From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8584FC433FF for ; Tue, 30 Jul 2019 12:36:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63084206E0 for ; Tue, 30 Jul 2019 12:36:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730459AbfG3MgK (ORCPT ); Tue, 30 Jul 2019 08:36:10 -0400 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:42196 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726190AbfG3MgJ (ORCPT ); Tue, 30 Jul 2019 08:36:09 -0400 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.89) (envelope-from ) id 1hsRLy-0003m8-Pk; Tue, 30 Jul 2019 14:35:42 +0200 Date: Tue, 30 Jul 2019 14:35:42 +0200 From: Florian Westphal To: Rundong Ge Cc: davem@davemloft.net, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, netdev@vger.kernel.org, pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de, roopa@cumulusnetworks.com, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux-foundation.org, nikolay@cumulusnetworks.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] bridge:fragmented packets dropped by bridge Message-ID: <20190730123542.zrsrfvcy7t2n3d4g@breakpoint.cc> References: <20190730122534.30687-1-rdong.ge@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190730122534.30687-1-rdong.ge@gmail.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rundong Ge wrote: > Given following setup: > -modprobe br_netfilter > -echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables > -brctl addbr br0 > -brctl addif br0 enp2s0 > -brctl addif br0 enp3s0 > -brctl addif br0 enp6s0 > -ifconfig enp2s0 mtu 1300 > -ifconfig enp3s0 mtu 1500 > -ifconfig enp6s0 mtu 1500 > -ifconfig br0 up > > multi-port > mtu1500 - mtu1500|bridge|1500 - mtu1500 > A | B > mtu1300 How can a bridge forward a frame from A/B to mtu1300? > With netfilter defragmentation/conntrack enabled, fragmented > packets from A will be defragmented in prerouting, and refragmented > at postrouting. Yes, but I don't see how that relates to the problem at hand. > But in this scenario the bridge found the frag_max_size(1500) is > larger than the dst mtu stored in the fake_rtable whitch is > always equal to the bridge's mtu 1300, then packets will be dopped. What happens without netfilter or non-fragmented packets? > This modifies ip_skb_dst_mtu to use the out dev's mtu instead > of bridge's mtu in bridge refragment. It seems quite a hack? The above setup should use a router, not a bridge.