Date: Sun, 01 Apr 2012 17:27:47 +1000 From: Darren Reed <darernr@freebsd.org> To: Andre Oppermann <andre@freebsd.org> Cc: darrenr@freebsd.org, freebsd-net@freebsd.org Subject: Re: FreeBSD TCP ignores zero window size Message-ID: <4F780373.6030107@freebsd.org> In-Reply-To: <4F75D9ED.7080707@freebsd.org> References: <4F75C1A3.4030401@freebsd.org> <4F75D9ED.7080707@freebsd.org>
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Andre, Your changes bring it closer to working correctly with a small change: rather than "tiwin > tp->snd_wnd", it should be "tiwin != tp->snd_wnd". In this trace, the remote end has set a window scale factor of 5 during connection establishment. The same change should be made in the if() a few lines down. The problem here is that it only tracks the window size as it grows, not as it shrinks. Thus the remote end setting its window size to 0 is ignored. But having made that change, there appears to be still one problem that still lingers. As can be seen below, freebsd 8.2 fails to properly ack the data that the remote end is trying to send, ultimately causing the connection to be dropped. Darren 16:06:50.207927 IP remote.ssh > freebsd82.62922: . 6268613:6270053(1440) ack 367219 win 128 <nop,nop,timestamp 321 41540> 16:06:50.208736 IP freebsd82.62922 > remote.ssh: . ack 6270053 win 8100 <nop,nop,timestamp 41562 321> 16:06:50.210902 IP remote.ssh > freebsd82.62922: . 6270053:6271493(1440) ack 367219 win 128 <nop,nop,timestamp 321 41540> 16:06:50.211752 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 41562 321> 16:06:50.229987 IP remote.ssh > freebsd82.62922: . ack 370099 win 38 <nop,nop,timestamp 321 41540> 16:06:50.419926 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 322 41540> 16:06:50.422858 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 322 41540> 16:06:51.207172 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 41662 322> 16:06:51.419263 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 324 41540> 16:06:53.203547 IP remote.ssh > freebsd82.62922: . 6267173:6268613(1440) ack 371315 win 0 <nop,nop,timestamp 327 41540> 16:06:53.204320 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 41861 324> 16:06:53.415648 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 328 41540> 16:06:59.207766 IP remote.ssh > freebsd82.62922: . 6267173:6268613(1440) ack 371315 win 0 <nop,nop,timestamp 339 41540> 16:06:59.208469 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 42462 328> 16:06:59.419342 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 340 41540> 16:07:11.212606 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 363 41540> 16:07:11.213158 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 43662 340> 16:07:11.424414 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 364 41540> 16:07:35.227356 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 411 41540> 16:07:35.227954 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 46064 364> 16:07:35.440105 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 412 41540> 16:08:23.257747 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 507 41540> 16:08:23.258471 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 50868 412> 16:08:23.469790 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 508 41540> 16:09:27.299037 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 635 41540> 16:09:27.299734 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 57273 508> 16:09:27.510740 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 636 41540> 16:10:31.340328 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 763 41540> 16:10:31.340996 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 63678 636> 16:10:31.552639 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 764 41540> 16:11:35.380906 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 891 41540> 16:11:35.381519 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 70083 764> 16:11:35.592948 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 892 41540> 16:12:39.421327 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 1019 41540> 16:12:39.421957 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 76487 892> 16:12:39.633531 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 1020 41540> 16:13:43.462137 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 1147 41540> 16:13:43.462625 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 82892 1020> 16:13:43.674110 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 1148 41540> 16:14:47.502951 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 1275 41540> 16:14:47.503637 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 89297 1148> 16:14:47.715729 IP remote.ssh > freebsd82.62922: . ack 371315 win 0 <nop,nop,timestamp 1276 41540> 16:15:51.542134 IP remote.ssh > freebsd82.62922: . 6267173:6267697(524) ack 371315 win 0 <nop,nop,timestamp 1403 41540> 16:15:51.542794 IP freebsd82.62922 > remote.ssh: . ack 6271493 win 8280 <nop,nop,timestamp 95702 1276> 16:16:55.581199 IP remote.ssh > freebsd82.62922: R 6271493:6271493(0) ack 371315 win 0
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