From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Clayton Subject: Re: Possible networking regression in 3.6.0 Date: Wed, 03 Oct 2012 16:01:02 +0100 Message-ID: <506C532E.9070001@googlemail.com> References: <1349192133.12401.768.camel@edumazet-glaptop> <1349192919.12401.778.camel@edumazet-glaptop> <20121002.231037.581571797430134988.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: ja@ssi.bg, eric.dumazet@gmail.com, netdev@vger.kernel.org, gpiez@web.de, davej@redhat.com To: David Miller Return-path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:39672 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756274Ab2JCPBD (ORCPT ); Wed, 3 Oct 2012 11:01:03 -0400 Received: by lbon3 with SMTP id n3so6282866lbo.19 for ; Wed, 03 Oct 2012 08:01:01 -0700 (PDT) In-Reply-To: <20121002.231037.581571797430134988.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 10/03/12 04:10, David Miller wrote: > From: Julian Anastasov > Date: Wed, 3 Oct 2012 02:24:53 +0300 (EEST) > >> Can it be a problem related to fib_info reuse >> from different routes. For example, when local IP address >> is created for subnet we have: >> >> broadcast 192.168.0.255 dev DEV proto kernel scope link src 192.168.0.1 >> 192.168.0.0/24 dev DEV proto kernel scope link src 192.168.0.1 >> local 192.168.0.1 dev DEV proto kernel scope host src 192.168.0.1 >> >> The "dev DEV proto kernel scope link src 192.168.0.1" is >> a reused fib_info structure where we put cached routes. >> The result can be same fib_info for 192.168.0.255 and >> 192.168.0.0/24. RTN_BROADCAST is cached only for input >> routes. Incoming broadcast to 192.168.0.255 can be cached >> and can cause problems for traffic forwarded to 192.168.0.0/24. >> So, this patch should solve the problem because it >> separates the broadcast from unicast traffic. > > Now I understand the problem. > > I think the way to fix this is to add cfg->fc_type as another > thing that fib_info objects are key'd by. > > I think it also would fix your obscure output multicast case too. > > I've seen the discussion about whether Eric's patch is OK or not, but thought I'd give it a spin anyway. It applies to 3.6.0 with some fuzz, but I can confirm that with the patch applied I can now ping my router and browse the internet from a KVM client, so the Eric's diagnosis matches the problem I reported. However, after closing the client, I got an oops. I've taken a photograph of the screen and uploaded it to http://i714.photobucket.com/albums/ww149/chris2553/IMAG0059.jpg. As it's not the final patch, this may be a red herring, but I thought I'd better give a heads up anyway. Chris