net: dsa: tag_sja1105: implement sub-VLAN decoding

Create a subvlan_map as part of each port's tagger private structure.
This keeps reverse mappings of bridge-to-dsa_8021q VLAN retagging rules.

Note that as of this patch, this piece of code is never engaged, due to
the fact that the driver hasn't installed any retagging rule, so we'll
always see packets with a subvlan code of 0 (untagged).
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_main.c

@@ -2856,6 +2856,7 @@ static int sja1105_probe(struct spi_device *spi)
 		struct sja1105_port *sp = &priv->ports[port];
 		struct dsa_port *dp = dsa_to_port(ds, port);
 		struct net_device *slave;
+		int subvlan;
 
 		if (!dsa_is_user_port(ds, port))
 			continue;
@@ -2876,6 +2877,9 @@ static int sja1105_probe(struct spi_device *spi)
 		}
 		skb_queue_head_init(&sp->xmit_queue);
 		sp->xmit_tpid = ETH_P_SJA1105;
+
+		for (subvlan = 0; subvlan < DSA_8021Q_N_SUBVLAN; subvlan++)
+			sp->subvlan_map[subvlan] = VLAN_N_VID;
 	}
 
 	return 0;

include/linux/dsa/sja1105.h

@@ -9,6 +9,7 @@
 
 #include <linux/skbuff.h>
 #include <linux/etherdevice.h>
+#include <linux/dsa/8021q.h>
 #include <net/dsa.h>
 
 #define ETH_P_SJA1105				ETH_P_DSA_8021Q
@@ -53,6 +54,7 @@ struct sja1105_skb_cb {
 	((struct sja1105_skb_cb *)DSA_SKB_CB_PRIV(skb))
 
 struct sja1105_port {
+	u16 subvlan_map[DSA_8021Q_N_SUBVLAN];
 	struct kthread_worker *xmit_worker;
 	struct kthread_work xmit_work;
 	struct sk_buff_head xmit_queue;

net/dsa/tag_sja1105.c

@@ -254,6 +254,20 @@ static struct sk_buff
 	return skb;
 }
 
+static void sja1105_decode_subvlan(struct sk_buff *skb, u16 subvlan)
+{
+	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
+	struct sja1105_port *sp = dp->priv;
+	u16 vid = sp->subvlan_map[subvlan];
+	u16 vlan_tci;
+
+	if (vid == VLAN_N_VID)
+		return;
+
+	vlan_tci = (skb->priority << VLAN_PRIO_SHIFT) | vid;
+	__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
+}
+
 static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
@@ -263,6 +277,7 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 	struct ethhdr *hdr;
 	u16 tpid, vid, tci;
 	bool is_link_local;
+	u16 subvlan = 0;
 	bool is_tagged;
 	bool is_meta;
 
@@ -286,6 +301,7 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 		source_port = dsa_8021q_rx_source_port(vid);
 		switch_id = dsa_8021q_rx_switch_id(vid);
 		skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
+		subvlan = dsa_8021q_rx_subvlan(vid);
 	} else if (is_link_local) {
 		/* Management traffic path. Switch embeds the switch ID and
 		 * port ID into bytes of the destination MAC, courtesy of
@@ -310,6 +326,9 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 		return NULL;
 	}
 
+	if (subvlan)
+		sja1105_decode_subvlan(skb, subvlan);
+
 	return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
 					      is_meta);
 }