[PATCH 3.12 07/39] route: Use ipv4_mtu instead of raw rt_pmtu

From: Jiri Slaby
Date: Mon Jan 25 2016 - 07:00:47 EST

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

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

Fixes: 3cdaa5be9e81 ("ipv4: Don't increase PMTU with Datagram Too Big message")
Reported-by: Gerd v. Egidy <gerd.von.egidy@xxxxxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
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))

- if (dst->dev->mtu < mtu)
- return;
- if (rt->rt_pmtu && rt->rt_pmtu < mtu)
+ if (ipv4_mtu(dst) < mtu)

if (mtu < ip_rt_min_pmtu)