4 files changed, 24 insertions, 6 deletions

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index db4867963247..94f4ec036669 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -827,7 +827,9 @@ static unsigned int dn_dst_default_advmss(const struct dst_entry *dst)
 
 static unsigned int dn_dst_mtu(const struct dst_entry *dst)
 {
-        return dst->dev->mtu;
+        unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+        return mtu ? : dst->dev->mtu;
 }
 
 static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f1ac3efc5524..11d1b2080a16 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1816,7 +1816,12 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 
 static unsigned int ipv4_mtu(const struct dst_entry *dst)
 {
-        unsigned int mtu = dst->dev->mtu;
+        unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+        if (mtu)
+                return mtu;
+
+        mtu = dst->dev->mtu;
 
         if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
                 const struct rtable *rt = (const struct rtable *) dst;
@@ -2757,7 +2762,9 @@ static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 coo
 
 static unsigned int ipv4_blackhole_mtu(const struct dst_entry *dst)
 {
-        return dst->dev->mtu;
+        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)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 76645d7077ff..3399dd326287 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -157,7 +157,9 @@ static struct dst_ops ip6_dst_ops_template = {
 
 static unsigned int ip6_blackhole_mtu(const struct dst_entry *dst)
 {
-        return dst->dev->mtu;
+        unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+        return mtu ? : dst->dev->mtu;
 }
 
 static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu)
@@ -1043,8 +1045,13 @@ static unsigned int ip6_default_advmss(const struct dst_entry *dst)
 
 static unsigned int ip6_mtu(const struct dst_entry *dst)
 {
-        unsigned int mtu = IPV6_MIN_MTU;
         struct inet6_dev *idev;
+        unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+        if (mtu)
+                return mtu;
+
+        mtu = IPV6_MIN_MTU;
 
         rcu_read_lock();
         idev = __in6_dev_get(dst->dev);
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index b8be51eb7e29..2118d6446630 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2384,7 +2384,9 @@ static unsigned int xfrm_default_advmss(const struct dst_entry *dst)
 
 static unsigned int xfrm_mtu(const struct dst_entry *dst)
 {
-        return dst_mtu(dst->path);
+        unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+        return mtu ? : dst_mtu(dst->path);
 }
 
 static struct neighbour *xfrm_neigh_lookup(const struct dst_entry *dst, const void *daddr)