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/sched/em_meta.c b/net/sched/em_meta.c
index b6b588b..266151a 100644
--- a/net/sched/em_meta.c
+++ b/net/sched/em_meta.c
@@ -246,11 +246,11 @@
 
 META_COLLECTOR(int_rtclassid)
 {
-	if (unlikely(skb->dst == NULL))
+	if (unlikely(skb_dst(skb) == NULL))
 		*err = -1;
 	else
 #ifdef CONFIG_NET_CLS_ROUTE
-		dst->value = skb->dst->tclassid;
+		dst->value = skb_dst(skb)->tclassid;
 #else
 		dst->value = 0;
 #endif