net: bridge: mcast: add support for raw L2 multicast groups

Extend the bridge multicast control and data path to configure routes
for L2 (non-IP) multicast groups.

The uapi struct br_mdb_entry union u is extended with another variant,
mac_addr, which does not change the structure size, and which is valid
when the proto field is zero.

To be compatible with the forwarding code that is already in place,
which acts as an IGMP/MLD snooping bridge with querier capabilities, we
need to declare that for L2 MDB entries (for which there exists no such
thing as IGMP/MLD snooping/querying), that there is always a querier.
Otherwise, these entries would be flooded to all bridge ports and not
just to those that are members of the L2 multicast group.

Needless to say, only permanent L2 multicast groups can be installed on
a bridge port.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20201028233831.610076-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/if_bridge.h

@@ -25,6 +25,7 @@ struct br_ip {
 #if IS_ENABLED(CONFIG_IPV6)
 		struct in6_addr ip6;
 #endif
+		unsigned char	mac_addr[ETH_ALEN];
 	} dst;
 	__be16		proto;
 	__u16           vid;

include/uapi/linux/if_bridge.h

@@ -651,6 +651,7 @@ struct br_mdb_entry {
 		union {
 			__be32	ip4;
 			struct in6_addr ip6;
+			unsigned char mac_addr[ETH_ALEN];
 		} u;
 		__be16		proto;
 	} addr;

net/bridge/br_device.c

@@ -93,7 +93,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		mdst = br_mdb_get(br, skb, vid);
 		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
-		    br_multicast_querier_exists(br, eth_hdr(skb)))
+		    br_multicast_querier_exists(br, eth_hdr(skb), mdst))
 			br_multicast_flood(mdst, skb, false, true);
 		else
 			br_flood(br, skb, BR_PKT_MULTICAST, false, true);

net/bridge/br_input.c

@@ -134,7 +134,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	case BR_PKT_MULTICAST:
 		mdst = br_mdb_get(br, skb, vid);
 		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
-		    br_multicast_querier_exists(br, eth_hdr(skb))) {
+		    br_multicast_querier_exists(br, eth_hdr(skb), mdst)) {
 			if ((mdst && mdst->host_joined) ||
 			    br_multicast_is_router(br)) {
 				local_rcv = true;

net/bridge/br_mdb.c

@@ -87,6 +87,8 @@ static void __mdb_entry_to_br_ip(struct br_mdb_entry *entry, struct br_ip *ip,
 			ip->src.ip6 = nla_get_in6_addr(mdb_attrs[MDBE_ATTR_SOURCE]);
 		break;
 #endif
+	default:
+		ether_addr_copy(ip->dst.mac_addr, entry->addr.u.mac_addr);
 	}
 
 }
@@ -174,9 +176,11 @@ static int __mdb_fill_info(struct sk_buff *skb,
 	if (mp->addr.proto == htons(ETH_P_IP))
 		e.addr.u.ip4 = mp->addr.dst.ip4;
 #if IS_ENABLED(CONFIG_IPV6)
-	if (mp->addr.proto == htons(ETH_P_IPV6))
+	else if (mp->addr.proto == htons(ETH_P_IPV6))
 		e.addr.u.ip6 = mp->addr.dst.ip6;
 #endif
+	else
+		ether_addr_copy(e.addr.u.mac_addr, mp->addr.dst.mac_addr);
 	e.addr.proto = mp->addr.proto;
 	nest_ent = nla_nest_start_noflag(skb,
 					 MDBA_MDB_ENTRY_INFO);
@@ -210,6 +214,8 @@ static int __mdb_fill_info(struct sk_buff *skb,
 		}
 		break;
 #endif
+	default:
+		ether_addr_copy(e.addr.u.mac_addr, mp->addr.dst.mac_addr);
 	}
 	if (p) {
 		if (nla_put_u8(skb, MDBA_MDB_EATTR_RTPROT, p->rt_protocol))
@@ -562,9 +568,12 @@ void br_mdb_notify(struct net_device *dev,
 		if (mp->addr.proto == htons(ETH_P_IP))
 			ip_eth_mc_map(mp->addr.dst.ip4, mdb.addr);
 #if IS_ENABLED(CONFIG_IPV6)
-		else
+		else if (mp->addr.proto == htons(ETH_P_IPV6))
 			ipv6_eth_mc_map(&mp->addr.dst.ip6, mdb.addr);
 #endif
+		else
+			ether_addr_copy(mdb.addr, mp->addr.dst.mac_addr);
+
 		mdb.obj.orig_dev = pg->key.port->dev;
 		switch (type) {
 		case RTM_NEWMDB:
@@ -693,6 +702,12 @@ static bool is_valid_mdb_entry(struct br_mdb_entry *entry,
 			return false;
 		}
 #endif
+	} else if (entry->addr.proto == 0) {
+		/* L2 mdb */
+		if (!is_multicast_ether_addr(entry->addr.u.mac_addr)) {
+			NL_SET_ERR_MSG_MOD(extack, "L2 entry group is not multicast");
+			return false;
+		}
 	} else {
 		NL_SET_ERR_MSG_MOD(extack, "Unknown entry protocol");
 		return false;
@@ -849,6 +864,11 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 		}
 	}
 
