[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/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index a1e4f39..aafbdfa 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -995,9 +995,10 @@
 	    !ip6_tnl_xmit_ctl(t) || ip6_tnl_addr_conflict(t, ipv6h))
 		return -1;
 
-	if ((offset = parse_tlv_tnl_enc_lim(skb, skb->nh.raw)) > 0) {
+	offset = parse_tlv_tnl_enc_lim(skb, skb_network_header(skb));
+	if (offset > 0) {
 		struct ipv6_tlv_tnl_enc_lim *tel;
-		tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->nh.raw[offset];
+		tel = (struct ipv6_tlv_tnl_enc_lim *)&skb_network_header(skb)[offset];
 		if (tel->encap_limit == 0) {
 			icmpv6_send(skb, ICMPV6_PARAMPROB,
 				    ICMPV6_HDR_FIELD, offset + 2, skb->dev);