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/cls_flow.c b/net/sched/cls_flow.c
index 0ef4e30..9402a7f 100644
--- a/net/sched/cls_flow.c
+++ b/net/sched/cls_flow.c
@@ -84,7 +84,7 @@
 	case htons(ETH_P_IPV6):
 		return ntohl(ipv6_hdr(skb)->daddr.s6_addr32[3]);
 	default:
-		return addr_fold(skb->dst) ^ (__force u16)skb->protocol;
+		return addr_fold(skb_dst(skb)) ^ (__force u16)skb->protocol;
 	}
 }
 
@@ -163,7 +163,7 @@
 		break;
 	}
 	default:
-		res = addr_fold(skb->dst) ^ (__force u16)skb->protocol;
+		res = addr_fold(skb_dst(skb)) ^ (__force u16)skb->protocol;
 	}
 
 	return res;
@@ -251,8 +251,8 @@
 static u32 flow_get_rtclassid(const struct sk_buff *skb)
 {
 #ifdef CONFIG_NET_CLS_ROUTE
-	if (skb->dst)
-		return skb->dst->tclassid;
+	if (skb_dst(skb))
+		return skb_dst(skb)->tclassid;
 #endif
 	return 0;
 }