Wireshark-bugs: [Wireshark-bugs] [Bug 6101] New: CSN Ack/Nack Description wrongly handled in gsm

Date: Thu, 7 Jul 2011 00:15:51 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6101

           Summary: CSN Ack/Nack Description wrongly handled in
                    gsm_rlcmac_dl dissector (3GPP TS 44.060)
           Product: Wireshark
           Version: 1.7.x (Experimental)
          Platform: x86
        OS/Version: Windows XP
            Status: NEW
          Severity: Normal
          Priority: Low
         Component: Wireshark
        AssignedTo: bugzilla-admin@xxxxxxxxxxxxx
        ReportedBy: lhaessler@xxxxxxxxxxxxxxxxxx


Build Information:
Version 1.7.0-TEST_BUILD_LHA-01 (SVN Rev Unknown from unknown)

Copyright 1998-2011 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled (32-bit) with GTK+ 2.22.1, with GLib 2.26.1, with WinPcap (version
unknown), with libz 1.2.5, without POSIX capabilities, without libpcre, with
SMI
0.4.8, with c-ares 1.7.1, with Lua 5.1, without Python, with GnuTLS 2.10.3,
with
Gcrypt 1.4.6, with MIT Kerberos, with GeoIP, with PortAudio V19-devel (built
Jul
 6 2011), with AirPcap.

Running on Windows XP Service Pack 3, build 2600, with WinPcap version 4.1.2
(packet.dll version 4.1.0.2001), based on libpcap version 1.0 branch 1_0_rel0b
(20091008), GnuTLS 2.10.3, Gcrypt 1.4.6, without AirPcap.

Built using Microsoft Visual C++ 9.0 build 21022
--
CSN description of IE Ack/Nack Description (3GPP TS 44.060) is not correctly
managed by CSN decoder.

That's lead to wrong decoding of GPRS RLC/MAC control blocks (Packet Uplink
Ack/Nack); the following error is observed: [Dissector bug, protocol GSM RLC
MAC: tvbuff.c:1739: failed assertion "DISSECTOR_ASSERT_NOT_REACHED"]

Please find attached a capture file (gprs.pcap) showing the bug with wireshark
v1.6.0.

Two issues observed: 
1) FINAL_ACK_INDICATION  bit not correctly displayed
2) 64 bits RECEIVED_BLOCK_BITMAP not correcly decoded


Please also find the patch fixing those issues (rlcmac_csn_acknack.patch)

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