IT25277: MQXR: Unexpected DISCONNECT packet from MQTT client causes FDC XR070013 PROTOCOL_HEADER error

APAR status

• Closed as program error.

Error description

• MQXR Service received an unexpected DISCONNECT packet from an
  MQTT client which caused the following FDC:
  
  
  | Source Class      :- com.ibm.mq.MQXRService.MQTTServerSession
                                     |
  | Source Method     :- makeStateChange
                                                              |
  | Probe Id          :- XR070013
  
  java.lang.Exception: State error state:=PROTOCOL_ERROR
  previousState:DISCONNECTED
  	at
  com.ibm.mq.MQXRService.MQTTServerSession.makeStateChange(MQTTSer
  verSession.java:1571)
  	at
  com.ibm.mq.MQXRService.MQTTServerSessionV311.receivePubComp(MQTT
  ServerSessionV311.java:1110)
  	at
  com.ibm.mq.MQXRService.MQTTServerSessionV311.handleReceive(MQTTS
  erverSessionV311.java:145)
  	at
  com.ibm.mq.MQXRService.MQTTServerContext.handleReceive(MQTTServe
  rContext.java:153)
  	at
  com.ibm.mq.MQXRService.MQTTWireContext.receive(MQTTWireContext.j
  ava:403)
  	at
  com.ibm.mq.communications.NonBlockingSslConnection.receive(NonBl
  ockingSslConnection.java:491)
  	at
  com.ibm.mq.communications.NonBlockingWorker.run(NonBlockingWorke
  r.java:398)
  	at java.lang.Thread.run(Thread.java:785)
  
  :---------------------------------------------------------------
  -----------------------------------:
  : Object            :- java.lang.Exception: State error
  state:=PROTOCOL_ERROR previousState:DISCON :
  :                   :- NECTED
  
      :
  
  state=PROTOCOL_ERROR(com.ibm.mq.MQXRService.MQTTServerSession$Co
  ntextState)
  
      Class: class
  com.ibm.mq.MQXRService.MQTTServerSession$ContextState
  previousState=DISCONNECTED(com.ibm.mq.MQXRService.MQTTServerSess
  ion$ContextState)
  history([Lcom.ibm.mq.MQXRService.MQTTServerSession$HistoryEvent;
  )
    0 Wed Apr 05 22:26:07 BST 2017 SEND_MQTT
  mqttMessageType:PUBREL
    1 Wed Apr 05 22:26:07 BST 2017 RECEIVED_MQTT
  mqttMessageType:DISCONNECT
    2 Wed Apr 05 22:26:07 BST 2017 RECEIVED_MQTT
  mqttMessageType:PUBCOMP
    3 Wed Apr 05 22:26:06 BST 2017 SEND_MQTT
  mqttMessageType:SUBACK
    4 Wed Apr 05 22:26:06 BST 2017 RECEIVED_MQTT
  mqttMessageType:PUBLISH
    5 Wed Apr 05 22:26:07 BST 2017 SEND_MQTT
  mqttMessageType:PUBREC
    6 Wed Apr 05 22:26:07 BST 2017 SEND_MQTT
  mqttMessageType:PUBLISH
    7 Wed Apr 05 22:26:07 BST 2017 RECEIVED_MQTT
  mqttMessageType:PUBREL
    8 Wed Apr 05 22:26:07 BST 2017 SEND_MQTT
  mqttMessageType:PUBCOMP
    9 Wed Apr 05 22:26:07 BST 2017 RECEIVED_MQTT
  mqttMessageType:PUBREC
  
    historyIndex=3(int)
  
  SPSS: XRASECB
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users connecting to a queue manager's MQXR
  service with Paho MQTT clients, which disconnect while receiving
  QoS 2 messages from the MQXR server as a result of a previously
  made subscriptions.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  The queue manager's MQXR service threw an FDC with probe ID
  XR070013, reporting a PROTOCOL_ERROR. The packet history in the
  FDC showed that a connected MQTT client sent a DISCONNECT packet
  followed by a PUBCOMP packet - for instance:
  
   RECEIVED_MQTT mqttMessageType:DISCONNECT
   RECEIVED_MQTT mqttMessageType:PUBCOMP
  

Problem conclusion

• When a MQTT client sends a DISCONNECT packet followed by a
  PUBCOMP packet (or other similar invalid combination of MQTT
  packets), an FDC is no longer thrown - instead a message is
  written to the mqxr.log file indicating that a protocol error
  has occurred as a result of MQTT packets being sent in the wrong
  order, giving some details to help identify the client which
  sent the invalid MQTT packets.
  
  For instance for a client which connected using a client
  identifier "client123" from a local IPv6 connection a message
  would be logged like:
  
  AMQXR2087I: Client with identifier 'client123' at network
  address '0:0:0:0:0:0:0:1' sent an unexpected MQTT packet causing
  a protocol error: state: 'PROTOCOL_ERROR' previousState:
  'DISCONNECTED'
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v8.0       8.0.0.11
  v9.0 LTS   9.0.0.6
  v9.1 CD    9.1.2
  v9.1 LTS   9.1.0.2
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  IBM MQ BASE M/P

• Fixed component ID

  5724H7261

Applicable component levels