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Re: [PATCH 2/2] ipvs: Extend MTU check to account for IPv6 NAT defrag ch

To: Julian Anastasov <ja@xxxxxx>
Subject: Re: [PATCH 2/2] ipvs: Extend MTU check to account for IPv6 NAT defrag changes
Cc: netdev@xxxxxxxxxxxxxxx, Patrick McHardy <kaber@xxxxxxxxx>, lvs-devel@xxxxxxxxxxxxxxx, Simon Horman <horms@xxxxxxxxxxxx>, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Hans Schillstrom <hans@xxxxxxxxxxxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, netfilter-devel@xxxxxxxxxxxxxxx
From: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Date: Tue, 28 Aug 2012 11:03:27 +0200
On Mon, 2012-08-27 at 18:20 +0300, Julian Anastasov wrote:
>       Hello,
> 
> On Mon, 27 Aug 2012, Jesper Dangaard Brouer wrote:
> 
> > This patch is necessary, to make IPVS work, after Patrick McHardys
> > IPv6 NAT defragmentation changes.
> > 
> > Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> > ---
> > 
> > I would appriciate, if someone (e.g. Julian) double check the tunnel mode 
> > code.
> 
>       Sure
> 
> > --Jesper
> > 
> >  net/netfilter/ipvs/ip_vs_xmit.c |   16 +++++++++++++---
> >  1 files changed, 13 insertions(+), 3 deletions(-)
> > 
> > @@ -956,8 +963,11 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct 
> > ip_vs_conn *cp,
> >             skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
> >  
> >     /* MTU checking: Special for tunnel mode */
> > -   if (mtu < ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr) &&

I guess:
 ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr)
Is the same as:
 skb->len

> > -       !skb_is_gso(skb)) {
> > +   if ((!IP6CB(skb)->frag_max_size &&
> > +        (mtu < ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr) &&
> > +         !skb_is_gso(skb)))
> > +       || IP6CB(skb)->frag_max_size + sizeof(struct ipv6hdr) > mtu) {

> 
>       mtu is already reduced with the new outer header size,
> may be we can just call __mtu_check_toobig_v6 with mtu?

To Julian, is the extra sizeof(struct ipv6hdr) addition to
frag_max_size, wrong? (as the mtu is already reduced)

If above statements hold, I think we can simply use
__mtu_check_toobig_v6() also for the tunnel case :-)

--Jesper

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