MQTT: Provide the message id for subscribe, unsubscribe and publish

Author: Matthew Bradbury

os/net/app-layer/mqtt/mqtt.c

@@ -1495,6 +1495,10 @@ mqtt_subscribe(struct mqtt_connection *conn, uint16_t *mid, char *topic,
   conn->out_packet.qos = qos_level;
   conn->out_packet.qos_state = MQTT_QOS_STATE_NO_ACK;
 
+  if(mid) {
+    *mid = conn->out_packet.mid;
+  }
+
   process_post(&mqtt_process, mqtt_do_subscribe_event, conn);
   return MQTT_STATUS_OK;
 }
@@ -1520,6 +1524,10 @@ mqtt_unsubscribe(struct mqtt_connection *conn, uint16_t *mid, char *topic)
   conn->out_packet.topic_length = strlen(topic);
   conn->out_packet.qos_state = MQTT_QOS_STATE_NO_ACK;
 
+  if(mid) {
+    *mid = conn->out_packet.mid;
+  }
+
   process_post(&mqtt_process, mqtt_do_unsubscribe_event, conn);
   return MQTT_STATUS_OK;
 }
@@ -1552,6 +1560,10 @@ mqtt_publish(struct mqtt_connection *conn, uint16_t *mid, char *topic,
   conn->out_packet.qos = qos_level;
   conn->out_packet.qos_state = MQTT_QOS_STATE_NO_ACK;
 
+  if(mid) {
+    *mid = conn->out_packet.mid;
+  }
+
   process_post(&mqtt_process, mqtt_do_publish_event, conn);
   return MQTT_STATUS_OK;
 }