net/sched: act_mirred: Add new tc_action_ops get_dev()

Adding support to a new tc_action_ops.
get_dev is a general option which allows to get the underline
device when trying to offload a tc rule.

In case of mirred action the returned device is the mirred (egress)
device.
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/act_api.h

@@ -119,6 +119,8 @@ struct tc_action_ops {
 	int     (*walk)(struct net *, struct sk_buff *,
 			struct netlink_callback *, int, const struct tc_action_ops *);
 	void	(*stats_update)(struct tc_action *, u64, u32, u64);
+	int	(*get_dev)(const struct tc_action *a, struct net *net,
+			   struct net_device **mirred_dev);
 };
 
 struct tc_action_net {

net/sched/act_mirred.c

@@ -315,6 +315,17 @@ static struct notifier_block mirred_device_notifier = {
 	.notifier_call = mirred_device_event,
 };
 
+static int tcf_mirred_device(const struct tc_action *a, struct net *net,
+			     struct net_device **mirred_dev)
+{
+	int ifindex = tcf_mirred_ifindex(a);
+
+	*mirred_dev = __dev_get_by_index(net, ifindex);
+	if (!mirred_dev)
+		return -EINVAL;
+	return 0;
+}
+
 static struct tc_action_ops act_mirred_ops = {
 	.kind		=	"mirred",
 	.type		=	TCA_ACT_MIRRED,
@@ -327,6 +338,7 @@ static struct tc_action_ops act_mirred_ops = {
 	.walk		=	tcf_mirred_walker,
 	.lookup		=	tcf_mirred_search,
 	.size		=	sizeof(struct tcf_mirred),
+	.get_dev	=	tcf_mirred_device,
 };
 
 static __net_init int mirred_init_net(struct net *net)