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/ipv4/ip_options.c b/net/ipv4/ip_options.c
index 7e1074f..94bf105 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -143,7 +143,7 @@
 						__be32 addr;
 
 						memcpy(&addr, sptr+soffset-1, 4);
-						if (inet_addr_type(dev_net(skb->dst->dev), addr) != RTN_LOCAL) {
+						if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_LOCAL) {
 							dopt->ts_needtime = 1;
 							soffset += 8;
 						}
@@ -624,12 +624,12 @@
 		memcpy(&nexthop, &optptr[srrptr-1], 4);
 
 		rt = skb_rtable(skb);
-		skb->dst = NULL;
+		skb_dst_set(skb, NULL);
 		err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 		rt2 = skb_rtable(skb);
 		if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 			ip_rt_put(rt2);
-			skb->dst = &rt->u.dst;
+			skb_dst_set(skb, &rt->u.dst);
 			return -EINVAL;
 		}
 		ip_rt_put(rt);