Commit 69647ce4 authored Feb 26, 2014 by Hannes Frederic Sowa Committed by David S. Miller Feb 26, 2014

ipv4: use ip_skb_dst_mtu to determine mtu in ip_fragment

ip_skb_dst_mtu mostly falls back to ip_dst_mtu_maybe_forward if no socket
is attached to the skb (in case of forwarding) or determines the mtu like
we do in ip_finish_output, which actually checks if we should branch to
ip_fragment. Thus use the same function to determine the mtu here, too.

This is important for the introduction of IP_PMTUDISC_OMIT, where we
want the packets getting cut in pieces of the size of the outgoing
interface mtu. IPv6 already does this correctly.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent a960ff81

net/ipv4/ip_output.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -449,7 +449,6 @@ int ip_fragment(struct sk_buff skb, int (output)(struct sk_buff *))
		__be16 not_last_frag;
		struct rtable *rt = skb_rtable(skb);
		int err = 0;
		bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;

		dev = rt->dst.dev;

		@@ -459,7 +458,7 @@ int ip_fragment(struct sk_buff skb, int (output)(struct sk_buff *))

		iph = ip_hdr(skb);

		mtu = ip_dst_mtu_maybe_forward(&rt->dst, forwarding);
		mtu = ip_skb_dst_mtu(skb);
		if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) \|\|
		(IPCB(skb)->frag_max_size &&
		IPCB(skb)->frag_max_size > mtu))) {