[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/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index d8c84d8..30df8e6 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -525,7 +525,7 @@
 	dst_release(skb2->dst);
 	skb2->dst = NULL;
 	skb_pull(skb2, offset);
-	skb2->nh.raw = skb2->data;
+	skb_reset_network_header(skb2);
 	eiph = skb2->nh.iph;
 
 	/* Try to guess incoming interface */
@@ -599,7 +599,7 @@
 		dst_release(skb2->dst);
 		skb2->dst = NULL;
 		skb_pull(skb2, offset);
-		skb2->nh.raw = skb2->data;
+		skb_reset_network_header(skb2);
 
 		/* Try to guess incoming interface */
 		rt = rt6_lookup(&skb2->nh.ipv6h->saddr, NULL, 0, 0);
@@ -704,7 +704,7 @@
 		}
 		secpath_reset(skb);
 		skb->mac.raw = skb->nh.raw;
-		skb->nh.raw = skb->data;
+		skb_reset_network_header(skb);
 		skb->protocol = htons(protocol);
 		skb->pkt_type = PACKET_HOST;
 		memset(skb->cb, 0, sizeof(struct inet6_skb_parm));