xfrm: Handle blackhole route creation via afinfo.

That way we don't have to potentially do this in every xfrm_lookup()
caller.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/route.h b/include/net/route.h
index 923e670..707cfc8 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -121,6 +121,7 @@
 extern int		__ip_route_output_key(struct net *, struct rtable **, const struct flowi *flp);
 extern int		ip_route_output_key(struct net *, struct rtable **, struct flowi *flp);
 extern int		ip_route_output_flow(struct net *, struct rtable **rp, struct flowi *flp, struct sock *sk);
+extern struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig);
 
 extern int ip_route_input_common(struct sk_buff *skb, __be32 dst, __be32 src,
 				 u8 tos, struct net_device *devin, bool noref);