relay.c

static void
send_dummy(int fd, short event, void *args) {
  (void)fd;
  (void)event;
  circuit_t *circ = args;
  crypt_path_t *cpath_layer = NULL;
  
  if (CIRCUIT_IS_ORIGIN(circ)) {
    cpath_layer = TO_ORIGIN_CIRCUIT(circ)->cpath->prev;
  }
  
  relay_send_command_from_edge(
    0,
    circ,
    RELAY_COMMAND_DROP,
    NULL,
    0,
    cpath_layer
  );
  
  log(LOG_DEBUG, LD_GENERAL, "Sent dummy packet");
}

int
relay_send_command_from_edge(streamid_t stream_id, circuit_t *circ,
                             uint8_t relay_command, const char *payload,
                             size_t payload_len, crypt_path_t *cpath_layer) { 

[...]

struct timeval timeout;
      static struct event *launch_event;
      
      launch_event = tor_evtimer_new(tor_libevent_get_base(), send_dummy, circ);
                                   
      timeout.tv_sec = 1;
      timeout.tv_usec = 0;
  
      if (evtimer_add(launch_event, &timeout)<0) {
        log_warn(LD_BUG, "Couldn't add timer");
      }

[...]

}