Date: Wed, 20 Aug 2008 20:47:24 -0400 From: Chris Buechler <freebsd@chrisbuechler.com> To: freebsd-net@freebsd.org Subject: Re: repeatable scp stalls from 7.0 to 7.0 Message-ID: <48ACBB1C.7080701@chrisbuechler.com> In-Reply-To: <48A878C6.9000001@chrisbuechler.com> References: <48A878C6.9000001@chrisbuechler.com>
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Chris Buechler wrote: > I've been seeing pretty frequent and repeatable scp stalls between two > FreeBSD 7.0 servers (7.0-RELEASE-p2 to be exact) on a 100 Mb LAN. > They're two HP servers, an Opteron 275 and a dual Xeon 3.4 (don't > recall the models but I can get them if it's relevant) using the > onboard bge(4) cards. The client side (builder7) SCPs a file to the > server side (hosting7) about 20 times a day. The stall happens about > 2-4 times a week or so, and has happened ever since we put these two > boxes online in their current functions. Initially they were the > original 7.0 release, prior to the TCP fix in June. It's behaved the > same way both prior to and after that fix. There are no apparent > network issues aside from this with either of the boxes. > > Since we had nothing to go on other than scp sessions going to > "stalled" (no relevant logs), I setup a tcpdump on each end filtering > on the TCP 22 traffic between these hosts, grabbing 100 bytes of each > frame to avoid chewing up too much disk space. When it happened again > I split the end out into its own file with editcap, 4.2-4.3 MB each. > > http://chrisbuechler.com/temp/lastcut-hosting7.pcap - server end, > capture taken on host but destination IP is a jail > http://chrisbuechler.com/temp/lastcut-builder7.pcap - client end, > connection is initiated from the host, no jails involved. > > The TCP window on the ACKs from server to client start decrementing > [1], to the point where it's down to a window of 0. From that point, > everything the server (172.29.29.181) sends back to the client > (172.29.29.170) has a window of 0. Restarting the scp makes it work > again. It doesn't happen every time, somewhere around 2-3% of the time > it does. I don't see any cause for the decrementing window in those > captures but maybe I'm missing something. > > 1 - lastcut-hosting7.pcap frame #21298; lastcut-builder7.pcap #25088 > > These are both very stock boxes, GENERIC kernels, no significant > changes in sysctl or anything else. I'm not sure where to go from > here, any assistance in resolving this would be appreciated. Cut the nasty stuff above that Thunderbird threw in there on the copy/paste, sorry about that. I haven't gotten any replies, thought I would bump this. thanks, Chris
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