[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>

net/ipv6/af_inet6.c

@@ -693,7 +693,8 @@ int ipv6_opt_accepted(struct sock *sk, struct sk_buff *skb)
 	if (np->rxopt.all) {
 		if ((opt->hop && (np->rxopt.bits.hopopts ||
 				  np->rxopt.bits.ohopopts)) ||
-		    ((IPV6_FLOWINFO_MASK & *(__be32*)skb->nh.raw) &&
+		    ((IPV6_FLOWINFO_MASK &
+		      *(__be32 *)skb_network_header(skb)) &&
 		     np->rxopt.bits.rxflow) ||
 		    (opt->srcrt && (np->rxopt.bits.srcrt ||
 		     np->rxopt.bits.osrcrt)) ||