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

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

[Hans Schillstrom]

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

[Julian Anastasov]

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	Hello,

On Wed, 22 Aug 2012, Hans Schillstrom wrote:

> >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)) {

	Better without local_df check, it is our job to
set it.

Regards

--
Julian Anastasov <ja@ssi.bg>

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

[Julian Anastasov]

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	Hello,

On Wed, 22 Aug 2012, Julian Anastasov wrote:

> On Wed, 22 Aug 2012, Hans Schillstrom wrote:
> 
> > >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)) {
> 
> 	Better without local_df check, it is our job to
> set it.

	Ops, sorry. It seems now nf_ct_frag6_reasm (Patch 02/18)
will set head->local_df = 1, so we should check local_df
as Hans said.

Regards

--
Julian Anastasov <ja@ssi.bg>

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

[Jesper Dangaard Brouer]

On Wed, 2012-08-22 at 10:16 +0300, Julian Anastasov wrote:
> 	Hello,
> 
> On Wed, 22 Aug 2012, Julian Anastasov wrote:
> 
> > On Wed, 22 Aug 2012, Hans Schillstrom wrote:
> > 
> > > >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)) {
> > 
> > 	Better without local_df check, it is our job to
> > set it.

Will the IPVS usage of local_df, conflict with Patrick's usage?



> 	Ops, sorry. It seems now nf_ct_frag6_reasm (Patch 02/18)
> will set head->local_df = 1, so we should check local_df
> as Hans said.

With Hans'es version of the MTU check, IPVS seems to work again (with
Patricks patches applied).

(Also spotted the GSO problem I had with IPv6 + DR, and send an upstream
fix...)

-- 
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