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net: ipv6: send pkttoobig immediately if orig frag size > mtu

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If conntrack defragments incoming ipv6 frags it stores largest original
frag size in ip6cb and sets ->local_df.

We must thus first test the largest original frag size vs. mtu, and not
vice versa.

Without this patch PKTTOOBIG is still generated in ip6_fragment() later
in the stack, but

1) IPSTATS_MIB_INTOOBIGERRORS won't increment
2) packet did (needlessly) traverse netfilter postrouting hook.

Fixes: fe6cc55f3a ("net: ip, ipv6: handle gso skbs in forwarding path")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2014-05-05 00:03:34 +02:00 committed by David S. Miller
parent ca6c5d4ad2
commit 418a31561d
1 changed files with 5 additions and 1 deletions
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6
net/ipv6/ip6_output.c
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@ -344,12 +344,16 @@ static unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
{
if (skb->len <= mtu || skb->local_df)
if (skb->len <= mtu)
return false;
/* ipv6 conntrack defrag sets max_frag_size + local_df */
if (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)
return true;
if (skb->local_df)
return false;
if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
return false;