From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 01/18] ipv4: fix path MTU discovery with connection tracking Date: Mon, 20 Aug 2012 09:41:24 +0200 Message-ID: <1345448484.5158.247.camel@edumazet-glaptop> References: <1345434006-16549-1-git-send-email-kaber@trash.net> <1345434006-16549-2-git-send-email-kaber@trash.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org To: Patrick McHardy Return-path: In-Reply-To: <1345434006-16549-2-git-send-email-kaber@trash.net> Sender: netfilter-devel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, 2012-08-20 at 05:39 +0200, Patrick McHardy wrote: > IPv4 conntrack defragments incoming packet at the PRE_ROUTING hook and > (in case of forwarded packets) refragments them at POST_ROUTING > independant of the IP_DF flag. Refragmentation uses the dst_mtu() of > the local route without caring about the original fragment sizes, > thereby breaking PMTUD. > > This patch fixes this by keeping track of the largest received fragment > with IP_DF set and generates an ICMP fragmentation required error during > refragmentation if that size exceeds the MTU. > > Signed-off-by: Patrick McHardy > --- Acked-by: Eric Dumazet