net: Checks skb_dst to be NULL in inet_iif

In inet_iif check if skb_rtable is NULL for the skb and return
skb->skb_iif if it is.

This change allows inet_iif to be called before the dst
information has been set in the skb (e.g. when doing socket based
UDP GRO).

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/route.h b/include/net/route.h
index 9b0a523..f4b11ee 100644 (file)
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -322,10 +322,11 @@ static inline struct rtable *ip_route_newports(struct flowi4 *fl4, struct rtable
 
 static inline int inet_iif(const struct sk_buff *skb)
 {
-       int iif = skb_rtable(skb)->rt_iif;
+       struct rtable *rt = skb_rtable(skb);
+
+       if (rt && rt->rt_iif)
+               return rt->rt_iif;
 
-       if (iif)
-               return iif;
        return skb->skb_iif;
 }