PM80004: NEW FUNCTION TO PROVIDE SUPPORT FOR NOTIFICATION WHEN A TCP CONNECTION IS TERMINATED.

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• New Function to provide support for notification when a TCP
  connection is terminated.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release(s) 13 IP          *
  ****************************************************************
  * PROBLEM DESCRIPTION: New Function to provide support for     *
  *                      notification when a TCP connection      *
  *                      is terminated.                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  New Function to provide support for notification when a TCP
  connection is terminated.
  
  In certain application models there is a need to recognize when
  the TCP connection has reached a point where the peer will send
  no additional data.  This can be caused by the peer application
  issuing a shutdown() or close() socket call.  The peer TCP/IP
  will generate a FIN or RST packet depending on the state of the
  connection and options set on the socket.  The local TCP/IP can
  generate a RST to the peer when a networking error is detected,
  preventing any new data from arriving.
  
  In the case of a RST packet in either direction, the local
  application can detect this condition using any i/o type socket
  operation.  In the case of a FIN packet inbound, a receive
  type socket operation will return with zero bytes after all
  queued data has been consumed.  If the local application is in
  a processing state unrelated to socket operations or is sending
  to the peer, the connection state change may not be detected.
  
  A mechanism that allows an application to issue a synchronous
  or asynchronous receive type socket API call that completes
  only when a TCP connection enters the state where no new data
  can arrive is being introduced.
  +-------------------------------------------------------------+
  + 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

Temporary fix

Comments

• The MSG_CONNTERM flag is being introduced to provide a method of
  requesting notification when a TCP connection reaches the state
  where no new data will arrive.  This support is available on the
  recv(), recvfrom(), and recvmsg() functions in the z/OS XL C/C++
  Run-Time library.  This support is also available on the
  recv(BPX1RCV,BPX4RCV), recvfrom(BPX1RFM,BPX4RFM),
  recvmsg(BPX1RMS,BPX4RMS), and asynchio(BPX1AIO,BPX4AIO)
  assembler callable services.
  
  Usage considerations:
  1. MSG_CONNTERM requests that the function completes only when a
     TCP connection is terminated.  It is valid for TCP sockets
     only.
  2. MSG_CONNTERM will always result in the socket call being
     handled as a blocking call.  Due to the blocking nature,
     using MSG_CONNTERM in a synchronous fashion may require using
     a dedicated thread so other processing can continue within
     the application.
  3. MSG_CONNTERM is mutually exclusive with other flag values
     (MSG_OOB, MSG_PEEK, MSG_WAITALL).
  4. MSG_CONNTERM must use a buffer length of zero for recv() and
     recvfrom(), or an IOV element number of zero for recvmsg().
  5. If there are other normal outstanding receive requests,
     those receive requests will be completed too.  The
     application must be able to deal with the fact that a normal
     receive and this special connection termination receive may
     be driven in parallel.
  
  AT-TLS considerations:  If AT-TLS is being used to provide
  transparent TLS/SLL support for a TCP socket and a receive
  request with MSG_CONNTERM is outstanding, AT-TLS will
  immediately honor any TLS/SLL close notify alerts sent by the
  peer and initiate TLS/SLL session shutdown immediately as well.
  For more information on AT-TLS and determining whether a TCP
  connection is using AT-TLS refer to the Comm Server IP
  Programmer's Guide and Reference chapter on AT-TLS.
  

APAR Information

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

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

  UK92097

Modules/Macros

•    EZBCTFME EZBITTRC EZBPFFSF EZBPFFSM EZBPFFSR
  EZBPFSDR EZBPFSRF EZBPFSRM EZBTCFRD EZBTCITS EZBTCRD  EZBZREAD
  EZB2TCB  ITEVENT  TOTCPDS
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1D0 PSY UK92097

     UP13/03/30 P F303

Fix is available

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