VM66502: PEVM66302 ABEND HTT001 IN HCPVNSDG

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Sending network packets to a virtual NIC during LOGOFF of the
  destination user resulted in ABEND HTT001 in HCPVNSDG. Both
  users were coupled to the same guest LAN using IP Layer
  transport.
  
  The failure occurred after upgrading a working Disaster Recovery
  system to z/VM CP Release 7.1.0 with the latest support.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: VSWITCH or Guest LAN using IP Layer          *
  *                 transport (IP vs ETHERNET option)            *
  *                 may be affected.                             *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  HCPVNSDG uses the results of a prior IP Table search when the
  sender is using the same IP destination that it used before.
  Before making that decision to use the cached NIDBK pointer,
  HCPVNSDG tests for NIDDXVER==LANDXVER (was the network changed
  after this search was made?).
  
  In the failing case, the destination guest was logging off and
  LANDXVER was incremented to indicate that the network was
  changing (the Virtual NIC is being removed and will soon be
  destroyed). However, the sender was sending another packet
  through HCPVNSDG after LANDXVER was updated and before the IP
  address (IPNBK) was removed from the LAN IP Table.
  
  In this case, the page containing that NIDBK was invalidated and
  the next reference to it led to the HTT001 ABEND. In other
  cases, the packets might just be discarded until the destination
  guest logs on (or some other guest connection is added or
  removed, forcing another LANDXVER update).
  
  It possible that a sender could see a persistent IP Address
  failure (instead of an ABEND HTT001) if HCPVNSDG gets the new
  LANDXVER after the IP address has been removed from the
  table (during LOGON processing for the target). In that case
  a NULL pointer is saved in cache for the target address.
  The result would be continued failures (even after the
  target interface is re-established) until either (a) the
  sender sends a packet to a different destination, or
  (b) some other action on the network increments LANDXVER
  (forcing a new lookup for the target IP address).
  

Problem conclusion

• Functions in HCPIPN and HCPIPM that update the LAN IP Tables
  are enhanced to also increment LANDXVER. This forces HCPVNSDG
  to perform a new search the next time it is invoked for a
  given sender.
  

Temporary fix

• *********
  * HIPER *
  *********
  FOR RELEASE VM/ESACP/ESAR710 :
  PREREQ: VM66264
  CO-REQ: NONE
  IF-REQ: NONE
  FOR RELEASE VM/ESA CP/ESA R720 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

APAR Information

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

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

  UM35847 UM35848

Modules/Macros

• HCPIPM   HCPIPN
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R710 PSY UM35847

     UP21/04/07 P 2101 ¢

• R720 PSY UM35848

     UP21/04/07 P 2102 ¢

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.