Re: SYNCOOKIE authentication problems

From: David Malone <dwmalone_at_maths.tcd.ie>
Date: Fri, 29 Jun 2007 11:51:40 +0100
On Wed, Jun 27, 2007 at 06:43:11PM -0700, Steve Kargl wrote:
> Any advice on how to isolate or avoid?
> 
> Jun 27 18:31:19 node11 kernel: TCP: [192.168.0.11]:59661 to 
> [192.168.0.11]:63266 tcpflags 0x10<ACK>; syncache_expand: Segment failed
> SYNCOOKIE authentication, segment rejected (probably spoofed)

It looks like you tried to open a TCP connection to yourself, but
the connection failed. You could try leaving a tcpdump running:

	tcpdump -i whatever_interface -w /tmp/synfinrstdata -s 1500 'tcp[tcpflags] & (tcp-syn|tcp-fin|tcp-rst) != 0'

while your MPI app runs and then we can have a look at the packets
that caused the problem. The above should collect all TCP SYN, FIN
and RST packets, which would probably be enough to diagnose the
problem.

	David.
Received on Fri Jun 29 2007 - 12:55:50 UTC

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