netpoll: fix rx_hook() interface by passing the skb

Right now skb->data is passed to rx_hook() even if the skb
has not been linearised and without giving rx_hook() a way
to linearise it.

Change the rx_hook() interface and make it accept the skb
and the offset to the UDP payload as arguments. rx_hook() is
also renamed to rx_skb_hook() to ensure that out of the tree
users notice the API change.

In this way any rx_skb_hook() implementation can perform all
the needed operations to properly (and safely) access the
skb data.

Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index f3c7c24..fbfdb9d 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -24,7 +24,8 @@
 	struct net_device *dev;
 	char dev_name[IFNAMSIZ];
 	const char *name;
-	void (*rx_hook)(struct netpoll *, int, char *, int);
+	void (*rx_skb_hook)(struct netpoll *np, int source, struct sk_buff *skb,
+			    int offset, int len);
 
 	union inet_addr local_ip, remote_ip;
 	bool ipv6;
@@ -41,7 +42,7 @@
 	unsigned long rx_flags;
 	spinlock_t rx_lock;
 	struct semaphore dev_lock;
-	struct list_head rx_np; /* netpolls that registered an rx_hook */
+	struct list_head rx_np; /* netpolls that registered an rx_skb_hook */
 
 	struct sk_buff_head neigh_tx; /* list of neigh requests to reply to */
 	struct sk_buff_head txq;