ipv4: Don't update the pmtu on mtu locked routes

Routes with locked mtu should not use learned pmtu informations,
so do not update the pmtu on these routes.

Reported-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 6e4a89c5e27e..259cbeee9a8b 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -912,6 +912,9 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
         struct dst_entry *dst = &rt->dst;
         struct fib_result res;
 
+        if (dst_metric_locked(dst, RTAX_MTU))
+                return;
+
         if (dst->dev->mtu < mtu)
                 return;