[SK_BUFF]: Introduce skb_transport_header(skb)

For the places where we need a pointer to the transport header, it is
still legal to touch skb->h.raw directly if just adding to,
subtracting from or setting it to another layer header.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/xfrm6_mode_transport.c b/net/ipv6/xfrm6_mode_transport.c
index 0134d74..d526f4e 100644
--- a/net/ipv6/xfrm6_mode_transport.c
+++ b/net/ipv6/xfrm6_mode_transport.c
@@ -51,10 +51,11 @@
  */
 static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
 {
-	int ihl = skb->data - skb->h.raw;
+	int ihl = skb->data - skb_transport_header(skb);
 
 	if (skb->h.raw != skb->nh.raw) {
-		memmove(skb->h.raw, skb_network_header(skb), ihl);
+		memmove(skb_transport_header(skb),
+			skb_network_header(skb), ihl);
 		skb->nh.raw = skb->h.raw;
 	}
 	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -