bridge: Add multicast forwarding functions

This patch adds code to perform selective multicast forwarding.

We forward multicast traffic to a set of ports plus all multicast
router ports.  In order to avoid duplications among these two
sets of ports, we order all ports by the numeric value of their
pointers.  The two lists are then walked in lock-step to eliminate
duplicates.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 44345c9..c85943c 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -293,6 +293,10 @@
 extern void br_multicast_init(struct net_bridge *br);
 extern void br_multicast_open(struct net_bridge *br);
 extern void br_multicast_stop(struct net_bridge *br);
+extern void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
+				 struct sk_buff *skb);
+extern void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
+				 struct sk_buff *skb, struct sk_buff *skb2);
 #else
 static inline int br_multicast_rcv(struct net_bridge *br,
 				   struct net_bridge_port *port,
@@ -334,6 +338,17 @@
 static inline void br_multicast_stop(struct net_bridge *br)
 {
 }
+
+static inline void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
+					struct sk_buff *skb)
+{
+}
+
+static inline void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
+					struct sk_buff *skb,
+					struct sk_buff *skb2)
+{
+}
 #endif
 
 static inline bool br_multicast_is_router(struct net_bridge *br)