ip: reject too-big defragmented DF-skb when forwarding
Send icmp pmtu error if we find that the largest fragment of df-skb
exceeded the output path mtu.
The ip output path will still catch this later on but we can avoid the
forward/postrouting hook traversal by rejecting right away.
This is what ipv6 already does.
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>