PQ46171: FTP LOGIN PERFORMANCE IS SLOW DUE TO UNNECESSARY GETHOSTBYADDR()CALLS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Starting in V2R10, the FTP server now issues a gethostbyaddr()
  call to resolve the remote IP address during login processing.
  This call is done on every login attempt whether it is needed
  or not.  The gethostbyaddr() should only be done if it is
  required for support of %R in the banner and login files.
  This can cause the login process to slow down due to the FTP
  server waiting for the DNS to return the gethostbyaddr() query.
  Also a trace entry before the call should identify the name
  being resolved and the trace after the call needs to identify
  results of the call.  With these trace entries, service will be
  in a position to identify network problems contributing to poor
  ftp logon performance.
  .
  ADDITIONAL SYMPTOMS:
  Netstat shows connection in ClosWait for port 21 with a
  connection ID of 0.
  KEYWORDS: FTPD FTPSERVE FTPSERVER
  
  KEYWORDS:
  HUNG WAIT TIMEOUT
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for OS/390 Release 10 IP: FTP                *
  ****************************************************************
  * PROBLEM DESCRIPTION: The FTP server issues a gethostbyaddr() *
  *                      call to resolve the remote IP address   *
  *                      during login processing. This call is   *
  *                      done on every login attempt causing     *
  *                      poor performance.                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  
  +-------------------------------------------------------------+
  + 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

• The gethostbyaddr() calls have been deleted from EZAFTPSD
  (handle_client_socket) and EZAFTPRX (main) in the main line
  login flow.  The gethostbyaddr() call will only be invoked
  from the subString() function if a %R (remote host name)
  magic cookie exists in the banner or login message text.
  
  The following documentation changes are required:
  ================================================================
  OS/390 Communications Server
  IP Configuration Guide
  Document Number SC31-8725
  
  Under the section: Configure the Welcome Banner Page, Login,
  and Directory Message.
  
  We need to add a section called
  "Using Magic Cookies to represent information"
  
  The following text should be added:
  
  The content of all the informational messages may include a
  predefined set of "magic cookies" which are substituted
  by the FTP server before  the data is sent to the FTP client.
  
  The following "magic cookies" are supported in the text:
  
  %T Local time
  %C Current working directory
  %E The FTP server administrators e-mail address
  %R Remote host name
  %L Local host name
  %U Username (logged in user)
  
  Usage Notes:
  If %R is used, a long delay in login processing may occur as
  the FTP server will issue a gethostbyaddr() DNS query to resolve
  the remote host IP address.
  
  In order to use %E, ADMINEMAILADDR ftp.data keyword must be
  specified in configuration file.
  
  
  * Cross Reference between External and Internal Names
  EZAFTPSR (FTPDRPLY)  PREFTPCX (EZAFTPCX)  PREFTPLD (EZAFTPLD)
  PREFTPLS (EZAFTPLS)
  

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:

  UQ52550

Modules/Macros

•    EZAFTPCX EZAFTPGU EZAFTPLD EZAFTPLS EZAFTPRX
  EZAFTPSC EZAFTPSD EZAFTPSR
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R50A PSY UQ52550

     UP01/04/16 P F104 Ž

Fix is available

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