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>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7e9443f..cf6fdea 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -870,11 +870,10 @@
 
 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 @@
 		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);