ipv4: Don't create nh exeption when the device mtu is smaller than the reported pmtu

[ Upstream commit 7f92d334ba19a0d8e96f8f8f092219553367d921 ]

When a local tool like tracepath tries to send packets bigger than
the device mtu, we create a nh exeption and set the pmtu to device
mtu. The device mtu does not expire, so check if the device mtu is
smaller than the reported pmtu and don't crerate a nh exeption in
that case.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 09e85c74e872a25966aa577d9e1568b607d54430..11814ad59fa6044bd047d4180da6d562a55a6a09 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -909,6 +909,9 @@ 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->dev->mtu < mtu)
+               return;
+
        if (mtu < ip_rt_min_pmtu)
                mtu = ip_rt_min_pmtu;