From: Russell King <rmk@arm.linux.org.uk>
To: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Cc: Netdev <netdev@vger.kernel.org>,
Ben Hutchings <bhutchings@solarflare.com>
Subject: Re: 2.6.27.8 (+the idr fix) TCP Ack issue
Date: Fri, 2 Jan 2009 14:26:09 +0000 [thread overview]
Message-ID: <20090102142608.GC26093@flint.arm.linux.org.uk> (raw)
In-Reply-To: <Pine.LNX.4.64.0812312215590.3247@wrl-59.cs.helsinki.fi>
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
next prev parent reply other threads:[~2009-01-02 14:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-30 19:58 2.6.27.8 (+the idr fix) TCP Ack issue Russell King
2008-12-31 10:38 ` Ilpo Järvinen
2008-12-31 17:10 ` Russell King
2008-12-31 20:20 ` Ilpo Järvinen
2009-01-02 14:26 ` Russell King [this message]
2009-01-02 21:34 ` David Miller
2009-01-02 22:02 ` Russell King
2009-01-02 8:43 ` Herbert Xu
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