netdev - Re: [PATCH V2 2/2] ipvs: Extend MTU check to account for IPv6 NAT defrag changes

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Date:	Tue, 28 Aug 2012 07:49:19 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	netdev@...r.kernel.org, Patrick McHardy <kaber@...sh.net>,
	lvs-devel@...r.kernel.org, Julian Anastasov <ja@....bg>,
	Simon Horman <horms@...ge.net.au>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Hans Schillstrom <hans@...illstrom.com>,
	Wensong Zhang <wensong@...ux-vs.org>,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] ipvs: Extend MTU check to account for IPv6 NAT
 defrag changes

On Tue, 2012-08-28 at 16:23 +0200, 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@...hat.com>
> ---
> In V2: the tunnel mode is no longer a special case.
> 
>  net/netfilter/ipvs/ip_vs_xmit.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
> index 67a3978..56f6d5d 100644
> --- a/net/netfilter/ipvs/ip_vs_xmit.c
> +++ b/net/netfilter/ipvs/ip_vs_xmit.c
> @@ -88,7 +88,14 @@ __ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos)
>  static inline bool
>  __mtu_check_toobig_v6(const struct sk_buff *skb, u32 mtu)
>  {
> -	if (skb->len > mtu && !skb_is_gso(skb)) {
> +	if (IP6CB(skb)->frag_max_size) {
> +		/* frag_max_size tell us that, this packet have been
> +		 * defragmented by netfilter IPv6 conntrack module.
> +		 */
> +		if (IP6CB(skb)->frag_max_size > mtu)
> +			return true; /* largest fragment violate MTU */
> +	}
> +	else if (skb->len > mtu && !skb_is_gso(skb)) {
>  		return true; /* Packet size violate MTU size */
>  	}

Couldnt you use a single test ?

if (IP6CB(skb)->frag_max_size > mtu)
	return true;

if (skb->len > mtu && !skb_is_gso(skb))
	return true;



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