From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling Date: Mon, 27 Aug 2012 12:13:48 +0200 Message-ID: <1346062428.3069.398.camel@localhost> References: <1344542943-11588-1-git-send-email-kaber@trash.net> <1344542943-11588-6-git-send-email-kaber@trash.net> <1345190795.3069.228.camel@localhost> <1345405069.3069.241.camel@localhost> <1345587697.3069.297.camel@localhost> 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, Julian Anastasov , Hans Schillstrom , Hans Schillstrom To: Patrick McHardy Return-path: In-Reply-To: Sender: netfilter-devel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sun, 2012-08-26 at 23:20 +0200, Patrick McHardy wrote: > On Wed, 22 Aug 2012, Jesper Dangaard Brouer wrote: > > > On Sun, 2012-08-19 at 21:44 +0200, Patrick McHardy wrote: > >> On Sun, 19 Aug 2012, Jesper Dangaard Brouer wrote: > >>> On Sat, 2012-08-18 at 14:26 +0200, Patrick McHardy wrote: > > [...] > > > >>> Don't I need to load some of the helper modules, or just the > >>> nf_conntrack_ipv6 module, or perhaps only nf_defrag_ipv6 ? > >> > >> Not with the entire patchset, just IPv6 conntrack is enough. Aith IPv6 NAT > >> the first packet of a connection must always be defragemented, independant > >> of an assigned helper. > > > > When loading "nf_conntrack_ipv6" I run into issues. > > > > When sending a fragmented UDP packet. With these patches, the IPVS > > stack will no longer see the fragmented packets, but instead see one > > large SKB. This will trigger a MTU path check in e.g. > > ip_vs_dr_xmit_v6() and an ICMPv6 too big packet is send back. > > > > IPVS: ip_vs_dr_xmit_v6(): frag needed > > > > Perhaps we could change/fix the MTU check in IPVS? > > (This would also solve issues I've seen with TSO/GSO frames, hitting > > this code path). > > I guess this should use the same check as in IPv6 output, check > whether IP6CB(skb)->max_frag_size is != 0 and > MTU and only send > an ICMPv6 error in that case. Hans have (already) proposed this solution: if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) || (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) { And I have tested it works. But I'm not sure about, if we really need the "!skb->local_df" check ? Thus, we should extend you patchset with a patch, that also address the MTU checks in IPVS. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer