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

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Date:	Mon, 25 Jan 2016 12:49:47 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Li Wei <lw@...fujitsu.com>,
	"David S . Miller" <davem@...emloft.net>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 06/39] ipv4: Don't increase PMTU with Datagram Too Big message.

From: Li Wei <lw@...fujitsu.com>

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@...fujitsu.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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