net: Add asynchronous callbacks for xfrm on layer 2.

This patch implements asynchronous crypto callbacks
and a backlog handler that can be used when IPsec
is done at layer 2 in the TX path. It also extends
the skb validate functions so that we can update
the driver transmit return codes based on async
crypto operation or to indicate that we queued the
packet in a backlog queue.

Joint work with: Aviv Heller <avivh@mellanox.com>

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cc4ce74..c82d207 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2793,7 +2793,9 @@ struct softnet_data {
 	struct Qdisc		*output_queue;
 	struct Qdisc		**output_queue_tailp;
 	struct sk_buff		*completion_queue;
-
+#ifdef CONFIG_XFRM_OFFLOAD
+	struct sk_buff_head	xfrm_backlog;
+#endif
 #ifdef CONFIG_RPS
 	/* input_queue_head should be written by cpu owning this struct,
 	 * and only read by other cpus. Worth using a cache line.
@@ -3325,7 +3327,7 @@ int dev_get_phys_port_id(struct net_device *dev,
 int dev_get_phys_port_name(struct net_device *dev,
 			   char *name, size_t len);
 int dev_change_proto_down(struct net_device *dev, bool proto_down);
-struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev);
+struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev, bool *again);
 struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);