netdev - Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

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Date:	Wed, 22 Aug 2012 07:01:24 +0200 (CEST)
From:	"Hans Schillstrom" <hans@...illstrom.com>
To:	"Jesper Dangaard Brouer" <brouer@...hat.com>
Cc:	"Patrick McHardy" <kaber@...sh.net>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	"Julian Anastasov" <ja@....bg>,
	"Hans Schillstrom" <hans.schillstrom@...csson.com>
Subject: Re[2]:  [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve 
	fragmentation handling

Hi
>
>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 ran into this as well, 
try this for the mtu check.

       if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
           (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {

/Hans

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