Wireshark-bugs: [Wireshark-bugs] [Bug 8802] New: Incorrect decoding of Layer2 Info Extended Comm
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Fri, 14 Jun 2013 20:32:52 +0000
Bug ID 8802
Summary Incorrect decoding of Layer2 Info Extended Community
Classification Unclassified
Product Wireshark
Version 1.10.0
Hardware x86-64
OS Windows 7
Status UNCONFIRMED
Severity Normal
Priority Low
Component Dissection engine (libwireshark)
Assignee bugzilla-admin@wireshark.org
Reporter alexander.okonnikov@gmail.com 

Created attachment 10987 [details]
BGP VPLS dump

Build Information:
Version 1.10.0 (SVN Rev 49790 from /trunk-1.10)

Copyright 1998-2013 Gerald Combs <gerald@wireshark.org> 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 (64-bit) with GTK+ 2.24.14, with Cairo 1.10.2, with Pango 1.30.1, with
GLib 2.34.1, with WinPcap (4_1_3), with libz 1.2.5, without POSIX capabilities,
without libnl, with SMI 0.4.8, with c-ares 1.9.1, with Lua 5.1, without Python,
with GnuTLS 2.12.18, with Gcrypt 1.4.6, without Kerberos, with GeoIP, with
PortAudio V19-devel (built Jun  5 2013), with AirPcap.

Running on 64-bit Windows 7 Service Pack 1, build 7601, with WinPcap version
4.1.3 (packet.dll version 4.1.0.2980), based on libpcap version 1.0 branch
1_0_rel0b (20091008), GnuTLS 2.12.18, Gcrypt 1.4.6, without AirPcap.
Intel(R) Core(TM)2 Duo CPU     P8400  @ 2.26GHz, with 8086MB of physical
memory.


Built using Microsoft Visual C++ 10.0 build 40219

Wireshark is Open Source Software released under the GNU General Public
License.

Check the man page and http://www.wireshark.org for more information.
--
Within BGP Update message for BGP VPLS (RFC 4761) some parts of Extended
Community "Layer2 Info" are incorrectly decoded:

1. Encapsulation - Unknown (0x13). Per RFC 4761 encap type 0x13 is "VPLS"
(clause 3.2.4);

2. Control Flags - per RFC 4761 (clause 3.2.4) two least-significant bits (6
and 7) are defined as:
"C" (bit 6, Control Word): value 1 - Control Word is required - and value 0 -
Control Word is not required; decoding is correct (at least for value 0);
"S" (bit 7, Sequence delivery): value 1 - Sequence delivery is required - and
value 0 - Sequence delivery is not required; decoding is incorrect, because for
value 0 (sequence delivery is not required) you provide description that
"Sequence delivery  is required".

Also, there is description (at the same string) "F Flag (reserved) set. IETF
document draft-ietf-l2vpn-vpls-multihoming (clause 3.3.1) updates RFC 4761 and
defines two additional bits within Control Flags byte - D (bit 0, "Down") and F
(bit 2, "Flush"). You provide description that "F Flag (reserved) set" when
this flag actually is not set (value 0). Furthermore, you don't provide
description about status of flag D (in attached dump in the first packet flag D
is set and unset in the second packet).

See attached dump for details.

Thanks.

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