PM14615: TCPIP HIGH CPU UTILIZATION DUE TO AT-TLS LOOP PROCESSING TLS ALERT AFTER TLS CLOSE NOTIFY

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The remote TLS application sent a TLS close alert,
  another TLS alert, and a FIN.  AT-TLS loops trying to read the
  second SSL alert because every read to SSL returns with a 437,
  indicating the SSL connection is closed.  The alert is never
  consumed from the TLSX control block, causing AT-TLS to
  schedule another attempt to read the alert because the local
  application has not requested TLS to be shutdown or issued
  it's own close. This loop will continue until the timewait
  timer expires and the connection is freed.
  
  Verification Steps:
  ip tcpipcs ttls will show 1 or more of the following:
  
  TTLS Worker Task: 7E626170
       Ducb FuncCode    Rcode     Busy Idle Time
   14D9C000       1F      1B5       FF 2010/05/12 22:23:39
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release(s)  10, 11, and   *
  *                 12 IP: AT-TLS                                *
  ****************************************************************
  * PROBLEM DESCRIPTION: TCPIP high CPU usage with AT-TLS        *
  *                      enabled                                 *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The remote application sends a close notify alert followed by
  another SSL alert.  The second SSL alert causes AT-TLS to
  schedule a read which fails with return code 437 because the SSL
  connection is closed.  The alert is never consumed from the TLSX
  control block, causing AT-TLS to schedule another attempt to
  read the alert.
  +-------------------------------------------------------------+
  + 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

• Module EZBTLCWK has been changed to reset the connection if
  the application receives data after the close notify.
  
  * Cross Reference between External and Internal Names
  

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:

  UK57452 UK57453 UK57454

Modules/Macros

•    EZBTLCWK
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1A0 PSY UK57452

     UP10/07/09 P F007

• R1B0 PSY UK57453

     UP10/07/09 P F007

• R1C0 PSY UK57454

     UP10/07/09 P F007

Fix is available

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