PI66272: DFHSO0126 CREATE SOCKET FAILED, MAXSOCKETS LIMIT REACHED DUE TO SOCKET LEAK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The customer is encountering a sockets leak. The leak is caused
  by the alias task failing to issue a DFHSOCK ESTABLISH call
  before trying to receive the request. When the alias fails to
  receive the request it returns an error to the client but leaves
  an outstanding reserve against the socket. This causes the
  sockets domain to believe there is still a task interested in
  this socket and so it does not get closed. This leads to the
  DFHSO0126 message being issued.
  Additional Keywords: KIXREVACC DFHSO0126 MSGDFHSO0126
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All CICS users.                                              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Incoming connections fail with DFHSO0126 messages.           *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * .                                                            *
  ****************************************************************
  CICS receives an HTTP request that meets the criteria for direct
  attachment of the user transaction by CSOL.  This means the web
  attach task (CWXN) is bypassed.
  However the HTTP request is malformed as the header is not
  correctly terminated by a CR LF sequence of characters.
  As a result, CICS waits for more data to arrive.  However,
  before the timeout interval expires the socket connection is
  closed by the client.  DFHWBXM performs cleanup, but no DFHSOCK
  ESTABLISH call was issued to convert the earlier RESERVE on the
  socket to a real association.  As a consequence the socket is
  not relinquished by the task at termination.
  The socket remains with an outstanding reserve indefinately and
  is never closed.
  If this sequence of events is repeated multiple times,
  eventually CICS runs out of sockets and no further connections
  are accepted unless the MAXSOCKETS value is increased.
  Additional keywords: msgDFHSO0126 SO0126
  

Problem conclusion

• DFHWBXM has been modified to ensure a DFHSOCK ESTABLISH call is
  always issued to ensure that if the RECEIVE processing in the
  optimised path fails the socket will still get cleaned up.
  

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:

  UI40174

Modules/Macros

• DFHWBXM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R000 PSY UI40174

     UP16/08/26 P F608

Fix is available

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