net: skb->dst accessors

Define three accessors to get/set dst attached to a skb

struct dst_entry *skb_dst(const struct sk_buff *skb)

void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)

void skb_dst_drop(struct sk_buff *skb)
This one should replace occurrences of :
dst_release(skb->dst)
skb->dst = NULL;

Delete skb->dst field

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/output.c b/net/sctp/output.c
index f0c91df..b764114 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -405,10 +405,10 @@
 			sctp_assoc_sync_pmtu(asoc);
 		}
 	}
-	nskb->dst = dst_clone(tp->dst);
-	if (!nskb->dst)
+	dst = dst_clone(tp->dst);
+	skb_dst_set(nskb, dst);
+	if (dst)
 		goto no_route;
-	dst = nskb->dst;
 
 	/* Build the SCTP header.  */
 	sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));