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Message-ID: <20090102142608.GC26093@flint.arm.linux.org.uk> Date: Fri, 2 Jan 2009 14:26:09 +0000 From: Russell King <rmk@....linux.org.uk> To: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi> Cc: Netdev <netdev@...r.kernel.org>, Ben Hutchings <bhutchings@...arflare.com> Subject: Re: 2.6.27.8 (+the idr fix) TCP Ack issue On Wed, Dec 31, 2008 at 10:20:46PM +0200, Ilpo Järvinen wrote: > No, it's a sequence number, there are two sequence number spaces per flow, > one for each direction (each has a corresponding field in the tcp header). > For pure ACKs tcpdump won't show the sequence number by default even > though it's still there... > > With tcpdump -n -v -v I get this for pure acks: > > ...: ., cksum 0x43c0 (correct), 671:671(0) ack 14649 win 36500 > > That 671:671(0) won't be visible with smaller verbosity. Ok, I think I see the problem - it's the remote end. 19:47:32.062670 IP (tos 0x0, ttl 64, id 30047, offset 0, flags [DF], proto: TCP (6), length: 60) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: S, cksum 0x6cf8 (correct), 3543174870:3543174870(0) win 5840 <mss 1460,sackOK,timestamp 26999689 0,nop,wscale 6> 19:47:32.135812 IP (tos 0x0, ttl 238, id 14, offset 0, flags [none], proto: TCP (6), length: 44) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: S, cksum 0x49e2 (correct), 3016012818:3016012818(0) ack 3543174871 win 8192 <mss 1276> 19:47:32.135837 IP (tos 0x0, ttl 64, id 30048, offset 0, flags [DF], proto: TCP (6), length: 40) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: ., cksum 0x6a17 (correct), 1:1(0) ack 1 win 5840 19:47:32.135899 IP (tos 0x0, ttl 64, id 30049, offset 0, flags [DF], proto: TCP (6), length: 683) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: P 1:644(643) ack 1 win 5840 19:47:32.167644 IP (tos 0x0, ttl 47, id 53954, offset 0, flags [DF], proto: TCP (6), length: 40) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: ., cksum 0x62c3 (correct), 1:1(0) ack 644 win 7073 19:47:32.174366 IP (tos 0x0, ttl 47, id 53955, offset 0, flags [DF], proto: TCP (6), length: 1229) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: P 1:1190(1189) ack 644 win 7073 Remote end sends 1:1190 19:47:32.174414 IP (tos 0x0, ttl 64, id 30050, offset 0, flags [DF], proto: TCP (6), length: 40) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: ., cksum 0x593c (correct), 644:644(0) ack 1190 win 8323 19:47:32.174701 IP (tos 0x0, ttl 64, id 30051, offset 0, flags [DF], proto: TCP (6), length: 2592) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: . 644:3196(2552) ack 1190 win 8323 We ack 1190 19:47:32.174720 IP (tos 0x0, ttl 64, id 30053, offset 0, flags [DF], proto: TCP (6), length: 60) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: P, cksum 0xcd57 (incorrect (-> 0x1cd0), 3196:3216(20) ack 1190 win 8323 19:47:32.218718 IP (tos 0x0, ttl 47, id 53956, offset 0, flags [DF], proto: TCP (6), length: 1065) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: P 1190:2215(1025) ack 1920 win 8932 Remote end sends 1190:2215 19:47:32.258402 IP (tos 0x0, ttl 64, id 30054, offset 0, flags [DF], proto: TCP (6), length: 40) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: ., cksum 0x41e5 (correct), 3216:3216(0) ack 2215 win 10701 We ack 2215 19:47:32.285388 IP (tos 0x0, ttl 238, id 5, offset 0, flags [none], proto: TCP (6), length: 40) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: ., cksum 0x45e6 (correct), 1190:1190(0) ack 3216 win 10701 Remote end sequence number is still at 1190. 19:47:32.285397 IP (tos 0x0, ttl 64, id 30055, offset 0, flags [DF], proto: TCP (6), length: 40) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: ., cksum 0x41e5 (correct), 3216:3216(0) ack 2215 win 10701 19:47:32.320287 IP (tos 0x0, ttl 238, id 10, offset 0, flags [none], proto: TCP (6), length: 40) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: ., cksum 0x45e6 (correct), 1190:1190(0) ack 3216 win 10701 19:47:32.320300 IP (tos 0x0, ttl 64, id 30056, offset 0, flags [DF], proto: TCP (6), length: 40) dyn-67.arm.linux.org.uk.38803 > 193.108.74.209.http: ., cksum 0x41e5 (correct), 3216:3216(0) ack 2215 win 10701 19:47:32.353016 IP (tos 0x0, ttl 238, id 12, offset 0, flags [none], proto: TCP (6), length: 40) 193.108.74.209.http > dyn-67.arm.linux.org.uk.38803: ., cksum 0x45e6 (correct), 1190:1190(0) ack 3216 win 10701 ... So it looks to me like the remote end doesn't like our ack of 2215 for some reason. -- Russell King -- 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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