[PATCH net-next 4/5] net: bridge: switchdev: notify on mcast active changes

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

Let the bridge notify switchdev if the multicast
active state toggles. So that switch drivers can act on it
accordingly, especially to avoid packetloss.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
 Documentation/networking/switchdev.rst |  8 +++----
 include/net/switchdev.h                | 10 ++++++++
 net/bridge/br_multicast.c              | 33 ++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/switchdev.rst b/Documentation/networking/switchdev.rst
index 2966b7122f05..130f7a36fc73 100644
--- a/Documentation/networking/switchdev.rst
+++ b/Documentation/networking/switchdev.rst
@@ -558,7 +558,7 @@ Because IGMP snooping can be turned on/off at runtime, the switchdev driver
 must be able to reconfigure the underlying hardware on the fly to honor the
 toggling of that option and behave appropriately.
 
-A switchdev driver can also refuse to support dynamic toggling of the multicast
-snooping knob at runtime and require the destruction of the bridge device(s)
-and creation of a new bridge device(s) with a different multicast snooping
-value.
+A switchdev driver must also be able to react to vanishing or appearing
+IGMP/MLD queriers. If no querier is present then, even if IGMP/MLD snooping
+is enabled, the switch must treat this as if IGMP/MLD snooping were disabled.
+The SWITCHDEV_ATTR_ID_BRIDGE_MC_ACTIVE notification allows to track this.
diff --git a/include/net/switchdev.h b/include/net/switchdev.h
index 8346b0d29542..abcc34a81e00 100644
--- a/include/net/switchdev.h
+++ b/include/net/switchdev.h
@@ -27,6 +27,7 @@ enum switchdev_attr_id {
 	SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING,
 	SWITCHDEV_ATTR_ID_BRIDGE_VLAN_PROTOCOL,
 	SWITCHDEV_ATTR_ID_BRIDGE_MC_DISABLED,
+	SWITCHDEV_ATTR_ID_BRIDGE_MC_ACTIVE,
 	SWITCHDEV_ATTR_ID_BRIDGE_MROUTER,
 	SWITCHDEV_ATTR_ID_BRIDGE_MST,
 	SWITCHDEV_ATTR_ID_MRP_PORT_ROLE,
@@ -43,6 +44,14 @@ struct switchdev_brport_flags {
 	unsigned long mask;
 };
 
+struct switchdev_mc_active {
+	short vid;
+	u8 ip4:1,
+	   ip6:1,
+	   ip4_changed:1,
+	   ip6_changed:1;
+};
+
 struct switchdev_vlan_msti {
 	u16 vid;
 	u16 msti;
@@ -64,6 +73,7 @@ struct switchdev_attr {
 		u16 vlan_protocol;			/* BRIDGE_VLAN_PROTOCOL */
 		bool mst;				/* BRIDGE_MST */
 		bool mc_disabled;			/* MC_DISABLED */
+		struct switchdev_mc_active mc_active;	/* MC_ACTIVE */
 		u8 mrp_port_role;			/* MRP_PORT_ROLE */
 		struct switchdev_vlan_msti vlan_msti;	/* VLAN_MSTI */
 	} u;
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 0bbaa21c1479..aec106f9c17d 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1138,6 +1138,27 @@ static int br_ip6_multicast_check_active(struct net_bridge_mcast *brmctx,
 #endif
 }
 
+static int br_multicast_notify_active(struct net_bridge_mcast *brmctx,
+				      bool ip4_active, bool ip6_active,
+				      bool ip4_changed, bool ip6_changed,
+				      struct netlink_ext_ack *extack)
+{
+	struct switchdev_attr attr = {
+		.orig_dev = brmctx->br->dev,
+		.id = SWITCHDEV_ATTR_ID_BRIDGE_MC_ACTIVE,
+		.flags = SWITCHDEV_F_DEFER,
+		.u.mc_active = {
+			.vid = brmctx->vlan ? brmctx->vlan->vid : -1,
+			.ip4 = ip4_active,
+			.ip6 = ip6_active,
+			.ip4_changed = ip4_changed,
+			.ip6_changed = ip6_changed,
+		},
+	};
+
+	return switchdev_port_attr_set(brmctx->br->dev, &attr, extack);
+}
+
 /**
  * __br_multicast_update_active() - update mcast active state
  * @brmctx: the bridge multicast context to check
@@ -1159,6 +1180,8 @@ static int br_ip6_multicast_check_active(struct net_bridge_mcast *brmctx,
  * This function should be called by anything that changes one of the
  * above prerequisites.
  *
+ * Any multicast active state toggling is further notified to switchdev.
+ *
  * Return: 0 on success, a negative value otherwise.
  */
 static int __br_multicast_update_active(struct net_bridge_mcast *brmctx,
@@ -1182,11 +1205,21 @@ static int __br_multicast_update_active(struct net_bridge_mcast *brmctx,
 	ip4_changed = br_ip4_multicast_check_active(brmctx, &ip4_active);
 	ip6_changed = br_ip6_multicast_check_active(brmctx, &ip6_active);
 
+	if (!ip4_changed && !ip6_changed)
+		goto out;
+
+	ret = br_multicast_notify_active(brmctx, ip4_active, ip6_active,
+					 ip4_changed, ip6_changed,
+					 extack);
+	if (ret && ret != -EOPNOTSUPP)
+		goto out;
+
 	if (ip4_changed)
 		brmctx->ip4_active = ip4_active;
 	if (ip6_changed)
 		brmctx->ip6_active = ip6_active;
 
+out:
 	return ret;
 }
 
-- 
2.49.0