Use server keep alive in MQTT 5 #1421

src/Clients.h

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2009, 2023 IBM Corp. and Ian Craggs
+ * Copyright (c) 2009, 2024 IBM Corp. and Ian Craggs
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
@@ -114,8 +114,9 @@ typedef struct
 
 /**
  * Data related to one client
+ * The entire structure is initialized to 0 on creation, so all fields default to 0.
  */
-typedef struct
+typedef struct Clients
 {
  char* clientID; /**< the string id of the client */
  const char* username; /**< MQTT v3.1 user name */
@@ -132,6 +133,7 @@ typedef struct
  networkHandles net; /**< network info for this client */
  int msgID; /**< the MQTT message id */
  int keepAliveInterval; /**< the MQTT keep alive interval */
+ int savedKeepAliveInterval; /**< saved keep alive interval, in case reset by server keep alive */
  int retryInterval; /**< the MQTT retry interval for QoS > 0 */
  int maxInflightMessages; /**< the max number of inflight outbound messages we allow */
  willMessages* will; /**< the MQTT will message, if any */

src/MQTTAsync.c

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2009, 2023 IBM Corp., Ian Craggs and others
+ * Copyright (c) 2009, 2024 IBM Corp., Ian Craggs and others
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
@@ -668,7 +668,7 @@ int MQTTAsync_connect(MQTTAsync handle, const MQTTAsync_connectOptions* options)
  if (locked)
  MQTTAsync_unlock_mutex(mqttasync_mutex);
 
- m->c->keepAliveInterval = options->keepAliveInterval;
+ m->c->keepAliveInterval = m->c->savedKeepAliveInterval = options->keepAliveInterval;
  setRetryLoopInterval(options->keepAliveInterval);
  m->c->cleansession = options->cleansession;
  m->c->maxInflightMessages = options->maxInflight;

src/MQTTAsyncUtils.c

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2009, 2023 IBM Corp., Ian Craggs and others
+ * Copyright (c) 2009, 2024 IBM Corp., Ian Craggs and others
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
@@ -1998,6 +1998,26 @@ static int MQTTAsync_completeConnection(MQTTAsyncs* m, Connack* connack)
  if (m->c->connected != 1)
  rc = MQTTASYNC_DISCONNECTED;
  }
+ if (m->c->MQTTVersion == MQTTVERSION_5)
+ {
+ if (MQTTProperties_hasProperty(&connack->properties, MQTTPROPERTY_CODE_SERVER_KEEP_ALIVE))
+ {
+ /* update the keep alive from the server keep alive */
+ int server_keep_alive = MQTTProperties_getNumericValue(&connack->properties, MQTTPROPERTY_CODE_SERVER_KEEP_ALIVE);
+ if (server_keep_alive != -999999)
+ {
+ Log(LOG_PROTOCOL, -1, "Setting keep alive interval to server keep alive %d", server_keep_alive);
+ m->c->keepAliveInterval = server_keep_alive;
+ }
+ }
+ else if (m->c->keepAliveInterval != m->c->savedKeepAliveInterval)
+ {
+ /* if the keep alive has been previously updated with a server keep alive, but there is no server keep alive
+ on this connect, reset it to the value requested in the original connect API */
+ Log(LOG_PROTOCOL, -1, "Resetting keep alive interval to %d", m->c->savedKeepAliveInterval);
+ m->c->keepAliveInterval = m->c->savedKeepAliveInterval;
+ }
+ }
  }
  m->pack = NULL;
 #if !defined(_WIN32) && !defined(_WIN64)

src/MQTTClient.c

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2009, 2023 IBM Corp., Ian Craggs and others
+ * Copyright (c) 2009, 2024 IBM Corp., Ian Craggs and others
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
@@ -1428,7 +1428,7 @@ static MQTTResponse MQTTClient_connectURIVersion(MQTTClient handle, MQTTClient_c
  m->c->connected = 1;
  m->c->good = 1;
  m->c->connect_state = NOT_IN_PROGRESS;
- if (MQTTVersion == 4)
+ if (MQTTVersion >= MQTTVERSION_3_1_1)
  sessionPresent = connack->flags.bits.sessionPresent;
  if (m->c->cleansession || m->c->cleanstart)
  rc = MQTTClient_cleanSession(m->c);
@@ -1454,6 +1454,24 @@ static MQTTResponse MQTTClient_connectURIVersion(MQTTClient handle, MQTTClient_c
  goto exit;
  }
  *resp.properties = MQTTProperties_copy(&connack->properties);
+
+ if (MQTTProperties_hasProperty(&connack->properties, MQTTPROPERTY_CODE_SERVER_KEEP_ALIVE))
+ {
+ /* update the keep alive from the server keep alive */
+ int server_keep_alive = MQTTProperties_getNumericValue(&connack->properties, MQTTPROPERTY_CODE_SERVER_KEEP_ALIVE);
+ if (server_keep_alive != -999999)
+ {
+ Log(LOG_PROTOCOL, -1, "Setting keep alive interval to server keep alive %d", server_keep_alive);
+ m->c->keepAliveInterval = server_keep_alive;
+ }
+ }
+ else if (m->c->keepAliveInterval != m->c->savedKeepAliveInterval)
+ {
+ /* if the keep alive has been previously updated with a server keep alive, but there is no server keep alive
+ on this connect, reset it to the value requested in the original connect API */
+ Log(LOG_PROTOCOL, -1, "Resetting keep alive interval to %d", m->c->savedKeepAliveInterval);
+ m->c->keepAliveInterval = m->c->savedKeepAliveInterval;
+ }
  }
  }
  MQTTPacket_freeConnack(connack);
@@ -1507,7 +1525,7 @@ static MQTTResponse MQTTClient_connectURI(MQTTClient handle, MQTTClient_connectO
  start = MQTTTime_start_clock();
 
  m->currentServerURI = serverURI;
- m->c->keepAliveInterval = options->keepAliveInterval;
+ m->c->keepAliveInterval = m->c->savedKeepAliveInterval = options->keepAliveInterval;
  m->c->retryInterval = options->retryInterval;
  setRetryLoopInterval(options->keepAliveInterval);
  m->c->MQTTVersion = options->MQTTVersion;