From mboxrd@z Thu Jan 1 00:00:00 1970 From: Denys Fedoryshchenko Subject: Re: Crazy TCP bug (keepalive flood?) in 2.6.32? Date: Sat, 23 Jan 2010 23:37:19 +0200 Message-ID: <201001232337.19122.denys@visp.net.lb> References: <200912261703.49067.denys@visp.net.lb> <201001191309.03927.denys@visp.net.lb> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit To: "Ilpo =?iso-8859-1?q?J=E4rvinen?=" , netdev@vger.kernel.org Return-path: Received: from hosting.visp.net.lb ([194.146.153.11]:47127 "EHLO hosting.visp.net.lb" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751783Ab0AWVfK (ORCPT ); Sat, 23 Jan 2010 16:35:10 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tuesday 19 January 2010 13:17:51 you wrote: > On Tue, 19 Jan 2010, Denys Fedoryshchenko wrote: > > On Tuesday 19 January 2010 11:10:12 you wrote: > > > Hi, > > > thank you for testing. So srtt and rttvar is zero in any of those > > > cases. Ilpo, it is a bug in tcp_rtt_estimator then, I suppose? > > > > > > There is also a code comment in tcp_input.c, saying: > > > > * NOTE: clamping at TCP_RTO_MIN is not required, current algo > > > > * guarantees that rto is higher. > > > > > > So we either fix tcp_rtt_estimator or simply clamp at TCP_RTO_MIN? > > > > > > Damian > > > > > > > On Monday 11 January 2010 15:02:34 you wrote: > > > >> On Sat, 26 Dec 2009, Denys Fedoryshchenko wrote: > > > >>> Few more dumps. I notice: > > > >>> 1)Ack always equal 1 > > > >>> 2)It is usually first segment of data sent (?) > > > >>> > > > >>> Maybe some value not initialised properly? > > > >> > > > >> Can you see if the RTO lower bound is violated (I added some > > > >> printing of vars there too already now if it turns out to be > > > >> something): > > > >> > > > >> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > > > >> index 65b8ebf..d84469f 100644 > > > >> --- a/net/ipv4/tcp_ipv4.c > > > >> +++ b/net/ipv4/tcp_ipv4.c > > > > As i see in code it is rounding RTO to minimum value. > > It fixes my problem seems. > > > > Btw just a bit about my environment - wireless networks (sometimes > > lossy!) with low speed (128-512Kbps) customers working over pppoe. Maybe > > it will give a tip why rtt value is too low. > > What I find most strange in it is the fact that when it triggers for the > first time, the srtt and mdev are zero, not some value in between 0 and > 200ms. Therefore I suspect that this case might be something that we've > overlooked where srtt/mdev are not valid at all. > > Maybe the patch below helps... > Seems after this patch (and debug patch with warnings) my dmesg is clean.