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Date: Wed, 03 Jan 2007 16:59:49 -0800 From: Sridhar Samudrala <sri@...ibm.com> To: Andrew Morton <akpm@...l.org> Cc: netdev@...r.kernel.org, Steve Hill <steve.hill@...logic.com>, lksctp-developers@...ts.sourceforge.net Subject: Re: Fw: Intermittent SCTP multihoming breakage On Wed, 2007-01-03 at 15:46 -0800, Andrew Morton wrote: > > Begin forwarded message: > > Date: Wed, 3 Jan 2007 11:54:26 +0000 > From: Steve Hill <steve.hill@...logic.com> > To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org> > Subject: Intermittent SCTP multihoming breakage > > > > Apologies if I'm posting to the wrong list - the lksctp lists seem to be a > bit dead these days and a bit of Googling seemed to inidicate that SCTP > developemnt discussions might have moved here. No. lksctp-developers mailing list is still the best place for SCTP related discussions. You can subscribe and look in the archives at http://lists.sourceforge.net/lists/listinfo/lksctp-developers > > I'm running under the 2.6.16.1 kernel and have an intermittent problem > with the SCTP stack. Having reviewed the git logs I can't see any > indication that the problem has been fixed in more recent kernels, but it > is very difficult to test since it is so intermittent. If possible, i would suggest moving to the latest mainline 2.6.19. But 2.6.16.1 should work OK for simple multihoming cases. > > I am running a multihomed connection between 2 machines, (2 NICs on > each machine, so 2 paths for the connection) and tcpdump shows heartbeat > requests and acks on both paths. Putting data over the link correctly > sends it over the first path. How are the 2 machines connected? Are they connected directly or via a router? Do you see both the addresses when you do cat /proc/net/sctp/assocs after the association is established on both the peers? > > If I drop the traffic on one of the NICs then most of the time it > correctly fails over the the second path and I see the data being sent > and acknowledged correctly on the second path. However, I also > intermittently see two failure conditions: How are you dropping traffic? You could try simulating failover by bringing down the interface or physically removing the link. > > 1. Sometimes, just after failing over to the second path I see an ABORT. This seems to indicate that somehow the app has terminated. > 2. More frequently, the association stays up indefinately, with heartbeat > requests and acks on the second path, but no data chunks are sent even > though the transmit queue on the transmitting end appears to be full and > the socket is blocking writes. This is strange. Can you collect tcpdump traces on sender and receiver when this happens? Thanks Sridhar > > I have been adding debugging to the kernel in an attempt to track down the > source of the second failure condition, and I am wondering if anyone else > has seen similar behaviour? > > -- > - Steve Hill > Software Engineer > Dialogic > Fordingbridge, Hampshire, UK > +44-1425-651392 > steve.hill@...logic.com > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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