From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754287Ab1KRIRi (ORCPT ); Fri, 18 Nov 2011 03:17:38 -0500 Received: from cust-95-128-94-82.breedbanddelft.nl ([95.128.94.82]:47514 "HELO abra2.bitwizard.nl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1752426Ab1KRIRh (ORCPT ); Fri, 18 Nov 2011 03:17:37 -0500 Date: Fri, 18 Nov 2011 09:17:35 +0100 From: Rogier Wolff To: Eric Dumazet Cc: linux-kernel@vger.kernel.org, netdev Subject: Re: Route cache problem. Message-ID: <20111118081734.GA25843@bitwizard.nl> References: <20111103143734.GA17218@bitwizard.nl> <1320333410.2344.13.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1320333410.2344.13.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Organization: BitWizard.nl User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 03, 2011 at 04:16:50PM +0100, Eric Dumazet wrote: > Le jeudi 03 novembre 2011 à 15:37 +0100, Rogier Wolff a écrit : > > Hi, > > > > My workstation has an incorrect route cache entry: > > > > What kernel version ? Linux version 3.0.0-12-generic (from Ubunutu oneiric.) > > assurancetourix:~> route -nC | head -2 ; route -nC | grep 234.34 > > Kernel IP routing cache > > Source Destination Gateway Flags Metric Ref Use Iface > > 192.168.235.8 192.168.234.34 192.168.235.251 0 0 3 eth0 > > 192.168.235.8 192.168.234.34 192.168.235.251 0 0 4 eth0 > > 192.168.235.8 192.168.234.34 192.168.235.251 0 0 2 eth0 > > > > (I don't know why there are three). Today there are four. > 192.168.20.108 10.37.168.112 192.168.20.254 0 1 2 eth3 That indeed got me a full complement of route cache entries. > Better use "ip -s route list cache" to diagnose problems (more > information) After doing the tos ping you suggested All TOS levels have a route cache entry. 192.168.234.34 from 192.168.235.8 tos 0x1c via 192.168.235.251 dev eth0 cache age 77sec ipid 0xaa09 rtt 47ms rttvar 15ms ssthresh 7 cwnd 9 192.168.234.34 tos 0x1c via 192.168.235.251 dev eth0 src 192.168.235.8 cache used 3 age 72sec ipid 0xaa09 rtt 47ms rttvar 15ms ssthresh 7 cwnd 9 192.168.234.34 from 192.168.235.8 tos 0x1c via 192.168.235.251 dev eth0 cache age 72sec ipid 0xaa09 rtt 47ms rttvar 15ms ssthresh 7 cwnd 9 > > Any suggestions? Any at all? Last time, as well as this time, it is triggered by a network error that leads to the 192.168.235.4 router not being able to reach 192.168.234.34 or any other host on the 192.168.234.0/24 network. During that time the VPN to 192.168.234.0/24 is down, so 192.168.235.4 doesn't have a route to 192.168.234.0/24 and it is logical that with that route gone, it sends packets for 192.168.234.0/24 to the default router 192.168.235.251. As it sees itself forwarding packets that come in on eth0 back to eth0, it will send a redirect. However that redirect should somehow expire, and not survive things like dropping the route to 192.168.234.0/24, dropping the default route, shutting down the interface or some time passing (that network problem was solved 20 hours ago)...... Roger. -- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 ** ** Delftechpark 26 2628 XH Delft, The Netherlands. KVK: 27239233 ** *-- BitWizard writes Linux device drivers for any device you may have! --* The plan was simple, like my brother-in-law Phil. But unlike Phil, this plan just might work.