     */
);
}

Let’s go through this a bit at a time. First we have some boilerplate include files. These will be pretty constant to start with.

Next we have an int that is initialised to -1 that records our protocol. This will get updated when we register this dissector with the main program. It’s good practice to make all variables and functions that aren’t exported static to keep name space pollution down. Normally this isn’t a problem unless your dissector gets so big it has to span multiple files.

Then a #define for the UDP port that carries foo traffic.

Now that we have the basics in place to interact with the main program, we’ll start with two protocol dissector setup functions.

First we’ll call proto_register_protocol() which registers the protocol. We can give it three names that will be used for display in various places. The full and short name are used in e.g. the "Preferences" and "Enabled protocols" dialogs as well as the generated field name list in the documentation. The abbreviation is used as the display filter name.

Next we need a handoff routine.

Example 9.2. Dissector Handoff.

void
proto_reg_handoff_foo(void)
{
static dissector_handle_t foo_handle;

foo_handle = create_dissector_handle(dissect_foo, proto_foo);
}

What’s happening here? We are initialising the dissector. First we create a dissector handle; It is associated with the foo protocol and with a routine to be called to do the actual dissecting. Then we associate the handle with a UDP port number so that the main program will know to call us when it gets UDP traffic on that port.

The standard Wireshark dissector convention is to put proto_register_foo() and proto_reg_handoff_foo() as the last two functions in the dissector source.

Now at last we get to write some dissecting code. For the moment we’ll leave it as a basic placeholder.

Example 9.3. Dissection.

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree _U_, void *data _U_)
{
col_set_str(pinfo->cinfo, COL_PROTOCOL, "FOO");
/* Clear out stuff in the info column */
col_clear(pinfo->cinfo,COL_INFO);

return tvb_captured_length(tvb);
}

This function is called to dissect the packets presented to it. The packet data is held in a special buffer referenced here as tvb. We shall become fairly familiar with this as we get deeper into the details of the protocol. The packet info structure contains general data about the protocol, and we can update information here. The tree parameter is where the detail dissection takes place.

For now we’ll do the minimum we can get away with. In the first line we set the text of this to our protocol, so everyone can see it’s being recognised. The only other thing we do is to clear out any data in the INFO column if it’s being displayed.

At this point we should have a basic dissector ready to compile and install. It doesn’t do much at present, other than identify the protocol and label it.

In order to compile this dissector and create a plugin a couple of support files are required, besides the dissector source in packet-foo.c:

• CMakeLists.txt - Contains the CMake file and version info for this plugin.
• packet-foo.c - Your dissector source.
• plugin.rc.in - Contains the DLL resource template for Windows. (optional)

You can find a good example for these files in the gryphon plugin directory. CMakeLists.txt has to be modified with the correct plugin name and version info, along with the relevant files to compile. In the main top-level source directory, copy CMakeListsCustom.txt.example to CMakeListsCustom.txt and add the path of your plugin to the list in CUSTOM_PLUGIN_SRC_DIR.

Compile the dissector to a DLL or shared library and either run Wireshark from the build directory as detailed in Section 3.6, “Run generated Wireshark” or copy the plugin binary into the plugin directory of your Wireshark installation and run that.

### 9.2.2. Dissecting the details of the protocol

Now that we have our basic dissector up and running, let’s do something with it. The simplest thing to do to start with is to just label the payload. This will allow us to set up some of the parts we will need.

The first thing we will do is to build a subtree to decode our results into. This helps to keep things looking nice in the detailed display.

Example 9.4. Plugin Packet Dissection.

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{

col_set_str(pinfo->cinfo, COL_PROTOCOL, "FOO");
/* Clear out stuff in the info column */
col_clear(pinfo->cinfo,COL_INFO);

proto_item *ti = proto_tree_add_item(tree, proto_foo, tvb, 0, -1, ENC_NA);

return tvb_captured_length(tvb);
}

What we’re doing here is adding a subtree to the dissection. This subtree will hold all the details of this protocol and so not clutter up the display when not required.

We are also marking the area of data that is being consumed by this protocol. In our case it’s all that has been passed to us, as we’re assuming this protocol does not encapsulate another. Therefore, we add the new tree node with proto_tree_add_item(), adding it to the passed in tree, label it with the protocol, use the passed in tvb buffer as the data, and consume from 0 to the end (-1) of this data. ENC_NA ("not applicable") is specified as the "encoding" parameter.

After this change, there should be a label in the detailed display for the protocol, and selecting this will highlight the remaining contents of the packet.

Now let’s go to the next step and add some protocol dissection. For this step we’ll need to construct a couple of tables that help with dissection. This needs some additions to the proto_register_foo() function shown previously.

Two statically allocated arrays are added at the beginning of proto_register_foo(). The arrays are then registered after the call to proto_register_protocol().

Example 9.5. Registering data structures.

void
proto_register_foo(void)
{
static hf_register_info hf[] = {
{ &hf_foo_pdu_type,
{ "FOO PDU Type", "foo.type",
FT_UINT8, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
}
};

/* Setup protocol subtree array */
static gint *ett[] = {
&ett_foo
};

proto_foo = proto_register_protocol (
"FOO Protocol", /* name       */
"FOO",      /* short name */
"foo"       /* abbrev     */
);

proto_register_field_array(proto_foo, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
}

The variables hf_foo_pdu_type and ett_foo also need to be declared somewhere near the top of the file.

Example 9.6. Dissector data structure globals.

static int hf_foo_pdu_type = -1;

static gint ett_foo = -1;

Now we can enhance the protocol display with some detail.

Example 9.7. Dissector starting to dissect the packets.

    proto_item *ti = proto_tree_add_item(tree, proto_foo, tvb, 0, -1, ENC_NA);
proto_tree_add_item(foo_tree, hf_foo_pdu_type, tvb, 0, 1, ENC_BIG_ENDIAN);

Now the dissection is starting to look more interesting. We have picked apart our first bit of the protocol. One byte of data at the start of the packet that defines the packet type for foo protocol.

The proto_item_add_subtree() call has added a child node to the protocol tree which is where we will do our detail dissection. The expansion of this node is controlled by the ett_foo variable. This remembers if the node should be expanded or not as you move between packets. All subsequent dissection will be added to this tree, as you can see from the next call. A call to proto_tree_add_item() in the foo_tree, this time using the hf_foo_pdu_type to control the formatting of the item. The pdu type is one byte of data, starting at 0. We assume it is in network order (also called big endian), so that is why we use ENC_BIG_ENDIAN. For a 1-byte quantity, there is no order issue, but it is good practice to make this the same as any multibyte fields that may be present, and as we will see in the next section, this particular protocol uses network order.

If we look in detail at the hf_foo_pdu_type declaration in the static array we can see the details of the definition.

• hf_foo_pdu_type - The index for this node.
• FOO PDU Type - The label for this item.
• foo.type - This is the filter string. It enables us to type constructs such as foo.type=1 into the filter box.
• FT_UINT8 - This specifies this item is an 8bit unsigned integer. This tallies with our call above where we tell it to only look at one byte.
• BASE_DEC - For an integer type, this tells it to be printed as a decimal number. It could be hexadecimal (BASE_HEX) or octal (BASE_OCT) if that made more sense.

We’ll ignore the rest of the structure for now.

If you install this plugin and try it out, you’ll see something that begins to look useful.

Now let’s finish off dissecting the simple protocol. We need to add a few more variables to the hfarray, and a couple more procedure calls.

Example 9.8. Wrapping up the packet dissection.

...
static int hf_foo_flags = -1;
static int hf_foo_sequenceno = -1;
static int hf_foo_initialip = -1;
...

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
gint offset = 0;

...
proto_item *ti = proto_tree_add_item(tree, proto_foo, tvb, 0, -1, ENC_NA);
proto_tree_add_item(foo_tree, hf_foo_pdu_type, tvb, offset, 1, ENC_BIG_ENDIAN);
offset += 1;
proto_tree_add_item(foo_tree, hf_foo_flags, tvb, offset, 1, ENC_BIG_ENDIAN);
offset += 1;
proto_tree_add_item(foo_tree, hf_foo_sequenceno, tvb, offset, 2, ENC_BIG_ENDIAN);
offset += 2;
proto_tree_add_item(foo_tree, hf_foo_initialip, tvb, offset, 4, ENC_BIG_ENDIAN);
offset += 4;
...

return tvb_captured_length(tvb);
}

void
proto_register_foo(void) {
...
...
{ &hf_foo_flags,
{ "FOO PDU Flags", "foo.flags",
FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_foo_sequenceno,
{ "FOO PDU Sequence Number", "foo.seqn",
FT_UINT16, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_foo_initialip,
{ "FOO PDU Initial IP", "foo.initialip",
FT_IPv4, BASE_NONE,
NULL, 0x0,
NULL, HFILL }
},
...
...
}
...

This dissects all the bits of this simple hypothetical protocol. We’ve introduced a new variable offsetinto the mix to help keep track of where we are in the packet dissection. With these extra bits in place, the whole protocol is now dissected.

### 9.2.3. Improving the dissection information

We can certainly improve the display of the protocol with a bit of extra data. The first step is to add some text labels. Let’s start by labeling the packet types. There is some useful support for this sort of thing by adding a couple of extra things. First we add a simple table of type to name.

Example 9.9. Naming the packet types.

static const value_string packettypenames[] = {
{ 1, "Initialise" },
{ 2, "Terminate" },
{ 3, "Data" },
{ 0, NULL }
};

This is a handy data structure that can be used to look up a name for a value. There are routines to directly access this lookup table, but we don’t need to do that, as the support code already has that added in. We just have to give these details to the appropriate part of the data, using the VALS macro.

Example 9.10. Adding Names to the protocol.

   { &hf_foo_pdu_type,
{ "FOO PDU Type", "foo.type",
FT_UINT8, BASE_DEC,
VALS(packettypenames), 0x0,
NULL, HFILL }
}

This helps in deciphering the packets, and we can do a similar thing for the flags structure. For this we need to add some more data to the table though.

Example 9.11. Adding Flags to the protocol.

#define FOO_START_FLAG      0x01
#define FOO_END_FLAG        0x02
#define FOO_PRIORITY_FLAG   0x04

static int hf_foo_startflag = -1;
static int hf_foo_endflag = -1;
static int hf_foo_priorityflag = -1;

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
...
...
static const int* bits[] = {
&hf_foo_startflag,
&hf_foo_endflag,
&hf_foo_priorityflag
};

offset += 1;
...
...
return tvb_captured_length(tvb);
}

void
proto_register_foo(void) {
...
...
{ &hf_foo_startflag,
{ "FOO PDU Start Flags", "foo.flags.start",
FT_BOOLEAN, 8,
NULL, FOO_START_FLAG,
NULL, HFILL }
},
{ &hf_foo_endflag,
{ "FOO PDU End Flags", "foo.flags.end",
FT_BOOLEAN, 8,
NULL, FOO_END_FLAG,
NULL, HFILL }
},
{ &hf_foo_priorityflag,
{ "FOO PDU Priority Flags", "foo.flags.priority",
FT_BOOLEAN, 8,
NULL, FOO_PRIORITY_FLAG,
NULL, HFILL }
},
...
...
}
...

Some things to note here. For the flags, as each bit is a different flag, we use the type FT_BOOLEAN, as the flag is either on or off. Second, we include the flag mask in the 7th field of the data, which allows the system to mask the relevant bit. We’ve also changed the 5th field to 8, to indicate that we are looking at an 8 bit quantity when the flags are extracted. Then finally we add the extra constructs to the dissection routine.

This is starting to look fairly full featured now, but there are a couple of other things we can do to make things look even more pretty. At the moment our dissection shows the packets as "Foo Protocol" which whilst correct is a little uninformative. We can enhance this by adding a little more detail. First, let’s get hold of the actual value of the protocol type. We can use the handy function tvb_get_guint8() to do this. With this value in hand, there are a couple of things we can do. First we can set the INFO column of the non-detailed view to show what sort of PDU it is - which is extremely helpful when looking at protocol traces. Second, we can also display this information in the dissection window.

Example 9.12. Enhancing the display.

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
gint offset = 0;
guint8 packet_type = tvb_get_guint8(tvb, 0);

col_set_str(pinfo->cinfo, COL_PROTOCOL, "FOO");
/* Clear out stuff in the info column */
col_clear(pinfo->cinfo,COL_INFO);
val_to_str(packet_type, packettypenames, "Unknown (0x%02x)"));

proto_item *ti = proto_tree_add_item(tree, proto_foo, tvb, 0, -1, ENC_NA);
proto_item_append_text(ti, ", Type %s",
val_to_str(packet_type, packettypenames, "Unknown (0x%02x)"));
proto_tree_add_item(foo_tree, hf_foo_pdu_type, tvb, offset, 1, ENC_BIG_ENDIAN);
offset += 1;

return tvb_captured_length(tvb);
}

So here, after grabbing the value of the first 8 bits, we use it with one of the built-in utility routines val_to_str(), to lookup the value. If the value isn’t found we provide a fallback which just prints the value in hex. We use this twice, once in the INFO field of the columns — if it’s displayed, and similarly we append this data to the base of our dissecting tree.

## 9.3. How to handle transformed data

Some protocols do clever things with data. They might possibly encrypt the data, or compress data, or part of it. If you know how these steps are taken it is possible to reverse them within the dissector.

As encryption can be tricky, let’s consider the case of compression. These techniques can also work for other transformations of data, where some step is required before the data can be examined.

What basically needs to happen here, is to identify the data that needs conversion, take that data and transform it into a new stream, and then call a dissector on it. Often this needs to be done "on-the-fly" based on clues in the packet. Sometimes this needs to be used in conjunction with other techniques, such as packet reassembly. The following shows a technique to achieve this effect.

Example 9.13. Decompressing data packets for dissection.

    guint8 flags = tvb_get_guint8(tvb, offset);
offset ++;
if (flags & FLAG_COMPRESSED) { /* the remainder of the packet is compressed */
guint16 orig_size = tvb_get_ntohs(tvb, offset);
guchar *decompressed_buffer = (guchar*)wmem_alloc(pinfo->pool, orig_size);
offset += 2;
decompress_packet(tvb_get_ptr(tvb, offset, -1),
tvb_captured_length_remaining(tvb, offset),
decompressed_buffer, orig_size);
/* Now re-setup the tvb buffer to have the new data */
next_tvb = tvb_new_child_real_data(tvb, decompressed_buffer, orig_size, orig_size);
} else {
next_tvb = tvb_new_subset_remaining(tvb, offset);
}
offset = 0;
/* process next_tvb from here on */

The first steps here are to recognise the compression. In this case a flag byte alerts us to the fact the remainder of the packet is compressed. Next we retrieve the original size of the packet, which in this case is conveniently within the protocol. If it’s not, it may be part of the compression routine to work it out for you, in which case the logic would be different.

So armed with the size, a buffer is allocated to receive the uncompressed data using wmem_alloc() in pinfo→pool memory, and the packet is decompressed into it. The tvb_get_ptr() function is useful to get a pointer to the raw data of the packet from the offset onwards. In this case the decompression routine also needs to know the length, which is given by the tvb_captured_length_remaining() function.

Next we build a new tvb buffer from this data, using the tvb_new_child_real_data() call. This data is a child of our original data, so calling this function also acknowledges that. No need to call tvb_set_free_cb() as the pinfo→pool was used (the memory block will be automatically freed when the pinfo pool lifetime expires). Finally we add this tvb as a new data source, so that the detailed display can show the decompressed bytes as well as the original.

After this has been set up the remainder of the dissector can dissect the buffer next_tvb, as it’s a new buffer the offset needs to be 0 as we start again from the beginning of this buffer. To make the rest of the dissector work regardless of whether compression was involved or not, in the case that compression was not signaled, we use tvb_new_subset_remaining() to deliver us a new buffer based on the old one but starting at the current offset, and extending to the end. This makes dissecting the packet from this point on exactly the same regardless of compression.

## 9.4. How to reassemble split packets

Some protocols have times when they have to split a large packet across multiple other packets. In this case the dissection can’t be carried out correctly until you have all the data. The first packet doesn’t have enough data, and the subsequent packets don’t have the expect format. To dissect these packets you need to wait until all the parts have arrived and then start the dissection.

The following sections will guide you through two common cases. For a description of all possible functions, structures and parameters, see epan/reassemble.h.

### 9.4.1. How to reassemble split UDP packets

As an example, let’s examine a protocol that is layered on top of UDP that splits up its own data stream. If a packet is bigger than some given size, it will be split into chunks, and somehow signaled within its protocol.

To deal with such streams, we need several things to trigger from. We need to know that this packet is part of a multi-packet sequence. We need to know how many packets are in the sequence. We also need to know when we have all the packets.

For this example we’ll assume there is a simple in-protocol signaling mechanism to give details. A flag byte that signals the presence of a multi-packet sequence and also the last packet, followed by an ID of the sequence and a packet sequence number.

msg_pkt ::= SEQUENCE {
.....
flags ::= SEQUENCE {
fragment    BOOLEAN,
last_fragment   BOOLEAN,
.....
}
msg_id  INTEGER(0..65535),
frag_id INTEGER(0..65535),
.....
}

Example 9.14. Reassembling fragments - Part 1

#include <epan/reassemble.h>
...
save_fragmented = pinfo->fragmented;
flags = tvb_get_guint8(tvb, offset); offset++;
if (flags & FL_FRAGMENT) { /* fragmented */
tvbuff_t* new_tvb = NULL;
fragment_data *frag_msg = NULL;
guint16 msg_seqid = tvb_get_ntohs(tvb, offset); offset += 2;
guint16 msg_num = tvb_get_ntohs(tvb, offset); offset += 2;

pinfo->fragmented = TRUE;
tvb, offset, pinfo,
msg_seqid, NULL, /* ID for fragments belonging together */
msg_num, /* fragment sequence number */
tvb_captured_length_remaining(tvb, offset), /* fragment length - to the end */
flags & FL_FRAG_LAST); /* More fragments? */

We start by saving the fragmented state of this packet, so we can restore it later. Next comes some protocol specific stuff, to dig the fragment data out of the stream if it’s present. Having decided it is present, we let the function fragment_add_seq_check() do its work. We need to provide this with a certain amount of parameters:

• The msg_reassembly_table table is for bookkeeping and is described later.
• The tvb buffer we are dissecting.
• The offset where the partial packet starts.
• The provided packet info.
• The sequence number of the fragment stream. There may be several streams of fragments in flight, and this is used to key the relevant one to be used for reassembly.
• Optional additional data for identifying the fragment. Can be set to NULL (as is done in the example) for most dissectors.
• msg_num is the packet number within the sequence.
• The length here is specified as the rest of the tvb as we want the rest of the packet data.
• Finally a parameter that signals if this is the last fragment or not. This might be a flag as in this case, or there may be a counter in the protocol.

Example 9.15. Reassembling fragments part 2

    new_tvb = process_reassembled_data(tvb, offset, pinfo,
"Reassembled Message", frag_msg, &msg_frag_items,
NULL, msg_tree);

if (frag_msg) { /* Reassembled */
col_append_str(pinfo->cinfo, COL_INFO,
" (Message Reassembled)");
} else { /* Not last packet of reassembled Short Message */
col_append_fstr(pinfo->cinfo, COL_INFO,
" (Message fragment %u)", msg_num);
}

if (new_tvb) { /* take it all */
next_tvb = new_tvb;
} else { /* make a new subset */
next_tvb = tvb_new_subset_remaining(tvb, offset);
}
}
else { /* Not fragmented */
next_tvb = tvb_new_subset_remaining(tvb, offset);
}

.....
pinfo->fragmented = save_fragmented;

Having passed the fragment data to the reassembly handler, we can now check if we have the whole message. If there is enough information, this routine will return the newly reassembled data buffer.

After that, we add a couple of informative messages to the display to show that this is part of a sequence. Then a bit of manipulation of the buffers and the dissection can proceed. Normally you will probably not bother dissecting further unless the fragments have been reassembled as there won’t be much to find. Sometimes the first packet in the sequence can be partially decoded though if you wish.

Now the mysterious data we passed into the fragment_add_seq_check().

Example 9.16. Reassembling fragments - Initialisation

static reassembly_table reassembly_table;

static void
proto_register_msg(void)
{
reassembly_table_register(&msg_reassemble_table,
}

First a reassembly_table structure is declared and initialised in the protocol initialisation routine. The second parameter specifies the functions that should be used for identifying fragments. We will use addresses_ports_reassembly_table_functions in order to identify fragments by the given sequence number (msg_seqid), the source and destination addresses and ports from the packet.

Following that, a fragment_items structure is allocated and filled in with a series of ett items, hf data items, and a string tag. The ett and hf values should be included in the relevant tables like all the other variables your protocol may use. The hf variables need to be placed in the structure something like the following. Of course the names may need to be adjusted.

Example 9.17. Reassembling fragments - Data

...
static int hf_msg_fragments = -1;
static int hf_msg_fragment = -1;
static int hf_msg_fragment_overlap = -1;
static int hf_msg_fragment_overlap_conflicts = -1;
static int hf_msg_fragment_multiple_tails = -1;
static int hf_msg_fragment_too_long_fragment = -1;
static int hf_msg_fragment_error = -1;
static int hf_msg_fragment_count = -1;
static int hf_msg_reassembled_in = -1;
static int hf_msg_reassembled_length = -1;
...
static gint ett_msg_fragment = -1;
static gint ett_msg_fragments = -1;
...
static const fragment_items msg_frag_items = {
/* Fragment subtrees */
&ett_msg_fragment,
&ett_msg_fragments,
/* Fragment fields */
&hf_msg_fragments,
&hf_msg_fragment,
&hf_msg_fragment_overlap,
&hf_msg_fragment_overlap_conflicts,
&hf_msg_fragment_multiple_tails,
&hf_msg_fragment_too_long_fragment,
&hf_msg_fragment_error,
&hf_msg_fragment_count,
/* Reassembled in field */
&hf_msg_reassembled_in,
/* Reassembled length field */
&hf_msg_reassembled_length,
/* Tag */
"Message fragments"
};
...
static hf_register_info hf[] =
{
...
{&hf_msg_fragments,
{"Message fragments", "msg.fragments",
FT_NONE, BASE_NONE, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment,
{"Message fragment", "msg.fragment",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_overlap,
{"Message fragment overlap", "msg.fragment.overlap",
FT_BOOLEAN, 0, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_overlap_conflicts,
{"Message fragment overlapping with conflicting data",
"msg.fragment.overlap.conflicts",
FT_BOOLEAN, 0, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_multiple_tails,
{"Message has multiple tail fragments",
"msg.fragment.multiple_tails",
FT_BOOLEAN, 0, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_too_long_fragment,
{"Message fragment too long", "msg.fragment.too_long_fragment",
FT_BOOLEAN, 0, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_error,
{"Message defragmentation error", "msg.fragment.error",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
{&hf_msg_fragment_count,
{"Message fragment count", "msg.fragment.count",
FT_UINT32, BASE_DEC, NULL, 0x00, NULL, HFILL } },
{&hf_msg_reassembled_in,
{"Reassembled in", "msg.reassembled.in",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
{&hf_msg_reassembled_length,
{"Reassembled length", "msg.reassembled.length",
FT_UINT32, BASE_DEC, NULL, 0x00, NULL, HFILL } },
...
static gint *ett[] =
{
...
&ett_msg_fragment,
&ett_msg_fragments
...

