Reallocate routes when the table shrinks a lot.

route.c

@@ -93,6 +93,15 @@ flush_route(struct route *route)
     numroutes--;
     VALGRIND_MAKE_MEM_UNDEFINED(routes + numroutes, sizeof(struct route));
 
+    if(maxroutes > 8 && numroutes < maxroutes / 4) {
+        struct route *new_routes;
+        int n = maxroutes / 2;
+        new_routes = realloc(routes, n * sizeof(struct route));
+        if(new_routes == NULL)
+            return;
+        routes = new_routes;
+    }
+
     if(lost)
         route_lost(src, oldmetric);
 }