ipv4: use skb_dst_copy() in ip_copy_metadata()

Avoid touching dst refcount in ip_fragment().

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 7d1f4b4..d647852 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -411,7 +411,7 @@
 	to->priority = from->priority;
 	to->protocol = from->protocol;
 	skb_dst_drop(to);
-	skb_dst_set(to, dst_clone(skb_dst(from)));
+	skb_dst_copy(to, from);
 	to->dev = from->dev;
 	to->mark = from->mark;