[PATCH net-next v3 04/14] net: bridge: mcast: track active state, IGMP/MLD querier appearance

["Linus Lüssing" <linus.luessing@c0d3.blue>]

This is the first step to track in dedicated, per protocol family
variables if we can actively and safely use multicast snooping.
To later use these in the fast/data path instead of performing
all these checks for every packet and to later notify DSA/switchdev
about this state.

This toggles these new variables to true after a Maximum Response Delay
(default: 10 seconds) if a new IGMP or MLD querier has appeared. This
can be triggered either through receiving an IGMP/MLD query from another
host or by a user enabling our own IGMP/MLD querier.

This is the first of several requirements, similar to what
br_multicast_querier_exists() already checks so far, to be able to
reliably receive IGMP/MLD reports, which in turn are needed to build
a complete multicast database.

No functional change for the fast/data path yet.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
 net/bridge/br_multicast.c | 109 ++++++++++++++++++++++++++++++++++++--
 net/bridge/br_private.h   |   2 +
 2 files changed, 108 insertions(+), 3 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b90f0e149c40..83c1331843f3 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1067,6 +1067,81 @@ static struct sk_buff *br_ip4_multicast_alloc_query(struct net_bridge_mcast *brm
 	return skb;
 }
 
+static bool br_ip4_multicast_querier_exists(struct net_bridge_mcast *brmctx)
+{
+	return __br_multicast_querier_exists(brmctx, &brmctx->ip4_other_query, false);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static bool br_ip6_multicast_querier_exists(struct net_bridge_mcast *brmctx)
+{
+	return __br_multicast_querier_exists(brmctx, &brmctx->ip6_other_query, true);
+}
+#endif
+
+static void br_ip4_multicast_update_active(struct net_bridge_mcast *brmctx,
+					   bool force_inactive)
+{
+	if (force_inactive)
+		brmctx->ip4_active = false;
+	else
+		brmctx->ip4_active = br_ip4_multicast_querier_exists(brmctx);
+}
+
+static void br_ip6_multicast_update_active(struct net_bridge_mcast *brmctx,
+					   bool force_inactive)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	if (force_inactive)
+		brmctx->ip6_active = false;
+	else
+		brmctx->ip6_active = br_ip6_multicast_querier_exists(brmctx);
+#endif
+}
+
+static void br_multicast_notify_active(struct net_bridge_mcast *brmctx,
+				       bool ip4_active_old, bool ip6_active_old)
+{
+	if (brmctx->ip4_active == ip4_active_old &&
+	    brmctx->ip6_active == ip6_active_old)
+		return;
+
+	br_debug(brmctx->br, "mc_active changed, vid: %i: v4: %i->%i, v6: %i->%i\n",
+		 brmctx->vlan ? brmctx->vlan->vid : -1,
+		 ip4_active_old, brmctx->ip4_active,
+		 ip6_active_old, brmctx->ip6_active);
+}
+
+/**
+ * br_multicast_update_active() - update mcast active state
+ * @brmctx: the bridge multicast context to check
+ *
+ * This (potentially) updates the IPv4/IPv6 multicast active state. And by
+ * that enables or disables snooping of multicast payload traffic in fast
+ * path.
+ *
+ * The multicast active state is set, per protocol family, if:
+ *
+ * - an IGMP/MLD querier is present
+ *
+ * And is unset otherwise.
+ *
+ * This function should be called by anything that changes one of the
+ * above prerequisites.
+ */
+static void br_multicast_update_active(struct net_bridge_mcast *brmctx)
+{
+	bool ip4_active_old = brmctx->ip4_active, ip6_active_old = brmctx->ip6_active;
+	bool force_inactive = false;
+
+	lockdep_assert_held_once(&brmctx->br->multicast_lock);
+
+	br_ip4_multicast_update_active(brmctx, force_inactive);
+	br_ip6_multicast_update_active(brmctx, force_inactive);
+
+	br_multicast_notify_active(brmctx, ip4_active_old, ip6_active_old);
+}
+
 #if IS_ENABLED(CONFIG_IPV6)
 static struct sk_buff *br_ip6_multicast_alloc_query(struct net_bridge_mcast *brmctx,
 						    struct net_bridge_mcast_port *pmctx,
@@ -1770,10 +1845,36 @@ static void br_ip6_multicast_querier_expired(struct timer_list *t)
 }
 #endif
 