These hf variables are used internally within the reassembly routines to make useful links, and to add data to the dissection. It produces links from one packet to another, such as a partial packet having a link to the fully reassembled packet. Likewise there are back pointers to the individual packets from the reassembled one. The other variables are used for flagging up errors.

### 9.4.2. How to reassemble split TCP Packets

A dissector gets a tvbuff_t pointer which holds the payload of a TCP packet. This payload contains the header and data of your application layer protocol.

When dissecting an application layer protocol you cannot assume that each TCP packet contains exactly one application layer message. One application layer message can be split into several TCP packets.

You also cannot assume that a TCP packet contains only one application layer message and that the message header is at the start of your TCP payload. More than one messages can be transmitted in one TCP packet, so that a message can start at an arbitrary position.

This sounds complicated, but there is a simple solution. tcp_dissect_pdus() does all this tcp packet reassembling for you. This function is implemented in epan/dissectors/packet-tcp.h.

Example 9.18. Reassembling TCP fragments

#include "config.h"

#include <epan/packet.h>
#include <epan/prefs.h>
#include "packet-tcp.h"

...

/* This method dissects fully reassembled messages */
static int
dissect_foo_message(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree _U_, void *data _U_)
{
/* TODO: implement your dissecting code */
return tvb_captured_length(tvb);
}

/* determine PDU length of protocol foo */
static guint
get_foo_message_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)
{
/* TODO: change this to your needs */
return (guint)tvb_get_ntohl(tvb, offset+4); /* e.g. length is at offset 4 */
}

/* The main dissecting routine */
static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
get_foo_message_len, dissect_foo_message, data);
return tvb_captured_length(tvb);
}

...

As you can see this is really simple. Just call tcp_dissect_pdus() in your main dissection routine and move you message parsing code into another function. This function gets called whenever a message has been reassembled.

The parameters tvb, pinfo, tree and data are just handed over to tcp_dissect_pdus(). The 4th parameter is a flag to indicate if the data should be reassembled or not. This could be set according to a dissector preference as well. Parameter 5 indicates how much data has at least to be available to be able to determine the length of the foo message. Parameter 6 is a function pointer to a method that returns this length. It gets called when at least the number of bytes given in the previous parameter is available. Parameter 7 is a function pointer to your real message dissector. Parameter 8 is the data passed in from parent dissector.

Protocols which need more data before the message length can be determined can return zero. Other values smaller than the fixed length will result in an exception.

## 9.5. How to tap protocols

Adding a Tap interface to a protocol allows it to do some useful things. In particular you can produce protocol statistics from the tap interface.

A tap is basically a way of allowing other items to see what’s happening as a protocol is dissected. A tap is registered with the main program, and then called on each dissection. Some arbitrary protocol specific data is provided with the routine that can be used.

To create a tap, you first need to register a tap. A tap is registered with an integer handle, and registered with the routine register_tap(). This takes a string name with which to find it again.

Example 9.19. Initialising a tap

#include <epan/packet.h>
#include <epan/tap.h>

static int foo_tap = -1;

struct FooTap {
gint packet_type;
gint priority;
...
};

void proto_register_foo(void)
{
...
foo_tap = register_tap("foo");

Whilst you can program a tap without protocol specific data, it is generally not very useful. Therefore it’s a good idea to declare a structure that can be passed through the tap. This needs to be a static structure as it will be used after the dissection routine has returned. It’s generally best to pick out some generic parts of the protocol you are dissecting into the tap data. A packet type, a priority or a status code maybe. The structure really needs to be included in a header file so that it can be included by other components that want to listen in to the tap.

Once you have these defined, it’s simply a case of populating the protocol specific structure and then calling tap_queue_packet, probably as the last part of the dissector.

Example 9.20. Calling a protocol tap

static int
dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
...
fooinfo = wmem_alloc(wmem_packet_scope(), sizeof(struct FooTap));
fooinfo->packet_type = tvb_get_guint8(tvb, 0);
fooinfo->priority = tvb_get_ntohs(tvb, 8);
...
tap_queue_packet(foo_tap, pinfo, fooinfo);

return tvb_captured_length(tvb);
}

This now enables those interested parties to listen in on the details of this protocol conversation.

## 9.6. How to produce protocol stats

Given that you have a tap interface for the protocol, you can use this to produce some interesting statistics (well presumably interesting!) from protocol traces.

This can be done in a separate plugin, or in the same plugin that is doing the dissection. The latter scheme is better, as the tap and stats module typically rely on sharing protocol specific data, which might get out of step between two different plugins.

Here is a mechanism to produce statistics from the above TAP interface.

Example 9.21. Initialising a stats interface

/* register all http trees */
static void register_foo_stat_trees(void) {
stats_tree_register_plugin("foo", "foo", "Foo/Packet Types", 0,
foo_stats_tree_packet, foo_stats_tree_init, NULL);
}

WS_DLL_PUBLIC_DEF void plugin_register_tap_listener(void)
{
register_foo_stat_trees();
}

Working from the bottom up, first the plugin interface entry point is defined, plugin_register_tap_listener(). This simply calls the initialisation function register_foo_stat_trees().

This in turn calls the stats_tree_register_plugin() function, which takes three strings, an integer, and three callback functions.

1. This is the tap name that is registered.
2. An abbreviation of the stats name.
3. The name of the stats module. A “/” character can be used to make sub menus.
4. Flags for per-packet callback
5. The function that will called to generate the stats.
6. A function that can be called to initialise the stats data.
7. A function that will be called to clean up the stats data.

In this case we only need the first two functions, as there is nothing specific to clean up.

Example 9.22. Initialising a stats session

static const guint8* st_str_packets = "Total Packets";
static const guint8* st_str_packet_types = "FOO Packet Types";
static int st_node_packets = -1;
static int st_node_packet_types = -1;

static void foo_stats_tree_init(stats_tree* st)
{
st_node_packets = stats_tree_create_node(st, st_str_packets, 0, TRUE);
st_node_packet_types = stats_tree_create_pivot(st, st_str_packet_types, st_node_packets);
}

In this case we create a new tree node, to handle the total packets, and as a child of that we create a pivot table to handle the stats about different packet types.

Example 9.23. Generating the stats

static int foo_stats_tree_packet(stats_tree* st, packet_info* pinfo, epan_dissect_t* edt, const void* p)
{
struct FooTap *pi = (struct FooTap *)p;
tick_stat_node(st, st_str_packets, 0, FALSE);
stats_tree_tick_pivot(st, st_node_packet_types,
val_to_str(pi->packet_type, msgtypevalues, "Unknown packet type (%d)"));
return 1;
}

In this case the processing of the stats is quite simple. First we call the tick_stat_node for the st_str_packets packet node, to count packets. Then a call to stats_tree_tick_pivot() on the st_node_packet_types subtree allows us to record statistics by packet type.

## 9.7. How to use conversations

Some info about how to use conversations in a dissector can be found in the file doc/README.dissector, chapter 2.2.

## 9.8. idl2wrs: Creating dissectors from CORBA IDL files

Many of Wireshark’s dissectors are automatically generated. This section shows how to generate one from a CORBA IDL file.

### 9.8.1. What is it?

As you have probably guessed from the name, idl2wrs takes a user specified IDL file and attempts to build a dissector that can decode the IDL traffic over GIOP. The resulting file is “C” code, that should compile okay as a Wireshark dissector.

idl2wrs parses the data struct given to it by the omniidl compiler, and using the GIOP API available in packet-giop.[ch], generates get_CDR_xxx calls to decode the CORBA traffic on the wire.

It consists of 4 main files.

This document
wireshark_be.py
The main compiler backend
wireshark_gen.py
A helper class, that generates the C code.
idl2wrs
A simple shell script wrapper that the end user should use to generate the dissector from the IDL file(s).

### 9.8.2. Why do this?

It is important to understand what CORBA traffic looks like over GIOP/IIOP, and to help build a tool that can assist in troubleshooting CORBA interworking. This was especially the case after seeing a lot of discussions about how particular IDL types are represented inside an octet stream.

I have also had comments/feedback that this tool would be good for say a CORBA class when teaching students what CORBA traffic looks like “on the wire”.

It is also COOL to work on a great Open Source project such as the case with “Wireshark” (https://www.wireshark.org/).

### 9.8.3. How to use idl2wrs

To use the idl2wrs to generate Wireshark dissectors, you need the following:

• Python must be installed. See https://python.org/
• omniidl from the omniORB package must be available. See http://omniorb.sourceforge.net/
• Of course you need Wireshark installed to compile the code and tweak it if required. idl2wrs is part of the standard Wireshark distribution

To use idl2wrs to generate an Wireshark dissector from an idl file use the following procedure:

• To write the C code to stdout.

$idl2wrs <your_file.idl> e.g.: $ idl2wrs echo.idl
• To write to a file, just redirect the output.

$idl2wrs echo.idl > packet-test-idl.c You may wish to comment out the register_giop_user_module() code and that will leave you with heuristic dissection. If you don’t want to use the shell script wrapper, then try steps 3 or 4 instead. • To write the C code to stdout. $ omniidl  -p ./ -b wireshark_be <your file.idl>

e.g.:

$omniidl -p ./ -b wireshark_be echo.idl • To write to a file, just redirect the output. $ omniidl  -p ./ -b wireshark_be echo.idl > packet-test-idl.c

You may wish to comment out the register_giop_user_module() code and that will leave you with heuristic dissection.

• Copy the resulting C code to subdirectory epan/dissectors/ inside your Wireshark source directory.

$cp packet-test-idl.c /dir/where/wireshark/lives/epan/dissectors/ The new dissector has to be added to CMakeLists.txt in the same directory. Look for the declaration DISSECTOR_SRC and add the new dissector there. For example, DISSECTOR_SRC = \${CMAKE_CURRENT_SOURCE_DIR}/packet-2dparityfec.c
${CMAKE_CURRENT_SOURCE_DIR}/packet-3com-njack.c ... becomes DISSECTOR_SRC = \${CMAKE_CURRENT_SOURCE_DIR}/packet-test-idl.c       \
${CMAKE_CURRENT_SOURCE_DIR}/packet-2dparityfec.c \${CMAKE_CURRENT_SOURCE_DIR}/packet-3com-njack.c     \
...

For the next steps, go up to the top of your Wireshark source directory.

