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Wireshark-dev: Re: [Wireshark-dev] Dissecting UDP conversations that encapsulate UDPdata

From: "Anders Broman" <anders.broman@xxxxxxxxxxxx>
Date: Wed, 11 Nov 2009 12:54:34 +0100
Hi,
I'm not intierly sure how this is supposed to work but my understanding
is that one of the heuristic
Conditions is that the "fp structure" is filled in/attatched to the
packet.

Does the code filling in this structure know the IP address and port
pair going to be used for the UDP transport?
If so that code could set up a conversation and set the UDP conversation
dissector.
That means that for that UDP IP and port par "dissect_fp..() would be
called directly not the heuristic.
I asume that any IP payload traffic carried inside of this UDP reaffic
would have other IP address port combinations?
With this setup there is no need for a FP heuristic dissector at all.

As for thye other question regarding the trace attached to the bug is
there enough iformation in the (NBAP?)
Message(s) to fill in the fp struct if so code to do that could be added
to the NBAP dissector + setting up of a conversation.

Regards
Anders


-----Original Message-----
From: wireshark-dev-bounces@xxxxxxxxxxxxx
[mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of Tobias Witek
Sent: den 11 november 2009 11:33
To: wireshark-dev@xxxxxxxxxxxxx
Subject: [Wireshark-dev] Dissecting UDP conversations that encapsulate
UDPdata

Hello,

I am currently trying to extend the UMTS FP protocol to also handle FP
frames sent via UDP. To avoid modifications in the UDP dissector, my
plan was to use a heuristic to detect the first UDP packet of each
stream that contains FP and assign a conversation dissector to the whole
conversation.

The problem is that these frames can in turn contain UDP (e.g. DNS
queries). The solution outlined above would dissect these as FP again,
if I understand correctly (as a separate conversation).

As far as I see, I would need a way to let the heuristic determine that
the current frame was already parsed as FP (respectively, is already
part of a different UDP conversation) and should not be treated as FP.

Currently, I see no way to do this and would be very happy about any
suggestions!

Regards,

Tobias
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