[SK_BUFF]: Introduce skb_network_header()

For the places where we need a pointer to the network header, it is still legal
to touch skb->nh.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/ipcomp6.c b/net/ipv6/ipcomp6.c
index 5724ba9..3e71d16 100644
--- a/net/ipv6/ipcomp6.c
+++ b/net/ipv6/ipcomp6.c
@@ -166,10 +166,10 @@
 	top_iph->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 
 	ipch = (struct ipv6_comp_hdr *)start;
-	ipch->nexthdr = *skb->nh.raw;
+	ipch->nexthdr = *skb_network_header(skb);
 	ipch->flags = 0;
 	ipch->cpi = htons((u16 )ntohl(x->id.spi));
-	*skb->nh.raw = IPPROTO_COMP;
+	*skb_network_header(skb) = IPPROTO_COMP;
 
 out_ok:
 	return 0;