Wireshark-dev: Re: [Wireshark-dev] Tshark: proto_tree not created on first pass with tap define
From: Paul Offord <[email protected]>
Date: Mon, 13 Feb 2017 07:40:16 +0000
I'll accept whatever strategy there is for taps vs. dissectors.  A few points:

* TRANSUM can only work if it is able to calculate values based on other dissected values (such as smb2.msg_id), so provided the dissected values are available to the tap on both passes (via a protocol tree or otherwise) that would be OK
* I've never written a tap before but I think if the tap runs after all other dissectors this wouldn't be a problem for TRANSUM
* When a dissector registers a tap, Wireshark passes a protocol tree to a dissector based on the criteria Michael defined, so some thought would be needed regarding this for consistency (unless Tshark shouldn't work like Wireshark)
* The LUA framework passes the protocol tree to a LUA dissectors when used with Wireshark or Tshark - again a consistency issue

Best regards...Paul

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Guy Harris
Sent: 13 February 2017 03:55
To: Developer support list for Wireshark <[email protected]>
Subject: Re: [Wireshark-dev] Tshark: proto_tree not created on first pass with tap defined

The underlying problem here appears to be that the TRANSUM post-dissector is not only adding stuff to the protocol tree, which obviously doesn't need to be done if there is no protocol tree, but is also doing *analysis* of the packet information.

The latter of those should *not* be done in a dissector - it should be done in a tap.

Unfortunately, *currently*, taps are run after all dissectors, including post-dissectors, are run, which might not work for this purpose.  If so, what we probably would need here is to have a mechanism to allow taps to be run "early".  For now, we could define "early" as "before the post-dissectors are run".
Sent via:    Wireshark-dev mailing list <[email protected]>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev
             mailto:[email protected]?subject=unsubscribe


This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system.

Any views or opinions expressed are solely those of the author and do not necessarily represent those of Advance Seven Ltd. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e-mail transmission.

Advance Seven Ltd. Registered in England & Wales numbered 2373877 at Endeavour House, Coopers End Lane, Stansted, Essex CM24 1SJ

This email has been scanned by the Symantec Email Security.cloud service.
For more information please visit http://www.symanteccloud.com