bridge: multicast: restore router configuration on port link down/up

commit 754bc547 upstream.

When a port goes through a link down/up the multicast router configuration
is not restored.
Signed-off-by: Satish Ashok <sashok@cumulusnetworks.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Fixes: 0909e117 ("bridge: Add multicast_router sysfs entries")
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/bridge/br_multicast.c

@@ -36,6 +36,9 @@
 #define mlock_dereference(X, br) \
 	rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))
 
+static void br_multicast_add_router(struct net_bridge *br,
+				    struct net_bridge_port *port);
+
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 static inline int ipv6_is_transient_multicast(const struct in6_addr *addr)
 {
@@ -842,6 +845,8 @@ void br_multicast_enable_port(struct net_bridge_port *port)
 		goto out;
 
 	__br_multicast_enable_port(port);
+	if (port->multicast_router == 2 && hlist_unhashed(&port->rlist))
+		br_multicast_add_router(br, port);
 
 out:
 	spin_unlock(&br->multicast_lock);