[SK_BUFF]: Introduce skb_transport_offset()

For the quite common 'skb->h.raw - skb->data' sequence.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index ed3deed..9576745 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -27,7 +27,7 @@
 	int nfrags;
 
 	/* Strip IP+ESP header. */
-	__skb_pull(skb, skb->h.raw - skb->data);
+	__skb_pull(skb, skb_transport_offset(skb));
 	/* Now skb is pure payload to encrypt */
 
 	err = -ENOMEM;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 13739cd..13875e8 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -435,7 +435,7 @@
 		 * fragments on the socket so that all csums of sk_buffs
 		 * should be together
 		 */
-		offset = skb->h.raw - skb->data;
+		offset = skb_transport_offset(skb);
 		skb->csum = skb_checksum(skb, offset, skb->len - offset, 0);
 
 		skb->ip_summed = CHECKSUM_NONE;