bridge: Implement MLD Querier wake-up calls / Android bug workaround

Implement a configurable MLD Querier wake-up calls "feature" which
works around a widely spread Android bug in connection with IGMP/MLD
snooping.

Currently there are mobile devices (e.g. Android) which are not able
to receive and respond to MLD Queries reliably because the Wifi driver
filters a lot of ICMPv6 when the device is asleep - including
MLD. This in turn breaks IPv6 communication when MLD Snooping is
enabled. However there is one ICMPv6 type which is allowed to pass and
which can be used to wake up the mobile device: ICMPv6 Echo Requests.

If this bridge is the selected MLD Querier then setting
"multicast_wakeupcall" to a number n greater than 0 will send n
ICMPv6 Echo Requests to each host behind this port to wake
them up with each MLD Query. Upon receiving a matching ICMPv6 Echo
Reply an MLD Query with a unicast ethernet destination will be sent
to the specific host(s).

Link: https://issuetracker.google.com/issues/149630944
Link: freifunk-gluon/gluon#1832

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

include/linux/if_bridge.h

@@ -50,6 +50,7 @@ struct br_ip_list {
 #define BR_MRP_AWARE		BIT(17)
 #define BR_MRP_LOST_CONT	BIT(18)
 #define BR_MRP_LOST_IN_CONT	BIT(19)
+#define BR_MULTICAST_WAKEUPCALL	BIT(20)
 
 #define BR_DEFAULT_AGEING_TIME	(300 * HZ)
 

include/uapi/linux/if_link.h

@@ -355,6 +355,7 @@ enum {
 	IFLA_BRPORT_BACKUP_PORT,
 	IFLA_BRPORT_MRP_RING_OPEN,
 	IFLA_BRPORT_MRP_IN_OPEN,
+	IFLA_BRPORT_MCAST_WAKEUPCALL,
 	__IFLA_BRPORT_MAX
 };
 #define IFLA_BRPORT_MAX (__IFLA_BRPORT_MAX - 1)

net/bridge/Kconfig

@@ -48,6 +48,32 @@ config BRIDGE_IGMP_SNOOPING
 
 	  If unsure, say Y.
 
+config BRIDGE_IGMP_SNOOPING_WAKEUPCALLS
+	bool "MLD Querier wake-up calls"
+	depends on BRIDGE_IGMP_SNOOPING
+	depends on IPV6
+	help
+	  If you say Y here, then the MLD Snooping Querier will be built
+	  with a per bridge port wake-up call "feature"/workaround.
+
+	  Currently there are mobile devices (e.g. Android) which are not able
+	  to receive and respond to MLD Queries reliably because the Wifi driver
+	  filters a lot of ICMPv6 when the device is asleep - including MLD.
+	  This in turn breaks IPv6 communication when MLD Snooping is enabled.
+	  However there is one ICMPv6 type which is allowed to pass and
+	  which can be used to wake up the mobile device: ICMPv6 Echo Requests.
+
+	  If this bridge is the selected MLD Querier then setting
+	  "multicast_wakeupcall" to a number n greater than 0 will send n
+	  ICMPv6 Echo Requests to each host behind this port to wake them up
+	  with each MLD Query. Upon receiving a matching ICMPv6 Echo Reply
+	  an MLD Query with a unicast ethernet destination will be sent to the
+	  specific host(s).
+
+	  Say N to exclude this support and reduce the binary size.
+
+	  If unsure, say N.
+
 config BRIDGE_VLAN_FILTERING
 	bool "VLAN filtering"
 	depends on BRIDGE

net/bridge/br_fdb.c

@@ -84,6 +84,10 @@ static void fdb_rcu_free(struct rcu_head *head)
 {
 	struct net_bridge_fdb_entry *ent
 		= container_of(head, struct net_bridge_fdb_entry, rcu);
+
+#ifdef CONFIG_BRIDGE_IGMP_SNOOPING_WAKEUPCALLS
+	del_timer_sync(&ent->wakeupcall_timer);
+#endif
 	kmem_cache_free(br_fdb_cache, ent);
 }
 
@@ -511,6 +515,12 @@ static struct net_bridge_fdb_entry *fdb_create(struct net_bridge *br,
 		fdb->key.vlan_id = vid;
 		fdb->flags = flags;
 		fdb->updated = fdb->used = jiffies;
+
+#ifdef CONFIG_BRIDGE_IGMP_SNOOPING_WAKEUPCALLS
+		timer_setup(&fdb->wakeupcall_timer,
+			    br_multicast_send_wakeupcall, 0);
+#endif
+
 		if (rhashtable_lookup_insert_fast(&br->fdb_hash_tbl,
 						  &fdb->rhnode,
 						  br_fdb_rht_params)) {

net/bridge/br_input.c

@@ -155,8 +155,10 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	if (dst) {
 		unsigned long now = jiffies;
 
-		if (test_bit(BR_FDB_LOCAL, &dst->flags))
+		if (test_bit(BR_FDB_LOCAL, &dst->flags)) {
+			br_multicast_wakeupcall_rcv(br, p, skb, vid);
 			return br_pass_frame_up(skb);
+		}
 
 		if (now != dst->used)
 			dst->used = now;