route: Use ipv4_mtu instead of raw rt_pmtu

The commit 3cdaa5be9e81a914e633a6be7b7d2ef75b528562 ("ipv4: Don't
increase PMTU with Datagram Too Big message") broke PMTU in cases
where the rt_pmtu value has expired but is smaller than the new
PMTU value.

This obsolete rt_pmtu then prevents the new PMTU value from being
installed.

Fixes: 3cdaa5be9e81 ("ipv4: Don't increase PMTU with Datagram Too Big message")
Reported-by: Gerd v. Egidy <gerd.von.egidy@intra2net.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 4 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a78540f28276..bff62fc87b8e 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -962,10 +962,7 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
         if (dst_metric_locked(dst, RTAX_MTU))
                 return;
 
-        if (dst->dev->mtu < mtu)
-                return;
-
-        if (rt->rt_pmtu && rt->rt_pmtu < mtu)
+        if (ipv4_mtu(dst) < mtu)
                 return;
 
         if (mtu < ip_rt_min_pmtu)