net-next: tag_mtk: add flow_dissect callback to the ops struct

The MT7530 inserts the 4 magic header in between the 802.3 address and
protocol field. The patch implements the callback that can be called by
the flow dissector to figure out the real protocol and offset of the
network header. With this patch applied we can properly parse the packet
and thus make hashing function properly.
Signed-off-by: NMuciri Gatimu <muciri@openmesh.com>
Signed-off-by: NShashidhar Lakkavalli <shashidhar.lakkavalli@openmesh.com>
Signed-off-by: NJohn Crispin <john@phrozen.org>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/dsa/tag_mtk.c

@@ -87,7 +87,17 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	return skb;
 }
 
+static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
+				int *offset)
+{
+	*offset = 4;
+	*proto = ((__be16 *)skb->data)[1];
+
+	return 0;
+}
+
 const struct dsa_device_ops mtk_netdev_ops = {
-	.xmit	= mtk_tag_xmit,
-	.rcv	= mtk_tag_rcv,
+	.xmit		= mtk_tag_xmit,
+	.rcv		= mtk_tag_rcv,
+	.flow_dissect	= mtk_tag_flow_dissect,
 };