ipv4: Add hash table of interface addresses.

This will be used to optimize __ip_dev_find() and friends.

With help from Eric Dumazet.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index ae8fdc5..5f81466 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -144,6 +144,7 @@
 #define IN_DEV_ARP_NOTIFY(in_dev)	IN_DEV_MAXCONF((in_dev), ARP_NOTIFY)
 
 struct in_ifaddr {
+	struct hlist_node	hash;
 	struct in_ifaddr	*ifa_next;
 	struct in_device	*ifa_dev;
 	struct rcu_head		rcu_head;