bridge: Add core IGMP snooping support

This patch adds the core functionality of IGMP snooping support
without actually hooking it up.  So this patch should be a no-op
as far as the bridge's external behaviour is concerned.

All the new code and data is controlled by the Kconfig option
BRIDGE_IGMP_SNOOPING.  A run-time toggle is also available.

The multicast switching is done using an hash table that is
lockless on the read-side through RCU.  On the write-side the
new multicast_lock is used for all operations.  The hash table
supports dynamic growth/rehashing.

The hash table will be rehashed if any chain length exceeds a
preset limit.  If rehashing does not reduce the maximum chain
length then snooping will be disabled.

These features may be added in future (in no particular order):

* IGMPv3 source support
* Non-querier router detection
* IPv6
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/Kconfig

@@ -31,3 +31,15 @@ config BRIDGE
 	  will be called bridge.
 
 	  If unsure, say N.
+
+config BRIDGE_IGMP_SNOOPING
+	bool "IGMP snooping"
+	default y
+	---help---
+	  If you say Y here, then the Ethernet bridge will be able selectively
+	  forward multicast traffic based on IGMP traffic received from each
+	  port.
+
+	  Say N to exclude this support and reduce the binary size.
+
+	  If unsure, say Y.

net/bridge/Makefile

@@ -12,4 +12,6 @@ bridge-$(CONFIG_SYSFS) += br_sysfs_if.o br_sysfs_br.o
 
 bridge-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o
 
+bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o
+
 obj-$(CONFIG_BRIDGE_NF_EBTABLES) += netfilter/

net/bridge/br_private.h

@@ -57,6 +57,41 @@ struct net_bridge_fdb_entry
 	unsigned char			is_static;
 };
 
+struct net_bridge_port_group {
+	struct net_bridge_port		*port;
+	struct net_bridge_port_group	*next;
+	struct hlist_node		mglist;
+	struct rcu_head			rcu;
+	struct timer_list		timer;
+	struct timer_list		query_timer;
+	__be32				addr;
+	u32				queries_sent;
+};
+
+struct net_bridge_mdb_entry
+{
+	struct hlist_node		hlist[2];
+	struct hlist_node		mglist;
+	struct net_bridge		*br;
+	struct net_bridge_port_group	*ports;
+	struct rcu_head			rcu;
+	struct timer_list		timer;
+	struct timer_list		query_timer;
+	__be32				addr;
+	u32				queries_sent;
+};
+
+struct net_bridge_mdb_htable
+{
+	struct hlist_head		*mhash;
+	struct rcu_head			rcu;
+	struct net_bridge_mdb_htable	*old;
+	u32				size;
+	u32				max;
+	u32				secret;
+	u32				ver;
+};
+
 struct net_bridge_port
 {
 	struct net_bridge		*br;
@@ -84,6 +119,15 @@ struct net_bridge_port
 
 	unsigned long 			flags;
 #define BR_HAIRPIN_MODE		0x00000001
+
+#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
+	u32				multicast_startup_queries_sent;
+	unsigned char			multicast_router;
+	struct timer_list		multicast_router_timer;
+	struct timer_list		multicast_query_timer;
+	struct hlist_head		mglist;
+	struct hlist_node		rlist;
+#endif
 };
 
 struct net_bridge
@@ -124,6 +168,35 @@ struct net_bridge
 	unsigned char			topology_change;
 	unsigned char			topology_change_detected;
 
+#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
+	unsigned char			multicast_router;
+
+	u8				multicast_disabled:1;
+
+	u32				hash_elasticity;
+	u32				hash_max;
+
+	u32				multicast_last_member_count;
+	u32				multicast_startup_queries_sent;
+	u32				multicast_startup_query_count;
+
+	unsigned long			multicast_last_member_interval;
+	unsigned long			multicast_membership_interval;
+	unsigned long			multicast_querier_interval;
+	unsigned long			multicast_query_interval;
+	unsigned long			multicast_query_response_interval;
+	unsigned long			multicast_startup_query_interval;
+
+	spinlock_t			multicast_lock;
+	struct net_bridge_mdb_htable	*mdb;
+	struct hlist_head		router_list;
+	struct hlist_head		mglist;
+
+	struct timer_list		multicast_router_timer;
+	struct timer_list		multicast_querier_timer;
+	struct timer_list		multicast_query_timer;
+#endif
+
 	struct timer_list		hello_timer;
 	struct timer_list		tcn_timer;
 	struct timer_list		topology_change_timer;
@@ -133,6 +206,8 @@ struct net_bridge
 
 struct br_input_skb_cb {
 	struct net_device *brdev;
+	int igmp;
+	int mrouters_only;
 };
 
 #define BR_INPUT_SKB_CB(__skb)	((struct br_input_skb_cb *)(__skb)->cb)
@@ -204,6 +279,70 @@ extern struct sk_buff *br_handle_frame(struct net_bridge_port *p,
 extern int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
 extern int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd, void __user *arg);
 
+/* br_multicast.c */
+#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
+extern int br_multicast_rcv(struct net_bridge *br,
+			    struct net_bridge_port *port,
+			    struct sk_buff *skb);
+extern struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
+					       struct sk_buff *skb);
+extern void br_multicast_add_port(struct net_bridge_port *port);
+extern void br_multicast_del_port(struct net_bridge_port *port);
+extern void br_multicast_enable_port(struct net_bridge_port *port);
+extern void br_multicast_disable_port(struct net_bridge_port *port);
+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);
+#else
+static inline int br_multicast_rcv(struct net_bridge *br,
+				   struct net_bridge_port *port,
+				   struct sk_buff *skb)
+{
+	return 0;
+}
+
+static inline struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
+						      struct sk_buff *skb)
+{
+	return NULL;
+}
+
+static inline void br_multicast_add_port(struct net_bridge_port *port)
+{
+}
+
+static inline void br_multicast_del_port(struct net_bridge_port *port)
+{
+}
+
+static inline void br_multicast_enable_port(struct net_bridge_port *port)
+{
+}
+
+static inline void br_multicast_disable_port(struct net_bridge_port *port)
+{
+}
+
+static inline void br_multicast_init(struct net_bridge *br)
+{
+}
+
+static inline void br_multicast_open(struct net_bridge *br)
+{
+}
+
+static inline void br_multicast_stop(struct net_bridge *br)
+{
+}
+#endif
+
+static inline bool br_multicast_is_router(struct net_bridge *br)
+{
+	return br->multicast_router == 2 ||
+	       (br->multicast_router == 1 &&
+		timer_pending(&br->multicast_router_timer));
+}
+
 /* br_netfilter.c */
 #ifdef CONFIG_BRIDGE_NETFILTER
 extern int br_netfilter_init(void);