netdev - [PATCH] ipv4: Don't increase PMTU with Datagram Too Big message.

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Date:	Thu, 29 Jan 2015 16:09:03 +0800
From:	Li Wei <lw@...fujitsu.com>
To:	<davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, Li Wei <lw@...fujitsu.com>
Subject: [PATCH] ipv4: Don't increase PMTU with Datagram Too Big message.

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@...fujitsu.com>
---
 net/ipv4/route.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d58dd0e..52e1f2b 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -966,6 +966,9 @@ 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;
 
-- 
2.1.0

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