Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161110AbVIBXJm (ORCPT ); Fri, 2 Sep 2005 19:09:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161113AbVIBXJm (ORCPT ); Fri, 2 Sep 2005 19:09:42 -0400 Received: from chicken.cs.columbia.edu ([128.59.21.28]:64971 "EHLO chicken.cs.columbia.edu") by vger.kernel.org with ESMTP id S1161110AbVIBXJk (ORCPT ); Fri, 2 Sep 2005 19:09:40 -0400 Date: Fri, 2 Sep 2005 19:09:18 -0400 (EDT) From: Ion Badulescu X-X-Sender: ionut@moisil.badula.org To: Alexey Kuznetsov cc: Ion Badulescu , "David S. Miller" , linux-kernel@vger.kernel.org, linux-net@vger.kernel.org, netdev@vger.kernel.org Subject: Re: Possible BUG in IPv4 TCP window handling, all recent 2.4.x/2.6.x kernels In-Reply-To: <20050902211810.GB18605@yakov.inr.ac.ru> Message-ID: References: <20050901.154300.118239765.davem@davemloft.net> <20050902183656.GA16537@yakov.inr.ac.ru> <20050902211810.GB18605@yakov.inr.ac.ru> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2090 Lines: 44 Hi Alexey, On Sat, 3 Sep 2005, Alexey Kuznetsov wrote: >> Well, take a look at the double acks for 84439343, 84440447 and 84441059, >> they seem pretty much identical to me. > > It is just a little tcpdump glitch. > > 19:34:54.532271 < 10.2.20.246.33060 > 65.171.224.182.8700: . 44:44(0) ack 84439343 win 24544 (DF) (ttl 64, id 60946) > 19:34:54.532432 < 10.2.20.246.33060 > 65.171.224.182.8700: . 44:44(0) ack 84439343 win 24544 (DF) (ttl 64, id 60946) > > It is one ACK (look at IP ID), shown twice. This happens sometimes > with our packet socket. Ahh... ack. :) That explains it. > I understood. I expect when 184*4, when you said 184. But minimum is > still 730 (unscaled 1460*2). If you really saw values lower than 730 > (unscaled 1460*2), there is another more severe problem and the suggested > patch will not solve it. I really did see very small values. This one is plucked from one of today's streams, after a full day's worth of data had passed through it: 19:03:19.659454 10.1.12.11.8001 > 10.2.10.212.56690: P 3:6(3) ack 1 win 65529 (DF) 19:03:19.659462 10.2.10.212.56690 > 10.1.12.11.8001: . ack 6 win 181 (DF) 19:03:20.690719 10.1.12.11.8001 > 10.2.10.212.56690: P 6:9(3) ack 1 win 65529 (DF) 19:03:20.690727 10.2.10.212.56690 > 10.1.12.11.8001: . ack 9 win 181 (DF) 10.1.12.11 is the Win2k box, 10.2.10.212 is the Linux box. The socket buffer sizes are the defaults, so the scaling is most likely 2^2. The packets being exchanged at this point are just heartbeats. On Tuesday I can try to capture a full session from the very begining, if you think it would help. Thanks, -Ion - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/