• Create a build dir

$mkdir build && cd build • Run cmake $ cmake ..
• Build the code

make • Good Luck !! ### 9.8.4. TODO • Exception code not generated (yet), but can be added manually. • Enums not converted to symbolic values (yet), but can be added manually. • Add command line options etc • More I am sure :-) ### 9.8.5. Limitations See the TODO list inside packet-giop.c ### 9.8.6. Notes The -p ./ option passed to omniidl indicates that the wireshark_be.py and wireshark_gen.py are residing in the current directory. This may need tweaking if you place these files somewhere else. If it complains about being unable to find some modules (e.g. tempfile.py), you may want to check if PYTHONPATH is set correctly. ## Chapter 10. Lua Support in Wireshark ## 10.1. Introduction Lua is a powerful light-weight programming language designed for extending applications. Wireshark contains an embedded Lua 5.2 interpreter which can be used to write dissectors, taps, and capture file readers and writers. Wireshark’s Lua interpreter starts by loading a file named init.lua from Wireshark’s global configuration directory. The global configuration directory's init.lua controls whether or not Lua scripts are enabled via the enable_lua variable. Lua scripts are enabled by default. To disable Lua scripts, set the enable_lua variable to false. Wireshark 2.6 and earlier enabled or disabled Lua scripts using the variable disable_lua (deprecated). If both enable_lua and disable_lua are present, disable_lua is ignored. If Lua is enabled, Wireshark will try to load a file named init.lua from the user’s personal configuration directory and all files ending with .lua in the global and the personal plugins directory. The command line option -X lua_script:file.lua can also be used to load specific Lua scripts. The Lua code is executed after all protocol dissectors are initialized and before reading any file. Wireshark for Windows uses a modified Lua runtime (lua-unicode) to support Unicode (UTF-8) filesystem paths. This brings consistency with other platforms (for example, Linux and macOS). ## 10.2. Example: Creating a Menu with Lua The code below adds a menu "Lua Dialog Test" under the Tools menu. When selected, it opens a dialog prompting the user for input and then opens a text window with the output. if gui_enabled() then local splash = TextWindow.new("Hello!"); splash:set("This time wireshark has been enhanced with a useless feature.\n") splash:append("Go to 'Tools->Lua Dialog Test' and check it out!") end local function dialog_menu() local function dialog_func(person,eyes,hair) local window = TextWindow.new("Person Info"); local message = string.format("Person %s with %s eyes and %s hair.", person, eyes, hair); window:set(message); end new_dialog("Dialog Test",dialog_func,"A Person","Eyes","Hair") end register_menu("Lua Dialog Test",dialog_menu,MENU_TOOLS_UNSORTED) ## 10.3. Example: Dissector written in Lua local p_multi = Proto("multi", "MultiProto"); local vs_protos = { [2] = "mtp2", [3] = "mtp3", [4] = "alcap", [5] = "h248", [6] = "ranap", [7] = "rnsap", [8] = "nbap" } local f_proto = ProtoField.uint8("multi.protocol", "Protocol", base.DEC, vs_protos) local f_dir = ProtoField.uint8("multi.direction", "Direction", base.DEC, { [1] = "incoming", [0] = "outgoing"}) local f_text = ProtoField.string("multi.text", "Text") p_multi.fields = { f_proto, f_dir, f_text } local data_dis = Dissector.get("data") local protos = { [2] = Dissector.get("mtp2"), [3] = Dissector.get("mtp3"), [4] = Dissector.get("alcap"), [5] = Dissector.get("h248"), [6] = Dissector.get("ranap"), [7] = Dissector.get("rnsap"), [8] = Dissector.get("nbap"), [9] = Dissector.get("rrc"), [10] = DissectorTable.get("sctp.ppi"):get_dissector(3), -- m3ua [11] = DissectorTable.get("ip.proto"):get_dissector(132), -- sctp } function p_multi.dissector(buf, pkt, tree) local subtree = tree:add(p_multi, buf(0,2)) subtree:add(f_proto, buf(0,1)) subtree:add(f_dir, buf(1,1)) local proto_id = buf(0,1):uint() local dissector = protos[proto_id] if dissector ~= nil then -- Dissector was found, invoke subdissector with a new Tvb, -- created from the current buffer (skipping first two bytes). dissector:call(buf(2):tvb(), pkt, tree) elseif proto_id < 2 then subtree:add(f_text, buf(2)) -- pkt.cols.info:set(buf(2, buf:len() - 3):string()) else -- fallback dissector that just shows the raw data. data_dis:call(buf(2):tvb(), pkt, tree) end end local wtap_encap_table = DissectorTable.get("wtap_encap") local udp_encap_table = DissectorTable.get("udp.port") wtap_encap_table:add(wtap.USER15, p_multi) wtap_encap_table:add(wtap.USER12, p_multi) udp_encap_table:add(7555, p_multi) ## 10.4. Example: Listener written in Lua -- This program will register a menu that will open a window with a count of occurrences -- of every address in the capture local function menuable_tap() -- Declare the window we will use local tw = TextWindow.new("Address Counter") -- This will contain a hash of counters of appearances of a certain address local ips = {} -- this is our tap local tap = Listener.new(); local function remove() -- this way we remove the listener that otherwise will remain running indefinitely tap:remove(); end -- we tell the window to call the remove() function when closed tw:set_atclose(remove) -- this function will be called once for each packet function tap.packet(pinfo,tvb) local src = ips[tostring(pinfo.src)] or 0 local dst = ips[tostring(pinfo.dst)] or 0 ips[tostring(pinfo.src)] = src + 1 ips[tostring(pinfo.dst)] = dst + 1 end -- this function will be called once every few seconds to update our window function tap.draw(t) tw:clear() for ip,num in pairs(ips) do tw:append(ip .. "\t" .. num .. "\n"); end end -- this function will be called whenever a reset is needed -- e.g. when reloading the capture file function tap.reset() tw:clear() ips = {} end -- Ensure that all existing packets are processed. retap_packets() end -- using this function we register our function -- to be called when the user selects the Tools->Test->Packets menu register_menu("Test/Packets", menuable_tap, MENU_TOOLS_UNSORTED) ## Chapter 11. Wireshark’s Lua API Reference Manual This Part of the User Guide describes the Wireshark specific functions in the embedded Lua. Classes group certain functionality, the following notational conventions are used: • Class.function() represents a class method (named function) on class Class, taking no arguments. • Class.function(a) represents a class method taking one argument. • Class.function(…​) represents a class method taking a variable number of arguments. • class:method() represents an instance method (named method) on an instance of class Class, taking no arguments. Note the lowercase notation in the documentation to clarify an instance. • class.prop represents a property prop on the instance of class Class. Trying to access a non-existing property, function or method currently gives an error, but do not rely on it as the behavior may change in the future. ## 11.1. Saving capture files The classes/functions defined in this module are for using a Dumper object to make Wireshark save a capture file to disk. Dumper represents Wireshark’s built-in file format writers (see the wtap_filetypes table in init.lua). To have a Lua script create its own file format writer, see the chapter titled "Custom file format reading/writing". ### 11.1.1. Dumper #### 11.1.1.1. Dumper.new(filename, [filetype], [encap]) Creates a file to write packets. Dumper:new_for_current() will probably be a better choice. ##### Arguments filename The name of the capture file to be created. filetype (optional) The type of the file to be created - a number entry from the wtap_filetypes table in init.lua. encap (optional) The encapsulation to be used in the file to be created - a number entry from the wtap_encaps table in init.lua. ##### Returns The newly created Dumper object #### 11.1.1.2. dumper:close() Closes a dumper. ##### Errors • Cannot operate on a closed dumper #### 11.1.1.3. dumper:flush() Writes all unsaved data of a dumper to the disk. #### 11.1.1.4. dumper:dump(timestamp, pseudoheader, bytearray) Dumps an arbitrary packet. Note: Dumper:dump_current() will fit best in most cases. ##### Arguments timestamp The absolute timestamp the packet will have. pseudoheader The PseudoHeader to use. bytearray The data to be saved #### 11.1.1.5. dumper:new_for_current([filetype]) Creates a capture file using the same encapsulation as the one of the current packet. ##### Arguments filetype (optional) The file type. Defaults to pcap. ##### Returns The newly created Dumper Object ##### Errors • Cannot be used outside a tap or a dissector #### 11.1.1.6. dumper:dump_current() Dumps the current packet as it is. ##### Errors • Cannot be used outside a tap or a dissector ### 11.1.2. PseudoHeader A pseudoheader to be used to save captured frames. #### 11.1.2.1. PseudoHeader.none() Creates a "no" pseudoheader. ##### Returns A null pseudoheader #### 11.1.2.2. PseudoHeader.eth([fcslen]) Creates an ethernet pseudoheader. ##### Arguments fcslen (optional) The fcs length ##### Returns The ethernet pseudoheader #### 11.1.2.3. PseudoHeader.atm([aal], [vpi], [vci], [channel], [cells], [aal5u2u], [aal5len]) Creates an ATM pseudoheader. ##### Arguments aal (optional) AAL number vpi (optional) VPI vci (optional) VCI channel (optional) Channel cells (optional) Number of cells in the PDU aal5u2u (optional) AAL5 User to User indicator aal5len (optional) AAL5 Len ##### Returns The ATM pseudoheader #### 11.1.2.4. PseudoHeader.mtp2([sent], [annexa], [linknum]) Creates an MTP2 PseudoHeader. ##### Arguments sent (optional) True if the packet is sent, False if received. annexa (optional) True if annex A is used. linknum (optional) Link Number. ##### Returns The MTP2 pseudoheader ## 11.2. Obtaining dissection data ### 11.2.1. Field A Field extractor to to obtain field values. A Field object can only be created outside of the callback functions of dissectors, post-dissectors, heuristic-dissectors, and taps. Once created, it is used inside the callback functions, to generate a FieldInfo object. #### 11.2.1.1. Field.new(fieldname) Create a Field extractor. ##### Arguments fieldname The filter name of the field (e.g. ip.addr) ##### Returns The field extractor ##### Errors • A Field extractor must be defined before Taps or Dissectors get called #### 11.2.1.2. Field.list() Gets a Lua array table of all registered field filter names. Note This is an expensive operation, and should only be used for troubleshooting. Since: 1.11.3 ##### Returns The array table of field filter names #### 11.2.1.3. field:__call() Obtain all values (see FieldInfo) for this field. ##### Returns All the values of this field ##### Errors • Fields cannot be used outside dissectors or taps #### 11.2.1.4. field:__tostring() Obtain a string with the field filter name. #### 11.2.1.5. field.name Mode: Retrieve only. The filter name of this field, or nil. Since: 1.99.8 #### 11.2.1.6. field.display Mode: Retrieve only. The full display name of this field, or nil. Since: 1.99.8 #### 11.2.1.7. field.type Mode: Retrieve only. The ftype of this field, or nil. Since: 1.99.8 ### 11.2.2. FieldInfo An extracted Field from dissected packet data. A FieldInfo object can only be used within the callback functions of dissectors, post-dissectors, heuristic-dissectors, and taps. A FieldInfo can be called on either existing Wireshark fields by using either Field.new() or Field() before-hand, or it can be called on new fields created by Lua from a ProtoField. #### 11.2.2.1. fieldinfo:__len() Obtain the Length of the field #### 11.2.2.2. fieldinfo:__unm() Obtain the Offset of the field #### 11.2.2.3. fieldinfo:__call() Obtain the Value of the field. Previous to 1.11.4, this function retrieved the value for most field types, but for ftypes.UINT_BYTES it retrieved the ByteArray of the field’s entire TvbRange. In other words, it returned a ByteArray that included the leading length byte(s), instead of just the value bytes. That was a bug, and has been changed in 1.11.4. Furthermore, it retrieved an ftypes.GUID as a ByteArray, which is also incorrect. If you wish to still get a ByteArray of the TvbRange, use FieldInfo:get_range() to get the TvbRange, and then use Tvb:bytes() to convert it to a ByteArray. #### 11.2.2.4. fieldinfo:__tostring() The string representation of the field. #### 11.2.2.5. fieldinfo:__eq() Checks whether lhs is within rhs. #### 11.2.2.6. fieldinfo:__le() Checks whether the end byte of lhs is before the end of rhs. ##### Errors • Data source must be the same for both fields #### 11.2.2.7. fieldinfo:__lt() Checks whether the end byte of rhs is before the beginning of rhs. ##### Errors • Data source must be the same for both fields #### 11.2.2.8. fieldinfo.len Mode: Retrieve only. The length of this field. #### 11.2.2.9. fieldinfo.offset Mode: Retrieve only. The offset of this field. #### 11.2.2.10. fieldinfo.value Mode: Retrieve only. The value of this field. #### 11.2.2.11. fieldinfo.label Mode: Retrieve only. The string representing this field. #### 11.2.2.12. fieldinfo.display Mode: Retrieve only. The string display of this field as seen in GUI. #### 11.2.2.13. fieldinfo.type Mode: Retrieve only. The internal field type, a number which matches one of the ftype values in init.lua. Since: 1.99.8 #### 11.2.2.14. fieldinfo.source Mode: Retrieve only. The source Tvb object the FieldInfo is derived from, or nil if there is none. Since: 1.99.8 #### 11.2.2.15. fieldinfo.range Mode: Retrieve only. The TvbRange covering the bytes of this field in a Tvb. #### 11.2.2.16. fieldinfo.generated Mode: Retrieve only. Whether this field was marked as generated (boolean). #### 11.2.2.17. fieldinfo.hidden Mode: Retrieve only. Whether this field was marked as hidden (boolean). Since: 1.99.8 #### 11.2.2.18. fieldinfo.is_url Mode: Retrieve only. Whether this field was marked as being a URL (boolean). Since: 1.99.8 #### 11.2.2.19. fieldinfo.little_endian Mode: Retrieve only. Whether this field is little-endian encoded (boolean). Since: 1.99.8 #### 11.2.2.20. fieldinfo.big_endian Mode: Retrieve only. Whether this field is big-endian encoded (boolean). Since: 1.99.8 #### 11.2.2.21. fieldinfo.name Mode: Retrieve only. The filter name of this field. Since: 1.99.8 ### 11.2.3. Global Functions #### 11.2.3.1. all_field_infos() Obtain all fields from the current tree. Note this only gets whatever fields the underlying dissectors have filled in for this packet at this time - there may be fields applicable to the packet that simply aren’t being filled in because at this time they’re not needed for anything. This function only gets what the C-side code has currently populated, not the full list. ##### Errors • Cannot be called outside a listener or dissector ## 11.3. GUI support ### 11.3.1. ProgDlg Manages a progress bar dialog. #### 11.3.1.1. ProgDlg.new([title], [task]) Creates a new ProgDlg progress dialog. ##### Arguments title (optional) Title of the new window, defaults to "Progress". task (optional) Current task, defaults to "". ##### Returns The newly created ProgDlg object. #### 11.3.1.2. progdlg:update(progress, [task]) Appends text. ##### Arguments progress Part done ( e.g. 0.75 ). task (optional) Current task, defaults to "". ##### Errors • GUI not available • Cannot be called for something not a ProgDlg • Progress value out of range (must be between 0.0 and 1.0) #### 11.3.1.3. progdlg:stopped() Checks whether the user has pressed the stop button. ##### Returns true if the user has asked to stop the progress. #### 11.3.1.4. progdlg:close() Closes the progress dialog. ##### Returns A string specifying whether the Progress Dialog has stopped or not. ##### Errors • GUI not available ### 11.3.2. TextWindow Manages a text window. #### 11.3.2.1. TextWindow.new([title]) Creates a new TextWindow text window. ##### Arguments title (optional) Title of the new window. ##### Returns The newly created TextWindow object. ##### Errors • GUI not available #### 11.3.2.2. textwindow:set_atclose(action) Set the function that will be called when the text window closes. ##### Arguments action A Lua function to be executed when the user closes the text window. ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.3. textwindow:set(text) Sets the text. ##### Arguments text The text to be used. ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.4. textwindow:append(text) Appends text ##### Arguments text The text to be appended ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.5. textwindow:prepend(text) Prepends text ##### Arguments text The text to be appended ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.6. textwindow:clear() Erases all text in the window. ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.7. textwindow:get_text() Get the text of the window ##### Returns The TextWindow’s text. ##### Errors • GUI not available #### 11.3.2.8. textwindow:close() Close the window ##### Errors • GUI not available #### 11.3.2.9. textwindow:set_editable([editable]) Make this text window editable. ##### Arguments editable (optional) A boolean flag, defaults to true. ##### Returns The TextWindow object. ##### Errors • GUI not available #### 11.3.2.10. textwindow:add_button(label, function) Adds a button to the text window. ##### Arguments label The label of the button function The Lua function to be called when clicked ##### Returns The TextWindow object. ##### Errors • GUI not available ### 11.3.3. Global Functions #### 11.3.3.1. gui_enabled() Checks whether the GUI facility is enabled. ##### Returns A boolean: true if it is enabled, false if it isn’t. #### 11.3.3.2. register_menu(name, action, [group]) Register a menu item in one of the main menus. ##### Arguments name The name of the menu item. The submenus are to be separated by '/’s. (string) action The function to be called when the menu item is invoked. (function taking no arguments and returning nothing) group (optional) The menu group into which the menu item is to be inserted. If omitted, defaults to MENU_STAT_GENERIC. One of: • MENU_STAT_UNSORTED (Statistics), • MENU_STAT_GENERIC (Statistics, first section), • MENU_STAT_CONVERSATION (Statistics/Conversation List), • MENU_STAT_ENDPOINT (Statistics/Endpoint List), • MENU_STAT_RESPONSE (Statistics/Service Response Time), • MENU_STAT_TELEPHONY (Telephony), • MENU_STAT_TELEPHONY_ANSI (Telephony/ANSI), • MENU_STAT_TELEPHONY_GSM (Telephony/GSM), • MENU_STAT_TELEPHONY_LTE (Telephony/LTE), • MENU_STAT_TELEPHONY_MTP3 (Telephony/MTP3), • MENU_STAT_TELEPHONY_SCTP (Telephony/SCTP), • MENU_ANALYZE (Analyze), • MENU_ANALYZE_CONVERSATION (Analyze/Conversation Filter), • MENU_TOOLS_UNSORTED (Tools). (number) #### 11.3.3.3. new_dialog(title, action, …​) Pops up a new dialog ##### Arguments title Title of the dialog’s window. action Action to be performed when OK’d. …​ A series of strings to be used as labels of the dialog’s fields. ##### Errors • GUI not available • At least one field required • All fields must be strings #### 11.3.3.4. retap_packets() Rescan all packets and just run taps - don’t reconstruct the display. #### 11.3.3.5. copy_to_clipboard(text) Copy a string into the clipboard. ##### Arguments text The string to be copied into the clipboard. #### 11.3.3.6. open_capture_file(filename, filter) Open and display a capture file. ##### Arguments filename The name of the file to be opened. filter A filter to be applied as the file gets opened. #### 11.3.3.7. get_filter() Get the main filter text. #### 11.3.3.8. set_filter(text) Set the main filter text. ##### Arguments text The filter’s text. #### 11.3.3.9. set_color_filter_slot(row, text) Set packet-coloring rule for the current session. ##### Arguments row The index of the desired color in the temporary coloring rules list. text Display filter for selecting packets to be colorized. #### 11.3.3.10. apply_filter() Apply the filter in the main filter box. #### 11.3.3.11. reload() Reload the current capture file. Obsolete, use reload_packets() #### 11.3.3.12. reload_packets() Reload the current capture file. #### 11.3.3.13. reload_lua_plugins() Reload all Lua plugins. #### 11.3.3.14. browser_open_url(url) Open an url in a browser. ##### Arguments url The url. #### 11.3.3.15. browser_open_data_file(filename) Open a file in a browser. ##### Arguments filename The file name. ## 11.4. Post-dissection packet analysis ### 11.4.1. Listener A Listener is called once for every packet that matches a certain filter or has a certain tap. It can read the tree, the packet’s Tvb buffer as well as the tapped data, but it cannot add elements to the tree. #### 11.4.1.1. Listener.new([tap], [filter], [allfields]) Creates a new Listener listener object. ##### Arguments tap (optional) The name of this tap. filter (optional) A filter that when matches the tap.packet function gets called (use nil to be called for every packet). allfields (optional) Whether to generate all fields. (default=false) Note: This impacts performance. ##### Returns The newly created Listener listener object ##### Errors • tap registration error #### 11.4.1.2. Listener.list() Gets a Lua array table of all registered Listener tap names. Note: This is an expensive operation, and should only be used for troubleshooting. Since: 1.11.3 ##### Returns The array table of registered tap names #### 11.4.1.3. listener:remove() Removes a tap Listener. #### 11.4.1.4. listener:__tostring() Generates a string of debug info for the tap Listener. #### 11.4.1.5. listener.packet Mode: Assign only. A function that will be called once every packet matches the Listener listener filter. When later called by Wireshark, the packet function will be given: 1. A Pinfo object 2. A Tvb object 3. A tapinfo table  function tap.packet(pinfo,tvb,tapinfo) ... end Note tapinfo is a table of info based on the Listener’s type, or nil. #### 11.4.1.6. listener.draw Mode: Assign only. A function that will be called once every few seconds to redraw the GUI objects; in Tshark this funtion is called only at the very end of the capture file. When later called by Wireshark, the draw function will not be given any arguments.  function tap.draw() ... end #### 11.4.1.7. listener.reset Mode: Assign only. A function that will be called at the end of the capture run. When later called by Wireshark, the reset function will not be given any arguments.  function tap.reset() ... end ## 11.5. Obtaining packet information ### 11.5.1. Address Represents an address. #### 11.5.1.1. Address.ip(hostname) Creates an Address Object representing an IPv4 address. ##### Arguments hostname The address or name of the IP host. ##### Returns The Address object. #### 11.5.1.2. Address.ipv6(hostname) Creates an Address Object representing an IPv6 address. ##### Arguments hostname The address or name of the IP host. ##### Returns The Address object #### 11.5.1.3. Address.ether(eth) Creates an Address Object representing an Ethernet address. ##### Arguments eth The Ethernet address. ##### Returns The Address object. #### 11.5.1.4. address:__tostring() ##### Returns The string representing the address. #### 11.5.1.5. address:__eq() Compares two Addresses. #### 11.5.1.6. address:__le() Compares two Addresses. #### 11.5.1.7. address:__lt() Compares two Addresses. ### 11.5.2. Column A Column in the packet list. #### 11.5.2.1. column:__tostring() ##### Returns The column’s string text (in parenthesis if not available). #### 11.5.2.2. column:clear() Clears a Column. #### 11.5.2.3. column:set(text) Sets the text of a Column. ##### Arguments text The text to which to set the Column. #### 11.5.2.4. column:append(text) Appends text to a Column. ##### Arguments text The text to append to the Column. #### 11.5.2.5. column:prepend(text) Prepends text to a Column. ##### Arguments text The text to prepend to the Column. #### 11.5.2.6. column:fence() Sets Column text fence, to prevent overwriting. Since: 1.10.6 #### 11.5.2.7. column:clear_fence() Clear Column text fence. Since: 1.11.3 ### 11.5.3. Columns The Columns of the packet list. #### 11.5.3.1. columns:__tostring() ##### Returns The string "Columns", no real use, just for debugging purposes. #### 11.5.3.2. columns:__newindex(column, text) Sets the text of a specific column. ##### Arguments column The name of the column to set. text The text for the column. #### 11.5.3.3. columns:__index() Gets a specific Column. ### 11.5.4. NSTime NSTime represents a nstime_t. This is an object with seconds and nanoseconds. #### 11.5.4.1. NSTime.new([seconds], [nseconds]) Creates a new NSTime object. ##### Arguments seconds (optional) Seconds. nseconds (optional) Nano seconds. ##### Returns The new NSTime object. #### 11.5.4.2. nstime:__call([seconds], [nseconds]) Creates a NSTime object. ##### Arguments seconds (optional) Seconds. nseconds (optional) Nanoseconds. ##### Returns The new NSTime object. #### 11.5.4.3. nstime:tonumber() Returns a Lua number of the NSTime representing seconds from epoch Since: 2.4.0 ##### Returns The Lua number. #### 11.5.4.4. nstime:__tostring() ##### Returns The string representing the nstime. #### 11.5.4.5. nstime:__add() Calculates the sum of two NSTimes. #### 11.5.4.6. nstime:__sub() Calculates the diff of two NSTimes. #### 11.5.4.7. nstime:__unm() Calculates the negative NSTime. #### 11.5.4.8. nstime:__eq() Compares two NSTimes. #### 11.5.4.9. nstime:__le() Compares two NSTimes. #### 11.5.4.10. nstime:__lt() Compares two NSTimes. #### 11.5.4.11. nstime.secs Mode: Retrieve or assign. The NSTime seconds. #### 11.5.4.12. nstime.nsecs Mode: Retrieve or assign. The NSTime nano seconds. ### 11.5.5. Pinfo Packet information. #### 11.5.5.1. pinfo.visited Mode: Retrieve only. Whether this packet has been already visited. #### 11.5.5.2. pinfo.number Mode: Retrieve only. The number of this packet in the current file. #### 11.5.5.3. pinfo.len Mode: Retrieve only. The length of the frame. #### 11.5.5.4. pinfo.caplen Mode: Retrieve only. The captured length of the frame. #### 11.5.5.5. pinfo.abs_ts Mode: Retrieve only. When the packet was captured. #### 11.5.5.6. pinfo.rel_ts Mode: Retrieve only. Number of seconds passed since beginning of capture. #### 11.5.5.7. pinfo.delta_ts Mode: Retrieve only. Number of seconds passed since the last captured packet. #### 11.5.5.8. pinfo.delta_dis_ts Mode: Retrieve only. Number of seconds passed since the last displayed packet. #### 11.5.5.9. pinfo.curr_proto Mode: Retrieve only. Which Protocol are we dissecting. #### 11.5.5.10. pinfo.can_desegment Mode: Retrieve or assign. Set if this segment could be desegmented. #### 11.5.5.11. pinfo.desegment_len Mode: Retrieve or assign. Estimated number of additional bytes required for completing the PDU. #### 11.5.5.12. pinfo.desegment_offset Mode: Retrieve or assign. Offset in the tvbuff at which the dissector will continue processing when next called. #### 11.5.5.13. pinfo.fragmented Mode: Retrieve only. If the protocol is only a fragment. #### 11.5.5.14. pinfo.in_error_pkt Mode: Retrieve only. If we’re inside an error packet. #### 11.5.5.15. pinfo.match_uint Mode: Retrieve only. Matched uint for calling subdissector from table. #### 11.5.5.16. pinfo.match_string Mode: Retrieve only. Matched string for calling subdissector from table. #### 11.5.5.17. pinfo.port_type Mode: Retrieve or assign. Type of Port of .src_port and .dst_port. #### 11.5.5.18. pinfo.src_port Mode: Retrieve or assign. Source Port of this Packet. #### 11.5.5.19. pinfo.dst_port Mode: Retrieve or assign. Source Address of this Packet. #### 11.5.5.20. pinfo.dl_src Mode: Retrieve or assign. Data Link Source Address of this Packet. #### 11.5.5.21. pinfo.dl_dst Mode: Retrieve or assign. Data Link Destination Address of this Packet. #### 11.5.5.22. pinfo.net_src Mode: Retrieve or assign. Network Layer Source Address of this Packet. #### 11.5.5.23. pinfo.net_dst Mode: Retrieve or assign. Network Layer Destination Address of this Packet. #### 11.5.5.24. pinfo.src Mode: Retrieve or assign. Source Address of this Packet. #### 11.5.5.25. pinfo.dst Mode: Retrieve or assign. Destination Address of this Packet. #### 11.5.5.26. pinfo.match Mode: Retrieve only. Port/Data we are matching. #### 11.5.5.27. pinfo.columns Mode: Retrieve only. Access to the packet list columns. #### 11.5.5.28. pinfo.cols Mode: Retrieve only. Access to the packet list columns (equivalent to pinfo.columns). #### 11.5.5.29. pinfo.private Mode: Retrieve only. Access to the private table entries. #### 11.5.5.30. pinfo.hi Mode: Retrieve or assign. Higher Address of this Packet. #### 11.5.5.31. pinfo.lo Mode: Retrieve only. Lower Address of this Packet. #### 11.5.5.32. pinfo.conversation Mode: Assign only. Sets the packet conversation to the given Proto object. ### 11.5.6. PrivateTable PrivateTable represents the pinfo→private_table. #### 11.5.6.1. privatetable:__tostring() Gets debugging type information about the private table. ##### Returns A string with all keys in the table, mostly for debugging. ## 11.6. Functions for new protocols and dissectors The classes and functions in this chapter allow Lua scripts to create new protocols for Wireshark. Proto protocol objects can have Pref preferences, ProtoField fields for filterable values that can be displayed in a details view tree, functions for dissecting the new protocol, and so on. The dissection function can be hooked into existing protocol tables through DissectorTables so that the new protocol dissector function gets called by that protocol, and the new dissector can itself call on other, already existing protocol dissectors by retrieving and calling the Dissector object. A Proto dissector can also be used as a post-dissector, at the end of every frame’s dissection, or as a heuristic dissector. ### 11.6.1. Dissector A refererence to a dissector, used to call a dissector against a packet or a part of it. #### 11.6.1.1. Dissector.get(name) Obtains a dissector reference by name. ##### Arguments name The name of the dissector. ##### Returns The Dissector reference. #### 11.6.1.2. Dissector.list() Gets a Lua array table of all registered Dissector names. Note: This is an expensive operation, and should only be used for troubleshooting. Since: 1.11.3 ##### Returns The array table of registered dissector names. #### 11.6.1.3. dissector:call(tvb, pinfo, tree) Calls a dissector against a given packet (or part of it). ##### Arguments tvb The buffer to dissect. pinfo The packet info. tree The tree on which to add the protocol items. ##### Returns Number of bytes dissected. Note that some dissectors always return number of bytes in incoming buffer, so be aware. #### 11.6.1.4. dissector:__call(tvb, pinfo, tree) Calls a dissector against a given packet (or part of it). ##### Arguments tvb The buffer to dissect. pinfo The packet info. tree The tree on which to add the protocol items. #### 11.6.1.5. dissector:__tostring() Gets the Dissector’s protocol short name. ##### Returns A string of the protocol’s short name. ### 11.6.2. DissectorTable A table of subdissectors of a particular protocol (e.g. TCP subdissectors like http, smtp, sip are added to table "tcp.port"). Useful to add more dissectors to a table so that they appear in the Decode As…​ dialog. #### 11.6.2.1. DissectorTable.new(tablename, [uiname], [type], [base]) Creates a new DissectorTable for your dissector’s use. ##### Arguments tablename The short name of the table. uiname (optional) The name of the table in the User Interface (defaults to the name given). type (optional) Either ftypes.UINT8, ftypes.UINT16, ftypes.UINT24, ftypes.UINT32, or ftypes.STRING (defaults to ftypes.UINT32). base (optional) Either base.NONE, base.DEC, base.HEX, base.OCT, base.DEC_HEX or base.HEX_DEC (defaults to base.DEC). ##### Returns The newly created DissectorTable. #### 11.6.2.2. DissectorTable.list() Gets a Lua array table of all DissectorTable names - i.e., the string names you can use for the first argument to DissectorTable.get(). Note: This is an expensive operation, and should only be used for troubleshooting. Since: 1.11.3 ##### Returns The array table of registered DissectorTable names. #### 11.6.2.3. DissectorTable.heuristic_list() Gets a Lua array table of all heuristic list names - i.e., the string names you can use for the first argument in Proto:register_heuristic(). Note: