[SK_BUFF]: Introduce ip_hdr(), remove skb->nh.iph

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index e9097cf..bf502c4 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -5286,7 +5286,7 @@
 		chunk->ecn_ce_done = 1;
 
 		af = sctp_get_af_specific(
-			ipver2af(chunk->skb->nh.iph->version));
+			ipver2af(ip_hdr(chunk->skb)->version));
 
 		if (af && af->is_ce(chunk->skb) && asoc->peer.ecn_capable) {
 			/* Do real work as sideffect. */