rps: Add flag to skb to indicate rxhash is based on L4 tuple

The l4_rxhash flag was added to the skb structure to indicate
that the rxhash value was computed over the 4 tuple for the
packet which includes the port information in the encapsulated
transport packet.  This is used by the stack to preserve the
rxhash value in __skb_rx_tunnel.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst.h b/include/net/dst.h
index 13d507d..4fb6c43 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -325,7 +325,14 @@
 static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev)
 {
 	skb->dev = dev;
-	skb->rxhash = 0;
+
+	/*
+	 * Clear rxhash so that we can recalulate the hash for the
+	 * encapsulated packet, unless we have already determine the hash
+	 * over the L4 4-tuple.
+	 */
+	if (!skb->l4_rxhash)
+		skb->rxhash = 0;
 	skb_set_queue_mapping(skb, 0);
 	skb_dst_drop(skb);
 	nf_reset(skb);