linux-kernel - [PATCH 3.12 07/39] route: Use ipv4_mtu instead of raw rt

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Date:	Mon, 25 Jan 2016 12:49:48 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S . Miller" <davem@...emloft.net>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 07/39] route: Use ipv4_mtu instead of raw rt_pmtu

From: Herbert Xu <herbert@...dor.apana.org.au>

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

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

commit cb6ccf09d6b94bec4def1ac5cf4678d12b216474 upstream.

The commit 3cdaa5be9e81a914e633a6be7b7d2ef75b528562 ("ipv4: Don't
increase PMTU with Datagram Too Big message") broke PMTU in cases
where the rt_pmtu value has expired but is smaller than the new
PMTU value.

This obsolete rt_pmtu then prevents the new PMTU value from being
installed.

Fixes: 3cdaa5be9e81 ("ipv4: Don't increase PMTU with Datagram Too Big message")
Reported-by: Gerd v. Egidy <gerd.von.egidy@...ra2net.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 net/ipv4/route.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index fe0c761a8fce..54874e4767de 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -985,10 +985,7 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
 	if (dst_metric_locked(dst, RTAX_MTU))
 		return;
 
-	if (dst->dev->mtu < mtu)
-		return;
-
-	if (rt->rt_pmtu && rt->rt_pmtu < mtu)
+	if (ipv4_mtu(dst) < mtu)
 		return;
 
 	if (mtu < ip_rt_min_pmtu)
-- 
2.7.0