From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valentijn Sessink Subject: IPv6 path discovery oddities - flushing the routing cache resolves Date: Wed, 16 Oct 2013 12:31:31 +0200 Message-ID: <525E6B03.1040409@blub.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from gateway.openoffice.nl ([95.97.76.242]:40243 "EHLO openoffice.kantoor.openoffice.nl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1760286Ab3JPKkX (ORCPT ); Wed, 16 Oct 2013 06:40:23 -0400 Received: from [192.168.112.50] (stout.kantoor.openoffice.nl [192.168.112.50]) by openoffice.kantoor.openoffice.nl (Postfix) with ESMTP id 8599DC0019 for ; Wed, 16 Oct 2013 12:31:31 +0200 (CEST) Sender: netdev-owner@vger.kernel.org List-ID: Hello list, I'm experiencing difficulties with IPv6 path discovery. The setup is quite simple, a machine with native IPv6, no special routing - let's call it the "server" for now. Unfortunately, I seem to loose connectivity multiple times a day - and after digging in, I found this to be "too big" messages that weren't honored at the server. The network consists of something like: server --- hosting --- others ---- SIXXS tunnel with 1280 MTU --- me. A "ip -6 route list cache" would show a cached route to my "client", but one without MTU. Then after "ip -6 route flush cache", and after trying to send a large packet (for example issuing "ps uaxww" on an ssh prompt), "ip -6 route list cache" will show a correct MTU. But after a while, things start to go wrong again, and another "ip -6 route flush cache" is needed. The server is running 3.8.0-something (ubuntu 12.04 with a newer kernel). tcpdump shows that on reception of icmpv6 "too big", nothing happens (i.e. the "too big" packet will be sent time and again), and after the "ip -6 route flush cache", suddenly the "too big" message is honored. I saw a couple of path discovery issues on this list, more specifically one with the subject "IPv6 path MTU discovery broken" earlier this month - but I'm not sure it's the same issue (because the original submitter specifically mentions kernels 3.10 and 3.11 and has a much more complicated routing table). The "server" just has: auto br0 iface br0 inet6 static address 2a01:xxxx:xxx:xxxx::2 netmask 64 gateway fe80::1 bridge_ports eth0 bridge_maxwait 0 Nothing special, no special routes, no routing daemons. If I can do anything to shine more light on this issue, please tell me so. Best regards, Valentijn