NetBSD Problem Report #39305
From dyoung@cuw.ojctech.com Wed Aug 6 19:29:08 2008
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Date: Wed, 6 Aug 2008 13:26:31 -0500 (CDT)
From: dyoung@cuw.ojctech.com
Reply-To: dyoung@cuw.ojctech.com
To: gnats-bugs@gnats.NetBSD.org
Subject: loops through gre(4) cause a hang or crash
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>Number: 39305
>Category: kern
>Synopsis: loops through gre(4) cause a hang or crash
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: dyoung
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Wed Aug 06 19:30:00 +0000 2008
>Last-Modified: Wed Aug 06 21:09:47 +0000 2008
>Originator: David Young
>Release: NetBSD 4.99.70
>Organization:
OJC Technologies * Urbana, Illinois
>Environment:
System: NetBSD cuw 4.99.70 NetBSD 4.99.70 (elan) #0: Fri Jul 18 17:21:29 CDT 2008 dyoung@cuw.ojctech.com:/u5/dyoung-scratch/scratch-pm/i386/O/sys/arch/i386/compile/elan i386
Architecture: i386
Machine: i386
>Description:
If a gre(4) is configured with inner destination address equal to
outer destination address, the kernel will loop forever trying
to deliver packets that pass through that gre(4) instance.
>How-To-Repeat:
ifconfig gre0 create inet$SIX $SRC0 $DST tunnel inet$SIX $SRC1 $DST
ifconfig gre0 up
ping$SIX $DST
>Fix:
Short-term: as packets traverse a gre(4), tag them in gre_output()
with an identifier for that gre instance. But first check
packets in gre_output() for that instance's tag. If the
instance tag is already present, send an ICMP/ICMPv6 error
response to the sender to indicate the loop.
Long-term: in addition to the above, let us configure two routes
to any destination---i.e., multipath routing. Qualify a
gre(4)'s outer destination address so that it resolves to
a different route than the route to itself. Use route
metrics (say) to make the system prefer the route through
gre(4).
>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: kern-bug-people->dyoung
Responsible-Changed-By: dyoung@NetBSD.org
Responsible-Changed-When: Wed, 06 Aug 2008 21:09:47 +0000
Responsible-Changed-Why:
I'll fix it in time for 5.0.
>Unformatted:
(Contact us)
$NetBSD: query-full-pr,v 1.39 2013/11/01 18:47:49 spz Exp $
$NetBSD: gnats_config.sh,v 1.8 2006/05/07 09:23:38 tsutsui Exp $
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