Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750786AbVJCL6E (ORCPT ); Mon, 3 Oct 2005 07:58:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750793AbVJCL6E (ORCPT ); Mon, 3 Oct 2005 07:58:04 -0400 Received: from leo.gold.ac.uk ([158.223.1.4]:28810 "EHLO leo.gold.ac.uk") by vger.kernel.org with ESMTP id S1750786AbVJCL6D (ORCPT ); Mon, 3 Oct 2005 07:58:03 -0400 Date: Mon, 3 Oct 2005 12:56:20 +0100 (BST) From: Martin Drallew To: linux-kernel@vger.kernel.org Subject: Connection reset by peer - TCP window size oddity ? Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Goldsmiths-MailScanner-Information: See http://www.gold.ac.uk/infos/cs/mailscanner/ for more information X-Goldsmiths-MailScanner: Found to be clean X-MailScanner-From: m.drallew@fatsquirrel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3598 Lines: 51 Gurus, apologies if this is a PEBKAC but I'm at my wits end with this one and have come to the conclusion, probably erroneously, that this may be a kernel bug. In a nutshell, mail transactions from our SMTP server to a handful of remote servers consistently fail with a 'connection reset by peer' during the transfer. Usually only larger messages (ie with attachments) are affected. A tcpdump follows and, unless I'm misunderstanding the output (quite possible) it looks like the kernel is sending outside of the peer's TCP window, to which the peer responds by resetting the connection. Things to note: 'leo' is our server and 'otter' is the remote. Leo is a dual processor 3GHz Xeon machine running 2.6.13.2. The problem was also there in 2.4. The owners of otter claim that we are the only site that they have problems with. The problem occurs less frequently if we force a stupidly small window size however otter seems immune. The "interesting" part of the session begins at timestamp 624177. Everything up to that point is a healthy SMTP session. Please could you CC me in on any replies as my mailbox takes enough of a daily beating already and lkml might just finish it off... Many thanks in advance, Martin 12:06:32.511347 leo.60039 > otter.smtp: S 3150703603:3150703603(0) win 5840 (DF) 12:06:32.519091 otter.smtp > leo.60039: S 1132102034:1132102034(0) ack 3150703604 win 1380 (DF) 12:06:32.519103 leo.60039 > otter.smtp: . ack 1 win 1460 (DF) 12:06:32.568277 otter.smtp > leo.60039: P 1:71(70) ack 1 win 1448 (DF) 12:06:32.568284 leo.60039 > otter.smtp: . ack 71 win 1460 (DF) 12:06:32.568306 leo.60039 > otter.smtp: P 1:22(21) ack 71 win 1460 (DF) 12:06:32.575440 otter.smtp > leo.60039: . ack 22 win 1448 (DF) 12:06:32.575481 otter.smtp > leo.60039: P 71:195(124) ack 22 win 1448 (DF) 12:06:32.575514 leo.60039 > otter.smtp: P 22:107(85) ack 195 win 1460 (DF) 12:06:32.616051 otter.smtp > leo.60039: P 195:273(78) ack 107 win 1448 (DF) 12:06:32.616075 leo.60039 > otter.smtp: P 107:616(509) ack 273 win 1460 (DF) 12:06:32.616095 leo.60039 > otter.smtp: P 616:1125(509) ack 273 win 1460 (DF) 12:06:32.624177 otter.smtp > leo.60039: . ack 1125 win 1984 (DF) 12:06:32.624183 leo.60039 > otter.smtp: P 1125:2493(1368) ack 273 win 1460 (DF) 12:06:32.624200 leo.60039 > otter.smtp: P 2493:2652(159) ack 273 win 1460 (DF) 12:06:32.624209 leo.60039 > otter.smtp: P 2652:3161(509) ack 273 win 1460 (DF) 12:06:32.624540 otter.smtp > leo.60039: R 1132102307:1132102307(0) win 0 12:06:32.634407 otter.smtp > leo.60039: . ack 2652 win 3352 (DF) 12:06:32.634437 leo.60039 > otter.smtp: R 3150706255:3150706255(0) win 0 (DF) - 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/