Wireshark mailing list archives

Re: DESEGMENT_ONE_MORE_SEGMENT usage/fault


From: wsgd <wsgd () free fr>
Date: Mon, 22 Mar 2010 20:32:50 +0100

Are you above TCP ?
Inside Wireshark,
 verify that  "Edit / Preferences / Protocols / TCP / Allow subdissector 
to reassemble TCP streams"
 is checked.


Olivier


Lajos Oláh a écrit :
Hi all,
 
I'm developing a dissector dissecting MTP2 packets from RTP stream 
(for semipermanent connections). I used part of the code from 
packet-lapd.c (it is almost tha same except that it is for the LAPD 
protocol).
 
In that code, when the RTP data ends in the middle of an MTP2 packet, 
the dissector sets pinfo->desegment_offset = 0 and 
pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT and exits.
 
In the README.developer, it is written that if a dissector sets these 
values and returns it will be called again with data from the actual 
packet plus the data from the next packet. But this never happens. My 
dissector is never called with more data than 1 RTP data filed (40 
byte in my case).
 
I've also created debug patches for the TELNET dissector 
(packet-telnet.c) (to test this defregmentation functionality outside 
my buggy code) to force the dissector to always request data from the 
next packet using DESEGMENT_ONE_MORE_SEGMENT but it was failing as well.
 
Have anyone of You encountered such problem? Am I doing something wrong?
 
Do I need to do something extra to get this feature work or we have a 
wireshark bug?
 
Please share experiences with these defregmentation method.
 
(I've attached my code with debug printing included)
 
Thanks.



*LAJOS OLAH *
*System Test Engineer*

Ericsson Telecom Hungary
RFT/D
Budapest, Irinyi Jozsef Street 4-20
1017, Hungary
Phone +36309537333
lajos.olah () ericsson com
_www.ericsson.com_





Ericsson Magyarország Kft., Székhely: Budapest, Laborc u.1. 
Nyilvántartó cégbíróság: Fővárosi Bíróság. Cégjegyzékszám: 01-09-070937

This Communication is Confidential. We only send and receive email on 
the basis of the term set out at _www.ericsson.com/email_disclaimer_ 
<http://www.ericsson.com/email_disclaimer>
 
 
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