Implement installed_routes_estimate.

route.c

@@ -134,6 +134,13 @@ find_installed_route(const unsigned char *prefix, unsigned char plen)
     return NULL;
 }
 
+/* Returns an overestimate of the number of installed routes. */
+int
+installed_routes_estimate(void)
+{
+    return route_slots;
+}
+
 static int
 resize_route_table(int new_slots)
 {

route.h

@@ -69,6 +69,7 @@ struct route *find_route(const unsigned char *prefix, unsigned char plen,
                          struct neighbour *neigh, const unsigned char *nexthop);
 struct route *find_installed_route(const unsigned char *prefix,
                                    unsigned char plen);
+int installed_routes_estimate(void);
 void flush_route(struct route *route);
 void flush_all_routes(void);
 void flush_neighbour_routes(struct neighbour *neigh);