Date: Tue, 07 Jan 2014 12:10:22 -0800 From: Peter Wemm <peter@wemm.org> To: freebsd-net@freebsd.org Subject: Re: TCP question: Is this simultaneous close handling broken? Message-ID: <52CC5F2E.5030201@wemm.org> In-Reply-To: <52CB3AE9.3030107@wemm.org> References: <52CB3AE9.3030107@wemm.org>
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[-- Attachment #1 --] On 1/6/14, 3:23 PM, Peter Wemm wrote: > We've hit a weird problem at work when dealing with simultaneous closes. > In this particular case, it's a FreeBSD-7.4 machine talking some random > Linux host. > > There is a client/server protocol in use, and both ends are doing a close > at the same time. It might be a shutdown, I haven't seen all the code yet. [..] > A packet capture, with relative timestamps: > > 000050 freebsd.28411 > linux.14001: F 6486:6486(0) ack 232 > 000031 linux.14001 > freebsd.28411: F 232:232(0) ack 6486 > 000333 linux.14001 > freebsd.28411: . ack 6487 > [200ms retransmit timer fires on linux] > 200490 linux.14001 > freebsd.28411: F 232:232(0) ack 6487 > 000011 freebsd.28411 > linux.14001: . ack 233 [..] > What am I looking at? Who's at fault? It looks like we're failing to > recognize the ack for our fin. It definitely looks like FreeBSD at fault. We've simply not acked their FIN until they retransmitted it. I've looked at the commit logs and I don't see anything obvious that stands out to me for a fix for this. Most of the changes seem to be lock structure changes than protocol fixes. I see things like ECN and other protocol features being added as well. Where should I look in the code? -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV UTF-8: for when a ' just won\342\200\231t do. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlLMXy4ACgkQFRKuUnJ3cX88nQCeLUtlGDcxkTWs9+bQoEm3sXJz Ay4AmwfEOyuOKCHgPl3Y4JfctaZDNIvx =T93F -----END PGP SIGNATURE-----
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