[PATCH net-next v2] bridge: export multicast database via netlink

[PATCH net-next v2] bridge: export multicast database via netlink

[Cong Wang]

V2: drop patch 1/2, export ifindex directly
    Redesign netlink attributes
    Improve netlink seq check
    Handle IPv6 addr as well

TODO: remove debugging printk's

This patch exports bridge multicast database via netlink
message type RTM_GETMDB. Similar to fdb, but currently bridge-specific.
We may need to support modify multicast database too (RTM_{ADD,DEL}MDB).

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Cong Wang <amwang@redhat.com>
    
---
 include/uapi/linux/if_bridge.h |   55 +++++++++++++
 include/uapi/linux/rtnetlink.h |    3 +
 net/bridge/Makefile            |    2 +-
 net/bridge/br_mdb.c            |  173 ++++++++++++++++++++++++++++++++++++++++
 net/bridge/br_multicast.c      |    2 +
 net/bridge/br_private.h        |    2 +
 6 files changed, 236 insertions(+), 1 deletions(-)

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index b388579..9a0f6ff 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -116,4 +116,59 @@ enum {
 	__IFLA_BRIDGE_MAX,
 };
 #define IFLA_BRIDGE_MAX (__IFLA_BRIDGE_MAX - 1)
+
+/* Bridge multicast database attributes
+ * [MDBA_MDB] = {
+ *     [MDBA_MDB_ENTRY] = {
+ *         [MDBA_MDB_ENTRY_INFO]
+ *     }
+ * }
+ * [MDBA_ROUTER] = {
+ *    [MDBA_ROUTER_PORT]
+ * }
+ */
+enum {
+	MDBA_UNSPEC,
+	MDBA_MDB,
+	MDBA_ROUTER,
+	__MDBA_MAX,
+};
+#define MDBA_MAX (__MDBA_MAX - 1)
+
+enum {
+	MDBA_MDB_UNSPEC,
+	MDBA_MDB_ENTRY,
+	__MDBA_MDB_MAX,
+};
+#define MDBA_MDB_MAX (__MDBA_MDB_MAX - 1)
+
+enum {
+	MDBA_MDB_ENTRY_UNSPEC,
+	MDBA_MDB_ENTRY_INFO,
+	__MDBA_MDB_ENTRY_MAX,
+};
+#define MDBA_MDB_ENTRY_MAX (__MDBA_MDB_ENTRY_MAX - 1)
+
+enum {
+	MDBA_ROUTER_UNSPEC,
+	MDBA_ROUTER_PORT,
+	__MDBA_ROUTER_MAX,
+};
+#define MDBA_ROUTER_MAX (__MDBA_ROUTER_MAX - 1)
+
+struct br_port_msg {
+	__u32 ifindex;
+};
+
+struct br_mdb_entry {
+	__u32 ifindex;
+	struct {
+		union {
+			__be32	ip4;
+			struct in6_addr ip6;
+		} u;
+		__be16		proto;
+	} addr;
+};
+
 #endif /* _UAPI_LINUX_IF_BRIDGE_H */
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 3dee071..0df623f 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -125,6 +125,9 @@ enum {
 	RTM_GETNETCONF = 82,
 #define RTM_GETNETCONF RTM_GETNETCONF
 
+	RTM_GETMDB = 86,
+#define RTM_GETMDB RTM_GETMDB
+
 	__RTM_MAX,
 #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
 };
diff --git a/net/bridge/Makefile b/net/bridge/Makefile
index d0359ea..e859098 100644
--- a/net/bridge/Makefile
+++ b/net/bridge/Makefile
@@ -12,6 +12,6 @@ bridge-$(CONFIG_SYSFS) += br_sysfs_if.o br_sysfs_br.o
 
 bridge-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o
 
-bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o
+bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o br_mdb.o
 
