net: dsa: reference count the FDB addresses at the cross-chip notifier level

The same concerns expressed for host MDB entries are valid for host FDBs
just as well:

- in the case of multiple bridges spanning the same switch chip, deleting
  a host FDB entry that belongs to one bridge will result in breakage to
  the other bridge
- not deleting FDB entries across DSA links means that the switch's
  hardware tables will eventually run out, given enough wear&tear

So do the same thing and introduce reference counting for CPU ports and
DSA links using the same data structures as we have for MDB entries.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -288,6 +288,7 @@ struct dsa_port {
 	/* List of MAC addresses that must be forwarded on this port.
 	 * These are only valid on CPU ports and DSA links.
 	 */
+	struct list_head	fdbs;
 	struct list_head	mdbs;
 
 	bool setup;

net/dsa/dsa2.c

@@ -348,6 +348,7 @@ static int dsa_port_setup(struct dsa_port *dp)
 	if (dp->setup)
 		return 0;
 
+	INIT_LIST_HEAD(&dp->fdbs);
 	INIT_LIST_HEAD(&dp->mdbs);
 
 	switch (dp->type) {
@@ -471,6 +472,11 @@ static void dsa_port_teardown(struct dsa_port *dp)
 		break;
 	}
 
+	list_for_each_entry_safe(a, tmp, &dp->fdbs, list) {
+		list_del(&a->list);
+		kfree(a);
+	}
+
 	list_for_each_entry_safe(a, tmp, &dp->mdbs, list) {
 		list_del(&a->list);
 		kfree(a);

net/dsa/switch.c

@@ -253,6 +253,71 @@ static int dsa_switch_do_mdb_del(struct dsa_switch *ds, int port,
 	return 0;
 }
 
+static int dsa_switch_do_fdb_add(struct dsa_switch *ds, int port,
+				 const unsigned char *addr, u16 vid)
+{
+	struct dsa_port *dp = dsa_to_port(ds, port);
+	struct dsa_mac_addr *a;
+	int err;
+
+	/* No need to bother with refcounting for user ports */
+	if (!(dsa_port_is_cpu(dp) || dsa_port_is_dsa(dp)))
+		return ds->ops->port_fdb_add(ds, port, addr, vid);
+
+	a = dsa_mac_addr_find(&dp->fdbs, addr, vid);
+	if (a) {
+		refcount_inc(&a->refcount);
+		return 0;
+	}
+
+	a = kzalloc(sizeof(*a), GFP_KERNEL);
+	if (!a)
+		return -ENOMEM;
+
+	err = ds->ops->port_fdb_add(ds, port, addr, vid);
+	if (err) {
+		kfree(a);
+		return err;
+	}
+
+	ether_addr_copy(a->addr, addr);
+	a->vid = vid;
+	refcount_set(&a->refcount, 1);
+	list_add_tail(&a->list, &dp->fdbs);
+
+	return 0;
+}
+
+static int dsa_switch_do_fdb_del(struct dsa_switch *ds, int port,
+				 const unsigned char *addr, u16 vid)
+{
+	struct dsa_port *dp = dsa_to_port(ds, port);
+	struct dsa_mac_addr *a;
+	int err;
+
+	/* No need to bother with refcounting for user ports */
+	if (!(dsa_port_is_cpu(dp) || dsa_port_is_dsa(dp)))
+		return ds->ops->port_fdb_del(ds, port, addr, vid);
+
+	a = dsa_mac_addr_find(&dp->fdbs, addr, vid);
+	if (!a)
+		return -ENOENT;
+
+	if (!refcount_dec_and_test(&a->refcount))
+		return 0;
+
+	err = ds->ops->port_fdb_del(ds, port, addr, vid);
+	if (err) {
+		refcount_inc(&a->refcount);
+		return err;
+	}
+
+	list_del(&a->list);
+	kfree(a);
+
+	return 0;
+}
+
 static int dsa_switch_host_fdb_add(struct dsa_switch *ds,
 				   struct dsa_notifier_fdb_info *info)
 {
@@ -265,7 +330,7 @@ static int dsa_switch_host_fdb_add(struct dsa_switch *ds,
 	for (port = 0; port < ds->num_ports; port++) {
 		if (dsa_switch_host_address_match(ds, port, info->sw_index,
 						  info->port)) {
-			err = ds->ops->port_fdb_add(ds, port, info->addr,
+			err = dsa_switch_do_fdb_add(ds, port, info->addr,
 						    info->vid);
 			if (err)
 				break;
@@ -278,14 +343,23 @@ static int dsa_switch_host_fdb_add(struct dsa_switch *ds,
 static int dsa_switch_host_fdb_del(struct dsa_switch *ds,
 				   struct dsa_notifier_fdb_info *info)
 {
+	int err = 0;
+	int port;
+
 	if (!ds->ops->port_fdb_del)
 		return -EOPNOTSUPP;
 
-	if (ds->index == info->sw_index)
+	for (port = 0; port < ds->num_ports; port++) {
-		return ds->ops->port_fdb_del(ds, info->port, info->addr,
+		if (dsa_switch_host_address_match(ds, port, info->sw_index,
-					     info->vid);
+						  info->port)) {
+			err = dsa_switch_do_fdb_del(ds, port, info->addr,
+						    info->vid);
+			if (err)
+				break;
+		}
+	}
 
-	return 0;
+	return err;
 }
 
 static int dsa_switch_fdb_add(struct dsa_switch *ds,
@@ -296,7 +370,7 @@ static int dsa_switch_fdb_add(struct dsa_switch *ds,
 	if (!ds->ops->port_fdb_add)
 		return -EOPNOTSUPP;
 
-	return ds->ops->port_fdb_add(ds, port, info->addr, info->vid);
+	return dsa_switch_do_fdb_add(ds, port, info->addr, info->vid);
 }
 
 static int dsa_switch_fdb_del(struct dsa_switch *ds,
@@ -307,7 +381,7 @@ static int dsa_switch_fdb_del(struct dsa_switch *ds,
 	if (!ds->ops->port_fdb_del)
 		return -EOPNOTSUPP;
 
-	return ds->ops->port_fdb_del(ds, port, info->addr, info->vid);
+	return dsa_switch_do_fdb_del(ds, port, info->addr, info->vid);
 }
 
 static int dsa_switch_hsr_join(struct dsa_switch *ds,