Merge branch 'bridge_batmanadv_exports'

Linus Lüssing says:

====================
bridge: multicast snooping exports #2

Some people pointed out to me that it might be helpful to add stubs for
the newly added multicast exports. That way e.g. batman-adv should continue
to be compile and useable without having to have a kernel compiled
with bridge code in the future. This is what the first patch is supposed
to do.

The second patch adds a third multicast export for the bridge which
e.g. batman-adv is supposed to use, too, soon: Just like the bridge
disables its multicast snooping activities if no querier is present,
batman-adv needs to do the same if bridges are involved.

These three exports should be the final ones needed to marry the bridge
multicast snooping with the batman-adv multicast optimizations recently
added for the 3.15 kernel, allowing to use these optimzations in common
setups having a bridge on top of e.g. bat0, too. So far these bridged
setups would fall back to simple flooding through the batman-adv mesh
network for any multicast packet entering bat0.

More information about the batman-adv multicast optimizations currently
implemented can be found here:

http://www.open-mesh.org/projects/batman-adv/wiki/Basic-multicast-optimizations

The integration on the batman-adv side could afterwards look like this,
for instance (now including the third export):

http://git.open-mesh.org/batman-adv.git/commitdiff/61e4f6af4b7a21ed4040f2e711d50c778e5b6d93?hp=6ae4281474675fbca5bedcf768972a32db586eb6
====================

include/linux/if_bridge.h

@@ -36,8 +36,28 @@ extern void brioctl_set(int (*ioctl_hook)(struct net *, unsigned int, void __use
 
 typedef int br_should_route_hook_t(struct sk_buff *skb);
 extern br_should_route_hook_t __rcu *br_should_route_hook;
+
+#if IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_BRIDGE_IGMP_SNOOPING)
 int br_multicast_list_adjacent(struct net_device *dev,
 			       struct list_head *br_ip_list);
+bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto);
 bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto);
+#else
+static inline int br_multicast_list_adjacent(struct net_device *dev,
+					     struct list_head *br_ip_list)
+{
+	return 0;
+}
+static inline bool br_multicast_has_querier_anywhere(struct net_device *dev,
+						     int proto)
+{
+	return false;
+}
+static inline bool br_multicast_has_querier_adjacent(struct net_device *dev,
+						     int proto)
+{
+	return false;
+}
+#endif
 
 #endif

net/bridge/br_multicast.c

@@ -2215,6 +2215,43 @@ int br_multicast_list_adjacent(struct net_device *dev,
 }
 EXPORT_SYMBOL_GPL(br_multicast_list_adjacent);
 
+/**
+ * br_multicast_has_querier_anywhere - Checks for a querier on a bridge
+ * @dev: The bridge port providing the bridge on which to check for a querier
+ * @proto: The protocol family to check for: IGMP -> ETH_P_IP, MLD -> ETH_P_IPV6
+ *
+ * Checks whether the given interface has a bridge on top and if so returns
+ * true if a valid querier exists anywhere on the bridged link layer.
+ * Otherwise returns false.
+ */
+bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto)
+{
+	struct net_bridge *br;
+	struct net_bridge_port *port;
+	struct ethhdr eth;
+	bool ret = false;
+
+	rcu_read_lock();
+	if (!br_port_exists(dev))
+		goto unlock;
+
+	port = br_port_get_rcu(dev);
+	if (!port || !port->br)
+		goto unlock;
+
+	br = port->br;
+
+	memset(&eth, 0, sizeof(eth));
+	eth.h_proto = htons(proto);
+
+	ret = br_multicast_querier_exists(br, &eth);
+
+unlock:
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(br_multicast_has_querier_anywhere);
+
 /**
  * br_multicast_has_querier_adjacent - Checks for a querier behind a bridge port
  * @dev: The bridge port adjacent to which to check for a querier