1 files changed, 15 insertions, 8 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0c74da8a0473..fb47c8f0cd86 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -138,7 +138,7 @@ static int rt_chain_length_max __read_mostly	= 20;
 
 static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie);
 static unsigned int	 ipv4_default_advmss(const struct dst_entry *dst);
-static unsigned int	 ipv4_default_mtu(const struct dst_entry *dst);
+static unsigned int	 ipv4_mtu(const struct dst_entry *dst);
 static void		 ipv4_dst_destroy(struct dst_entry *dst);
 static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst);
 static void		 ipv4_link_failure(struct sk_buff *skb);
@@ -193,7 +193,7 @@ static struct dst_ops ipv4_dst_ops = {
 	.gc =			rt_garbage_collect,
 	.check =		ipv4_dst_check,
 	.default_advmss =	ipv4_default_advmss,
-	.default_mtu =		ipv4_default_mtu,
+	.mtu =			ipv4_mtu,
 	.cow_metrics =		ipv4_cow_metrics,
 	.destroy =		ipv4_dst_destroy,
 	.ifdown =		ipv4_dst_ifdown,
@@ -1814,12 +1814,17 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 	return advmss;
 }
 
-static unsigned int ipv4_default_mtu(const struct dst_entry *dst)
+static unsigned int ipv4_mtu(const struct dst_entry *dst)
 {
-	unsigned int mtu = dst->dev->mtu;
+	const struct rtable *rt = (const struct rtable *) dst;
+	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+	if (mtu && rt_is_output_route(rt))
+		return mtu;
+
+	mtu = dst->dev->mtu;
 
 	if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
-		const struct rtable *rt = (const struct rtable *) dst;
 
 		if (rt->rt_gateway != rt->rt_dst && mtu > 576)
 			mtu = 576;
@@ -2755,9 +2760,11 @@ static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 coo
 	return NULL;
 }
 
-static unsigned int ipv4_blackhole_default_mtu(const struct dst_entry *dst)
+static unsigned int ipv4_blackhole_mtu(const struct dst_entry *dst)
 {
-	return 0;
+	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+	return mtu ? : dst->dev->mtu;
 }
 
 static void ipv4_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu)
@@ -2775,7 +2782,7 @@ static struct dst_ops ipv4_dst_blackhole_ops = {
 	.protocol		=	cpu_to_be16(ETH_P_IP),
 	.destroy		=	ipv4_dst_destroy,
 	.check			=	ipv4_blackhole_dst_check,
-	.default_mtu		=	ipv4_blackhole_default_mtu,
+	.mtu			=	ipv4_blackhole_mtu,
 	.default_advmss		=	ipv4_default_advmss,
 	.update_pmtu		=	ipv4_rt_blackhole_update_pmtu,
 	.cow_metrics		=	ipv4_rt_blackhole_cow_metrics,