 obj-$(CONFIG_BRIDGE_NF_EBTABLES) += netfilter/
diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
new file mode 100644
index 0000000..6ab6149
--- /dev/null
+++ b/net/bridge/br_mdb.c
@@ -0,0 +1,173 @@
+#include <linux/err.h>
+#include <linux/if_ether.h>
+#include <linux/igmp.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/rculist.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/ip.h>
+#if IS_ENABLED(CONFIG_IPV6)
+#include <net/ipv6.h>
+#include <net/mld.h>
+#include <net/addrconf.h>
+#include <net/ip6_checksum.h>
+#endif
+
+#include "br_private.h"
+
+static int br_rports_fill_info(struct sk_buff *skb, struct netlink_callback *cb,
+			       struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_port *p;
+	struct hlist_node *n;
+	struct nlattr *nest;
+
+	if (!br->multicast_router || hlist_empty(&br->router_list)) {
+		printk(KERN_INFO "no router on bridge\n");
+		return 0;
+	}
+
+	nest = nla_nest_start(skb, MDBA_ROUTER);
+	if (nest == NULL)
+		return -EMSGSIZE;
+
+	hlist_for_each_entry_rcu(p, n, &br->router_list, rlist) {
+		if (p && nla_put_u32(skb, MDBA_ROUTER_PORT, p->dev->ifindex))
+			goto fail;
+	}
+
+	nla_nest_end(skb, nest);
+	return 0;
+fail:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+static int br_mdb_fill_info(struct sk_buff *skb, struct netlink_callback *cb,
+			    struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_mdb_htable *mdb;
+	struct nlattr *nest, *nest2;
+	int i, err = 0;
+	int idx = 0, s_idx = cb->args[1];
+
+	if (br->multicast_disabled) {
+		printk(KERN_INFO "multicast is disabled on bridge\n");
+		return 0;
+	}
+
+	mdb = rcu_dereference(br->mdb);
+	if (!mdb) {
+		printk(KERN_INFO "no mdb on bridge\n");
+		return 0;
+	}
+
+	nest = nla_nest_start(skb, MDBA_MDB);
+	if (nest == NULL)
+		return -EMSGSIZE;
+
+	printk(KERN_INFO "s_idx = %d\n", s_idx);
+	for (i = 0; i < mdb->max; i++) {
+		struct hlist_node *h;
+		struct net_bridge_mdb_entry *mp;
+		struct net_bridge_port_group *p, **pp;
+		struct net_bridge_port *port;
+
+		hlist_for_each_entry_rcu(mp, h, &mdb->mhash[i], hlist[mdb->ver]) {
+			if (idx < s_idx)
+				goto skip;
+
+			nest2 = nla_nest_start(skb, MDBA_MDB_ENTRY);
+			if (nest2 == NULL) {
+				err = -EMSGSIZE;
+				goto out;
+			}
+
+			for (pp = &mp->ports;
+			     (p = rcu_dereference(*pp)) != NULL;
+			      pp = &p->next) {
+				port = p->port;
+				if (port) {
+					struct br_mdb_entry e;
+					e.ifindex = port->dev->ifindex;
+					e.addr.u.ip4 = p->addr.u.ip4;
+#if IS_ENABLED(CONFIG_IPV6)
+					e.addr.u.ip6 = p->addr.u.ip6;
+#endif
+					e.addr.proto = p->addr.proto;
+					if (nla_put(skb, MDBA_MDB_ENTRY_INFO, sizeof(e), &e)) {
+						nla_nest_cancel(skb, nest2);
+						err = -EMSGSIZE;
+						goto out;
+					}
+					printk(KERN_INFO "port %s, mcaddr: %pI4\n", port->dev->name, &p->addr.u.ip4);
+				}
+			}
+			nla_nest_end(skb, nest2);
+		skip:
+			idx++;
+		}
+	}
+
+out:
+	cb->args[1] = idx;
+	cb->args[2] = mdb->seq;
+	nla_nest_end(skb, nest);
+	return err;
+}
+
+static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct net_device *dev;
+	struct net *net = sock_net(skb->sk);
+	struct nlmsghdr *nlh;
+	int idx = 0, s_idx;
+
+	s_idx = cb->args[0];
+
+	rcu_read_lock();
+
+	for_each_netdev_rcu(net, dev) {
+		if (dev->priv_flags & IFF_EBRIDGE) {
+			struct br_port_msg *bpm;
+
+			if (idx < s_idx)
+				goto cont;
+
+			nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+					cb->nlh->nlmsg_seq, RTM_GETMDB,
+					sizeof(*bpm), NLM_F_MULTI);
+			if (nlh == NULL)
+				break;
+
+			bpm = nlmsg_data(nlh);
+			bpm->ifindex = dev->ifindex;
+			if (br_mdb_fill_info(skb, cb, dev) < 0) {
+				printk(KERN_INFO "br_mdb_fill_info failed\n");
+				goto out;
+			}
+			if (br_rports_fill_info(skb, cb, dev) < 0) {
+				printk(KERN_INFO "br_rports_fill_info failed\n");
+				goto out;
+			}
+
+			nlmsg_end(skb, nlh);
+		cont:
+			idx++;
+		}
+	}
+
+out:
+	cb->seq = cb->args[2];
+	rcu_read_unlock();
+	cb->args[0] = idx;
+	return skb->len;
+}
+
+void br_mdb_init(void)
+{
+	rtnl_register(PF_BRIDGE, RTM_GETMDB, NULL, br_mdb_dump, NULL);
+}
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 2417434..d53e4f4 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -322,6 +322,7 @@ static int br_mdb_rehash(struct net_bridge_mdb_htable __rcu **mdbp, int max,
 
