Wireshark-dev: Re: [Wireshark-dev] Fileshark (AKA Dissecting Files with Wireshark)
From: Gilbert Ramirez <[email protected]>
Date: Thu, 20 Jun 2013 14:39:56 -0700
I've written some tools to read various file formats, and what I have learned from this is that it's really most useful to create:

1. a generic library for reading a file format.
2. an application dissector (i.e, a FileShark dissector) for using the generic library, and providing the API that the application (FileShark) wnats.
3. And on top of that, FileShark itself.

This is good so that other programs besides FileShark can make use of the generic libraries.

This is different from how we did wiretap, in which the logic for dissecting a packet capture is embedded directly in the wiretap module. If another application wanted to decode packet captures, it would have to link against wiretap, and use its APIs.

This would mean we might spawn some new projects that read the file formats, and those would be separate from FileShark itself. But, that's more generally useful.

Taking this a step further, maybe it's time to "harden" the APIs of the various modules of Wireshark, and also break apart Wireshark. wiretap could be removed entirely out of the Wireshark source base, and put into its own SCM repo and released independently.

Gilbert





On Thu, Jun 20, 2013 at 2:15 PM, Guy Harris <[email protected]> wrote:

On Jun 20, 2013, at 11:54 AM, Evan Huus <[email protected]> wrote:

> 3. Create a separate application called Fileshark that doesn't use
> wiretap and links only against libfiledissectors. When dissecting
> files directly, wiretap simply gets in the way. Additionally, people
> have pointed out several possible UI changes that make sense for files
> but not for packets. While hopefully Fileshark and Wireshark will be
> able to share much of their code, there are still places where they
> will diverge and we want to be able to do that cleanly.

Yes.  For example, in Fileshark, you either:

        1) might want to show, in a summary pane, multiple items for multiple sections/records/etc. of a file

or

        2) show only one pane, a detail pane, so that with everything closed up, you have a list of sections/records/etc..

> Some of the consequences of this:
> - Wireshark proper will not open non-capture files directly. It will
> parse files it sees over transport protocols, but to parse an on-disk
> file directly will require opening it in Fileshark.

Note, BTW, that you might well want to have file dissectors for various forms of capture files that Wireshark can read; if you open those files in Wireshark, they'd show you the packets (and perhaps other records), but if you open them in Fileshark, they'd show you the file header (if there is one) and the file records (including the raw contents of record headers, etc.) - that might be a useful tool for Wireshark developers reverse-engineering features of not-publicly-documented file formats.
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