This is an expensive operation, and should only be used for troubleshooting. Since: 1.11.3 ##### Returns The array table of registered heuristic list names #### 11.6.2.4. DissectorTable.get(tablename) Obtain a reference to an existing dissector table. ##### Arguments tablename The short name of the table. ##### Returns The DissectorTable. #### 11.6.2.5. dissectortable:add(pattern, dissector) Add a Proto with a dissector function, or a Dissector object, to the dissector table. ##### Arguments pattern The pattern to match (either an integer, a integer range or a string depending on the table’s type). dissector The dissector to add (either a Proto or a Dissector). #### 11.6.2.6. dissectortable:set(pattern, dissector) Remove existing dissectors from a table and add a new or a range of new dissectors. Since: 1.11.3 ##### Arguments pattern The pattern to match (either an integer, a integer range or a string depending on the table’s type). dissector The dissector to add (either a Proto or a Dissector). #### 11.6.2.7. dissectortable:remove(pattern, dissector) Remove a dissector or a range of dissectors from a table ##### Arguments pattern The pattern to match (either an integer, a integer range or a string depending on the table’s type). dissector The dissector to remove (either a Proto or a Dissector). #### 11.6.2.8. dissectortable:remove_all(dissector) Remove all dissectors from a table. Since: 1.11.3 ##### Arguments dissector The dissector to remove (either a Proto or a Dissector). #### 11.6.2.9. dissectortable:try(pattern, tvb, pinfo, tree) Try to call a dissector from a table ##### Arguments pattern The pattern to be matched (either an integer or a string depending on the table’s type). tvb The buffer to dissect. pinfo The packet info. tree The tree on which to add the protocol items. ##### Returns Number of bytes dissected. Note that some dissectors always return number of bytes in incoming buffer, so be aware. #### 11.6.2.10. dissectortable:get_dissector(pattern) Try to obtain a dissector from a table. ##### Arguments pattern The pattern to be matched (either an integer or a string depending on the table’s type). ##### Returns The dissector handle if found. nil if not found. #### 11.6.2.11. dissectortable:add_for_decode_as(proto) Add the given Proto to the "Decode as…​" list for this DissectorTable. The passed-in Proto object’s dissector() function is used for dissecting. Since: 1.99.1 ##### Arguments proto The Proto to add. #### 11.6.2.12. dissectortable:__tostring() Gets some debug information about the DissectorTable. ##### Returns A string of debug information about the DissectorTable. ### 11.6.3. Pref A preference of a Protocol. #### 11.6.3.1. Pref.bool(label, default, descr) Creates a boolean preference to be added to a Proto.prefs Lua table. ##### Arguments label The Label (text in the right side of the preference input) for this preference. default The default value for this preference. descr A description of what this preference is. #### 11.6.3.2. Pref.uint(label, default, descr) Creates an (unsigned) integer preference to be added to a Proto.prefs Lua table. ##### Arguments label The Label (text in the right side of the preference input) for this preference. default The default value for this preference. descr A description of what this preference is. #### 11.6.3.3. Pref.string(label, default, descr) Creates a string preference to be added to a Proto.prefs Lua table. ##### Arguments label The Label (text in the right side of the preference input) for this preference. default The default value for this preference. descr A description of what this preference is. #### 11.6.3.4. Pref.enum(label, default, descr, enum, radio) Creates an enum preference to be added to a Proto.prefs Lua table. ##### Arguments label The Label (text in the right side of the preference input) for this preference. default The default value for this preference. descr A description of what this preference is. enum An enum Lua table. radio Radio button (true) or Combobox (false). #### 11.6.3.5. Pref.range(label, default, descr, max) Creates a range preference to be added to a Proto.prefs Lua table. ##### Arguments label The Label (text in the right side of the preference input) for this preference. default The default value for this preference, e.g., "53", "10-30", or "10-30,53,55,100-120". descr A description of what this preference is. max The maximum value. #### 11.6.3.6. Pref.statictext(label, descr) Creates a static text string to be added to a Proto.prefs Lua table. ##### Arguments label The static text. descr The static text description. ### 11.6.4. Prefs The table of preferences of a protocol. #### 11.6.4.1. prefs:__newindex(name, pref) Creates a new preference. ##### Arguments name The abbreviation of this preference. pref A valid but still unassigned Pref object. ##### Errors • Unknown Pref type #### 11.6.4.2. prefs:__index(name) Get the value of a preference setting. ##### Arguments name The abbreviation of this preference. ##### Returns The current value of the preference. ##### Errors • Unknown Pref type ### 11.6.5. Proto A new protocol in Wireshark. Protocols have more uses, the main one is to dissect a protocol. But they can also be just dummies used to register preferences for other purposes. #### 11.6.5.1. Proto.new(name, desc) ##### Arguments name The name of the protocol. desc A Long Text description of the protocol (usually lowercase). ##### Returns The newly created protocol. #### 11.6.5.2. proto:__call(name, desc) Creates a Proto object. ##### Arguments name The name of the protocol. desc A Long Text description of the protocol (usually lowercase). ##### Returns The new Proto object. #### 11.6.5.3. proto:register_heuristic(listname, func) Registers a heuristic dissector function for this Proto protocol, for the given heuristic list name. When later called, the passed-in function will be given: 1. A Tvb object 2. A Pinfo object 3. A TreeItem object The function must return true if the payload is for it, else false. The function should perform as much verification as possible to ensure the payload is for it, and dissect the packet (including setting TreeItem info and such) only if the payload is for it, before returning true or false. Since version 1.99.1, this function also accepts a Dissector object as the second argument, to allow re-using the same Lua code as the function proto.dissector(…​). In this case, the Dissector must return a Lua number of the number of bytes consumed/parsed: if 0 is returned, it will be treated the same as a false return for the heuristic; if a positive or negative number is returned, then the it will be treated the same as a true return for the heuristic, meaning the packet is for this protocol and no other heuristic will be tried. Since: 1.11.3 ##### Arguments listname The heuristic list name this function is a heuristic for (e.g., "udp" or "infiniband.payload"). func A Lua function that will be invoked for heuristic dissection. #### 11.6.5.4. proto.dissector Mode: Retrieve or assign. The protocol’s dissector, a function you define. When later called, the function will be given: 1. A Tvb object 2. A Pinfo object 3. A TreeItem object #### 11.6.5.5. proto.prefs Mode: Retrieve only. The preferences of this dissector. #### 11.6.5.6. proto.prefs_changed Mode: Assign only. The preferences changed routine of this dissector, a Lua function you define. #### 11.6.5.7. proto.init Mode: Assign only. The init routine of this dissector, a function you define. The called init function is passed no arguments. #### 11.6.5.8. proto.name Mode: Retrieve only. The name given to this dissector. #### 11.6.5.9. proto.description Mode: Retrieve only. The description given to this dissector. #### 11.6.5.10. proto.fields Mode: Retrieve or assign. The ProtoFields Lua table of this dissector. #### 11.6.5.11. proto.experts Mode: Retrieve or assign. The expert info Lua table of this Proto. Since: 1.11.3 ### 11.6.6. ProtoExpert A Protocol expert info field, to be used when adding items to the dissection tree. Since: 1.11.3 #### 11.6.6.1. ProtoExpert.new(abbr, text, group, severity) Creates a new ProtoExpert object to be used for a protocol’s expert information notices. Since: 1.11.3 ##### Arguments abbr Filter name of the expert info field (the string that is used in filters). text The default text of the expert field. group Expert group type: one of: expert.group.CHECKSUM, expert.group.SEQUENCE, expert.group.RESPONSE_CODE, expert.group.REQUEST_CODE, expert.group.UNDECODED, expert.group.REASSEMBLE, expert.group.MALFORMED, expert.group.DEBUG, expert.group.PROTOCOL, expert.group.SECURITY, expert.group.COMMENTS_GROUP or expert.group.DECRYPTION. severity Expert severity type: one of: expert.severity.COMMENT, expert.severity.CHAT, expert.severity.NOTE, expert.severity.WARN, or expert.severity.ERROR. ##### Returns The newly created ProtoExpert object. #### 11.6.6.2. protoexpert:__tostring() Returns a string with debugging information about a ProtoExpert object. Since: 1.11.3 ### 11.6.7. ProtoField A Protocol field (to be used when adding items to the dissection tree). #### 11.6.7.1. ProtoField.new(name, abbr, type, [valuestring], [base], [mask], [descr]) Creates a new ProtoField object to be used for a protocol field. ##### Arguments name Actual name of the field (the string that appears in the tree). abbr Filter name of the field (the string that is used in filters). type Field Type: one of: ftypes.BOOLEAN, ftypes.UINT8, ftypes.UINT16, ftypes.UINT24, ftypes.UINT32, ftypes.UINT64, ftypes.INT8, ftypes.INT16, ftypes.INT24, ftypes.INT32, ftypes.INT64, ftypes.FLOAT, ftypes.DOUBLE , ftypes.ABSOLUTE_TIME, ftypes.RELATIVE_TIME, ftypes.STRING, ftypes.STRINGZ, ftypes.UINT_STRING, ftypes.ETHER, ftypes.BYTES, ftypes.UINT_BYTES, ftypes.IPv4, ftypes.IPv6, ftypes.IPXNET, ftypes.FRAMENUM, ftypes.PCRE, ftypes.GUID, ftypes.OID, ftypes.PROTOCOL, ftypes.REL_OID, ftypes.SYSTEM_ID, ftypes.EUI64 or ftypes.NONE. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that corresponds to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING, or one of frametype.NONE, frametype.REQUEST, frametype.RESPONSE, frametype.ACK or frametype.DUP_ACK if field type is ftypes.FRAMENUM. base (optional) The representation, one of: base.NONE, base.DEC, base.HEX, base.OCT, base.DEC_HEX, base.HEX_DEC, base.UNIT_STRING or base.RANGE_STRING. mask (optional) The bitmask to be used. descr (optional) The description of the field. ##### Returns The newly created ProtoField object. #### 11.6.7.2. ProtoField.uint8(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of an unsigned 8-bit integer (i.e., a byte). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.HEX or base.OCT, base.DEC_HEX, base.HEX_DEC or base.UNIT_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing the unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.3. ProtoField.uint16(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of an unsigned 16-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.HEX, base.OCT, base.DEC_HEX, base.HEX_DEC, base.UNIT_STRING or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.4. ProtoField.uint24(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of an unsigned 24-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.HEX, base.OCT, base.DEC_HEX, base.HEX_DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing the unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.5. ProtoField.uint32(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of an unsigned 32-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.HEX, base.OCT, base.DEC_HEX, base.HEX_DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing the unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.6. ProtoField.uint64(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of an unsigned 64-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.HEX, base.OCT, base.DEC_HEX, base.HEX_DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing the unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.7. ProtoField.int8(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of a signed 8-bit integer (i.e., a byte). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.8. ProtoField.int16(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of a signed 16-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.9. ProtoField.int24(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of a signed 24-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.10. ProtoField.int32(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of a signed 32-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.UNIT_STRING, or base.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.11. ProtoField.int64(abbr, [name], [base], [valuestring], [mask], [desc]) Creates a ProtoField of a signed 64-bit integer. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.DEC, base.UNIT_STRING, orbase.RANGE_STRING. valuestring (optional) A table containing the text that corresponds to the values, or a table containing tables of range string values that correspond to the values ({min, max, "string"}) if the base is base.RANGE_STRING, or a table containing unit name for the values if base is base.UNIT_STRING. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.12. ProtoField.framenum(abbr, [name], [base], [frametype], [mask], [desc]) Creates a ProtoField for a frame number (for hyperlinks between frames). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) Only base.NONE is supported for framenum. frametype (optional) One of frametype.NONE, frametype.REQUEST, frametype.RESPONSE, frametype.ACK or frametype.DUP_ACK. mask (optional) Integer mask of this field, which must be 0 for framenum. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.13. ProtoField.bool(abbr, [name], [display], [valuestring], [mask], [desc]) Creates a ProtoField for a boolean true/false value. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). display (optional) How wide the parent bitfield is (base.NONE is used for NULL-value). valuestring (optional) A table containing the text that corresponds to the values. mask (optional) Integer mask of this field. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.14. ProtoField.absolute_time(abbr, [name], [base], [desc]) Creates a ProtoField of a time_t structure value. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). base (optional) One of base.LOCAL, base.UTC or base.DOY_UTC. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.15. ProtoField.relative_time(abbr, [name], [desc]) Creates a ProtoField of a time_t structure value. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.16. ProtoField.float(abbr, [name], [valuestring], [desc]) Creates a ProtoField of a floating point number (4 bytes). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). valuestring (optional) A table containing unit name for the values. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.17. ProtoField.double(abbr, [name], [valuestring], [desc]) Creates a ProtoField of a double-precision floating point (8 bytes). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). valuestring (optional) A table containing unit name for the values. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.18. ProtoField.string(abbr, [name], [display], [desc]) Creates a ProtoField of a string value. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). display (optional) One of base.ASCII or base.UNICODE. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.19. ProtoField.stringz(abbr, [name], [display], [desc]) Creates a ProtoField of a zero-terminated string value. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). display (optional) One of base.ASCII or base.UNICODE. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.20. ProtoField.bytes(abbr, [name], [display], [desc]) Creates a ProtoField for an arbitrary number of bytes. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). display (optional) One of base.NONE, base.DOT, base.DASH, base.COLON or base.SPACE. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.21. ProtoField.ubytes(abbr, [name], [display], [desc]) Creates a ProtoField for an arbitrary number of unsigned bytes. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). display (optional) One of base.NONE, base.DOT, base.DASH, base.COLON or base.SPACE. desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.22. ProtoField.none(abbr, [name], [desc]) Creates a ProtoField of an unstructured type. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.23. ProtoField.ipv4(abbr, [name], [desc]) Creates a ProtoField of an IPv4 address (4 bytes). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.24. ProtoField.ipv6(abbr, [name], [desc]) Creates a ProtoField of an IPv6 address (16 bytes). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.25. ProtoField.ether(abbr, [name], [desc]) Creates a ProtoField of an Ethernet address (6 bytes). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.26. ProtoField.guid(abbr, [name], [desc]) Creates a ProtoField for a Globally Unique IDentifier (GUID). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.27. ProtoField.oid(abbr, [name], [desc]) Creates a ProtoField for an ASN.1 Organizational IDentified (OID). ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.28. ProtoField.protocol(abbr, [name], [desc]) Creates a ProtoField for a sub-protocol. Since 1.99.9. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.29. ProtoField.rel_oid(abbr, [name], [desc]) Creates a ProtoField for an ASN.1 Relative-OID. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.30. ProtoField.systemid(abbr, [name], [desc]) Creates a ProtoField for an OSI System ID. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.31. ProtoField.eui64(abbr, [name], [desc]) Creates a ProtoField for an EUI64. ##### Arguments abbr Abbreviated name of the field (the string used in filters). name (optional) Actual name of the field (the string that appears in the tree). desc (optional) Description of the field. ##### Returns A ProtoField object to be added to a table set to the Proto.fields attribute. #### 11.6.7.32. protofield:__tostring() Returns a string with info about a protofield (for debugging purposes). ### 11.6.8. Global Functions #### 11.6.8.1. register_postdissector(proto, [allfields]) Make a Proto protocol (with a dissector function) a post-dissector. It will be called for every frame after dissection. ##### Arguments proto The protocol to be used as post-dissector. allfields (optional) Whether to generate all fields. Note: This impacts performance (default=false). #### 11.6.8.2. dissect_tcp_pdus(tvb, tree, min_header_size, get_len_func, dissect_func, [desegment]) Make the TCP-layer invoke the given Lua dissection function for each PDU in the TCP segment, of the length returned by the given get_len_func function. This function is useful for protocols that run over TCP and that are either a fixed length always, or have a minimum size and have a length field encoded within that minimum portion that identifies their full length. For such protocols, their protocol dissector function can invoke this dissect_tcp_pdus() function to make it easier to handle dissecting their protocol’s messages (i.e., their protocol data unit (PDU)). This function shouild not be used for protocols whose PDU length cannot be determined from a fixed minimum portion, such as HTTP or Telnet. Since: 1.99.2 ##### Arguments tvb The Tvb buffer to dissect PDUs from. tree The Tvb buffer to dissect PDUs from. min_header_size The number of bytes in the fixed-length part of the PDU. get_len_func A Lua function that will be called for each PDU, to determine the full length of the PDU. The called function will be given (1) the Tvb object of the whole Tvb (possibly reassembled), (2) the Pinfo object, and (3) an offset number of the index of the first byte of the PDU (i.e., its first header byte). The Lua function must return a Lua number of the full length of the PDU. dissect_func A Lua function that will be called for each PDU, to dissect the PDU. The called function will be given (1) the Tvb object of the PDU’s Tvb (possibly reassembled), (2) the Pinfo object, and (3) the TreeItem object. The Lua function must return a Lua number of the number of bytes read/handled, which would typically be the Tvb:len(). desegment (optional) Whether to reassemble PDUs crossing TCP segment boundaries or not. (default=true) ## 11.7. Adding information to the dissection tree ### 11.7.1. TreeItem TreeItems represent information in the packet-details pane of Wireshark, and the packet details view of Tshark. A TreeItem represents a node in the tree, which might also be a subtree and have a list of children. The children of a subtree have zero or more siblings: other children of the same TreeItem subtree. During dissection, heuristic-dissection, and post-dissection, a root TreeItem is passed to dissectors as the third argument of the function callback (e.g., myproto.dissector(tvbuf,pktinfo,root)). In some cases the tree is not truly added to, in order to improve performance. For example for packets not currently displayed/selected in Wireshark’s visible window pane, or if Tshark isn’t invoked with the -V switch. However the "add" type TreeItem functions can still be called, and still return TreeItem objects - but the info isn’t really added to the tree. Therefore you do not typically need to worry about whether there’s a real tree or not. If, for some reason, you need to know it, you can use the tree.visible attribute getter to retrieve the state. #### 11.7.1.1. treeitem:add_packet_field(protofield, [tvbrange], encoding, [label]) Adds a new child tree for the given ProtoField object to this tree item, returning the new child TreeItem. Unlike TreeItem:add() and TreeItem:add_le(), the ProtoField argument is not optional, and cannot be a Proto object. Instead, this function always uses the ProtoField to determine the type of field to extract from the passed-in TvbRange, highlighting the relevant bytes in the Packet Bytes pane of the GUI (if there is a GUI), etc. If no TvbRange is given, no bytes are highlighted and the field’s value cannot be determined; the ProtoField must have been defined/created not to have a length in such a case, or an error will occur. For backwards-compatibility reasons the encoding argument, however, must still be given. Unlike TreeItem:add() and TreeItem:add_le(), this function performs both big-endian and little-endian decoding, by setting the encoding argument to be ENC_BIG_ENDIAN or ENC_LITTLE_ENDIAN. The signature of this function:  tree_item:add_packet_field(proto_field [,tvbrange], encoding, ...) In Wireshark version 1.11.3, this function was changed to return more than just the new child TreeItem. The child is the first return value, so that function chaining will still work as before; but it now also returns the value of the extracted field (i.e., a number, UInt64, Address, etc.). If the value could not be extracted from the TvbRange, the child TreeItem is still returned, but the second returned value is nil. Another new feature added to this function in Wireshark version 1.11.3 is the ability to extract native number ProtoFields from string encoding in the TvbRange, for ASCII-based and similar string encodings. For example, a ProtoField of as ftypes.UINT32 type can be extracted from a TvbRange containing the ASCII string "123", and it will correctly decode the ASCII to the number 123, both in the tree as well as for the second return value of this function. To do so, you must set the encoding argument of this function to the appropriate string ENC_* value, bitwise-or’d with the ENC_STRING value (see init.lua). ENC_STRING is guaranteed to be a unique bit flag, and thus it can added instead of bitwise-or’ed as well. Only single-byte ASCII digit string encoding types can be used for this, such as ENC_ASCII and ENC_UTF_8. For example, assuming the Tvb named tvb contains the string "123":  -- this is done earlier in the script local myfield = ProtoField.new("Transaction ID", "myproto.trans_id", ftypes.UINT16) -- this is done inside a dissector, post-dissector, or heuristic function -- child will be the created child tree, and value will be the number 123 or nil on failure local child, value = tree:add_packet_field(myfield, tvb:range(0,3), ENC_UTF_8 + ENC_STRING) ##### Arguments protofield The ProtoField field object to add to the tree. tvbrange (optional) The TvbRange of bytes in the packet this tree item covers/represents. encoding The field’s encoding in the TvbRange. label (optional) One or more strings to append to the created TreeItem. ##### Returns The new child TreeItem, the field’s extracted value or nil, and offset or nil. #### 11.7.1.2. treeitem:add([protofield], [tvbrange], [value], [label]) Adds a child item to this tree item, returning the new child TreeItem. If the ProtoField represents a numeric value (int, uint or float), then it’s treated as a Big Endian (network order) value. This function has a complicated form: 'treeitem:add([protofield,] [tvbrange,] value], label)', such that if the first argument is a ProtoField or a Proto, the second argument is a TvbRange, and a third argument is given, it’s a value; but if the second argument is a non-TvbRange, then it’s the value (as opposed to filling that argument with 'nil', which is invalid for this function). If the first argument is a non-ProtoField and a non-Proto then this argument can be either a TvbRange or a label, and the value is not in use. ##### Arguments protofield (optional) The ProtoField field or Proto protocol object to add to the tree. tvbrange (optional) The TvbRange of bytes in the packet this tree item covers/represents. value (optional) The field’s value, instead of the ProtoField/Proto one. label (optional) One or more strings to use for the tree item label, instead of the ProtoField/Proto one. ##### Returns The new child TreeItem. #### 11.7.1.3. treeitem:add_le([protofield], [tvbrange], [value], [label]) Adds a child item to this tree item, returning the new child TreeItem. If the ProtoField represents a numeric value (int, uint or float), then it’s treated as a Little Endian value. This function has a complicated form: 'treeitem:add_le([protofield,] [tvbrange,] value], label)', such that if the first argument is a ProtoField or a Proto, the second argument is a TvbRange, and a third argument is given, it’s a value; but if the second argument is a non-TvbRange, then it’s the value (as opposed to filling that argument with 'nil', which is invalid for this function). If the first argument is a non-ProtoField and a non-Proto then this argument can be either a TvbRange or a label, and the value is not in use. ##### Arguments protofield (optional) The ProtoField field or Proto protocol object to add to the tree. tvbrange (optional) The TvbRange of bytes in the packet this tree item covers/represents. value (optional) The field’s value, instead of the ProtoField/Proto one. label (optional) One or more strings to use for the tree item label, instead of the ProtoField/Proto one. ##### Returns The new child TreeItem. #### 11.7.1.4. treeitem:set_text(text) Sets the text of the label. This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments text The text to be used. ##### Returns The same TreeItem. #### 11.7.1.5. treeitem:append_text(text) Appends text to the label. This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments text The text to be appended. ##### Returns The same TreeItem. #### 11.7.1.6. treeitem:prepend_text(text) Prepends text to the label. This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments text The text to be prepended. ##### Returns The same TreeItem. #### 11.7.1.7. treeitem:add_expert_info([group], [severity], [text]) Sets the expert flags of the item and adds expert info to the packet. This function does not create a truly filterable expert info for a protocol. Instead you should use TreeItem.add_proto_expert_info(). Note: This function is provided for backwards compatibility only, and should not be used in new Lua code. It may be removed in the future. You should only use TreeItem.add_proto_expert_info(). ##### Arguments group (optional) One of PI_CHECKSUM, PI_SEQUENCE, PI_RESPONSE_CODE, PI_REQUEST_CODE, PI_UNDECODED, PI_REASSEMBLE, PI_MALFORMED or PI_DEBUG. severity (optional) One of PI_CHAT, PI_NOTE, PI_WARN, or PI_ERROR. text (optional) The text for the expert info display. ##### Returns The same TreeItem. #### 11.7.1.8. treeitem:add_proto_expert_info(expert, [text]) Sets the expert flags of the tree item and adds expert info to the packet. Since: 1.11.3 ##### Arguments expert The ProtoExpert object to add to the tree. text (optional) Text for the expert info display (default is to use the registered text). ##### Returns The same TreeItem. #### 11.7.1.9. treeitem:add_tvb_expert_info(expert, tvb, [text]) Sets the expert flags of the tree item and adds expert info to the packet associated with the Tvb or TvbRange bytes in the packet. Since: 1.11.3 ##### Arguments expert The ProtoExpert object to add to the tree. tvb The Tvb or TvbRange object bytes to associate the expert info with. text (optional) Text for the expert info display (default is to use the registered text). ##### Returns The same TreeItem. #### 11.7.1.10. treeitem:set_generated([bool]) Marks the TreeItem as a generated field (with data inferred but not contained in the packet). This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments bool (optional) A Lua boolean, which if true sets the TreeItem generated flag, else clears it (default=true) ##### Returns The same TreeItem. #### 11.7.1.11. treeitem:set_hidden([bool]) Marks the TreeItem as a hidden field (neither displayed nor used in filters). This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments bool (optional) A Lua boolean, which if true sets the TreeItem hidden flag, else clears it (default=true) ##### Returns The same TreeItem. #### 11.7.1.12. treeitem:set_len(len) Set TreeItem’s length inside tvb, after it has already been created. This used to return nothing, but as of 1.11.3 it returns the same tree item to allow chained calls. ##### Arguments len The length to be used. ##### Returns The same TreeItem. #### 11.7.1.13. treeitem:referenced(protofield) Checks if a ProtoField or Dissector is referenced by a filter/tap/UI. If this function returns FALSE, it means that the field (or dissector) does not need to be dissected and can be safely skipped. By skipping a field rather than dissecting it, the dissector will usually run faster since Wireshark will not do extra dissection work when it doesn’t need the field. You can use this in conjunction with the TreeItem.visible attribute. This function will always return TRUE when the TreeItem is visible. When it is not visible and the field is not referenced, you can speed up the dissection by not dissecting the field as it is not needed for display or filtering. This function takes one parameter that can be a ProtoField or a Dissector. The Dissector form is usefull when you need to decide whether to call a sub-dissector. Since: 2.4.0 ##### Arguments protofield The ProtoField or Dissector to check if referenced. ##### Returns A boolean indicating if the ProtoField/Dissector is referenced #### 11.7.1.14. treeitem:__tostring() Returns string debug information about the TreeItem. Since: 1.99.8 #### 11.7.1.15. treeitem.text Mode: Retrieve or assign. Set/get the TreeItem’s display string (string). For the getter, if the TreeItem has no display string, then nil is returned. Since: 1.99.3 #### 11.7.1.16. treeitem.visible Mode: Retrieve only. Get the TreeItem’s subtree visibility status (boolean). Since: 1.99.8 #### 11.7.1.17. treeitem.generated Mode: Retrieve or assign. Set/get the TreeItem’s generated state (boolean). Since: 1.99.8 #### 11.7.1.18. treeitem.hidden Mode: Retrieve or assign. Set/get TreeItem’s hidden state (boolean). Since: 1.99.8 #### 11.7.1.19. treeitem.len Mode: Retrieve or assign. Set/get TreeItem’s length inside tvb, after it has already been created. Since: 1.99.8 ## 11.8. Functions for handling packet data ### 11.8.1. ByteArray #### 11.8.1.1. ByteArray.new([hexbytes], [separator]) Creates a ByteArray object. Starting in version 1.11.3, if the second