if (listen_mode != LISTEN_NONE && fd < 0) {
            if (listen_mode == LISTEN_KERNEL)
                fd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
            else
                fd = raw_socket(client_config.ifindex);
            if (fd < 0) {
                LOG(LOG_ERR, "FATAL: couldn't listen on socket, %m");
                return 0;
            }
        }