From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Hannemann Subject: Re: [Bugme-new] [Bug 15571] New: TCP madness - some packets are shunned. Date: Thu, 25 Mar 2010 16:34:25 +0100 Message-ID: <4BAB8281.8000905@nets.rwth-aachen.de> References: <20100322143711.b78c7a93.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7BIT Cc: netdev@vger.kernel.org, bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, jasen@treshna.com To: Andrew Morton Return-path: Received: from mta-2.ms.rz.RWTH-Aachen.DE ([134.130.7.73]:38752 "EHLO mta-2.ms.rz.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754032Ab0CYPel (ORCPT ); Thu, 25 Mar 2010 11:34:41 -0400 Received: from ironport-out-1.rz.rwth-aachen.de ([134.130.5.40]) by mta-2.ms.rz.RWTH-Aachen.de (Sun Java(tm) System Messaging Server 6.3-7.04 (built Sep 26 2008)) with ESMTP id <0KZU001GLGLRTTF0@mta-2.ms.rz.RWTH-Aachen.de> for netdev@vger.kernel.org; Thu, 25 Mar 2010 16:34:39 +0100 (CET) In-reply-to: <20100322143711.b78c7a93.akpm@linux-foundation.org> Sender: netdev-owner@vger.kernel.org List-ID: Am 22.03.2010 22:37, schrieb Andrew Morton: > > (switched to email. Please respond via emailed reply-to-all, not via the > bugzilla web interface). > > On Thu, 18 Mar 2010 02:46:29 GMT > bugzilla-daemon@bugzilla.kernel.org wrote: > >> http://bugzilla.kernel.org/show_bug.cgi?id=15571 >> >> URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=53646 >> 2 >> Summary: TCP madness - some packets are shunned. >> Product: Networking >> Version: 2.5 >> Kernel Version: 2.6.30 >> Platform: All >> OS/Version: Linux >> Tree: Mainline >> Status: NEW >> Severity: normal >> Priority: P1 >> Component: Other >> AssignedTo: acme@ghostprotocols.net >> ReportedBy: jasen@treshna.com >> Regression: No >> >> >> The host http://www.cv-it.com is virtually unreachable with kernel 2.6.26 >> (and later) slow with kernel 2.6.18 and just fine with windows XP. >> >> I used telnet to port 80 for testing. >> >> it seems to be a TCP issue, as the having the XP machine behind a linux based >> iptables firewall pc causes no problems, but telnet from the firewall pc itself >> to port 80 on www.cv-it.com does not work For me it seems to be the host is messing up with the window scale option. Although it claims to support window scaling: 16:23:17.466592 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [S], seq 2159265664, win 5840, options [mss 1460,sackOK,TS val 8382141 ecr 0,nop,wscale 7], length 0 16:23:17.761697 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [S.], seq 3910885479, ack 2159265665, win 65535, options [mss 1448,sackOK,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,wscale 8], length 0 My host (linux 2.6.32) is offering a window of 5888 (46<<7): 16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0 And cv-it.com seems to think there is only a window of 46 ignoring the previously negotiated window scaling: 16:23:23.066318 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [.], seq 1:47, ack 112, win 65160, length 46 You can disable window scaling with: sysctl -w "net.ipv4.tcp_window_scaling=0" Best regards, Arnd