argument is a boolean true, then the first argyument is treated as a raw Lua string of bytes to use, instead of a hexadecimal string. ##### Arguments hexbytes (optional) A string consisting of hexadecimal bytes like "00 B1 A2" or "1a2b3c4d". separator (optional) A string separator between hex bytes/words (default=" "), or if the boolean value true is used, then the first argument is treated as raw binary data ##### Returns The new ByteArray object. #### 11.8.1.2. bytearray:__concat(first, second) Concatenate two ByteArrays. ##### Arguments first First array. second Second array. ##### Returns The new composite ByteArray. #### 11.8.1.3. bytearray:__eq(first, second) Compares two ByteArray values. Since: 1.11.4 ##### Arguments first First array. second Second array. #### 11.8.1.4. bytearray:prepend(prepended) Prepend a ByteArray to this ByteArray. ##### Arguments prepended ByteArray to be prepended. #### 11.8.1.5. bytearray:append(appended) Append a ByteArray to this ByteArray. ##### Arguments appended ByteArray to be appended. #### 11.8.1.6. bytearray:set_size(size) Sets the size of a ByteArray, either truncating it or filling it with zeros. ##### Arguments size New size of the array. ##### Errors • ByteArray size must be non-negative #### 11.8.1.7. bytearray:set_index(index, value) Sets the value of an index of a ByteArray. ##### Arguments index The position of the byte to be set. value The char value to set [0-255]. #### 11.8.1.8. bytearray:get_index(index) Get the value of a byte in a ByteArray. ##### Arguments index The position of the byte to get. ##### Returns The value [0-255] of the byte. #### 11.8.1.9. bytearray:len() Obtain the length of a ByteArray. ##### Returns The length of the ByteArray. #### 11.8.1.10. bytearray:subset(offset, length) Obtain a segment of a ByteArray, as a new ByteArray. ##### Arguments offset The position of the first byte (0=first). length The length of the segment. ##### Returns A ByteArray containing the requested segment. #### 11.8.1.11. bytearray:base64_decode() Obtain a Base64 decoded ByteArray. Since: 1.11.3 ##### Returns The created ByteArray. #### 11.8.1.12. bytearray:raw([offset], [length]) Obtain a Lua string of the binary bytes in a ByteArray. Since: 1.11.3 ##### Arguments offset (optional) The position of the first byte (default=0/first). length (optional) The length of the segment to get (default=all). ##### Returns A Lua string of the binary bytes in the ByteArray. #### 11.8.1.13. bytearray:tohex([lowercase], [separator]) Obtain a Lua string of the bytes in a ByteArray as hex-ascii, with given separator Since: 1.11.3 ##### Arguments lowercase (optional) True to use lower-case hex characters (default=false). separator (optional) A string separator to insert between hex bytes (default=nil). ##### Returns A hex-ascii string representation of the ByteArray. #### 11.8.1.14. bytearray:__tostring() Obtain a Lua string containing the bytes in a ByteArray so that it can be used in display filters (e.g. "01FE456789AB"). ##### Returns A hex-ascii string representation of the ByteArray. #### 11.8.1.15. bytearray:tvb(name) Creates a new Tvb from a ByteArray (it gets added to the current frame too). ##### Arguments name The name to be given to the new data-source. ##### Returns The created Tvb. ### 11.8.2. Tvb A Tvb represents the packet’s buffer. It is passed as an argument to listeners and dissectors, and can be used to extract information (via TvbRange) from the packet’s data. To create a TvbRange the Tvb must be called with offset and length as optional arguments; the offset defaults to 0 and the length to tvb:len(). Warning Tvbs are usable only by the current listener or dissector call and are destroyed as soon as the listener/dissector returns, so references to them are unusable once the function has returned. #### 11.8.2.1. tvb:__tostring() Convert the bytes of a Tvb into a string, to be used for debugging purposes, as '…​' will be appended if the string is too long. ##### Returns The string. #### 11.8.2.2. tvb:reported_len() Obtain the reported (not captured) length of a Tvb. ##### Returns The reported length of the Tvb. #### 11.8.2.3. tvb:len() Obtain the actual (captured) length of a Tvb. ##### Returns The captured length of the Tvb. #### 11.8.2.4. tvb:reported_length_remaining() Obtain the reported (not captured) length of packet data to end of a Tvb or -1 if the offset is beyond the end of the Tvb. ##### Returns The captured length of the Tvb. #### 11.8.2.5. tvb:bytes([offset], [length]) Obtain a ByteArray from a Tvb. Since: 1.99.8 ##### Arguments offset (optional) The offset (in octets) from the beginning of the Tvb. Defaults to 0. length (optional) The length (in octets) of the range. Defaults to until the end of the Tvb. ##### Returns The ByteArray object or nil. #### 11.8.2.6. tvb:offset() Returns the raw offset (from the beginning of the source Tvb) of a sub Tvb. ##### Returns The raw offset of the Tvb. #### 11.8.2.7. tvb:__call() Equivalent to tvb:range(…​) #### 11.8.2.8. tvb:range([offset], [length]) Creates a TvbRange from this Tvb. ##### Arguments offset (optional) The offset (in octets) from the beginning of the Tvb. Defaults to 0. length (optional) The length (in octets) of the range. Defaults to until the end of the Tvb. ##### Returns The TvbRange #### 11.8.2.9. tvb:raw([offset], [length]) Obtain a Lua string of the binary bytes in a Tvb. Since: 1.11.3 ##### Arguments offset (optional) The position of the first byte (default=0/first). length (optional) The length of the segment to get (default=all). ##### Returns A Lua string of the binary bytes in the Tvb. #### 11.8.2.10. tvb:__eq() Checks whether the two Tvb contents are equal. Since: 1.99.8 ### 11.8.3. TvbRange A TvbRange represents a usable range of a Tvb and is used to extract data from the Tvb that generated it. TvbRanges are created by calling a Tvb (e.g. 'tvb(offset,length)'). If the TvbRange span is outside the Tvb’s range the creation will cause a runtime error. #### 11.8.3.1. tvbrange:tvb() Creates a (sub)Tvb from a TvbRange. #### 11.8.3.2. tvbrange:uint() Get a Big Endian (network order) unsigned integer from a TvbRange. The range must be 1-4 octets long. ##### Returns The unsigned integer value. #### 11.8.3.3. tvbrange:le_uint() Get a Little Endian unsigned integer from a TvbRange. The range must be 1-4 octets long. ##### Returns The unsigned integer value #### 11.8.3.4. tvbrange:uint64() Get a Big Endian (network order) unsigned 64 bit integer from a TvbRange, as a UInt64 object. The range must be 1-8 octets long. ##### Returns The UInt64 object. #### 11.8.3.5. tvbrange:le_uint64() Get a Little Endian unsigned 64 bit integer from a TvbRange, as a UInt64 object. The range must be 1-8 octets long. ##### Returns The UInt64 object. #### 11.8.3.6. tvbrange:int() Get a Big Endian (network order) signed integer from a TvbRange. The range must be 1-4 octets long. ##### Returns The signed integer value #### 11.8.3.7. tvbrange:le_int() Get a Little Endian signed integer from a TvbRange. The range must be 1-4 octets long. ##### Returns The signed integer value. #### 11.8.3.8. tvbrange:int64() Get a Big Endian (network order) signed 64 bit integer from a TvbRange, as an Int64 object. The range must be 1-8 octets long. ##### Returns The Int64 object. #### 11.8.3.9. tvbrange:le_int64() Get a Little Endian signed 64 bit integer from a TvbRange, as an Int64 object. The range must be 1-8 octets long. ##### Returns The Int64 object. #### 11.8.3.10. tvbrange:float() Get a Big Endian (network order) floating point number from a TvbRange. The range must be 4 or 8 octets long. ##### Returns The floating point value. #### 11.8.3.11. tvbrange:le_float() Get a Little Endian floating point number from a TvbRange. The range must be 4 or 8 octets long. ##### Returns The floating point value. #### 11.8.3.12. tvbrange:ipv4() Get an IPv4 Address from a TvbRange, as an Address object. ##### Returns The IPv4 Address object. #### 11.8.3.13. tvbrange:le_ipv4() Get an Little Endian IPv4 Address from a TvbRange, as an Address object. ##### Returns The IPv4 Address object. #### 11.8.3.14. tvbrange:ipv6() Get an IPv6 Address from a TvbRange, as an Address object. ##### Returns The IPv6 Address object. #### 11.8.3.15. tvbrange:ether() Get an Ethernet Address from a TvbRange, as an Address object. ##### Returns The Ethernet Address object. ##### Errors • The range must be 6 bytes long #### 11.8.3.16. tvbrange:nstime([encoding]) Obtain a time_t structure from a TvbRange, as an NSTime object. ##### Arguments encoding (optional) An optional ENC_* encoding value to use ##### Returns The NSTime object and number of bytes used, or nil on failure. ##### Errors • The range must be 4 or 8 bytes long #### 11.8.3.17. tvbrange:le_nstime() Obtain a nstime from a TvbRange, as an NSTime object. ##### Returns The NSTime object. ##### Errors • The range must be 4 or 8 bytes long #### 11.8.3.18. tvbrange:string([encoding]) Obtain a string from a TvbRange. ##### Arguments encoding (optional) The encoding to use. Defaults to ENC_ASCII. ##### Returns The string #### 11.8.3.19. tvbrange:ustring() Obtain a Big Endian (network order) UTF-16 encoded string from a TvbRange. ##### Returns The string. #### 11.8.3.20. tvbrange:le_ustring() Obtain a Little Endian UTF-16 encoded string from a TvbRange. ##### Returns The string. #### 11.8.3.21. tvbrange:stringz([encoding]) Obtain a zero terminated string from a TvbRange. ##### Arguments encoding (optional) The encoding to use. Defaults to ENC_ASCII. ##### Returns The zero terminated string. #### 11.8.3.22. tvbrange:strsize([encoding]) Find the size of a zero terminated string from a TvbRange. The size of the string includes the terminating zero. Since: 1.11.3 ##### Arguments encoding (optional) The encoding to use. Defaults to ENC_ASCII. ##### Returns Length of the zero terminated string. #### 11.8.3.23. tvbrange:ustringz() Obtain a Big Endian (network order) UTF-16 encoded zero terminated string from a TvbRange. ##### Returns Two return values: the zero terminated string, and the length. #### 11.8.3.24. tvbrange:le_ustringz() Obtain a Little Endian UTF-16 encoded zero terminated string from a TvbRange ##### Returns Two return values: the zero terminated string, and the length. #### 11.8.3.25. tvbrange:bytes([encoding]) Obtain a ByteArray from a TvbRange. Starting in 1.11.4, this function also takes an optional encoding argument, which can be set to ENC_STR_HEX to decode a hex-string from the TvbRange into the returned ByteArray. The encoding can be bitwise-or’ed with one or more separator encodings, such as ENC_SEP_COLON, to allow separators to occur between each pair of hex characters. The return value also now returns the number of bytes used as a second return value. On failure or error, nil is returned for both return values. Note The encoding type of the hex string should also be set, for example ENC_ASCII or ENC_UTF_8, along with ENC_STR_HEX. ##### Arguments encoding (optional) An optional ENC_* encoding value to use ##### Returns The ByteArray object or nil, and number of bytes consumed or nil. #### 11.8.3.26. tvbrange:bitfield([position], [length]) Get a bitfield from a TvbRange. ##### Arguments position (optional) The bit offset from the beginning of the TvbRange. Defaults to 0. length (optional) The length (in bits) of the field. Defaults to 1. ##### Returns The bitfield value #### 11.8.3.27. tvbrange:range([offset], [length]) Creates a sub-TvbRange from this TvbRange. ##### Arguments offset (optional) The offset (in octets) from the beginning of the TvbRange. Defaults to 0. length (optional) The length (in octets) of the range. Defaults to until the end of the TvbRange. ##### Returns The TvbRange #### 11.8.3.28. tvbrange:uncompress(name) Obtain an uncompressed TvbRange from a TvbRange ##### Arguments name The name to be given to the new data-source. ##### Returns The TvbRange #### 11.8.3.29. tvbrange:len() Obtain the length of a TvbRange. #### 11.8.3.30. tvbrange:offset() Obtain the offset in a TvbRange. #### 11.8.3.31. tvbrange:raw([offset], [length]) Obtain a Lua string of the binary bytes in a TvbRange. Since: 1.11.3 ##### Arguments offset (optional) The position of the first byte (default=0/first). length (optional) The length of the segment to get (default=all). ##### Returns A Lua string of the binary bytes in the TvbRange. #### 11.8.3.32. tvbrange:__eq() Checks whether the two TvbRange contents are equal. Since: 1.99.8 #### 11.8.3.33. tvbrange:__tostring() Converts the TvbRange into a string. Since the string gets truncated, you should use this only for debugging purposes or if what you want is to have a truncated string in the format 67:89:AB:…​ ##### Returns A Lua hex string of the first 24 binary bytes in the TvbRange. ## 11.9. Custom file format reading/writing The classes/functions defined in this section allow you to create your own custom Lua-based "capture" file reader, or writer, or both. Since: 1.11.3 ### 11.9.1. CaptureInfo A CaptureInfo object, passed into Lua as an argument by FileHandler callback function read_open(), read(), seek_read(), seq_read_close(), and read_close(). This object represents capture file data and meta-data (data about the capture file) being read into Wireshark/Tshark. This object’s fields can be written-to by Lua during the read-based function callbacks. In other words, when the Lua plugin’s FileHandler.read_open() function is invoked, a CaptureInfo object will be passed in as one of the arguments, and its fields should be written to by your Lua code to tell Wireshark about the capture. Since: 1.11.3 #### 11.9.1.1. captureinfo:__tostring() Generates a string of debug info for the CaptureInfo ##### Returns String of debug information. #### 11.9.1.2. captureinfo.encap Mode: Retrieve or assign. The packet encapsulation type for the whole file. See wtap_encaps in init.lua for available types. Set to wtap_encaps.PER_PACKET if packets can have different types, then later set FrameInfo.encap for each packet during read()/seek_read(). #### 11.9.1.3. captureinfo.time_precision Mode: Retrieve or assign. The precision of the packet timestamps in the file. See wtap_file_tsprec in init.lua for available precisions. #### 11.9.1.4. captureinfo.snapshot_length Mode: Retrieve or assign. The maximum packet length that could be recorded. Setting it to 0 means unknown. #### 11.9.1.5. captureinfo.comment Mode: Retrieve or assign. A string comment for the whole capture file, or nil if there is no comment. #### 11.9.1.6. captureinfo.hardware Mode: Retrieve or assign. A string containing the description of the hardware used to create the capture, or nil if there is no hardware string. #### 11.9.1.7. captureinfo.os Mode: Retrieve or assign. A string containing the name of the operating system used to create the capture, or nil if there is no os string. #### 11.9.1.8. captureinfo.user_app Mode: Retrieve or assign. A string containing the name of the application used to create the capture, or nil if there is no user_app string. #### 11.9.1.9. captureinfo.hosts Mode: Assign only. Sets resolved ip-to-hostname information. The value set must be a Lua table of two key-ed names: ipv4_addresses and ipv6_addresses. The value of each of these names are themselves array tables, of key-ed tables, such that the inner table has a key addr set to the raw 4-byte or 16-byte IP address Lua string and a name set to the resolved name. For example, if the capture file identifies one resolved IPv4 address of 1.2.3.4 to foo.com, then you must set CaptureInfo.hosts to a table of:  { ipv4_addresses = { { addr = "\01\02\03\04", name = "foo.com" } } } Note that either the ipv4_addresses or the ipv6_addresses table, or both, may be empty or nil. #### 11.9.1.10. captureinfo.private_table Mode: Retrieve or assign. A private Lua value unique to this file. The private_table is a field you set/get with your own Lua table. This is provided so that a Lua script can save per-file reading/writing state, because multiple files can be opened and read at the same time. For example, if the user issued a reload-file command, or Lua called the reload() function, then the current capture file is still open while a new one is being opened, and thus Wireshark will invoke read_open() while the previous capture file has not caused read_close() to be called; and if the read_open() succeeds then read_close() will be called right after that for the previous file, rather than the one just opened. Thus the Lua script can use this private_table to store a table of values specific to each file, by setting this private_table in the read_open() function, which it can then later get back inside its read(), seek_read(), and read_close() functions. ### 11.9.2. CaptureInfoConst A CaptureInfoConst object, passed into Lua as an argument to the FileHandler callback function write_open(). This object represents capture file data and meta-data (data about the capture file) for the current capture in Wireshark/Tshark. This object’s fields are read-from when used by write_open function callback. In other words, when the Lua plugin’s FileHandler write_open function is invoked, a CaptureInfoConst object will be passed in as one of the arguments, and its fields should be read from by your Lua code to get data about the capture that needs to be written. Since: 1.11.3 #### 11.9.2.1. captureinfoconst:__tostring() Generates a string of debug info for the CaptureInfoConst ##### Returns String of debug information. #### 11.9.2.2. captureinfoconst.type Mode: Retrieve only. The file type. #### 11.9.2.3. captureinfoconst.snapshot_length Mode: Retrieve only. The maximum packet length that is actually recorded (vs. the original length of any given packet on-the-wire). A value of 0 means the snapshot length is unknown or there is no one such length for the whole file. #### 11.9.2.4. captureinfoconst.encap Mode: Retrieve only. The packet encapsulation type for the whole file. See wtap_encaps in init.lua for available types. It is set to wtap_encaps.PER_PACKET if packets can have different types, in which case each Frame identifies its type, in FrameInfo.packet_encap. #### 11.9.2.5. captureinfoconst.comment Mode: Retrieve or assign. A comment for the whole capture file, if the wtap_presence_flags.COMMENTS was set in the presence flags; nil if there is no comment. #### 11.9.2.6. captureinfoconst.hardware Mode: Retrieve only. A string containing the description of the hardware used to create the capture, or nil if there is no hardware string. #### 11.9.2.7. captureinfoconst.os Mode: Retrieve only. A string containing the name of the operating system used to create the capture, or nil if there is no os string. #### 11.9.2.8. captureinfoconst.user_app Mode: Retrieve only. A string containing the name of the application used to create the capture, or nil if there is no user_app string. #### 11.9.2.9. captureinfoconst.hosts Mode: Retrieve only. A ip-to-hostname Lua table of two key-ed names: ipv4_addresses and ipv6_addresses. The value of each of these names are themselves array tables, of key-ed tables, such that the inner table has a key addr set to the raw 4-byte or 16-byte IP address Lua string and a name set to the resolved name. For example, if the current capture has one resolved IPv4 address of 1.2.3.4 to foo.com, then getting CaptureInfoConst.hosts will get a table of:  { ipv4_addresses = { { addr = "\01\02\03\04", name = "foo.com" } }, ipv6_addresses = { } } Note that either the ipv4_addresses or the ipv6_addresses table, or both, may be empty, however they will not be nil. #### 11.9.2.10. captureinfoconst.private_table Mode: Retrieve or assign. A private Lua value unique to this file. The private_table is a field you set/get with your own Lua table. This is provided so that a Lua script can save per-file reading/writing state, because multiple files can be opened and read at the same time. For example, if two Lua scripts issue a Dumper:new_for_current() call and the current file happens to use your script’s writer, then the Wireshark will invoke write_open() while the previous capture file has not had write_close() called. Thus the Lua script can use this private_table to store a table of values specific to each file, by setting this private_table in the write_open() function, which it can then later get back inside its write(), and write_close() functions. ### 11.9.3. File A File object, passed into Lua as an argument by FileHandler callback functions (e.g., read_open, read, write, etc.). This behaves similarly to the Lua io library’s file object, returned when calling io.open(), except in this case you cannot call file:close(), file:open(), nor file:setvbuf(), since Wireshark/tshark manages the opening and closing of files. You also cannot use the io library itself on this object, i.e. you cannot do io.read(file, 4). Instead, use this File with the object-oriented style calling its methods, i.e. myfile:read(4). (see later example) The purpose of this object is to hide the internal complexity of how Wireshark handles files, and instead provide a Lua interface that is familiar, by mimicking the io library. The reason true/raw io files cannot be used is because Wireshark does many things under the hood, such as compress the file, or write to stdout, or various other things based on configuration/commands. When a File object is passed in through reading-based callback functions, such as read_open(), read(), and read_close(), then the File object’s write() and flush() functions are not usable and will raise an error if used. When a File object is passed in through writing-based callback functions, such as write_open(), write(), and write_close(), then the File object’s read() and lines() functions are not usable and will raise an error if used. Note: A File object should never be stored/saved beyond the scope of the callback function it is passed in to. For example:  function myfilehandler.read_open(file, capture) local position = file:seek() -- read 24 bytes local line = file:read(24) -- do stuff -- it's not our file type, seek back (unnecessary but just to show it...) file:seek("set",position) -- return false because it's not our file type return false end Since: 1.11.3 #### 11.9.3.1. file:read() Reads from the File, similar to Lua’s file:read(). See Lua 5.x ref manual for file:read(). #### 11.9.3.2. file:seek() Seeks in the File, similar to Lua’s file:seek(). See Lua 5.x ref manual for file:seek(). ##### Returns The current file cursor position as a number. #### 11.9.3.3. file:lines() Lua iterator function for retrieving ASCII File lines, similar to Lua’s file:lines(). See Lua 5.x ref manual for file:lines(). #### 11.9.3.4. file:write() Writes to the File, similar to Lua’s file:write(). See Lua 5.x ref manual for file:write(). #### 11.9.3.5. file:__tostring() Generates a string of debug info for the File object ##### Returns String of debug information. #### 11.9.3.6. file.compressed Mode: Retrieve only. Whether the File is compressed or not. See wtap_encaps in init.lua for available types. Set to wtap_encaps.PER_PACKET if packets can have different types, then later set FrameInfo.encap for each packet during read()/seek_read(). ### 11.9.4. FileHandler A FileHandler object, created by a call to FileHandler.new(arg1, arg2, …​). The FileHandler object lets you create a file-format reader, or writer, or both, by setting your own read_open/read or write_open/write functions. Since: 1.11.3 #### 11.9.4.1. FileHandler.new(name, shortname, description, type) Creates a new FileHandler ##### Arguments name The name of the file type, for display purposes only. E.g., "Wireshark - pcapng" shortname The file type short name, used as a shortcut in various places. E.g., "pcapng". Note: The name cannot already be in use. description Descriptive text about this file format, for display purposes only type The type of FileHandler, "r"/"w"/"rw" for reader/writer/both, include "m" for magic, "s" for strong heuristic ##### Returns The newly created FileHandler object #### 11.9.4.2. filehandler:__tostring() Generates a string of debug info for the FileHandler ##### Returns String of debug information. #### 11.9.4.3. filehandler.read_open Mode: Assign only. The Lua function to be called when Wireshark opens a file for reading. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfo object The purpose of the Lua function set to this read_open field is to check if the file Wireshark is opening is of its type, for example by checking for magic numbers or trying to parse records in the file, etc. The more can be verified the better, because Wireshark tries all file readers until it finds one that accepts the file, so accepting an incorrect file prevents other file readers from reading their files. The called Lua function should return true if the file is its type (it accepts it), false if not. The Lua function must also set the File offset position (using file:seek()) to where it wants it to be for its first read() call. #### 11.9.4.4. filehandler.read Mode: Assign only. The Lua function to be called when Wireshark wants to read a packet from the file. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfo object 3. A FrameInfo object The purpose of the Lua function set to this read field is to read the next packet from the file, and setting the parsed/read packet into the frame buffer using FrameInfo.data = foo or FrameInfo:read_data(file, frame.captured_length). The called Lua function should return the file offset/position number where the packet begins, or false if it hit an error. The file offset will be saved by Wireshark and passed into the set seek_read() Lua function later. #### 11.9.4.5. filehandler.seek_read Mode: Assign only. The Lua function to be called when Wireshark wants to read a packet from the file at the given offset. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfo object 3. A FrameInfo object 4. The file offset number previously set by the read() function call The called Lua function should return true if the read was successful, or false if it hit an error. Since 2.4.0, a number is also acceptable to signal success, this allows for reuse of FileHandler:read:  local function fh_read(file, capture, frame) ... end myfilehandler.read = fh_read function myfilehandler.seek_read(file, capture, frame, offset) if not file:seek("set", offset) then -- Seeking failed, return failure return false end -- Now try to read one frame return fh_read(file, capture, frame) end #### 11.9.4.6. filehandler.read_close Mode: Assign only. The Lua function to be called when Wireshark wants to close the read file completely. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfo object It is not necessary to set this field to a Lua function - FileHandler can be registered without doing so - it is available in case there is memory/state to clear in your script when the file is closed. #### 11.9.4.7. filehandler.seq_read_close Mode: Assign only. The Lua function to be called when Wireshark wants to close the sequentially-read file. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfo object It is not necessary to set this field to a Lua function - FileHandler can be registered without doing so - it is available in case there is memory/state to clear in your script when the file is closed for the sequential reading portion. After this point, there will be no more calls to read(), only seek_read(). #### 11.9.4.8. filehandler.can_write_encap Mode: Assign only. The Lua function to be called when Wireshark wants to write a file, by checking if this file writer can handle the wtap packet encapsulation(s). When later called by Wireshark, the Lua function will be given a Lua number, which matches one of the encapsulations in the Lua wtap_encaps table. This might be the wtap_encap.PER_PACKET number, meaning the capture contains multiple encapsulation types, and the file reader should only return true if it can handle multiple encap types in one file. The function will then be called again, once for each encap type in the file, to make sure it can write each one. If the Lua file writer can write the given type of encapsulation into a file, then it returns the boolean true, else false. #### 11.9.4.9. filehandler.write_open Mode: Assign only. The Lua function to be called when Wireshark opens a file for writing. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfoConst object The purpose of the Lua function set to this write_open field is similar to the read_open callback function: to initialize things necessary for writing the capture to a file. For example, if the output file format has a file header, then the file header should be written within this write_open function. The called Lua function should return true on success, or false if it hit an error. Also make sure to set the FileHandler.write (and potentially FileHandler.write_finish) functions before returning true from this function. #### 11.9.4.10. filehandler.write Mode: Assign only. The Lua function to be called when Wireshark wants to write a packet to the file. