net-next: dsa: add flow_dissect callback to struct dsa_device_ops

When the flow dissector first sees packets coming in on a DSA devices the
802.3 header wont be located where the code expects it to be as the tag
is still present. Adding this new callback allows a DSA device to provide a
new function that the flow_dissector can use to get the correct protocol
and offset of the network header.
Signed-off-by: Muciri Gatimu <muciri@openmesh.com>
Signed-off-by: Shashidhar Lakkavalli <shashidhar.lakkavalli@openmesh.com>
Signed-off-by: John Crispin <john@phrozen.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -106,6 +106,8 @@ struct dsa_device_ops {
 	struct sk_buff *(*rcv)(struct sk_buff *skb, struct net_device *dev,
 			       struct packet_type *pt,
 			       struct net_device *orig_dev);
+	int (*flow_dissect)(const struct sk_buff *skb, __be16 *proto,
+			    int *offset);
 };
 
 struct dsa_switch_tree {