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/ipv6/xfrm6_mode_tunnel.c b/net/ipv6/xfrm6_mode_tunnel.c
index e20529b..3927832 100644
--- a/net/ipv6/xfrm6_mode_tunnel.c
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -31,7 +31,7 @@
  */
 static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 {
-	struct dst_entry *dst = skb->dst;
+	struct dst_entry *dst = skb_dst(skb);
 	struct ipv6hdr *top_iph;
 	int dsfield;
 
@@ -45,7 +45,7 @@
 
 	memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
 	       sizeof(top_iph->flow_lbl));
-	top_iph->nexthdr = xfrm_af2proto(skb->dst->ops->family);
+	top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);
 
 	dsfield = XFRM_MODE_SKB_CB(skb)->tos;
 	dsfield = INET_ECN_encapsulate(dsfield, dsfield);