net: dsa: provide an option for drivers to always receive bridge VLANs

DSA assumes that a bridge which has vlan filtering disabled is not
vlan aware, and ignores all vlan configuration. However, the kernel
software bridge code allows configuration in this state.

This causes the kernel's idea of the bridge vlan state and the
hardware state to disagree, so "bridge vlan show" indicates a correct
configuration but the hardware lacks all configuration. Even worse,
enabling vlan filtering on a DSA bridge immediately blocks all traffic
which, given the output of "bridge vlan show", is very confusing.

Provide an option that drivers can set to indicate they want to receive
vlan configuration even when vlan filtering is disabled. At the very
least, this is safe for Marvell DSA bridges, which do not look up
ingress traffic in the VTU if the port is in 8021Q disabled state. It is
also safe for the Ocelot switch family. Whether this change is suitable
for all DSA bridges is not known.

Signed-off-by: Russell King <[e-mail]>
Signed-off-by: Vladimir Oltean <[e-mail]>
Reviewed-by: Florian Fainelli <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/dsa.h

···
 	 */
 	bool			vlan_filtering_is_global;
 
+	/* Pass .port_vlan_add and .port_vlan_del to drivers even for bridges
+	 * that have vlan_filtering=0. All drivers should ideally set this (and
+	 * then the option would get removed), but it is unknown whether this
+	 * would break things or not.
+	 */
+	bool			configure_vlan_while_not_filtering;
+
 	/* In case vlan_filtering_is_global is set, the VLAN awareness state
 	 * should be retrieved from here and not from the per-port settings.
 	 */

net/dsa/dsa_priv.h

···
 void dsa_port_bridge_leave(struct dsa_port *dp, struct net_device *br);
 int dsa_port_vlan_filtering(struct dsa_port *dp, bool vlan_filtering,
 			    struct switchdev_trans *trans);
+bool dsa_port_skip_vlan_configuration(struct dsa_port *dp);
 int dsa_port_ageing_time(struct dsa_port *dp, clock_t ageing_clock,
 			 struct switchdev_trans *trans);
 int dsa_port_mtu_change(struct dsa_port *dp, int new_mtu,

net/dsa/port.c

···
 	return 0;
 }
 
+/* This enforces legacy behavior for switch drivers which assume they can't
+ * receive VLAN configuration when enslaved to a bridge with vlan_filtering=0
+ */
+bool dsa_port_skip_vlan_configuration(struct dsa_port *dp)
+{
+	struct dsa_switch *ds = dp->ds;
+
+	if (!dp->bridge_dev)
+		return false;
+
+	return (!ds->configure_vlan_while_not_filtering &&
+		!br_vlan_enabled(dp->bridge_dev));
+}
+
 int dsa_port_ageing_time(struct dsa_port *dp, clock_t ageing_clock,
 			 struct switchdev_trans *trans)
 {

net/dsa/slave.c

···
 	if (obj->orig_dev != dev)
 		return -EOPNOTSUPP;
 
-	if (dp->bridge_dev && !br_vlan_enabled(dp->bridge_dev))
+	if (dsa_port_skip_vlan_configuration(dp))
 		return 0;
 
 	vlan = *SWITCHDEV_OBJ_PORT_VLAN(obj);
···
 	if (obj->orig_dev != dev)
 		return -EOPNOTSUPP;
 
-	if (dp->bridge_dev && !br_vlan_enabled(dp->bridge_dev))
+	if (dsa_port_skip_vlan_configuration(dp))
 		return 0;
 
 	/* Do not deprogram the CPU port as it may be shared with other user
···
 	 * need to emulate the switchdev prepare + commit phase.
 	 */
 	if (dp->bridge_dev) {
-		if (!br_vlan_enabled(dp->bridge_dev))
+		if (dsa_port_skip_vlan_configuration(dp))
 			return 0;
 
 		/* br_vlan_get_info() returns -EINVAL or -ENOENT if the
···
 	 * need to emulate the switchdev prepare + commit phase.
 	 */
 	if (dp->bridge_dev) {
-		if (!br_vlan_enabled(dp->bridge_dev))
+		if (dsa_port_skip_vlan_configuration(dp))
 			return 0;
 
 		/* br_vlan_get_info() returns -EINVAL or -ENOENT if the