use actual remote address when ip stack clients connect to proxy

src/IPStackSimulator.hh

@@ -27,6 +27,10 @@ public:
   void listen(int port);
   void add_socket(int fd);
 
+  inline void set_proxy_destination_address(uint32_t addr) {
+    this->proxy_destination_address = addr;
+  }
+
   static uint32_t connect_address_for_remote_address(uint32_t remote_addr);
 
 private:
@@ -34,6 +38,7 @@ private:
   std::shared_ptr<Server> game_server;
   std::shared_ptr<ProxyServer> proxy_server;
   std::shared_ptr<ServerState> state;
+  uint32_t proxy_destination_address;
 
   using unique_listener = std::unique_ptr<struct evconnlistener, void(*)(struct evconnlistener*)>;
   using unique_bufferevent = std::unique_ptr<struct bufferevent, void(*)(struct bufferevent*)>;