Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759432Ab2EVPZK (ORCPT ); Tue, 22 May 2012 11:25:10 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:47372 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759250Ab2EVPZG (ORCPT ); Tue, 22 May 2012 11:25:06 -0400 From: Miklos Szeredi To: Eric Dumazet Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: tcp timestamp issues with google servers References: <87r4ujno34.fsf@tucsk.pomaz.szeredi.hu> <1337278363.3403.39.camel@edumazet-glaptop> Date: Tue, 22 May 2012 17:25:37 +0200 In-Reply-To: <1337278363.3403.39.camel@edumazet-glaptop> (Eric Dumazet's message of "Thu, 17 May 2012 20:12:43 +0200") Message-ID: <87zk90s0em.fsf@tucsk.pomaz.szeredi.hu> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2022 Lines: 55 Eric Dumazet writes: > On Thu, 2012-05-17 at 11:39 +0200, Miklos Szeredi wrote: >> Sometimes connection to google.com, gmail.com and other google servers >> doesn't work or takes ages to connect. When this hits it hits all >> google servers at the same time and it's persistent. It never happens >> to anything other than google. Rebooting helps. Rarely it goes away >> spontaneously. >> >> Apparently google is sometimes replying with an invalid TSecr timestamp >> value (smaller than the one sent in the last packet) and this confuses >> the Linux TCP stack which either discards the packet or sends a Reset. >> >> Network dump attached. >> >> I found only a couple of references to this issue: >> >> http://gotchas.livejournal.com/3028.html >> >> http://groups.google.com/group/comp.os.linux.networking/browse_thread/thread/29f56feded11b42a >> >> Turning tcp timestamps fixes the issue: >> >> sysctl -w net.ipv4.tcp_timestamps=0 >> >> Not sure why this happens only to me and a very few others. >> >> It appears to be an issue with google TCP stack (is it a modified >> stack?) but I thought about issues in my network switch (restarting it >> doesn't help) or something in the ISP, but those look unlikely. >> >> Any ideas? >> >> Thanks, >> Miklos >> >> >> >> 1 0.000000 192.168.28.100 -> 74.125.232.226 TCP 51303 > http [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSV=35355050 TSER=0 WS=5 >> 2 0.002730 74.125.232.226 -> 192.168.28.100 TCP http > 51303 [SYN, ACK] Seq=0 Ack=1 Win=14180 Len=0 MSS=1430 SACK_PERM=1 TSV=1184565067 TSER=35325344 WS=6 > > > Do you really have 2730 usec RTT between you and this (Google ?) > server ? So it appears. The IP address is certainly registered to Google. Thanks, Miklos -- 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/