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfoConst object 3. A FrameInfoConst object of the current frame/packet to be written The purpose of the Lua function set to this write field is to write the next packet to the file. The called Lua function should return true on success, or false if it hit an error. #### 11.9.4.11. filehandler.write_finish Mode: Assign only. The Lua function to be called when Wireshark wants to close the written file. When later called by Wireshark, the Lua function will be given: 1. A File object 2. A CaptureInfoConst object It is not necessary to set this field to a Lua function - FileHandler can be registered without doing so - it is available in case there is memory/state to clear in your script when the file is closed. #### 11.9.4.12. filehandler.type Mode: Retrieve only. The internal file type. This is automatically set with a new number when the FileHandler is registered. #### 11.9.4.13. filehandler.extensions Mode: Retrieve or assign. One or more semicolon-separated file extensions that this file type usually uses. For readers using heuristics to determine file type, Wireshark will try the readers of the file’s extension first, before trying other readers. But ultimately Wireshark tries all file readers for any file extension, until it finds one that accepts the file. (Since 2.6) For writers, the first extension is used to suggest the default file extension. #### 11.9.4.14. filehandler.writing_must_seek Mode: Retrieve or assign. True if the ability to seek is required when writing this file format, else false. This will be checked by Wireshark when writing out to compressed file formats, because seeking is not possible with compressed files. Usually a file writer only needs to be able to seek if it needs to go back in the file to change something, such as a block or file length value earlier in the file. #### 11.9.4.15. filehandler.writes_name_resolution Mode: Retrieve or assign. True if the file format supports name resolution records, else false. #### 11.9.4.16. filehandler.supported_comment_types Mode: Retrieve or assign. Set to the bit-wise OR’ed number representing the type of comments the file writer supports writing, based on the numbers in the wtap_comments table. ### 11.9.5. FrameInfo A FrameInfo object, passed into Lua as an argument by FileHandler callback functions (e.g., read, seek_read, etc.). This object represents frame data and meta-data (data about the frame/packet) for a given read/seek_read/write’s frame. This object’s fields are written-to/set when used by read function callbacks, and read-from/get when used by file write function callbacks. In other words, when the Lua plugin’s FileHandler read/seek_read/etc. functions are invoked, a FrameInfo object will be passed in as one of the arguments, and its fields should be written-to/set based on the frame information read from the file; whereas when the Lua plugin’s FileHandler.write() function is invoked, the FrameInfo object passed in should have its fields read-from/get, to write that frame information to the file. Since: 1.11.3 #### 11.9.5.1. frameinfo:__tostring() Generates a string of debug info for the FrameInfo ##### Returns String of debug information. #### 11.9.5.2. frameinfo:read_data(file, length) Tells Wireshark to read directly from given file into frame data buffer, for length bytes. Returns true if succeeded, else false. ##### Arguments file The File object userdata, provided by Wireshark previously in a reading-based callback. length The number of bytes to read from the file at the current cursor position. ##### Returns True if succeeded, else returns false along with the error number and string error description. A Lua string of the frame buffer’s data. #### 11.9.5.3. frameinfo.time Mode: Retrieve or assign. The packet timestamp as an NSTime object. Note: Set the FileHandler.time_precision to the appropriate wtap_file_tsprec value as well. #### 11.9.5.4. frameinfo.data Mode: Retrieve or assign. The data buffer containing the packet. Note This cannot be cleared once set. #### 11.9.5.5. frameinfo.rec_type Mode: Retrieve or assign. The record type of the packet frame See wtap_rec_types in init.lua for values. #### 11.9.5.6. frameinfo.flags Mode: Retrieve or assign. The presence flags of the packet frame. See wtap_presence_flags in init.lua for bit values. #### 11.9.5.7. frameinfo.captured_length Mode: Retrieve or assign. The captured packet length, and thus the length of the buffer passed to the FrameInfo.data field. #### 11.9.5.8. frameinfo.original_length Mode: Retrieve or assign. The on-the-wire packet length, which may be longer than the captured_length. #### 11.9.5.9. frameinfo.encap Mode: Retrieve or assign. The packet encapsulation type for the frame/packet, if the file supports per-packet types. See wtap_encaps in init.lua for possible packet encapsulation types to use as the value for this field. #### 11.9.5.10. frameinfo.comment Mode: Retrieve or assign. A string comment for the packet, if the wtap_presence_flags.COMMENTS was set in the presence flags; nil if there is no comment. ### 11.9.6. FrameInfoConst A constant FrameInfo object, passed into Lua as an argument by the FileHandler write callback function. This has similar attributes/properties as FrameInfo, but the fields can only be read from, not written to. Since: 1.11.3 #### 11.9.6.1. frameinfoconst:__tostring() Generates a string of debug info for the FrameInfo ##### Returns String of debug information. #### 11.9.6.2. frameinfoconst:write_data(file, [length]) Tells Wireshark to write directly to given file from the frame data buffer, for length bytes. Returns true if succeeded, else false. ##### Arguments file The File object userdata, provided by Wireshark previously in a writing-based callback. length (optional) The number of bytes to write to the file at the current cursor position, or all if not supplied. ##### Returns True if succeeded, else returns false along with the error number and string error description. #### 11.9.6.3. frameinfoconst.time Mode: Retrieve only. The packet timestamp as an NSTime object. #### 11.9.6.4. frameinfoconst.data Mode: Retrieve only. The data buffer containing the packet. #### 11.9.6.5. frameinfoconst.rec_type Mode: Retrieve only. The record type of the packet frame - see wtap_presence_flags in init.lua for values. #### 11.9.6.6. frameinfoconst.flags Mode: Retrieve only. The presence flags of the packet frame - see wtap_presence_flags in init.lua for bits. #### 11.9.6.7. frameinfoconst.captured_length Mode: Retrieve only. The captured packet length, and thus the length of the buffer in the FrameInfoConst.data field. #### 11.9.6.8. frameinfoconst.original_length Mode: Retrieve only. The on-the-wire packet length, which may be longer than the captured_length. #### 11.9.6.9. frameinfoconst.encap Mode: Retrieve only. The packet encapsulation type, if the file supports per-packet types. See wtap_encaps in init.lua for possible packet encapsulation types to use as the value for this field. #### 11.9.6.10. frameinfoconst.comment Mode: Retrieve only. A comment for the packet; nil if there is none. ### 11.9.7. Global Functions #### 11.9.7.1. register_filehandler(filehandler) Register the FileHandler into Wireshark/tshark, so they can read/write this new format. All functions and settings must be complete before calling this registration function. This function cannot be called inside the reading/writing callback functions. ##### Arguments filehandler The FileHandler object to be registered ##### Returns the new type number for this file reader/write #### 11.9.7.2. deregister_filehandler(filehandler) Deregister the FileHandler from Wireshark/tshark, so it no longer gets used for reading/writing/display. This function cannot be called inside the reading/writing callback functions. ##### Arguments filehandler The FileHandler object to be deregistered ## 11.10. Directory handling functions ### 11.10.1. Dir A Directory object, as well as associated functions. #### 11.10.1.1. Dir.make(name) Creates a directory. The created directory is set for permission mode 0755 (octal), meaning it is read+write+execute by owner, but only read+execute by group and others. IF the directory was created successfully, a boolean true is returned. If the directory cannot be made because it already exists, false is returned. If the directory cannot be made because an error occurred, nil is returned. Since: 1.11.3 ##### Arguments name The name of the directory, possibly including path. ##### Returns Boolean true on success, false if already exists, nil on error. #### 11.10.1.2. Dir.exists(name) Returns true if the given directory name exists. If the directory exists, a boolean true is returned. If the path is a file instead, false is returned. If the path does not exist or an error occurred, nil is returned. Since: 1.11.3 ##### Arguments name The name of the directory, possibly including path. ##### Returns Boolean true if the directory exists, false if it’s a file, nil on error/not-exist. #### 11.10.1.3. Dir.remove(name) Removes an empty directory. If the directory was removed successfully, a boolean true is returned. If the directory cannot be removed because it does not exist, false is returned. If the directory cannot be removed because an error occurred, nil is returned. This function only removes empty directories. To remove a directory regardless, use Dir.remove_all(). Since: 1.11.3 ##### Arguments name The name of the directory, possibly including path. ##### Returns Boolean true on success, false if does not exist, nil on error. #### 11.10.1.4. Dir.remove_all(name) Removes an empty or non-empty directory. If the directory was removed successfully, a boolean true is returned. If the directory cannot be removed because it does not exist, false is returned. If the directory cannot be removed because an error occurred, nil is returned. Since: 1.11.3 ##### Arguments name The name of the directory, possibly including path. ##### Returns Boolean true on success, false if does not exist, nil on error. #### 11.10.1.5. Dir.open(pathname, [extension]) Opens a directory and returns a Dir object representing the files in the directory.  for filename in Dir.open(path) do ... end ##### Arguments pathname The pathname of the directory. extension (optional) If given, only files with this extension will be returned. ##### Returns the Dir object. #### 11.10.1.6. Dir.personal_config_path([filename]) Gets the personal configuration directory path, with filename if supplied. Since: 1.11.3 ##### Arguments filename (optional) A filename. ##### Returns The full pathname for a file in the personal configuration directory. #### 11.10.1.7. Dir.global_config_path([filename]) Gets the global configuration directory path, with filename if supplied. Since: 1.11.3 ##### Arguments filename (optional) A filename ##### Returns The full pathname for a file in wireshark’s configuration directory. #### 11.10.1.8. Dir.personal_plugins_path() Gets the personal plugins directory path. Since: 1.11.3 ##### Returns The pathname for the personal plugins directory. #### 11.10.1.9. Dir.global_plugins_path() Gets the global plugins directory path. Since: 1.11.3 ##### Returns The pathname for the global plugins directory. #### 11.10.1.10. dir:__call() At every invocation will return one file (nil when done). #### 11.10.1.11. dir:close() Closes the directory. ## 11.11. Utility Functions ### 11.11.1. Global Functions #### 11.11.1.1. get_version() Gets a string of the Wireshark version. ##### Returns version string #### 11.11.1.2. set_plugin_info(table) Set a Lua table with meta-data about the plugin, such as version. The passed-in Lua table entries need to be keyed/indexed by the following: • "version" with a string value identifying the plugin version (required) • "description" with a string value describing the plugin (optional) • "author" with a string value of the author’s name(s) (optional) • "repository" with a string value of a URL to a repository (optional) Not all of the above key entries need to be in the table. The 'version' entry is required, however. The others are not currently used for anything, but might be in the future and thus using them might be useful. Table entries keyed by other strings are ignored, and do not cause an error. Example:  local my_info = { version = "1.0.1", author = "Jane Doe", repository = "https://github.com/octocat/Spoon-Knife" } set_plugin_info(my_info) Since: 1.99.8 ##### Arguments table The Lua table of information. #### 11.11.1.3. format_date(timestamp) Formats an absolute timestamp into a human readable date. ##### Arguments timestamp A timestamp value to convert. ##### Returns A string with the formated date #### 11.11.1.4. format_time(timestamp) Formats a relative timestamp in a human readable form. ##### Arguments timestamp A timestamp value to convert. ##### Returns A string with the formated time #### 11.11.1.5. report_failure(text) Reports a failure to the user. ##### Arguments text Message text to report. #### 11.11.1.6. loadfile(filename) Lua’s loadfile() has been modified so that if a file does not exist in the current directory it will look for it in wireshark’s user and system directories. ##### Arguments filename Name of the file to be loaded. #### 11.11.1.7. dofile(filename) Lua’s dofile() has been modified so that if a file does not exist in the current directory it will look for it in wireshark’s user and system directories. ##### Arguments filename Name of the file to be run. #### 11.11.1.8. register_stat_cmd_arg(argument, [action]) Register a function to handle a -z option ##### Arguments argument Argument action (optional) Action ## 11.12. Handling 64-bit Integers Lua uses one single number representation which can be chosen at compile time and since it is often set to IEEE 754 double precision floating point, one cannot store a 64 bit integer with full precision. For details, see https://wiki.wireshark.org/LuaAPI/Int64. ### 11.12.1. Int64 Int64 represents a 64 bit signed integer. For details, see https://wiki.wireshark.org/LuaAPI/Int64. #### 11.12.1.1. Int64.decode(string, [endian]) Decodes an 8-byte Lua string, using given endianness, into a new Int64 object. Since: 1.11.3 ##### Arguments string The Lua string containing a binary 64-bit integer. endian (optional) If set to true then little-endian is used, if false then big-endian; if missing/nil, native host endian. ##### Returns The Int64 object created, or nil on failure. #### 11.12.1.2. Int64.new([value], [highvalue]) Creates a Int64 Object. Since: 1.11.3 ##### Arguments value (optional) A number, UInt64, Int64, or string of ASCII digits to assign the value of the new Int64 (default=0). highvalue (optional) If this is a number and the first argument was a number, then the first will be treated as a lower 32-bits, and this is the high-order 32 bit number. ##### Returns The new Int64 object. #### 11.12.1.3. Int64.max() Gets the max possible value. Since: 1.11.3 ##### Returns The new Int64 object of the max value. #### 11.12.1.4. Int64.min() Gets the min possible value. Since: 1.11.3 ##### Returns The new Int64 object of the min value. #### 11.12.1.5. Int64.fromhex(hex) Creates an Int64 object from the given hex string. Since: 1.11.3 ##### Arguments hex The hex-ascii Lua string. ##### Returns The new Int64 object. #### 11.12.1.6. int64:encode([endian]) Encodes the Int64 number into an 8-byte Lua string, using given endianness. Since: 1.11.3 ##### Arguments endian (optional) If set to true then little-endian is used, if false then big-endian; if missing/nil, native host endian. ##### Returns The Lua string. #### 11.12.1.7. int64:__call() Creates a Int64 Object. Since: 1.11.3 ##### Returns The new Int64 object. #### 11.12.1.8. int64:tonumber() Returns a Lua number of the Int64 value - this may lose precision. Since: 1.11.3 ##### Returns The Lua number. #### 11.12.1.9. int64:tohex([numbytes]) Returns a hex string of the Int64 value. Since: 1.11.3 ##### Arguments numbytes (optional) The number of hex-chars/nibbles to generate, negative means uppercase (default=16). ##### Returns The string hex. #### 11.12.1.10. int64:higher() Returns a Lua number of the higher 32-bits of the Int64 value. (negative Int64 will return a negative Lua number). Since: 1.11.3 ##### Returns The Lua number. #### 11.12.1.11. int64:lower() Returns a Lua number of the lower 32-bits of the Int64 value. (always positive). Since: 1.11.3 ##### Returns The Lua number. #### 11.12.1.12. int64:__tostring() Converts the Int64 into a string of decimal digits. ##### Returns The Lua string. #### 11.12.1.13. int64:__unm() Returns the negative of the Int64, in a new Int64. Since: 1.11.3 ##### Returns The new Int64. #### 11.12.1.14. int64:__add() Adds two Int64 together and returns a new one (this may wrap the value). Since: 1.11.3 #### 11.12.1.15. int64:__sub() Subtracts two Int64 and returns a new one (this may wrap the value). Since: 1.11.3 #### 11.12.1.16. int64:__mul() Multiplies two Int64 and returns a new one (this may truncate the value). Since: 1.11.3 #### 11.12.1.17. int64:__div() Divides two Int64 and returns a new one (integer divide, no remainder). Trying to divide by zero results in a Lua error. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.18. int64:__mod() Divides two Int64 and returns a new one of the remainder. Trying to modulo by zero results in a Lua error. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.19. int64:__pow() The first Int64 is taken to the power of the second Int64, returning a new one (this may truncate the value). Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.20. int64:__eq() Returns true if both Int64 are equal. Since: 1.11.3 #### 11.12.1.21. int64:__lt() Returns true if first Int64 < second. Since: 1.11.3 #### 11.12.1.22. int64:__le() Returns true if first Int64 ⇐ second. Since: 1.11.3 #### 11.12.1.23. int64:bnot() Returns a Int64 of the bitwise 'not' operation. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.24. int64:band() Returns a Int64 of the bitwise 'and' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.25. int64:bor() Returns a Int64 of the bitwise 'or' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.26. int64:bxor() Returns a Int64 of the bitwise 'xor' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The Int64 object. #### 11.12.1.27. int64:lshift(numbits) Returns a Int64 of the bitwise logical left-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to left-shift by. ##### Returns The Int64 object. #### 11.12.1.28. int64:rshift(numbits) Returns a Int64 of the bitwise logical right-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to right-shift by. ##### Returns The Int64 object. #### 11.12.1.29. int64:arshift(numbits) Returns a Int64 of the bitwise arithmetic right-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to right-shift by. ##### Returns The Int64 object. #### 11.12.1.30. int64:rol(numbits) Returns a Int64 of the bitwise left rotation operation, by the given number of bits (up to 63). Since: 1.11.3 ##### Arguments numbits The number of bits to roll left by. ##### Returns The Int64 object. #### 11.12.1.31. int64:ror(numbits) Returns a Int64 of the bitwise right rotation operation, by the given number of bits (up to 63). Since: 1.11.3 ##### Arguments numbits The number of bits to roll right by. ##### Returns The Int64 object. #### 11.12.1.32. int64:bswap() Returns a Int64 of the bytes swapped. This can be used to convert little-endian 64-bit numbers to big-endian 64 bit numbers or vice versa. Since: 1.11.3 ##### Returns The Int64 object. ### 11.12.2. UInt64 UInt64 represents a 64 bit unsigned integer, similar to Int64. For details, see: https://wiki.wireshark.org/LuaAPI/Int64. #### 11.12.2.1. UInt64.decode(string, [endian]) Decodes an 8-byte Lua binary string, using given endianness, into a new UInt64 object. Since: 1.11.3 ##### Arguments string The Lua string containing a binary 64-bit integer. endian (optional) If set to true then little-endian is used, if false then big-endian; if missing/nil, native host endian. ##### Returns The UInt64 object created, or nil on failure. #### 11.12.2.2. UInt64.new([value], [highvalue]) Creates a UInt64 Object. Since: 1.11.3 ##### Arguments value (optional) A number, UInt64, Int64, or string of digits to assign the value of the new UInt64 (default=0). highvalue (optional) If this is a number and the first argument was a number, then the first will be treated as a lower 32-bits, and this is the high-order 32-bit number. ##### Returns The new UInt64 object. #### 11.12.2.3. UInt64.max() Gets the max possible value. Since: 1.11.3 ##### Returns The max value. #### 11.12.2.4. UInt64.min() Gets the min possible value (i.e., 0). Since: 1.11.3 ##### Returns The min value. #### 11.12.2.5. UInt64.fromhex(hex) Creates a UInt64 object from the given hex string. Since: 1.11.3 ##### Arguments hex The hex-ascii Lua string. ##### Returns The new UInt64 object. #### 11.12.2.6. uint64:encode([endian]) Encodes the UInt64 number into an 8-byte Lua binary string, using given endianness. Since: 1.11.3 ##### Arguments endian (optional) If set to true then little-endian is used, if false then big-endian; if missing/nil, native host endian. ##### Returns The Lua binary string. #### 11.12.2.7. uint64:__call() Creates a UInt64 Object. Since: 1.11.3 ##### Returns The new UInt64 object. #### 11.12.2.8. uint64:tonumber() Returns a Lua number of the UInt64 value - this may lose precision. Since: 1.11.3 ##### Returns The Lua number. #### 11.12.2.9. uint64:__tostring() Converts the UInt64 into a string. ##### Returns The Lua string. #### 11.12.2.10. uint64:tohex([numbytes]) Returns a hex string of the UInt64 value. Since: 1.11.3 ##### Arguments numbytes (optional) The number of hex-chars/nibbles to generate, negative means uppercase (default=16). ##### Returns The string hex. #### 11.12.2.11. uint64:higher() Returns a Lua number of the higher 32-bits of the UInt64 value. ##### Returns The Lua number. #### 11.12.2.12. uint64:lower() Returns a Lua number of the lower 32-bits of the UInt64 value. ##### Returns The Lua number. #### 11.12.2.13. uint64:__unm() Returns the UInt64, in a new UInt64, since unsigned integers can’t be negated. Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.14. uint64:__add() Adds two UInt64 together and returns a new one (this may wrap the value). Since: 1.11.3 #### 11.12.2.15. uint64:__sub() Subtracts two UInt64 and returns a new one (this may wrap the value). Since: 1.11.3 #### 11.12.2.16. uint64:__mul() Multiplies two UInt64 and returns a new one (this may truncate the value). Since: 1.11.3 #### 11.12.2.17. uint64:__div() Divides two UInt64 and returns a new one (integer divide, no remainder). Trying to divide by zero results in a Lua error. Since: 1.11.3 ##### Returns The UInt64 result. #### 11.12.2.18. uint64:__mod() Divides two UInt64 and returns a new one of the remainder. Trying to modulo by zero results in a Lua error. Since: 1.11.3 ##### Returns The UInt64 result. #### 11.12.2.19. uint64:__pow() The first UInt64 is taken to the power of the second UInt64/number, returning a new one (this may truncate the value). Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.20. uint64:__eq() Returns true if both UInt64 are equal. Since: 1.11.3 #### 11.12.2.21. uint64:__lt() Returns true if first UInt64 < second. Since: 1.11.3 #### 11.12.2.22. uint64:__le() Returns true if first UInt64 ⇐ second. Since: 1.11.3 #### 11.12.2.23. uint64:bnot() Returns a UInt64 of the bitwise 'not' operation. Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.24. uint64:band() Returns a UInt64 of the bitwise 'and' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.25. uint64:bor() Returns a UInt64 of the bitwise 'or' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.26. uint64:bxor() Returns a UInt64 of the bitwise 'xor' operation, with the given number/Int64/UInt64. Note that multiple arguments are allowed. Since: 1.11.3 ##### Returns The UInt64 object. #### 11.12.2.27. uint64:lshift(numbits) Returns a UInt64 of the bitwise logical left-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to left-shift by. ##### Returns The UInt64 object. #### 11.12.2.28. uint64:rshift(numbits) Returns a UInt64 of the bitwise logical right-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to right-shift by. ##### Returns The UInt64 object. #### 11.12.2.29. uint64:arshift(numbits) Returns a UInt64 of the bitwise arithmetic right-shift operation, by the given number of bits. Since: 1.11.3 ##### Arguments numbits The number of bits to right-shift by. ##### Returns The UInt64 object. #### 11.12.2.30. uint64:rol(numbits) Returns a UInt64 of the bitwise left rotation operation, by the given number of bits (up to 63). Since: 1.11.3 ##### Arguments numbits The number of bits to roll left by. ##### Returns The UInt64 object. #### 11.12.2.31. uint64:ror(numbits) Returns a UInt64 of the bitwise right rotation operation, by the given number of bits (up to 63). Since: 1.11.3 ##### Arguments numbits The number of bits to roll right by. ##### Returns The UInt64 object. #### 11.12.2.32. uint64:bswap() Returns a UInt64 of the bytes swapped. This can be used to convert little-endian 64-bit numbers to big-endian 64 bit numbers or vice versa. Since: 1.11.3 ##### Returns The UInt64 object. ## 11.13. Binary encode/decode support The Struct class offers basic facilities to convert Lua values to and from C-style structs in binary Lua strings. This is based on Roberto Ierusalimschy’s Lua struct library found in http://www.inf.puc-rio.br/~roberto/struct/, with some minor modifications as follows: • Added support for Int64/UInt64 being packed/unpacked, using 'e'/'E'. • Can handle 'long long' integers (i8 / I8); though they’re converted to doubles. • Can insert/specify padding anywhere in a struct. ('X' eg. when a string is following a union). • Can report current offset in both pack and unpack (=). • Can mask out return values when you only want to calculate sizes or unmarshal pascal-style strings using ( & ). All but the first of those changes are based on an email from Flemming Madsen, on the lua-users mailing list, which can be found here. The main functions are Struct.pack, which packs multiple Lua values into a struct-like Lua binary string; and Struct.unpack, which unpacks multiple Lua values from a given struct-like Lua binary string. There are some additional helper functions available as well. All functions in the Struct library are called as static member functions, not object methods, so they are invoked as "Struct.pack(…​)" instead of "object:pack(…​)". The fist argument to several of the Struct functions is a format string, which describes the layout of the structure. The format string is a sequence of conversion elements, which respect the current endianness and the current alignment requirements. Initially, the current endianness is the machine’s native endianness and the current alignment requirement is 1 (meaning no alignment at all). You can change these settings with appropriate directives in the format string. The supported elements in the format string are as follows: •  ' (empty space) ignored. • !n' flag to set the current alignment requirement to 'n' (necessarily a power of 2); an absent 'n' means the machine’s native alignment. • >' flag to set mode to big endian (i.e., network-order). • <' flag to set mode to little endian. • x' a padding zero byte with no corresponding Lua value. • b' a signed char. • B' an unsigned char. • h' a signed short (native size). • H' an unsigned short (native size). • l' a signed long (native size). • L' an unsigned long (native size). • T' a size_t (native size). • in' a signed integer with 'n' bytes. An absent 'n' means the native size of an int. • In' like in' but unsigned. • e' signed 8-byte Integer (64-bits, long long), to/from a Int64 object. • E' unsigned 8-byte Integer (64-bits, long long), to/from a UInt64 object. • f' a float (native size). • d' a double (native size). • s' a zero-terminated string. • cn' a sequence of exactly 'n' chars corresponding to a single Lua string. An absent 'n' means 1. When packing, the given string must have at least 'n' characters (extra characters are discarded). • c0' this is like cn', except that the 'n' is given by other means: When packing, 'n' is the length of the given string; when unpacking, 'n' is the value of the previous unpacked value (which must be a number). In that case, this previous value is not returned. • xn' pad to 'n' number of bytes, default 1. • Xn' pad to 'n' alignment, default MAXALIGN. • (' to stop assigning items, and )' start assigning (padding when packing). • =' to return the current position / offset. Note Using i, I, h, H, l, L, f, and T is strongly discouraged, as those sizes are system-dependent. Use the explicitly sized variants instead, such as i4 or E. Unpacking of i/I is done to a Lua number, a double-precision floating point, so unpacking a 64-bit field (i8/I8) will lose precision. Use e/E to unpack into a Wireshark Int64/UInt64 object instead. Since: 1.11.3 ### 11.13.1. Struct #### 11.13.1.1. Struct.pack(format, value) Returns a string containing the values arg1, arg2, etc. packed/encoded according to the format string. ##### Arguments format The format string value One or more Lua value(s) to encode, based on the given format. ##### Returns The packed binary Lua string, plus any positions due to '=' being used in format. #### 11.13.1.2. Struct.unpack(format, struct, [begin]) Unpacks/decodes multiple Lua values from a given struct-like binary Lua string. The number of returned values depends on the format given, plus an additional value of the position where it stopped reading is returned. ##### Arguments format The format string struct The binary Lua string to unpack begin (optional) The position to begin reading from (default=1) ##### Returns One or more values based on format, plus the position it stopped unpacking. #### 11.13.1.3. Struct.size(format) Returns the length of a binary string that would be consumed/handled by the given format string. ##### Arguments format The format string ##### Returns The size number #### 11.13.1.4. Struct.values(format) Returns the number of Lua values contained in the given format string. This will be the number of returned values from a call to Struct.unpack() not including the extra return value of offset position. (i.e., Struct.values() does not count that extra return value) This will also be the number of arguments Struct.pack() expects, not including the format string argument. ##### Arguments format The format string ##### Returns The number of values #### 11.13.1.5. Struct.tohex(bytestring, [lowercase], [separator]) Converts the passed-in binary string to a hex-ascii string. ##### Arguments bytestring A Lua string consisting of binary bytes lowercase (optional) True to use lower-case hex characters (default=false). separator (optional) A string separator to insert between hex bytes (default=nil). ##### Returns The Lua hex-ascii string #### 11.13.1.6. Struct.fromhex(hexbytes, [separator]) Converts the passed-in hex-ascii string to a binary string. ##### Arguments hexbytes A string consisting of hexadecimal bytes like "00 B1 A2" or "1a2b3c4d" separator (optional) A string separator between hex bytes/words (default none). ##### Returns The Lua binary string ## 11.14. GLib Regular Expressions Lua has its own native pattern syntax in the string library, but sometimes a real regex engine is more useful. Wireshark comes with GLib’s Regex implementation, which itself is based on Perl Compatible Regular Expressions (PCRE). This engine is exposed into Wireshark’s Lua engine through the well-known Lrexlib library, following the same syntax and semantics as the Lrexlib PCRE implementation, with a few differences as follows: • There is no support for using custom locale/chartables • dfa_exec() doesn’t take ovecsize nor wscount arguments • dfa_exec() returns boolean true for partial match, without subcapture info • Named subgroups do not return name-keyed entries in the return table (i.e., in match/tfind/exec) • The flags() function still works, returning all flags, but two new functions compile_flags() and match_flags() return just their respective flags, since GLib has a different and smaller set of such flags, for regex compile vs. match functions • Using some assertions and POSIX character classes against strings with non-ASCII characters might match high-order characters, because glib always sets PCRE_UCP even if G_REGEX_RAW is set. For example, [:alpha;] matches certain non-ASCII bytes. The following assertions have this issue: \b, \B, \s, \S, \w, \W. The following character classes have this issue: [:alpha:], [:alnum:], [:lower:], [:upper:], [:space:], [:word:], and [:graph:]. • The compile flag G_REGEX_RAW is always set/used, even if you didn’t specify it. This is because GLib runs PCRE in UTF-8 mode by default, whereas Lua strings are not UTF-aware. Since: 1.11.3 This page is based on the full documentation for Lrexlib at http://rrthomas.github.io/lrexlib/manual.html The GLib Regular expression syntax (which is essentially PCRE syntax) can be found at https://developer.gnome.org/glib/2.38/glib-regex-syntax.html ### 11.14.1. GRegex GLib Regular Expressions based on PCRE. Since: 1.11.3 #### 11.14.1.1. Notes All functions that take a regular expression pattern as an argument will generate an error if that pattern is found invalid by the regex library. All functions that take a string-type regex argument accept a compiled regex too. In this case, the compile flags argument is ignored (should be either supplied as nils or omitted). The capture flag argument cf may also be supplied as a string, whose characters stand for compilation flags. Combinations of the following characters (case sensitive) are supported: • i = G_REGEX_CASELESS - Letters in the pattern match both upper- and lowercase letters. This option can be changed within a pattern by a “(?i)” option setting. • m = G_REGEX_MULTILINE - By default, GRegex treats the strings as consisting of a single line of characters (even if it actually contains newlines). The “start of line” metacharacter (“^”) matches only at the start of the string, while the “end of line” metacharacter (“”) matches only at the end of the string, or before a terminating newline (unless G_REGEX_DOLLAR_ENDONLY is set). When G_REGEX_MULTILINE is set, the “start of line” and “end of line” constructs match immediately following or immediately before any newline in the string, respectively, as well as at the very start and end. This can be changed within a pattern by a “(?m)” option setting.
• s = G_REGEX_DOTALL - A dot metacharater (“.”) in the pattern matches all characters, including newlines. Without it, newlines are excluded. This option can be changed within a pattern by a ("?s") option setting.
• x = G_REGEX_EXTENDED - Whitespace data characters in the pattern are totally ignored except when escaped or inside a character class. Whitespace does not include the VT character (code 11). In addition, characters between an unescaped “#” outside a character class and the next newline character, inclusive, are also ignored. This can be changed within a pattern by a “(?x)” option setting.
• U = G_REGEX_UNGREEDY - Inverts the “greediness” of the quantifiers so that they are not greedy by default, but become greedy if followed by “?”. It can also be set by a “(?U)” option setting within the pattern.

