net: bridge: multicast: add mdb context support

Choose the proper bridge multicast context when user-spaces is adding
mdb entries. Currently we require the vlan to be configured on at least
one device (port or bridge) in order to add an mdb entry if vlan
mcast snooping is enabled (vlan snooping implies vlan filtering).
Note that we always allow deleting an entry, regardless of the vlan state.

Signed-off-by: Nikolay Aleksandrov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

net/bridge/br_mdb.c

@@ -1019,14 +1019,47 @@ static int br_mdb_parse(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return 0;
 }
 
+static struct net_bridge_mcast *
+__br_mdb_choose_context(struct net_bridge *br,
+			const struct br_mdb_entry *entry,
+			struct netlink_ext_ack *extack)
+{
+	struct net_bridge_mcast *brmctx = NULL;
+	struct net_bridge_vlan *v;
+
+	if (!br_opt_get(br, BROPT_MCAST_VLAN_SNOOPING_ENABLED)) {
+		brmctx = &br->multicast_ctx;
+		goto out;
+	}
+
+	if (!entry->vid) {
+		NL_SET_ERR_MSG_MOD(extack, "Cannot add an entry without a vlan when vlan snooping is enabled");
+		goto out;
+	}
+
+	v = br_vlan_find(br_vlan_group(br), entry->vid);
+	if (!v) {
+		NL_SET_ERR_MSG_MOD(extack, "Vlan is not configured");
+		goto out;
+	}
+	if (br_multicast_ctx_vlan_global_disabled(&v->br_mcast_ctx)) {
+		NL_SET_ERR_MSG_MOD(extack, "Vlan's multicast processing is disabled");
+		goto out;
+	}
+	brmctx = &v->br_mcast_ctx;
+out:
+	return brmctx;
+}
+
 static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 			    struct br_mdb_entry *entry,
 			    struct nlattr **mdb_attrs,
 			    struct netlink_ext_ack *extack)
 {
 	struct net_bridge_mdb_entry *mp, *star_mp;
-	struct net_bridge_port_group *p;
 	struct net_bridge_port_group __rcu **pp;
+	struct net_bridge_port_group *p;
+	struct net_bridge_mcast *brmctx;
 	struct br_ip group, star_group;
 	unsigned long now = jiffies;
 	unsigned char flags = 0;
@@ -1035,6 +1068,10 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 
 	__mdb_entry_to_br_ip(entry, &group, mdb_attrs);
 
+	brmctx = __br_mdb_choose_context(br, entry, extack);
+	if (!brmctx)
+		return -EINVAL;
+
 	/* host join errors which can happen before creating the group */
 	if (!port) {
 		/* don't allow any flags for host-joined groups */
@@ -1100,14 +1137,14 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 	rcu_assign_pointer(*pp, p);
 	if (entry->state == MDB_TEMPORARY)
 		mod_timer(&p->timer,
-			  now + br->multicast_ctx.multicast_membership_interval);
+			  now + brmctx->multicast_membership_interval);
 	br_mdb_notify(br->dev, mp, p, RTM_NEWMDB);
 	/* if we are adding a new EXCLUDE port group (*,G) it needs to be also
 	 * added to all S,G entries for proper replication, if we are adding
 	 * a new INCLUDE port (S,G) then all of *,G EXCLUDE ports need to be
 	 * added to it for proper replication
 	 */
-	if (br_multicast_should_handle_mode(&br->multicast_ctx, group.proto)) {
+	if (br_multicast_should_handle_mode(brmctx, group.proto)) {
 		switch (filter_mode) {
 		case MCAST_EXCLUDE:
 			br_multicast_star_g_handle_mode(p, MCAST_EXCLUDE);