ipv6: Normalize arguments to ip6_dst_blackhole().

Return a dst pointer which is potentitally error encoded.

Don't pass original dst pointer by reference, pass a struct net
instead of a socket, and elide the flow argument since it is
unnecessary.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -520,9 +520,8 @@ extern struct dst_entry *	ip6_sk_dst_lookup_flow(struct sock *sk,
 						       struct flowi *fl,
 						       const struct in6_addr *final_dst,
 						       bool can_sleep);
-extern int			ip6_dst_blackhole(struct sock *sk,
-						  struct dst_entry **dst,
-						  struct flowi *fl);
+extern struct dst_entry *	ip6_dst_blackhole(struct net *net,
+						  struct dst_entry *orig_dst);
 
 /*
  *	skb processing functions

net/ipv6/ip6_output.c

@@ -1029,7 +1029,7 @@ struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, struct flowi *fl,
 		fl->flags |= FLOWI_FLAG_CAN_SLEEP;
 		err = __xfrm_lookup(sock_net(sk), &dst, fl, sk, 0);
 		if (err == -EREMOTE)
-			err = ip6_dst_blackhole(sk, &dst, fl);
+			return ip6_dst_blackhole(sock_net(sk), dst);
 		if (err)
 			return ERR_PTR(err);
 	} else {
@@ -1074,7 +1074,7 @@ struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi *fl,
 		fl->flags |= FLOWI_FLAG_CAN_SLEEP;
 		err = __xfrm_lookup(sock_net(sk), &dst, fl, sk, 0);
 		if (err == -EREMOTE)
-			err = ip6_dst_blackhole(sk, &dst, fl);
+			return ip6_dst_blackhole(sock_net(sk), dst);
 		if (err)
 			return ERR_PTR(err);
 	} else {

net/ipv6/route.c

@@ -870,11 +870,10 @@ struct dst_entry * ip6_route_output(struct net *net, struct sock *sk,
 
 EXPORT_SYMBOL(ip6_route_output);
 
-int ip6_dst_blackhole(struct sock *sk, struct dst_entry **dstp, struct flowi *fl)
+struct dst_entry *ip6_dst_blackhole(struct net *net, struct dst_entry *dst_orig)
 {
-	struct rt6_info *ort = (struct rt6_info *) *dstp;
-	struct rt6_info *rt = (struct rt6_info *)
-		dst_alloc(&ip6_dst_blackhole_ops, 1);
+	struct rt6_info *rt = dst_alloc(&ip6_dst_blackhole_ops, 1);
+	struct rt6_info *ort = (struct rt6_info *) dst_orig;
 	struct dst_entry *new = NULL;
 
 	if (rt) {
@@ -905,9 +904,8 @@ int ip6_dst_blackhole(struct sock *sk, struct dst_entry **dstp, struct flowi *fl
 		dst_free(new);
 	}
 
-	dst_release(*dstp);
-	*dstp = new;
-	return new ? 0 : -ENOMEM;
+	dst_release(dst_orig);
+	return new ? new : ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL_GPL(ip6_dst_blackhole);