-static void br_multicast_query_delay_expired(struct timer_list *t)
+static void br_ip4_multicast_query_delay_expired(struct timer_list *t)
 {
+	struct net_bridge_mcast *brmctx = timer_container_of(brmctx, t,
+							     ip4_other_query.delay_timer);
+
+	spin_lock(&brmctx->br->multicast_lock);
+	if (!br_multicast_is_stopping(brmctx->br, t))
+		/* an own or other IGMP querier appeared some seconds ago and all
+		 * reports should have arrived by now, maybe set multicast state to active
+		 */
+		br_multicast_update_active(brmctx);
+	spin_unlock(&brmctx->br->multicast_lock);
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
+static void br_ip6_multicast_query_delay_expired(struct timer_list *t)
+{
+	struct net_bridge_mcast *brmctx = timer_container_of(brmctx, t,
+							     ip6_other_query.delay_timer);
+
+	spin_lock(&brmctx->br->multicast_lock);
+	if (!br_multicast_is_stopping(brmctx->br, t))
+		/* an own or other MLD querier appeared some seconds ago and all
+		 * reports should have arrived, maybe set multicast state to active
+		 */
+		br_multicast_update_active(brmctx);
+	spin_unlock(&brmctx->br->multicast_lock);
+}
+#endif
+
 static void br_multicast_select_own_querier(struct net_bridge_mcast *brmctx,
 					    struct br_ip *ip,
 					    struct sk_buff *skb)
@@ -4115,11 +4216,13 @@ void br_multicast_ctx_init(struct net_bridge *br,
 	brmctx->multicast_membership_interval = 260 * HZ;
 
 	brmctx->ip4_querier.port_ifidx = 0;
+	brmctx->ip4_active = 0;
 	seqcount_spinlock_init(&brmctx->ip4_querier.seq, &br->multicast_lock);
 	brmctx->multicast_igmp_version = 2;
 #if IS_ENABLED(CONFIG_IPV6)
 	brmctx->multicast_mld_version = 1;
 	brmctx->ip6_querier.port_ifidx = 0;
+	brmctx->ip6_active = 0;
 	seqcount_spinlock_init(&brmctx->ip6_querier.seq, &br->multicast_lock);
 #endif
 
@@ -4232,12 +4335,12 @@ void br_multicast_reset_timer_cbs(struct net_bridge_mcast *brmctx)
 
 	brmctx->ip4_mc_router_timer.function = br_ip4_multicast_local_router_expired;
 	brmctx->ip4_other_query.timer.function = br_ip4_multicast_querier_expired;
-	brmctx->ip4_other_query.delay_timer.function = br_multicast_query_delay_expired;
+	brmctx->ip4_other_query.delay_timer.function = br_ip4_multicast_query_delay_expired;
 	brmctx->ip4_own_query.timer.function = br_ip4_multicast_query_expired;
 #if IS_ENABLED(CONFIG_IPV6)
 	brmctx->ip6_mc_router_timer.function = br_ip6_multicast_local_router_expired;
 	brmctx->ip6_other_query.timer.function = br_ip6_multicast_querier_expired;
-	brmctx->ip6_other_query.delay_timer.function = br_multicast_query_delay_expired;
+	brmctx->ip6_other_query.delay_timer.function = br_ip6_multicast_query_delay_expired;
 	brmctx->ip6_own_query.timer.function = br_ip6_multicast_query_expired;
 #endif
 }
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index a181a27aa559..4cc59abdb8e1 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -160,12 +160,14 @@ struct net_bridge_mcast {
 	struct bridge_mcast_other_query	ip4_other_query;
 	struct bridge_mcast_own_query	ip4_own_query;
 	struct bridge_mcast_querier	ip4_querier;
+	bool				ip4_active;
 #if IS_ENABLED(CONFIG_IPV6)
 	struct hlist_head		ip6_mc_router_list;
 	struct timer_list		ip6_mc_router_timer;
 	struct bridge_mcast_other_query	ip6_other_query;
 	struct bridge_mcast_own_query	ip6_own_query;
 	struct bridge_mcast_querier	ip6_querier;
+	bool				ip6_active;
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 #endif /* CONFIG_BRIDGE_IGMP_SNOOPING */
 };
-- 
2.51.0