[PATCH 3.12 06/39] ipv4: Don't increase PMTU with Datagram Too Big message.

[Jiri Slaby]

From: Li Wei <lw@xxxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 3cdaa5be9e81a914e633a6be7b7d2ef75b528562 upstream.

RFC 1191 said, "a host MUST not increase its estimate of the Path
MTU in response to the contents of a Datagram Too Big message."

Signed-off-by: Li Wei <lw@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 net/ipv4/route.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index bd5f3461d1ce..fe0c761a8fce 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -988,6 +988,9 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
 	if (dst->dev->mtu < mtu)
 		return;
 
+	if (rt->rt_pmtu && rt->rt_pmtu < mtu)
+		return;
+
 	if (mtu < ip_rt_min_pmtu)
 		mtu = ip_rt_min_pmtu;
 
-- 
2.7.0