buglwIP - A Lightweight TCP/IP stack - Bugs: bug #59561, [mqtt] Stop sending a keep-alive...

 
 

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bug #59561: [mqtt] Stop sending a keep-alive if the connection is closed for a previously unacked keep-alive

Submitter:  Giuseppe Modugno <giusloq>
Submitted:  Fri 27 Nov 2020 05:38:25 PM UTC
   
 
Category:  apps Severity:  3 - Normal
Item Group:  Faulty Behaviour Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open Planned Release:  None
lwIP version:  git head

Fri 27 Nov 2020 05:38:25 PM UTC, original submission:  

In mqtt_cyclic_timer() I read:

    if (client->keep_alive > 0) {

      client->server_watchdog++;
      /* If reception from server has been idle for 1.5*keep_alive time, server is considered unresponsive */
      if ((client->server_watchdog * MQTT_CYCLIC_TIMER_INTERVAL) > (client->keep_alive + client->keep_alive / 2)) {
        LWIP_DEBUGF(MQTT_DEBUG_WARN, ("mqtt_cyclic_timer: Server incoming keep-alive timeout\n"));
        mqtt_close(client, MQTT_CONNECT_TIMEOUT);
        restart_timer = 0;
      }

      /* If time for a keep alive message to be sent, transmission has been idle for keep_alive time */
      client->cyclic_tick++;
      if ((client->cyclic_tick * MQTT_CYCLIC_TIMER_INTERVAL) >= client->keep_alive) {
        LWIP_DEBUGF(MQTT_DEBUG_TRACE, ("mqtt_cyclic_timer: Sending keep-alive message to server\n"));
        if (mqtt_output_check_space(&client->output, 0) != 0) {
          mqtt_output_append_fixed_header(&client->output, MQTT_MSG_TYPE_PINGREQ, 0, 0, 0, 0);
          client->cyclic_tick = 0;
        }
      }
    }

If the condition of the first if was true, mqtt_close() has been called. We can't enqueue a new keep-alive. So I propose to include the second block in an else statement:

    if (client->keep_alive > 0) {

      client->server_watchdog++;
      /* If reception from server has been idle for 1.5*keep_alive time, server is considered unresponsive */
      if ((client->server_watchdog * MQTT_CYCLIC_TIMER_INTERVAL) > (client->keep_alive + client->keep_alive / 2)) {
        LWIP_DEBUGF(MQTT_DEBUG_WARN, ("mqtt_cyclic_timer: Server incoming keep-alive timeout\n"));
        mqtt_close(client, MQTT_CONNECT_TIMEOUT);
        restart_timer = 0;

      } else {

        /* If time for a keep alive message to be sent, transmission has been idle for keep_alive time */
        client->cyclic_tick++;
        if ((client->cyclic_tick * MQTT_CYCLIC_TIMER_INTERVAL) >= client->keep_alive) {
          LWIP_DEBUGF(MQTT_DEBUG_TRACE, ("mqtt_cyclic_timer: Sending keep-alive message to server\n"));
          if (mqtt_output_check_space(&client->output, 0) != 0) {
            mqtt_output_append_fixed_header(&client->output, MQTT_MSG_TYPE_PINGREQ, 0, 0, 0, 0);
            client->cyclic_tick = 0;
          }
        }
      }
    }

Giuseppe Modugno <giusloq>

 

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