bridge: add export of multicast database adjacent to net_dev

With this new, exported function br_multicast_list_adjacent(net_dev) a
list of IPv4/6 addresses is returned. This list contains all multicast
addresses sensed by the bridge multicast snooping feature on all bridge
ports of the bridge interface of net_dev, excluding addresses from the
specified net_device itself.

Adding bridge support to the batman-adv multicast optimization requires
batman-adv knowing about the existence of bridged-in multicast
listeners to be able to reliably serve them with multicast packets.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 76 insertions, 12 deletions

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 1085ffeef956..44d6eb0eb852 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -16,9 +16,27 @@
 #include <linux/netdevice.h>
 #include <uapi/linux/if_bridge.h>
 
+struct br_ip {
+        union {
+                __be32  ip4;
+#if IS_ENABLED(CONFIG_IPV6)
+                struct in6_addr ip6;
+#endif
+        } u;
+        __be16          proto;
+        __u16           vid;
+};
+
+struct br_ip_list {
+        struct list_head list;
+        struct br_ip addr;
+};
+
 extern void brioctl_set(int (*ioctl_hook)(struct net *, unsigned int, void __user *));
 
 typedef int br_should_route_hook_t(struct sk_buff *skb);
 extern br_should_route_hook_t __rcu *br_should_route_hook;
+int br_multicast_list_adjacent(struct net_device *dev,
+                               struct list_head *br_ip_list);
 
 #endif
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b3f17c9b4d06..772476b7c4b7 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -11,6 +11,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/export.h>
 #include <linux/if_ether.h>
 #include <linux/igmp.h>
 #include <linux/jhash.h>
@@ -2141,3 +2142,60 @@ unlock:
 
         return err;
 }
+
+/**
+ * br_multicast_list_adjacent - Returns snooped multicast addresses
+ * @dev:        The bridge port adjacent to which to retrieve addresses
+ * @br_ip_list: The list to store found, snooped multicast IP addresses in
+ *
+ * Creates a list of IP addresses (struct br_ip_list) sensed by the multicast
+ * snooping feature on all bridge ports of dev's bridge device, excluding
+ * the addresses from dev itself.
+ *
+ * Returns the number of items added to br_ip_list.
+ *
+ * Notes:
+ * - br_ip_list needs to be initialized by caller
+ * - br_ip_list might contain duplicates in the end
+ *   (needs to be taken care of by caller)
+ * - br_ip_list needs to be freed by caller
+ */
+int br_multicast_list_adjacent(struct net_device *dev,
+                               struct list_head *br_ip_list)
+{
+        struct net_bridge *br;
+        struct net_bridge_port *port;
+        struct net_bridge_port_group *group;
+        struct br_ip_list *entry;
+        int count = 0;
+
+        rcu_read_lock();
+        if (!br_ip_list || !br_port_exists(dev))
+                goto unlock;
+
+        port = br_port_get_rcu(dev);
+        if (!port || !port->br)
+                goto unlock;
+
+        br = port->br;
+
+        list_for_each_entry_rcu(port, &br->port_list, list) {
+                if (!port->dev || port->dev == dev)
+                        continue;
+
+                hlist_for_each_entry_rcu(group, &port->mglist, mglist) {
+                        entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
+                        if (!entry)
+                                goto unlock;
+
+                        entry->addr = group->addr;
+                        list_add(&entry->list, br_ip_list);
+                        count++;
+                }
+        }
+
+unlock:
+        rcu_read_unlock();
+        return count;
+}
+EXPORT_SYMBOL_GPL(br_multicast_list_adjacent);
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 97c5e46dde72..50e2ab021484 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -54,18 +54,6 @@ struct mac_addr
         unsigned char   addr[ETH_ALEN];
 };
 
-struct br_ip
-{
-        union {
-                __be32  ip4;
-#if IS_ENABLED(CONFIG_IPV6)
-                struct in6_addr ip6;
-#endif
-        } u;
-        __be16          proto;
-        __u16           vid;
-};
-
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 /* our own querier */
 struct bridge_mcast_own_query {