PH23551: CGI error handling improvement

APAR status

• Closed as program error.

Error description

• Error handling for CGI (mod_cgi) on z/OS and Windows platforms
  needs improvements.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  Users of mod_cgi in IBM HTTP Server (IHS)   *
  *                  8.5.5 or 9.0                                *
  ****************************************************************
  * PROBLEM DESCRIPTION: Inadequate CGI error handling           *
  ****************************************************************
  * RECOMMENDATION:  Apply this fix if using the mod_cgi module  *
  *                  with IHS                                    *
  ****************************************************************
  Case example:
  1. Slightly-slow CGI causes a browser to navigate away from
  the page, closing the connection.
  2. IHS does not keep reading from the CGI once the client is
  gone.
  3. The CGI will keep writing until it fills its side of the
  buffer on the pipe it writes responses to, so it will not exit
  on its own.
  4. IHS will eventually finish the request, and an exit has
  been registered to terminate the CGI if it's still running.
  5. This triggers a SIGTERM, wait, SIGKILL.
  No errors are written to the IHS error log to indicate this
  situation has happened.  The MVS system log will show an
  abendEC6 REASON=0000FF0F for the SIGTERM.  It may also show
  a message like this:
  BPXP023I THREAD 2473000000000000, IN PROCESS 16845413,
  TERMINATED BY SIGNAL SIGTERM, SENT FROM THREAD IN PROCESS
  65683, UID 123456, IN JOB IHSSERVR.
  

Problem conclusion

• Log a warning (IHS00018) when a client reading CGI output
  disconnects before the CGI has completed.  By default, the CGI
  is sent a SIGTERM signal when the request ends which may be
  recorded in the z/OS system log if the CGI does not handle the
  SIGTERM itself.
  
  To reduce the warning to a trace message, set per-request
  environment variable ihs-cgi-brokenpipe to "trace":
  SetEnvIf Request_URI .* ihs-cgi-brokenpipe=trace
  
  To have the server continue reading from the CGI after the
  client has disconnected, giving it a chance to exit
  gracefully, set ihs-cgi-brokenpipe to "soak":
  SetEnvIf Request_URI .* ihs-cgi-brokenpipe=soak
  
  This fix is targeted for IBM HTTP Server fix packs:
  - 8.5.5.18
  - 9.0.5.4
  
  For more information, see 'Recommended Updates for WebSphere
  Application Server':
  http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
  

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:

Fix information

• Fixed component name

  WAS IHS ZOS

• Fixed component ID

  5655I3510

Applicable component levels

• R850 PSY

     UP

• R90P PSY

     UP