[Fwd: [OCCAID] Advisory: Extended Community bit crashing Quagga and Zebra BGPd]

Andrew Alston aa at tenet.ac.za
Tue Dec 20 16:44:32 CET 2005

Hi Guys,

Just figured I would pass this onto the list, to let people know about 
this particular bug.  AS5430 as ceased the announcement in the mean time 
till they figure out the problem (My thanks to them for that), but 
figured people should be aware of the quagga bug.

Thanks also to James for finding this one so fast.

Andrew Alston
TENET - Technical Officer

-------- Original Message --------
Subject: 	[OCCAID] Advisory: Extended Community bit crashing Quagga and 
Zebra BGPd
Date: 	Tue, 20 Dec 2005 10:19:36 -0500
From: 	James Jun <james at towardex.com>
Organization: 	TowardEX Technologies, Inc.
To: 	<occaid at cnacs.occaid.org>

It appears Extended Community bit used for MPLS VPN, when improperly set,
crashes Quagga version 0.96.5, Zebra versions 0.93 through 0.94 running on
FreeBSD 5.x and 6.0 platforms.

APC4 release is not affected, running on OCCAID backbone, however there are
many downstream BGP sessions running off of Quagga 0.96.5 going down a lot
lately, which lead us to find out what prefix is crashing them.

It seems it is being received from AS5430 peering, with unknown Extended
Community, which happens to segfault bunch of bgpd's:

  5430 25538
    2001:4830:1::3 (metric 1980) from 2001:4830:1::3 (
      Origin IGP, metric 0, localpref 200, valid, internal, best
      Community: 30071:58012
      Extended Community: Unknown

Courtesy of Andrew Alston from TENET:

(gdb) bt
#0  0x2818237b in kill () from /lib/libc.so.5
#1  0x28177422 in raise () from /lib/libc.so.5
#2  0x281e9c1b in abort () from /lib/libc.so.5
#3  0x2818d5b9 in ldexp () from /lib/libc.so.5
#4  0x2818d5fd in ldexp () from /lib/libc.so.5
#5  0x2818e163 in ldexp () from /lib/libc.so.5
#6  0x2818e743 in ldexp () from /lib/libc.so.5
#7  0x2818e874 in free () from /lib/libc.so.5
#8  0x0807102a in ecommunity_free (ecom=0x832a710) at
#9  0x0805596b in bgp_attr_unintern (attr=0x832c480) at
#10 0x0806abbd in bgp_update_packet (peer=0x8251000,
                  afi=2, safi=1 '\001') at bgp_packet.c:224
#11 0x0806b361 in bgp_write_packet (peer=0x8251000) at
#12 0x0806b45b in bgp_write (thread=0x0) at
#13 0x0808c705 in thread_call (thread=0xbfbfecfc) at
#14 0x0804a2ae in main (argc=4, argv=0xbfbfedcc) at

Until we can reproduce the problem here at the lab and get this resolved,
for the purpose of ensuring stable network operations for our customers, we
are temporarily filtering all Extended Communities bits entering our


James Jun
IP Infrastructure & Technology Services
TowardEX Technologies, Inc.
WWW: http://www.towardex.com
Email: james at towardex.com
Office: +1 (617) 459-4051 Ext. 179
Mobile: +1 (978) 394-2867

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