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/core/dev.c b/net/core/dev.c
index e2fcc5f..34b49a6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1693,10 +1693,9 @@
 		 * If device doesnt need skb->dst, release it right now while
 		 * its hot in this cpu cache
 		 */
-		if ((dev->priv_flags & IFF_XMIT_DST_RELEASE) && skb->dst) {
-			dst_release(skb->dst);
-			skb->dst = NULL;
-		}
+		if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
+			skb_dst_drop(skb);
+
 		rc = ops->ndo_start_xmit(skb, dev);
 		if (rc == 0)
 			txq_trans_update(txq);