#### 11.14.1.2. GRegex.new(pattern)

Compiles regular expression pattern into a regular expression object whose internal representation is corresponding to the library used. The returned result then can be used by the methods, e.g. match, exec, etc. Regular expression objects are automatically garbage collected.

Since: 1.11.3

##### Arguments
pattern
A Perl-compatible regular expression pattern string
##### Returns

The compiled regular expression (a userdata object)

##### Errors
• A malformed pattern generates a Lua error

#### 11.14.1.3. GRegex.flags([table])

Returns a table containing the numeric values of the constants defined by the regex library, with the keys being the (string) names of the constants. If the table argument is supplied then it is used as the output table, otherwise a new table is created. The constants contained in the returned table can then be used in most functions and methods where compilation flags or execution flags can be specified. They can also be used for comparing with return codes of some functions and methods for determining the reason of failure.

Since: 1.11.3

##### Arguments
table (optional)
A table for placing results into
##### Returns

A table filled with the results.

#### 11.14.1.4. GRegex.compile_flags([table])

Returns a table containing the numeric values of the constants defined by the regex library for compile flags, with the keys being the (string) names of the constants. If the table argument is supplied then it is used as the output table, otherwise a new table is created.

Since: 1.11.3

##### Arguments
table (optional)
A table for placing results into
##### Returns

A table filled with the results.

#### 11.14.1.5. GRegex.match_flags([table])

Returns a table containing the numeric values of the constants defined by the regex library for match flags, with the keys being the (string) names of the constants. If the table argument is supplied then it is used as the output table, otherwise a new table is created.

Since: 1.11.3

##### Arguments
table (optional)
A table for placing results into
##### Returns

A table filled with the results.

#### 11.14.1.6. GRegex.match(subject, pattern, [init], [cf], [ef])

Searches for the first match of the regexp pattern in the string subject, starting from offset init, subject to flags cf and ef. The pattern is compiled each time this is called, unlike the class method match function.

Since: 1.11.3

##### Arguments
subject
Subject string to search
pattern
A Perl-compatible regular expression pattern string or GRegex object
init (optional)
start offset in the subject (can be negative)
cf (optional)
compilation flags (bitwise OR)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns all substring matches ("captures"), in the order they appear in the pattern. false is returned for sub-patterns that did not participate in the match. If the pattern specified no captures then the whole matched substring is returned. On failure, returns nil.

#### 11.14.1.7. GRegex.find(subject, pattern, [init], [cf], [ef])

Searches for the first match of the regexp pattern in the string subject, starting from offset init, subject to flags ef. The pattern is compiled each time this is called, unlike the class method find function.

Since: 1.11.3

##### Arguments
subject
Subject string to search
pattern
A Perl-compatible regular expression pattern string or GRegex object
init (optional)
start offset in the subject (can be negative)
cf (optional)
compilation flags (bitwise OR)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns the start point of the match (a number), the end point of the match (a number), and all substring matches ("captures"), in the order they appear in the pattern. false is returned for sub-patterns that did not participate in the match. On failure, returns nil.

#### 11.14.1.8. GRegex.gmatch(subject, pattern, [init], [cf], [ef])

Returns an iterator for repeated matching of the pattern patt in the string subj, subject to flags cf and ef. The function is intended for use in the generic for Lua construct. The pattern can be a string or a GRegex object previously compiled with GRegex.new().

Since: 1.11.3

##### Arguments
subject
Subject string to search
pattern
A Perl-compatible regular expression pattern string or GRegex object
init (optional)
start offset in the subject (can be negative)
cf (optional)
compilation flags (bitwise OR)
ef (optional)
match execution flags (bitwise OR)
##### Returns

The iterator function is called by Lua. On every iteration (that is, on every match), it returns all captures in the order they appear in the pattern (or the entire match if the pattern specified no captures). The iteration will continue till the subject fails to match.

#### 11.14.1.9. GRegex.gsub(subject, pattern, [repl], [max], [cf], [ef])

Searches for all matches of the pattern in the string subject and replaces them according to the parameters repl and max. The pattern can be a string or a GRegex object previously compiled with GRegex.new().

Since: 1.11.3

For details see: http://rrthomas.github.io/lrexlib/manual.html#gsub

##### Arguments
subject
Subject string to search
pattern
A Perl-compatible regular expression pattern string or GRegex object
repl (optional)
Substitution source string, function, table, false or nil
max (optional)
Maximum number of matches to search for, or control function, or nil
cf (optional)
Compilation flags (bitwise OR)
ef (optional)
Match execution flags (bitwise OR)
##### Returns

On success, returns the subject string with the substitutions made, the number of matches found, and the number of substitutions made.

#### 11.14.1.10. GRegex.split(subject, sep, [cf], [ef])

Splits a subject string subj into parts (sections). The sep parameter is a regular expression pattern representing separators between the sections. The function is intended for use in the generic for Lua construct. The function returns an iterator for repeated matching of the pattern sep in the string subj, subject to flags cf and ef. The sep pattern can be a string or a GRegex object previously compiled with GRegex.new(). Unlike gmatch, there will always be at least one iteration pass, even if there are no matches in the subject.

Since: 1.11.3

##### Arguments
subject
Subject string to search
sep
A Perl-compatible regular expression pattern string or GRegex object
cf (optional)
compilation flags (bitwise OR)
ef (optional)
match execution flags (bitwise OR)
##### Returns

The iterator function is called by Lua. On every iteration, it returns a subject section (can be an empty string), followed by all captures in the order they appear in the sep pattern (or the entire match if the sep pattern specified no captures). If there is no match (this can occur only in the last iteration), then nothing is returned after the subject section. The iteration will continue till the end of the subject.

#### 11.14.1.11. GRegex.version()

Returns a returns a string containing the version of the used library.

Since: 1.11.3

##### Returns

The version string

#### 11.14.1.12. gregex:match(subject, [init], [ef])

Searches for the first match of the regexp pattern in the string subject, starting from offset init, subject to flags ef.