 	mdb->size = old ? old->size : 0;
 	mdb->ver = old ? old->ver ^ 1 : 0;
+	mdb->seq = old ? (old->seq + 1): 0;
 
 	if (!old || elasticity)
 		get_random_bytes(&mdb->secret, sizeof(mdb->secret));
@@ -1584,6 +1585,7 @@ void br_multicast_init(struct net_bridge *br)
 		    br_multicast_querier_expired, (unsigned long)br);
 	setup_timer(&br->multicast_query_timer, br_multicast_query_expired,
 		    (unsigned long)br);
+	br_mdb_init();
 }
 
 void br_multicast_open(struct net_bridge *br)
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index eb9cd42..6484069 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -105,6 +105,7 @@ struct net_bridge_mdb_htable
 	u32				max;
 	u32				secret;
 	u32				ver;
+	u32				seq;
 };
 
 struct net_bridge_port
@@ -432,6 +433,7 @@ extern int br_multicast_set_port_router(struct net_bridge_port *p,
 extern int br_multicast_toggle(struct net_bridge *br, unsigned long val);
 extern int br_multicast_set_querier(struct net_bridge *br, unsigned long val);
 extern int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val);
+extern void br_mdb_init(void);
 
 static inline bool br_multicast_is_router(struct net_bridge *br)
 {

[PATCH iproute2 v2] Add mdb command to bridge

[Cong Wang]

V2: sync with the kernel patch
    handle IPv6 addr
    a few cleanup

Sample output:

	# ./bridge/bridge mdb
	bridge dev br0
	multicast database:
	port eth0, group 224.8.8.9
	port eth1, group 224.8.8.8
	router ports: 2

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Cong Wang <amwang@redhat.com>
---
 bridge/Makefile    |    2 +-
 bridge/br_common.h |    1 +
 bridge/bridge.c    |    1 +
 bridge/mdb.c       |  181 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 184 insertions(+), 1 deletions(-)

diff --git a/bridge/Makefile b/bridge/Makefile
index 9a6743e..67aceb4 100644
--- a/bridge/Makefile
+++ b/bridge/Makefile
@@ -1,4 +1,4 @@
-BROBJ = bridge.o fdb.o monitor.o link.o
+BROBJ = bridge.o fdb.o monitor.o link.o mdb.o
 
 include ../Config
 
diff --git a/bridge/br_common.h b/bridge/br_common.h
index 718ecb9..67fd75c 100644
--- a/bridge/br_common.h
+++ b/bridge/br_common.h
@@ -5,6 +5,7 @@ extern int print_fdb(const struct sockaddr_nl *who,
 		     struct nlmsghdr *n, void *arg);
 
 extern int do_fdb(int argc, char **argv);
+extern int do_mdb(int argc, char **argv);
 extern int do_monitor(int argc, char **argv);
 
