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>

net/xfrm/xfrm_policy.c

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 9c068ab..cb81ca3 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2027,6 +2027,8 @@
 {
 	struct net *net = dev_net(skb->dev);
 	struct flowi fl;
+	struct dst_entry *dst;
+	int res;
 
 	if (xfrm_decode_session(skb, &fl, family) < 0) {
 		/* XXX: we should have something like FWDHDRERROR here. */
@@ -2034,7 +2036,11 @@
 		return 0;
 	}
 
-	return xfrm_lookup(net, &skb->dst, &fl, NULL, 0) == 0;
+	dst = skb_dst(skb);
+
+	res = xfrm_lookup(net, &dst, &fl, NULL, 0) == 0;
+	skb_dst_set(skb, dst);
+	return res;
 }
 EXPORT_SYMBOL(__xfrm_route_forward);