[SK_BUFF]: Introduce skb_reset_network_header(skb)

For the common, open coded 'skb->nh.raw = skb->data' operation, so that we can
later turn skb->nh.raw into a offset, reducing the size of struct sk_buff in
64bit land while possibly keeping it as a pointer on 32bit.

This one touches just the most simple case, next will handle the slightly more
"complex" cases.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 0ad3896..b4d1cdd 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -359,7 +359,8 @@
 				 (2 * sizeof(u32)))))
 		return;
 
-	skb->h.raw = skb->nh.raw = skb->data;
+	skb_reset_network_header(skb);
+	skb->h.raw = skb->data;
 	arp = skb->nh.arph;
 
 	if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
@@ -389,7 +390,7 @@
 	if (!send_skb)
 		return;
 
-	send_skb->nh.raw = send_skb->data;
+	skb_reset_network_header(send_skb);
 	arp = (struct arphdr *) skb_put(send_skb, size);
 	send_skb->dev = skb->dev;
 	send_skb->protocol = htons(ETH_P_ARP);