 extern int preferred_family;
diff --git a/bridge/bridge.c b/bridge/bridge.c
index e2c33b0..1fcd365 100644
--- a/bridge/bridge.c
+++ b/bridge/bridge.c
@@ -43,6 +43,7 @@ static const struct cmd {
 	int (*func)(int argc, char **argv);
 } cmds[] = {
 	{ "fdb", 	do_fdb },
+	{ "mdb", 	do_mdb },
 	{ "monitor",	do_monitor },
 	{ "help",	do_help },
 	{ 0 }
diff --git a/bridge/mdb.c b/bridge/mdb.c
new file mode 100644
index 0000000..3e62331
--- /dev/null
+++ b/bridge/mdb.c
@@ -0,0 +1,181 @@
+/*
+ * Get mdb table with netlink
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <linux/if_bridge.h>
+#include <linux/if_ether.h>
+#include <linux/neighbour.h>
+#include <linux/if_bridge.h>
+#include <string.h>
+#include <arpa/inet.h>
+
+#include "libnetlink.h"
+#include "br_common.h"
+#include "rt_names.h"
+#include "utils.h"
+
+#ifndef MDBA_RTA
+#define MDBA_RTA(r) \
+	((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct br_port_msg))))
+#endif
+
+int filter_index;
+
+static void usage(void)
+{
+	fprintf(stderr, "       bridge mdb {show} [ dev DEV ]\n");
+	exit(-1);
+}
+
+static void br_print_router_ports(FILE *f, struct rtattr *attr)
+{
+	uint32_t *port_ifindex;
+	struct rtattr *i;
+	int rem;
+
+	rem = RTA_PAYLOAD(attr);
+	for (i = RTA_DATA(attr); RTA_OK(i, rem); i = RTA_NEXT(i, rem)) {
+		port_ifindex = RTA_DATA(i);
+		fprintf(f, "%s ", ll_index_to_name(*port_ifindex));
+	}
+	fprintf(f, "\n");
+}
+
+static void print_mdb_entry(FILE *f, struct br_mdb_entry *e)
+{
+	SPRINT_BUF(abuf);
+
+	if (e->addr.proto == htons(ETH_P_IP))
+		fprintf(f, "port %s, group %s\n", ll_index_to_name(e->ifindex),
+			inet_ntop(AF_INET, &e->addr.u.ip4, abuf, sizeof(abuf)));
+	else
+		fprintf(f, "port %s, group %s\n", ll_index_to_name(e->ifindex),
+			inet_ntop(AF_INET6, &e->addr.u.ip6, abuf, sizeof(abuf)));
+}
+
+static void br_print_mdb_entry(FILE *f, struct rtattr *attr)
+{
+	struct rtattr *i;
+	int rem;
+	struct br_mdb_entry *e;
+
+	rem = RTA_PAYLOAD(attr);
+	for (i = RTA_DATA(attr); RTA_OK(i, rem); i = RTA_NEXT(i, rem)) {
+		e = RTA_DATA(i);
+		print_mdb_entry(f, e);
+	}
+}
+
+int print_mdb(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
+{
+	FILE *fp = arg;
+	struct br_port_msg *r = NLMSG_DATA(n);
+	int len = n->nlmsg_len;
+	struct rtattr * tb[MDBA_MAX+1];
+
+	if (n->nlmsg_type != RTM_GETMDB) {
+		fprintf(stderr, "Not RTM_GETMDB: %08x %08x %08x\n",
+			n->nlmsg_len, n->nlmsg_type, n->nlmsg_flags);
+
+		return 0;
+	}
+
+	len -= NLMSG_LENGTH(sizeof(*r));
+	if (len < 0) {
+		fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
+		return -1;
+	}
+
+	if (filter_index && filter_index != r->ifindex)
+		return 0;
+
+	if (!filter_index && r->ifindex)
+		fprintf(fp, "bridge dev %s\n", ll_index_to_name(r->ifindex));
+
+	parse_rtattr(tb, MDBA_MAX, MDBA_RTA(r), n->nlmsg_len - NLMSG_LENGTH(sizeof(*r)));
+
+	if (tb[MDBA_MDB]) {
+		struct rtattr *i;
+		int rem = RTA_PAYLOAD(tb[MDBA_MDB]);
+
+		fprintf(fp, "multicast database:\n");
+
+		for (i = RTA_DATA(tb[MDBA_MDB]); RTA_OK(i, rem); i = RTA_NEXT(i, rem))
+			br_print_mdb_entry(fp, i);
+	}
+
+	if (tb[MDBA_ROUTER]) {
+		struct rtattr *i;
+		int rem = RTA_PAYLOAD(tb[MDBA_ROUTER]);
+
+		fprintf(fp, "router ports: ");
+
+		for (i = RTA_DATA(tb[MDBA_ROUTER]); RTA_OK(i, rem); i = RTA_NEXT(i, rem))
+			br_print_router_ports(fp, i);
+	}
+
+	return 0;
+}
+
+static int mdb_show(int argc, char **argv)
+{
+	char *filter_dev = NULL;
+
+	while (argc > 0) {
+		if (strcmp(*argv, "dev") == 0) {
+			NEXT_ARG();
+			if (filter_dev)
+				duparg("dev", *argv);
+			filter_dev = *argv;
+		}
+		argc--; argv++;
+	}
+
+	if (filter_dev) {
+		filter_index = if_nametoindex(filter_dev);
+		if (filter_index == 0) {
+			fprintf(stderr, "Cannot find device \"%s\"\n",
+				filter_dev);
+			return -1;
+		}
+	}
+
+	if (rtnl_wilddump_request(&rth, PF_BRIDGE, RTM_GETMDB) < 0) {
+		perror("Cannot send dump request");
+		exit(1);
+	}
+
+	if (rtnl_dump_filter(&rth, print_mdb, stdout) < 0) {
+		fprintf(stderr, "Dump terminated\n");
+		exit(1);
+	}
+
+	return 0;
+}
+
+int do_mdb(int argc, char **argv)
+{
+	ll_init_map(&rth);
+
+	if (argc > 0) {
+		if (matches(*argv, "show") == 0 ||
+		    matches(*argv, "lst") == 0 ||
+		    matches(*argv, "list") == 0)
+			return mdb_show(argc-1, argv+1);
+		if (matches(*argv, "help") == 0)
+			usage();
+	} else
+		return mdb_show(0, NULL);
+
+	fprintf(stderr, "Command \"%s\" is unknown, try \"bridge mdb help\".\n", *argv);
+	exit(-1);
+}

