Date: Fri, 29 Jun 2007 11:51:40 +0100 From: David Malone <dwmalone@maths.tcd.ie> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: freebsd-current@freebsd.org Subject: Re: SYNCOOKIE authentication problems Message-ID: <20070629105140.GA51586@walton.maths.tcd.ie> In-Reply-To: <20070628014311.GA50012@troutmask.apl.washington.edu>
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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.home | help
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