PM78535: ABEND EZBXFUT3(UK76159 12.044)+00C542 S0C4 USING SYSPLEXPORTS DVIPA

A fix is available

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APAR status

  • Closed as program error.

Error description

  • A DVIPA is distributed with sysplexports enabled.  A timing
    sequence exists with a connection attempting to connect to
    the DVIPA on a non-distributed port and the DVIPA listener being
    started multiple times.  This can cause an incorrect entry to be
    left in the VCRT hash table pointing to freed storage.  This can
    cause abends attempting to free the storage twice or reference
    storage.
    .
    ADDITIONAL SYMPTOMS:
    1) EZBXFGP2(HIP61D0 11.090)+018B1C S0C4
    2) EZBXFUT5(HIP61D0 11.090)+0019DE S4C5/77C10402
    EZBXFMS6 ABEND4C5 77BD0402
    EZBXFGP2 ABEND4C5 773B0402
    CRHTE Bad Ref Ct Reference Count
    3) EZBXFTMR(UK80455 125)+000718 S0C4/00000011
    
    .
    VERIFICATION STEPS:
    1) VCRT entry will point to freed storage or storage for a
    different entry.  Netstat VCRT may show the same connection
    twice.
    2) TCPIPCS XCF report may show a CRHTE with an IFR of
    In Flight Recorder Area (oldest to newest):
        IFR24:RTE_SYN      IFR23:MERGE_PENDING      IFR09:SRV_PASV
        IFR0D:INC_NUMTERMCONNS
    3) Netstat VCRT will not have an entry for a listener on a
    sysplexports DVIPA, but the hash table key in the HASE will have
    the correct key.
    

Local fix

  • If listener is started on a configured port which does not
    change, code that port on the VIPADISTRIBUTE statement.  This
    will prevent the SYSPLEXPORTS logic from being used for
    connections to that port.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of the IBM Communications Server   *
    *                 for z/OS Version 1 Release 13 IP:            *
    *                 Distributed DVIPA                            *
    ****************************************************************
    * PROBLEM DESCRIPTION: Abend S0C4 in EZBXFUT3 using            *
    *                      SYSPLEXPORTS DVIPA.                     *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    A timing scenario exists during which connections
    attempted to a distributed DVIPA using sysplexports
    may reference storage after it has been freed and
    cause an abend. The problem can be summarized as follows:
    1. A connection is attempted to DVIPA A port B and
       the SYN request is queued at the sysplex distributor.
    2. A listener is not yet started for DVIPA A port B and the
       connection is reset after approximately 15 seconds.
    3. A listener is started on the DVIPA target and
       notifies the distributor it can accept connections
       to DVIPA A port B.
    4. The listener closes on the DVIPA target and notifies
       the distributor it is not accepting connections on
       DVIPA A port B.
    5. A listener is started again on the DVIPA target and
       notifies the distributor it can accept connections
       to DVIPA A port B. If steps 1 through 5 occur within
       several minutes, TCP incorrectly frees storage at
       the distributor related to the target DVIPA A Port B,
       but  maintains a pointer to the freed storage.
    6. A connection is attempted to DVIPA A port B and and at the
       sysplex distributor the pointer to the freed storage is
       used and causes an abend.
    +-------------------------------------------------------------+
    + 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

  • TCPIP has been modified to not free the referenced storage.
    
    * Cross Reference between External and Internal Names
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM78535

  • Reported component name

    TCP/IP V3 MVS

  • Reported component ID

    5655HAL00

  • Reported release

    1D0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-12-05

  • Closed date

    2013-01-02

  • Last modified date

    2013-06-21

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

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

    UK90704

Modules/Macros

  • EZBCTFME EZBITTRC EZBXFACI EZBXFHSH EZBXFUTL
    EZBXFUT3 EZBX6ACI EZBX6HSH EZBX6UT3
    

Fix information

  • Fixed component name

    TCP/IP V3 MVS

  • Fixed component ID

    5655HAL00

Applicable component levels

  • R1D0 PSY UK90704

       UP13/02/02 P F302

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.



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Document information


More support for:

z/OS family

Software version:

1D0

Operating system(s):

z/OS

Reference #:

PM78535

Modified date:

2013-06-21

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