Re: [PATCH net-next v2] bridge: export multicast database via netlink

[Stephen Hemminger]

On Mon,  3 Dec 2012 21:03:43 +0800
Cong Wang <amwang@redhat.com> wrote:

> V2: drop patch 1/2, export ifindex directly
>     Redesign netlink attributes
>     Improve netlink seq check
>     Handle IPv6 addr as well
> 
> TODO: remove debugging printk's
> 
> This patch exports bridge multicast database via netlink
> message type RTM_GETMDB. Similar to fdb, but currently bridge-specific.
> We may need to support modify multicast database too (RTM_{ADD,DEL}MDB).
> 
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: Stephen Hemminger <shemminger@vyatta.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Thomas Graf <tgraf@suug.ch>
> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Cong Wang <amwang@redhat.com>
>     

Minor nit reported by checkpatch was the messages should be using the api
which provides the most info in the log to identify.

WARNING: Prefer netdev_info(netdev, ... then dev_info(dev, ... then pr_info(...  to printk(KERN_INFO ...
#190: FILE: net/bridge/br_mdb.c:28:
+		printk(KERN_INFO "no router on bridge\n")

There is a set of macro's already for use in bridging code:
                br_info(br, "no router on bridge\n");

Re: [PATCH net-next v2] bridge: export multicast database via netlink

[Cong Wang]

On Tue, 2012-12-04 at 08:53 -0800, Stephen Hemminger wrote:
> On Mon,  3 Dec 2012 21:03:43 +0800
> Cong Wang <amwang@redhat.com> wrote:
> 
> > V2: drop patch 1/2, export ifindex directly
> >     Redesign netlink attributes
> >     Improve netlink seq check
> >     Handle IPv6 addr as well
> > 
> > TODO: remove debugging printk's
> > 
> > This patch exports bridge multicast database via netlink
> > message type RTM_GETMDB. Similar to fdb, but currently bridge-specific.
> > We may need to support modify multicast database too (RTM_{ADD,DEL}MDB).
> > 
> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > Cc: Stephen Hemminger <shemminger@vyatta.com>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Thomas Graf <tgraf@suug.ch>
> > Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> > Signed-off-by: Cong Wang <amwang@redhat.com>
> >     
> 
> Minor nit reported by checkpatch was the messages should be using the api
> which provides the most info in the log to identify.
> 
> WARNING: Prefer netdev_info(netdev, ... then dev_info(dev, ... then pr_info(...  to printk(KERN_INFO ...
> #190: FILE: net/bridge/br_mdb.c:28:
> +		printk(KERN_INFO "no router on bridge\n")
> 
> There is a set of macro's already for use in bridging code:
>                 br_info(br, "no router on bridge\n");
> 

Never mind, removing these printk's is in my TODO list. :)

Re: [PATCH net-next v2] bridge: export multicast database via netlink

[David Miller]

From: Cong Wang <amwang@redhat.com>
Date: Mon,  3 Dec 2012 21:03:43 +0800

> TODO: remove debugging printk's

Can you please take care of this so we can consider this patch
seriously for inclusion?

Thanks.

Re: [PATCH net-next v2] bridge: export multicast database via netlink

[Cong Wang]

On Tue, 2012-12-04 at 13:25 -0500, David Miller wrote:
> From: Cong Wang <amwang@redhat.com>
> Date: Mon,  3 Dec 2012 21:03:43 +0800
> 
> > TODO: remove debugging printk's
> 
> Can you please take care of this so we can consider this patch
> seriously for inclusion?
> 

Sure. I planned to send V3 when I wrote this TODO. ;) And it seems
Thomas and Stephen are ok with it now, I will remove these printk's.

Thanks.