From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rogier Wolff Subject: Re: Route cache problem. Date: Fri, 18 Nov 2011 09:17:35 +0100 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-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-kernel@vger.kernel.org, netdev To: Eric Dumazet Return-path: Content-Disposition: inline In-Reply-To: <1320333410.2344.13.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Nov 03, 2011 at 04:16:50PM +0100, Eric Dumazet wrote: > Le jeudi 03 novembre 2011 =E0 15:37 +0100, Rogier Wolff a =E9crit : > > Hi,=20 > >=20 > > My workstation has an incorrect route cache entry:=20 > >=20 >=20 > 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 > >=20 > > (I don't know why there are three).=20 Today there are four.=20 > 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.=20 > 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.=20 192.168.234.34 from 192.168.235.8 tos 0x1c via 192.168.235.251 dev eth0= =20 cache age 77sec ipid 0xaa09 rtt 47ms rttvar 15ms ssth= resh 7 cwnd 9 192.168.234.34 tos 0x1c via 192.168.235.251 dev eth0 src 192.168.235.8= =20 cache used 3 age 72sec ipid 0xaa09 rtt 47ms rttvar 15= ms ssthresh 7 cwnd 9 192.168.234.34 from 192.168.235.8 tos 0x1c via 192.168.235.251 dev eth0= =20 cache age 72sec ipid 0xaa09 rtt 47ms rttvar 15ms ssth= resh 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=20 192.168.234.34 or any other host on the 192.168.234.0/24 network.=20 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 defa= ult 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=20 interface or some time passing (that network problem was solved 20=20 hours ago)......=20 Roger.=20 --=20 ** 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.