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/xfrm.h b/include/net/xfrm.h
index efded23..d5dcf39 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -280,6 +280,7 @@
 	int			(*fill_dst)(struct xfrm_dst *xdst,
 					    struct net_device *dev,
 					    const struct flowi *fl);
+	struct dst_entry	*(*blackhole_route)(struct net *net, struct dst_entry *orig);
 };
 
 extern int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo);