From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH][v4] tcp: fix ICMP-RTO war Date: Wed, 10 Feb 2010 18:04:20 -0800 (PST) Message-ID: <20100210.180420.149959191.davem@davemloft.net> References: <4B7303C2.5000703@tvk.rwth-aachen.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, ilpo.jarvinen@helsinki.fi To: damian@tvk.rwth-aachen.de Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:36408 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753702Ab0BKCEF (ORCPT ); Wed, 10 Feb 2010 21:04:05 -0500 In-Reply-To: <4B7303C2.5000703@tvk.rwth-aachen.de> Sender: netdev-owner@vger.kernel.org List-ID: From: Damian Lukowski Date: Wed, 10 Feb 2010 20:06:42 +0100 > Make sure, that TCP has a nonzero RTT estimation after three-way > handshake. Currently, a listening TCP has a value of 0 for srtt, > rttvar and rto right after the three-way handshake is completed > with TCP timestamps disabled. > This will lead to corrupt RTO recalculation and retransmission > flood when RTO is recalculated on backoff reversion as introduced > in "Revert RTO on ICMP destination unreachable" > (f1ecd5d9e7366609d640ff4040304ea197fbc618). > This behaviour can be provoked by connecting to a server which > "responds first" (like SMTP) and rejecting every packet after > the handshake with dest-unreachable, which will lead to softirq > load on the server (up to 30% per socket in some tests). > > Thanks to Ilpo Jarvinen for providing debug patches and to > Denys Fedoryshchenko for reporting and testing. > > Changes since v3: Removed bad characters in patchfile. > > Reported-by: Denys Fedoryshchenko > Signed-off-by: Damian Lukowski Applied, thank you very much for fixing this bug.