net: dsa: allow 8021q uppers while the bridge has vlan_filtering=0

When the bridge has VLAN awareness disabled there isn't any duplication
of functionality, since the bridge does not process VLAN. Don't deny
adding 8021q uppers to DSA switch ports in that case. The switch is
supposed to simply pass traffic leaving the VLAN tag as-is, and the
stack will happily strip the VLAN tag for all 8021q uppers that exist.

We need to ensure that there are no 8021q uppers when the user attempts
to enable bridge vlan_filtering.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/port.c

@@ -193,11 +193,44 @@ void dsa_port_bridge_leave(struct dsa_port *dp, struct net_device *br)
 	dsa_port_set_state_now(dp, BR_STATE_FORWARDING);
 }
 
+/* Must be called under rcu_read_lock() */
 static bool dsa_port_can_apply_vlan_filtering(struct dsa_port *dp,
 					      bool vlan_filtering)
 {
 	struct dsa_switch *ds = dp->ds;
-	int i;
+	int err, i;
+
+	/* VLAN awareness was off, so the question is "can we turn it on".
+	 * We may have had 8021q uppers, those need to go. Make sure we don't
+	 * enter an inconsistent state: deny changing the VLAN awareness state
+	 * as long as we have 8021q uppers.
+	 */
+	if (vlan_filtering && dsa_is_user_port(ds, dp->index)) {
+		struct net_device *upper_dev, *slave = dp->slave;
+		struct net_device *br = dp->bridge_dev;
+		struct list_head *iter;
+
+		netdev_for_each_upper_dev_rcu(slave, upper_dev, iter) {
+			struct bridge_vlan_info br_info;
+			u16 vid;
+
+			if (!is_vlan_dev(upper_dev))
+				continue;
+
+			vid = vlan_dev_vlan_id(upper_dev);
+
+			/* br_vlan_get_info() returns -EINVAL or -ENOENT if the
+			 * device, respectively the VID is not found, returning
+			 * 0 means success, which is a failure for us here.
+			 */
+			err = br_vlan_get_info(br, vid, &br_info);
+			if (err == 0) {
+				dev_err(ds->dev, "Must remove upper %s first\n",
+					upper_dev->name);
+				return false;
+			}
+		}
+	}
 
 	if (!ds->vlan_filtering_is_global)
 		return true;
@@ -233,10 +266,19 @@ int dsa_port_vlan_filtering(struct dsa_port *dp, bool vlan_filtering,
 	int err;
 
 	if (switchdev_trans_ph_prepare(trans)) {
+		bool apply;
+
 		if (!ds->ops->port_vlan_filtering)
 			return -EOPNOTSUPP;
 
-		if (!dsa_port_can_apply_vlan_filtering(dp, vlan_filtering))
+		/* We are called from dsa_slave_switchdev_blocking_event(),
+		 * which is not under rcu_read_lock(), unlike
+		 * dsa_slave_switchdev_event().
+		 */
+		rcu_read_lock();
+		apply = dsa_port_can_apply_vlan_filtering(dp, vlan_filtering);
+		rcu_read_unlock();
+		if (!apply)
 			return -EINVAL;
 
 		return 0;

net/dsa/slave.c

@@ -344,7 +344,7 @@ static int dsa_slave_vlan_add(struct net_device *dev,
 	/* Deny adding a bridge VLAN when there is already an 802.1Q upper with
 	 * the same VID.
 	 */
-	if (trans->ph_prepare) {
+	if (trans->ph_prepare && br_vlan_enabled(dp->bridge_dev)) {
 		rcu_read_lock();
 		err = dsa_slave_vlan_check_for_8021q_uppers(dev, &vlan);
 		rcu_read_unlock();
@@ -1936,7 +1936,7 @@ dsa_slave_check_8021q_upper(struct net_device *dev,
 	int err = NOTIFY_DONE;
 	u16 vid;
 
-	if (!br)
+	if (!br || !br_vlan_enabled(br))
 		return NOTIFY_DONE;
 
 	extack = netdev_notifier_info_to_extack(&info->info);