Fix xfrm hash collisions by changing __xfrm4_daddr_saddr_hash to hash addresses with addition

This patch fixes hash collisions in cases where number
of entries have incrementing IP source and destination addresses
from single respective subnets (i.e. 192.168.0.1-172.16.0.1,
192.168.0.2-172.16.0.2, and so on.).
Signed-off-by: NJussi Maki <joamaki@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/xfrm/xfrm_hash.h

@@ -16,7 +16,7 @@ static inline unsigned int __xfrm6_addr_hash(xfrm_address_t *addr)
 
 static inline unsigned int __xfrm4_daddr_saddr_hash(xfrm_address_t *daddr, xfrm_address_t *saddr)
 {
-	return ntohl(daddr->a4 ^ saddr->a4);
+	return ntohl(daddr->a4 + saddr->a4);
 }
 
 static inline unsigned int __xfrm6_daddr_saddr_hash(xfrm_address_t *daddr, xfrm_address_t *saddr)