PK20944: TCPIP STACK DOES NOT TERMINATE AFTER STOP COMMAND

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• .
  When the Telnet server is run in the TCPIP address space, the
  stack will wait for the Telnet related tasks to end before
  completing the shutdown process.  If one of these tasks does
  not respond to the shutdown request, the entire TCPIP stack
  shutdown hangs.
                                                                 .
  

Local fix

• .
   - A 'FORCE TCPIP,ARM' command will be needed to terminate the
     address space.
                                                                 .
   - Ensure that address spaces which provide applications that
     TN3270 sessions use are shut down normally (a FORCE command
     without the ARM option may cause telnet sessions to not be
     properly cleaned up).
                                                                 .
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of Communications Server for z/OS  *
  *                 Version 1 Release 4, Version 1 Release 5,    *
  *                 Version 1 Release 6, and Version 1 Release   *
  *                 7 IP Telnet facilities.                      *
  ****************************************************************
  * PROBLEM DESCRIPTION: Stop command for TCPIP stack hangs.     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The problem may be summarized as follows:
  
  1. A TN3270 client was connected to the Telnet server
     and in session with a host application.  The client
     disconnected and a VTAM CLOSE ACB was issued by
     module EZBTVCLS under a Telnet utility task (module
     EZBTTTSK).
  
  2. The CLOSE ACB hung.  Documentation was not available
     to determine the cause of the hang.  One possibility
     was that LOSTERM=IMMED needed to be coded on the
     APPL statement for the host application.
  
  3. A stop command was later issued against the TCPIP stack:
  
       P TCPCS
  
  4. The stop command hung.  The Telnet server posted an ECB
     requesting that the utility task terminate.  The server
     then proceeded to wait for the utility task.  Because
     the utility task was still hung in CLOSE ACB, stop
     command processing could not complete.
  
  5. The operator had to issue a force command to terminate
     the TCPIP stack:
  
     FORCE TCPCS,ARM
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• To resolve this problem, the Telnet server will now
  set a timer prior to requesting termination of a
  utility task.  If the timer elapses before the utility
  task responds that termination is complete, the Telnet
  server will detach the task.
  
  The timer will be set for three minutes.  The timer will
  also be employed for a stop port command.  Adding the timer
  will enable the Telnet server to terminate a hung utility
  task.
  
  The following changes have been made:
  
  1. Control block EZBZUTSK has been changed to add two new
     flags.  The first is used to indicate if the task
     termination routine (RESMGR) for the utility task
     has been invoked.  The second is used to indicate
     if connection cleanup has occurred.
  
  2. Macro EZBTZTDF has been changed to add a new Telnet
     ITTIMER definition.
  
  3. Module EZBTTTKE is the RESMGR for the utility task.
     EZBTTTKE has been modified to set the new UTSK based
     flag indicating that the RESMGR has been invoked.
     EZBTTTKE will also not invoke EZBTTCCE if the UTSK
     based connection cleanup flag is set.
  
  4. Module EZBTTMST has been modified to start a three
     minute timer before posting a given utility task
     with a request to terminate.  If the timer expires
     before the utility task terminates, then EZBTTMST
     will detach the task.
  
  5. Module EZBTVCLS has been modified to not issue a VTAM
     CLOSE ACB if called from the RESMGR for the utility
     task.
  
  6. Module EZBTTTSK has been changed in releases r140 and
     r150 to call EZBTTCCE to perform connection cleanup.
     EZBTTTSK has been changed for all releases to set the
     new UTSK based flag when EZBTTCCE returns.
  
  * Cross Reference between External and Internal Names
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

• ×**** PE06/06/07 FIX IN ERROR. SEE APAR PK26147  FOR DESCRIPTION
  

APAR Information

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

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

  UK13193 UK13194 UK13195 UK13196 PK26026

Modules/Macros

• EZBTTMST EZBTTTKE EZBTTTSK EZBTVCLS EZBTZTDF
  EZBZUTSK
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R140 PSY UK13193

     UP06/05/31 P F605 Ž

• R150 PSY UK13194

     UP06/05/31 P F605 Ž

• R160 PSY UK13195

     UP06/05/31 P F605 Ž

• R170 PSY UK13196

     UP06/05/31 P F605 Ž

Fix is available

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