Since: 1.11.3

##### Arguments
subject
Subject string to search
init (optional)
start offset in the subject (can be negative)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns all substring matches (“captures”), in the order they appear in the pattern. false is returned for sub-patterns that did not participate in the match. If the pattern specified no captures then the whole matched substring is returned. nil is returned if the pattern did not match.

#### 11.14.1.13. gregex:find(subject, [init], [ef])

Searches for the first match of the regexp pattern in the string subject, starting from offset init, subject to flags ef.

Since: 1.11.3

##### Arguments
subject
Subject string to search
init (optional)
start offset in the subject (can be negative)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns the start point of the match (a number), the end point of the match (a number), and all substring matches ("captures"), in the order they appear in the pattern. false is returned for sub-patterns that did not participate in the match. On failure, returns nil.

#### 11.14.1.14. gregex:exec(subject, [init], [ef])

Searches for the first match of the compiled GRegex object in the string subject, starting from offset init, subject to the execution match flags ef.

Since: 1.11.3

##### Arguments
subject
Subject string to search
init (optional)
start offset in the subject (can be negative)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns the start point of the first match (a number), the end point of the first match (a number), and the offsets of substring matches (“captures” in Lua terminology) are returned as a third result, in a table. This table contains false in the positions where the corresponding sub-pattern did not participate in the match. On failure, returns nil. Example: If the whole match is at offsets 10,20 and substring matches are at offsets 12,14 and 16,19 then the function returns the following: 10, 20, { 12,14,16,19 }.

#### 11.14.1.15. gregex:dfa_exec(subject, [init], [ef])

Matches a compiled regular expression GRegex object against a given subject string subj, using a DFA matching algorithm.

Since: 1.11.3

##### Arguments
subject
Subject string to search
init (optional)
start offset in the subject (can be negative)
ef (optional)
match execution flags (bitwise OR)
##### Returns

On success, returns the start point of the matches found (a number), a table containing the end points of the matches found, the longer matches first, and the number of matches found as the third return value. On failure, returns nil. Example: If there are 3 matches found starting at offset 10 and ending at offsets 15, 20 and 25 then the function returns the following: 10, { 25,20,15 }, 3

#### 11.14.1.16. gregex:__tostring()

Returns a string containing debug information about the GRegex object.

Since: 1.11.3

The debug string

## 12.1. Introduction

Wireshark can be logically separated into the backend (dissecting protocols, file loading and saving, capturing, etc.) and the frontend (the user interface).

The following frontends are currently maintained by the Wireshark development team:

• Wireshark, Qt based
• TShark, console based

This chapter is focused on the Wireshark frontend, and especially on the Qt interface.

## 12.2. The Qt Application Framework

Qt is a cross-platform application development framework. While we mainly use the core (QtCore) and user interface (QtWidgets) modules, it also supports a number of other modules for specialized application development, such as networking (QtNetwork) and web browsing (QtWebKit).

At the time of this writing (September 2016) most of the main Wireshark application has been ported to Qt. The sections below provide an overview of the application and tips for Qt development in our environment.

### 12.2.1. User Experience Considerations

When creating or modifying Wireshark try to make sure that it will work well on Windows, macOS, and Linux. See Section 12.3, “Human Interface Reference Documents” for details. Additionally, try to keep the following in mind:

Workflow. Excessive navigation and gratuitous dialogs should be avoided or reduced. For example, compared to the legacy UI many alert dialogs have been replaced with status bar messages. Statistics dialogs are displayed immediately instead of requiring that options be specified.

Discoverability and feedback. Most users don’t like to read documentation and instead prefer to learn an application as they use it. Providing feedback increases your sense of control and awareness, and makes the application more enjoyable to use. Most of the Qt dialogs provide a “hint” area near the bottom which shows useful information. For example, the “Follow Stream” dialog shows the packet corresponding to the text under the mouse. The profile management dialog shows a clickable path to the current profile. The main welcome screen shows live interface traffic. Most dialogs have a context menu that shows keyboard shortcuts.

### 12.2.2. Qt Creator

Qt Creator is a full-featured IDE and user interface editor. It makes adding new UI features much easier. It doesn’t work well on Windows at the present time, so it’s recommended that you use it on macOS or Linux.

To edit and build Wireshark using Qt Creator, open the top-level CMakeLists.txt within Qt Creator. It should ask you to choose a build location. Do so. It should then ask you to run CMake. Fill in any desired build arguments (e.g. -D CMAKE_BUILD_TYPE=Debug or -D ENABLE_CCACHE=ON) and click the button. When that completes select BuildOpen Build and Run Kit Selector…​ and make sure wireshark is selected.

Note that Qt Creator uses output created by CMake’s “CodeBlocks” generator. If you run CMake outside of Qt Creator you should use the “CodeBlocks - Unix Makefiles” generator, otherwise Qt Creator will prompt you to re-run CMake.

### 12.2.3. Source Code Overview

Wireshark’s main entry point is in ui/qt/main.cpp. Command-line arguments are processed there and the main application class (WiresharkApplication) instance is created there along with the main window.

The main window along with the rest of the application resides in ui/qt. Due to its size the main window code is split into two modules, main_window.cpp and main_window_slots.cpp.

Most of the modules in ui/qt are dialogs. Although we follow Qt naming conventions for class names, we follow our own conventions by separating file name components with underscores. For example, ColoringRulesDialog is defined in coloring_rules_dialog.cpp, coloring_rules_dialog.h, and coloring_rules_dialog.ui.

General-purpose dialogs are subclasses of QDialog. Dialogs that rely on the current capture file can subclass WiresharkDialog, which provides methods and members that make it easier to access the capture file and to keep the dialog open when the capture file closes.

### 12.2.4. Coding Practices and Naming Conventions

#### 12.2.4.1. Names

The code in ui/qt directory uses three APIs: Qt (which uses InterCapConvention), GLib (which uses underscore_convention), and the Wireshark API (which also uses underscore_convention). As a general rule Wireshark’s Qt code uses InterCapConvention for class names, interCapConvention for methods, and underscore_convention for variables, with a trailing_underscore_ for member variables.

#### 12.2.4.2. Dialogs

Dialogs that work with capture file information shouldn’t close just because the capture file closes. Subclassing WiresharkDialog as described above can make it easier to persist across capture files.

When you create a window with a row of standard “OK” and “Close” buttons at the bottom using Qt Creator you will end up with a subclass of QDialog. This is fine for traditional modal dialogs, but many times the “dialog” needs to behave like a QWindow instead.

Modal dialogs should be constructed with QDialog(parent). Modeless dialogs (windows) should be constructed with QDialog(NULL, Qt::Window). Other combinations (particularly QDialog(parent, Qt::Window)) can lead to odd and inconsistent behavior. Again, subclassing WiresharkDialog will take care of this for you.

Most of the dialogs in ui/qt share many similarities, including method names, widget names, and behavior. Most dialogs should have the following, although it’s not strictly required:

• An updateWidgets() method, which enables and disables widgets depending on the current state and constraints of the dialog. For example, the Coloring Rules dialog disables the Save button if the user has entered an invalid display filter.
• A hintLabel() widget subclassed from QLabel or ElidedLabel, placed just above the dialog button box. The hint label provides guidance and feedback to the user.
• A context menu (ctx_menu_) for additional actions not present in the button box.
• If the dialog box contains a QTreeWidget you might want to add your own QTreeWidgetItem subclass with the following methods:

drawData()
Draws column data with any needed formatting.
colData()
Returns the data for each column as a QVariant. Used for copying as CSV, YAML, etc.
operator<()
Allows sorting columns based on their raw data.

#### 12.2.4.3. Strings

Wireshark’s C code and GLib use UTF-8 encoded character arrays. Qt (specifically QString) uses UTF-16. You can convert a char * to a QString using simple assignment. You can convert a QString to a const char * using qUtf8Printable.

If you’re using GLib string functions or plain old C character array idioms in Qt-only code you’re probably doing something wrong, particularly if you’re manually allocating and releasing memory. QStrings are generally much safer and easier to use. They also make translations easier.

If you need to pass strings between Qt and GLib you can use a number of convenience routines which are defined in ui/qt/qt_ui_utils.h.

If you’re calling a function that returns wmem-allocated memory it might make more sense to add a wrapper function to qt_ui_utils than to call wmem_free in your code.

#### 12.2.4.4. Mixing C and C++

Sometimes we have to call C++ functions from one of Wireshark’s C callbacks and pass C++ objects to or from C. Tap listeners are a common example. The C++ FAQ link:http://www. parashift.com/c++-faq/mixing-c-and-cpp.html:[describes how to do this safely].

Tapping usually involves declaring static methods for callbacks, passing this as the tap data.

#### 12.2.4.5. Internationalization and Translation

Qt provides a convenient method for translating text: Qobject::tr(), usually available as tr().

However, please avoid using tr() for static strings and define them in *.ui files instead. tr() on manually created objects like QMenu are not automatically retranslated and must instead be manually translated using changeEvent() and retranslateUi(). See summary_dialog.[ch] for an example of this.

Note If your object life is short and your components are (re)created dynamically then it is ok to use tr().

In most cases you should handle the changeEvent in order to catch QEvent::LanguageChange.

Qt makes translating the Wireshark UI into different languages easy. To add a new translation, do the following:

• (Recommended) Add a flag image for your language in images/languages/XX.svg. Update image/languages/languages.qrc accordingly.
• Run lupdate ui/qt -ts ui/qt/wireshark_XX.ts to generate/update your translation file.
• Translate with Qt Linguist: linguist ui/qt/wireshark_XX.ts.
• Do a test build and make sure the generated wireshark_XX.qm binary file is included.
• Push your translation to Gerrit for review. See Section 3.9, “Contribute your changes” for details.

Alternatively you can put your QM and flag files in the languages directory in the Wireshark user configuration directory ($XDG_CONFIG_HOME/wireshark/languages/ or$HOME/.wireshark/languages/ on UNIX).

You can also manage translations online with Transifex.

Each week translations are automatically synchronized with the source code through the following steps:

• pull ts from Transifex
• lupdate ts file
• push and commit on Gerrit
• push ts on Transifex

#### 12.2.4.6. Colors

Qt provides a number of colors via the QPalette class. Use this class when you need a standard color provided by the underlying operating system.

Wireshark uses an extended version of the Tango Color Palette for many interface elements that require custom colors. This includes the I/O graphs, sequence diagrams, and RTP streams. Please use this palette (defined in tango_colors.h and the ColorUtils class) if QPalette doesn’t meet your needs.

### 12.2.5. Other Issues and Information

The main window has many QActions which are shared with child widgets. See ui/qt/proto_tree.cpp for an example of this.

GammaRay lets you inspect the internals of a running Qt application similar to Spy++ on Windows.

## 12.3. Human Interface Reference Documents

Wireshark runs on a number of platforms, primarily Windows, macOS, and Linux. It should conform to the Windows, macOS, GNOME, and KDE human interface guidelines as much as possible. Unfortunately, creating a feature that works well across these platforms can sometimes be a juggling act since the human interface guidelines for each platform often contradict one another. If you run into trouble you can ask the wireshark-dev mailing list as well as the User Experience Stack Exchange listed below.

For further reference, see the following:

## Chapter 13. Wireshark Tests

The Wireshark sources include a collection of Python scripts that test the features of Wireshark, TShark, Dumpcap, and other programs that accompany Wireshark. These are located in the test directory of the Wireshark source tree.

The command line options of Wireshark and its companion command line tools are numerous. These tests help to ensure that we don’t introduce bugs as Wireshark grows and evolves.

## 13.1. Quick Start

The recommended steps to prepare for and to run tests:

• Install two Python packages, pytest: pip install pytest pytest-xdist
• Build programs (“wireshark”, “tshark”, etc.): ninja
• Build additional programs for the “unittests” suite: ninja test-programs
• Run tests in the build directory: pytest

Replace ninja test-programs by make test-programs as needed.

The test suite will attempt to test as much as possible and skip tests when its dependencies are not satisfied. For example, packet capture tests require a Loopback interface and capture privileges. To avoid capture tests, pass the --disable-capture option.

List available tests with pytest --collectonly. Enable verbose output with pytest --verbose. For more details, see Section 13.4, “Listing And Running Tests (pytest)”.

If for whatever reason pytest is too old or unavailable, you could use a more limited test runner, test/test.py. Use test/test.py --help to see all options. For more details, see Section 13.3, “Listing And Running Tests”.

CMake currently runs test/test.py when the “test” target is built.

## 13.2. Test suite structure

The following sections describes how the test suite is organized.

### 13.2.1. Test Coverage And Availability

The testing framework can run programs and check their stdout, stderr, and exit codes. It cannot interact with the Wireshark UI. Tests cover capture, command line options, decryption, file format support and conversion, Lua scripting, and other functionality.

Available tests depend on the libraries with which Wireshark was built. For example, some decryption tests depend on a minimum version of Libgcrypt and Lua tests depend on Lua.

Capture tests depend on the permissions of the user running the test script. We assume that the test user has capture permissions on Windows and macOS and capture tests are enabled by default on those platforms.

If a feature is unavailable, the test will be skipped. For example, if an old version of Libgcrypt is in use, then some decryption tests will be skipped while other tests can still run to completion.

### 13.2.2. Suites, Cases, and Tests

The test/test.py script uses Python’s “unittest” module. Our tests are patterned after it, and individual tests are organized according to suites, cases, and individual tests. Suites correspond to python modules that match the pattern “suite_*.py”. Cases correspond to one or more classes in each module, and case class methods matching the pattern ”test_*” correspond to individual tests. For example, the invalid capture filter test in the TShark capture command line options test case in the command line options suite has the ID “suite_clopts.case_tshark_capture_clopts.test_tshark_invalid_capfilter”.

### 13.2.3. pytest fixtures

A test has typically additional dependencies, like the path to an executable, the path to a capture file, a configuration directory, the availability of an optional library, and so on. The Python unittest library is quite limited in expressing test dependencies, these are typically specified on the class instance itself (self) or via globals.

pytest is a better test framework which has full parallelization support (test-level instead of just suite-level), provides nicer test reports, and allows modular fixtures. Ideally the test suite should fully switch to pytest, but in meantime a compatibility layer is provided via the “fixtures” module.

A fixture is a function decorated with @fixtures.fixture and can either call fixtures.skip("reason") to skip tests that depend on the fixture, or return/yield a value. Test functions (and other fixture functions) can receive the fixture value by using the name of the fixture function as function parameters. Common fixtures are available in fixtures_ws.py and includes cmd_tshark for the path to the tshark executable and capture_file for a factory function that produces the path to a capture file.

Each unittest test case must be decorated with @fixtures.uses_fixtures to ensure that unittest test classes can actually request fixture dependencies.

## 13.3. Listing And Running Tests

Tests can be run via the test/test.py Python script. To run all tests, either run test/test.py in the directory that contains the Wireshark executables (wireshark, tshark, etc.), or pass the the executable path via the -p flag:

$python3 test/test.py -p /path/to/wireshark-build/run You can list tests by passing one or more complete or partial names to tshark.py. The -l flag lists tests. By default all tests are shown. # List all tests$ python3 test/test.py -l
$python3 test/test.py -l all$ python3 test/test.py --list
$python3 test/test.py --list all # List only tests containing "dumpcap"$ python3 test/test.py -l dumpcap

# List all suites
$python3 test/test.py --list-suites # List all suites and cases$ python3 test/test.py --list-cases

If one of the listing flags is not present, tests are run. If no names or all is supplied, all tests are run. Otherwise tests that match are run.

# Run all tests
$python3 test/test.py$ python3 test/test.py all

# Only run tests containing "dumpcap"
$python3 test/test.py -l dumpcap # Run the "clopts" suite$ python3 test/test.py suite_clopts

Run python3 test/test.py --help for all available options.

## 13.4. Listing And Running Tests (pytest)

Tests can also be run with pytest. Advantages include finer test selection, full parallelism, nicer test execution summaries, better output in case of failures (containing the contents of variables) and the ability to open the PDB debugger on failing tests.

To get started, install pytest 3.0 or newer and pytest-xdist:

# Install required packages on Ubuntu 18.04 or Debian jessie-backports
$sudo apt install python3-pytest python3-pytest-xdist # Install required packages on other systems$ pip install pytest pytest-xdist

Run pytest in the Wireshark build directory, Wireshark binaries are assumed to be present in the run subdirectory (or run\RelWithDebInfo on Windows).

# Run all tests
$cd /path/to/wireshark/build$ pytest

# Run all except capture tests
$pytest --disable-capture # Run all tests with "decryption" in its name$ pytest -k decryption

# Run all tests with an explicit path to the Wireshark executables
$pytest --program-path /path/to/wireshark/build/run To list tests without actually executing them, use the --collect-only option: # List all tests$ pytest --collect-only

# List only tests containing both "dfilter" and "tvb"
$pytest --collect-only -k "dfilter and tvb" The test suite will fail tests when programs are missing. When only a subset of programs are built or when some programs are disabled, then the test suite can be instructed to skip instead of fail tests: # Run tests when libpcap support is disabled (-DENABLE_PCAP=OFF)$ pytest --skip-missing-programs dumpcap,rawshark

# Run tests and ignore all tests with missing program dependencies
$pytest --skip-missing-programs all To open a Python debugger (PDB) on failing tests, use the --pdb option and disable parallelism with the -n0 option: # Run decryption tests sequentially and open a debugger on failing tests$ pytest -n0 --pdb -k decryption

Note that with the option --pdb, stray processes are not killed on test failures since the SubprocessTestCase.tearDown method is not executed. This limitation might be addressed in the future.

## 13.5. Adding Or Modifying Tests

Tests must be in a Python module whose name matches “suite_*.py”. The module must contain one or more subclasses of “SubprocessTestCase” or “unittest.TestCase”. “SubprocessTestCase” is recommended since it contains several convenience methods for running processes, checking output, and displaying error information. Each test case method whose name starts with “test_” constitutes an individual test.

Success or failure conditions can be signalled using the “unittest.assertXXX()” or “subprocesstest.assertXXX()” methods.

Test dependencies (such as programs, directories, or the environment variables) are injected through method parameters. Commonly used fixtures include cmd_tshark and capture_file. See also Section 13.2.3, “pytest fixtures”.

The “subprocesstest” class contains the following methods for running processes. Stdout and stderr is written to “<test id>.log”:

startProcess
Start a process without waiting for it to finish.
runProcess
Start a process and wait for it to finish.
assertRun
Start a process, wait for it to finish, and check its exit code.

All of the current tests run one or more of Wireshark’s suite of executables and either check their return code or their output. A simple example is “suite_clopts.case_basic_clopts.test_existing_file”, which reads a capture file using TShark and checks its exit code.

import subprocesstest
import fixtures

@fixtures.mark_usefixtures('test_env')
@fixtures.uses_fixtures
class case_basic_clopts(subprocesstest.SubprocessTestCase):
def test_existing_file(self, cmd_tshark, capture_file):
self.assertRun((cmd_tshark, '-r', capture_file('dhcp.pcap')))

Program output can be checked using SubprocessTestCase.grepOutput, SubprocessTestCase.countOutput or other unittest.assert* methods:

import subprocesstest
import fixtures

@fixtures.mark_usefixtures('test_env')
@fixtures.uses_fixtures
class case_decrypt_80211(subprocesstest.SubprocessTestCase):
def test_80211_wpa_psk(self, cmd_tshark, capture_file):
tshark_proc = self.assertRun((cmd_tshark,
'-o', 'wlan.enable_decryption: TRUE',
'-Tfields',
'-e', 'http.request.uri',
'-r', capture_file('wpa-Induction.pcap.gz'),
'-Y', 'http',
))
self.assertIn('favicon.ico', tshark_proc.stdout_str)

Tests can be run in parallel. This means that any files you create must be unique for each test. “subprocesstest.filename_from_id” can be used to generate a filename based on the current test name. It also ensures that the file will be automatically removed after the test has run.

## Chapter 14. This Document’s License (GPL)

As with the original license and documentation distributed with Wireshark, this document is covered by the GNU General Public License (GNU GPL).

If you haven’t read the GPL before, please do so. It explains all the things that you are allowed to do with this code and documentation.

		    GNU GENERAL PUBLIC LICENSE
Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

Preamble

The licenses for most software are designed to take away your
freedom to share and change it.  By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users.  This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it.  (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.)  You can apply it to

When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it
in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their
rights.

We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
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program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and
modification follow.

TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License.  The "Program", below,
refers to any such program or work, and a "work based on the Program"
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language.  (Hereinafter, translation is included without limitation in

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.

1. You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.

You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.

2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

a) You must cause the modified files to carry prominent notices
stating that you changed the files and the date of any change.

b) You must cause any work that you distribute or publish, that in
whole or in part contains or is derived from the Program or any
part thereof, to be licensed as a whole at no charge to all third
parties under the terms of this License.

c) If the modified program normally reads commands interactively
when run, you must cause it, when started running for such
interactive use in the most ordinary way, to print or display an
announcement including an appropriate copyright notice and a
notice that there is no warranty (or else, saying that you provide
a warranty) and that users may redistribute the program under
these conditions, and telling the user how to view a copy of this
License.  (Exception: if the Program itself is interactive but
does not normally print such an announcement, your work based on
the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
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distribute the same sections as part of a whole which is a work based
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Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
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In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
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3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
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a) Accompany it with the complete corresponding machine-readable
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b) Accompany it with a written offer, valid for at least three
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If distribution of executable or object code is made by offering
access to copy the source code from the same place counts as
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4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
However, parties who have received copies, or rights, from you under
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Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

6. Each time you redistribute the Program (or any work based on the
original licensor to copy, distribute or modify the Program subject to
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You are not responsible for enforcing compliance by third parties to

7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
excuse you from the conditions of this License.  If you cannot
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License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.

It is not the purpose of this section to induce you to infringe any
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such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

9. The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and "any
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either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
Foundation.

10. If you wish to incorporate parts of the Program into other free
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Software Foundation, write to the Free Software Foundation; we sometimes
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NO WARRANTY

11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.

12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year>  <name of author>

This program is free software; you can redistribute it and/or modify
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:

Gnomovision version 69, Copyright (C) year  name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type show c' for details.

The hypothetical commands show w' and show c' should show the appropriate
parts of the General Public License.  Of course, the commands you use may
be called something other than show w' and show c'; they could even be

You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary.  Here is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright interest in the program
Gnomovision' (which makes passes at compilers) written by James Hacker.

<signature of Ty Coon>, 1 April 1989
Ty Coon, President of Vice

Public License instead of this License.