xfrm: revert ipv4 mtu determination to dst_mtu

In commit 0ea9d5e3e0e03a63b11392f5613378977dae7eca ("xfrm: introduce
helper for safe determination of mtu") I switched the determination of
ipv4 mtus from dst_mtu to ip_skb_dst_mtu. This was an error because in
case of IP_PMTUDISC_PROBE we fall back to the interface mtu, which is
never correct for ipv4 ipsec.

This patch partly reverts 0ea9d5e3e0e03a63b11392f5613378977dae7eca
("xfrm: introduce helper for safe determination of mtu").

Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index e092e306882d..6cd625e37706 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -140,10 +140,12 @@ static int __xfrm6_output(struct sk_buff *skb)
 {
         struct dst_entry *dst = skb_dst(skb);
         struct xfrm_state *x = dst->xfrm;
-        int mtu = xfrm_skb_dst_mtu(skb);
+        int mtu;
 
-        if (mtu < IPV6_MIN_MTU)
-                mtu = IPV6_MIN_MTU;
+        if (skb->protocol == htons(ETH_P_IPV6))
+                mtu = ip6_skb_dst_mtu(skb);
+        else
+                mtu = dst_mtu(skb_dst(skb));
 
         if (skb->len > mtu && xfrm6_local_dontfrag(skb)) {
                 xfrm6_local_rxpmtu(skb, mtu);