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/dccp/ipv6.c b/net/dccp/ipv6.c
index b963f35..05ea744 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -314,8 +314,9 @@
 	struct ipv6hdr *rxip6h;
 	struct sk_buff *skb;
 	struct flowi fl;
-	struct net *net = dev_net(rxskb->dst->dev);
+	struct net *net = dev_net(skb_dst(rxskb)->dev);
 	struct sock *ctl_sk = net->dccp.v6_ctl_sk;
+	struct dst_entry *dst;
 
 	if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 		return;
@@ -342,8 +343,9 @@
 	security_skb_classify_flow(rxskb, &fl);
 
 	/* sk = NULL, but it is safe for now. RST socket required. */
-	if (!ip6_dst_lookup(ctl_sk, &skb->dst, &fl)) {
-		if (xfrm_lookup(net, &skb->dst, &fl, NULL, 0) >= 0) {
+	if (!ip6_dst_lookup(ctl_sk, &dst, &fl)) {
+		if (xfrm_lookup(net, &dst, &fl, NULL, 0) >= 0) {
+			skb_dst_set(skb, dst);
 			ip6_xmit(ctl_sk, skb, &fl, NULL, 0);
 			DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 			DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);