net: dsa: sja1105: deny alterations of dsa_8021q VLANs from the bridge

At the moment, this can never happen. The 2 modes that we operate in do
not permit that:

 - SJA1105_VLAN_UNAWARE: we are guarded from bridge VLANs added by the
   user by the DSA core. We will later lift this restriction by setting
   ds->vlan_bridge_vtu = true, and that is where we'll need it.

 - SJA1105_VLAN_FILTERING_FULL: in this mode, dsa_8021q configuration is
   disabled. So the user is free to add these VLANs in the 1024-3071
   range.

The reason for the patch is that we'll introduce a third VLAN awareness
state, where both dsa_8021q as well as the bridge are going to call our
.port_vlan_add and .port_vlan_del methods.

For that, we need a good way to discriminate between the 2. The easiest
(and less intrusive way for upper layers) is to recognize the fact that
dsa_8021q configurations are always driven by our driver - we _know_
when a .port_vlan_add method will be called from dsa_8021q because _we_
initiated it.

So introduce an expect_dsa_8021q boolean which is only used, at the
moment, for blacklisting VLANs in range 1024-3071 in the modes when
dsa_8021q is active.
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>

drivers/net/dsa/sja1105/sja1105.h

@@ -198,6 +198,7 @@ struct sja1105_private {
 	 * the switch doesn't confuse them with one another.
 	 */
 	struct mutex mgmt_lock;
+	bool expect_dsa_8021q;
 	enum sja1105_vlan_state vlan_state;
 	struct sja1105_tagger_data tagger_data;
 	struct sja1105_ptp_data ptp_data;

drivers/net/dsa/sja1105/sja1105_main.c

@@ -1811,15 +1811,19 @@ static int sja1105_crosschip_bridge_join(struct dsa_switch *ds,
 		if (dsa_to_port(ds, port)->bridge_dev != br)
 			continue;
 
+		other_priv->expect_dsa_8021q = true;
 		rc = dsa_8021q_crosschip_bridge_join(ds, port, other_ds,
 						     other_port, br,
 						     &priv->crosschip_links);
+		other_priv->expect_dsa_8021q = false;
 		if (rc)
 			return rc;
 
+		priv->expect_dsa_8021q = true;
 		rc = dsa_8021q_crosschip_bridge_join(other_ds, other_port, ds,
 						     port, br,
 						     &other_priv->crosschip_links);
+		priv->expect_dsa_8021q = false;
 		if (rc)
 			return rc;
 	}
@@ -1846,12 +1850,16 @@ static void sja1105_crosschip_bridge_leave(struct dsa_switch *ds,
 		if (dsa_to_port(ds, port)->bridge_dev != br)
 			continue;
 
+		other_priv->expect_dsa_8021q = true;
 		dsa_8021q_crosschip_bridge_leave(ds, port, other_ds, other_port,
 						 br, &priv->crosschip_links);
+		other_priv->expect_dsa_8021q = false;
 
+		priv->expect_dsa_8021q = true;
 		dsa_8021q_crosschip_bridge_leave(other_ds, other_port, ds,
 						 port, br,
 						 &other_priv->crosschip_links);
+		priv->expect_dsa_8021q = false;
 	}
 }
 
@@ -1862,8 +1870,10 @@ static int sja1105_replay_crosschip_vlans(struct dsa_switch *ds, bool enabled)
 	int rc;
 
 	list_for_each_entry(c, &priv->crosschip_links, list) {
+		priv->expect_dsa_8021q = true;
 		rc = dsa_8021q_crosschip_link_apply(ds, c->port, c->other_ds,
 						    c->other_port, enabled);
+		priv->expect_dsa_8021q = false;
 		if (rc)
 			break;
 	}
@@ -1873,10 +1883,13 @@ static int sja1105_replay_crosschip_vlans(struct dsa_switch *ds, bool enabled)
 
 static int sja1105_setup_8021q_tagging(struct dsa_switch *ds, bool enabled)
 {
+	struct sja1105_private *priv = ds->priv;
 	int rc, i;
 
 	for (i = 0; i < SJA1105_NUM_PORTS; i++) {
+		priv->expect_dsa_8021q = true;
 		rc = dsa_port_setup_8021q_tagging(ds, i, enabled);
+		priv->expect_dsa_8021q = false;
 		if (rc < 0) {
 			dev_err(ds->dev, "Failed to setup VLAN tagging for port %d: %d\n",
 				i, rc);
@@ -1901,10 +1914,26 @@ sja1105_get_tag_protocol(struct dsa_switch *ds, int port,
 	return DSA_TAG_PROTO_SJA1105;
 }
 
-/* This callback needs to be present */
 static int sja1105_vlan_prepare(struct dsa_switch *ds, int port,
 				const struct switchdev_obj_port_vlan *vlan)
 {
+	struct sja1105_private *priv = ds->priv;
+	u16 vid;
+
+	if (priv->vlan_state == SJA1105_VLAN_FILTERING_FULL)
+		return 0;
+
+	/* If the user wants best-effort VLAN filtering (aka vlan_filtering
+	 * bridge plus tagging), be sure to at least deny alterations to the
+	 * configuration done by dsa_8021q.
+	 */
+	for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++) {
+		if (!priv->expect_dsa_8021q && vid_is_dsa_8021q(vid)) {
+			dev_err(ds->dev, "Range 1024-3071 reserved for dsa_8021q operation\n");
+			return -EBUSY;
+		}
+	}
+
 	return 0;
 }