+	if (br_group_is_l2(&group) && entry->state != MDB_PERMANENT) {
+		NL_SET_ERR_MSG_MOD(extack, "Only permanent L2 entries allowed");
+		return -EINVAL;
+	}
+
 	mp = br_mdb_ip_get(br, &group);
 	if (!mp) {
 		mp = br_multicast_new_group(br, &group);

net/bridge/br_multicast.c

@@ -179,7 +179,8 @@ struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 		break;
 #endif
 	default:
-		return NULL;
+		ip.proto = 0;
+		ether_addr_copy(ip.dst.mac_addr, eth_hdr(skb)->h_dest);
 	}
 
 	return br_mdb_ip_get_rcu(br, &ip);
@@ -1203,6 +1204,10 @@ void br_multicast_host_join(struct net_bridge_mdb_entry *mp, bool notify)
 		if (notify)
 			br_mdb_notify(mp->br->dev, mp, NULL, RTM_NEWMDB);
 	}
+
+	if (br_group_is_l2(&mp->addr))
+		return;
+
 	mod_timer(&mp->timer, jiffies + mp->br->multicast_membership_interval);
 }
 
@@ -1254,8 +1259,8 @@ __br_multicast_add_group(struct net_bridge *br,
 			break;
 	}
 
-	p = br_multicast_new_port_group(port, group, *pp, 0, src, filter_mode,
-					RTPROT_KERNEL);
+	p = br_multicast_new_port_group(port, group, *pp, 0, src,
+					filter_mode, RTPROT_KERNEL);
 	if (unlikely(!p)) {
 		p = ERR_PTR(-ENOMEM);
 		goto out;
@@ -3690,7 +3695,7 @@ bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto)
 	memset(&eth, 0, sizeof(eth));
 	eth.h_proto = htons(proto);
 
-	ret = br_multicast_querier_exists(br, &eth);
+	ret = br_multicast_querier_exists(br, &eth, NULL);
 
 unlock:
 	rcu_read_unlock();

net/bridge/br_private.h

@@ -854,6 +854,11 @@ void br_multicast_star_g_handle_mode(struct net_bridge_port_group *pg,
 void br_multicast_sg_add_exclude_ports(struct net_bridge_mdb_entry *star_mp,
 				       struct net_bridge_port_group *sg);
 
+static inline bool br_group_is_l2(const struct br_ip *group)
+{
+	return group->proto == 0;
+}
+
 #define mlock_dereference(X, br) \
 	rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))
 
@@ -885,7 +890,8 @@ __br_multicast_querier_exists(struct net_bridge *br,
 }
 
 static inline bool br_multicast_querier_exists(struct net_bridge *br,
-					       struct ethhdr *eth)
+					       struct ethhdr *eth,
+					       const struct net_bridge_mdb_entry *mdb)
 {
 	switch (eth->h_proto) {
 	case (htons(ETH_P_IP)):
@@ -897,7 +903,7 @@ static inline bool br_multicast_querier_exists(struct net_bridge *br,
 			&br->ip6_other_query, true);
 #endif
 	default:
-		return false;
+		return !!mdb && br_group_is_l2(&mdb->addr);
 	}
 }