IT37606: "Connection refused" and "connection is closed by foreign host" exceptions handled incorrectly by protocol bridge agents

APAR status

• Closed as program error.

Error description

• An MQ 9.2 Managed File Transfer protocol bridge agent (PBA) has
  been configured to communicate with a remote file server using
  the SFTP protocol, and acts as the destination agent for managed
  transfers. As part of a test, the file server is configured in
  such a way to prevent the PBA from connecting to it. After this
  change has been made, whenever the PBA tries to connect to the
  file server, it encounters an error and the following messages
  to its event log (output0.log),:
  
  BFGTR0029E: A recoverable I/O error has occurred during a write
  operation. The agent will attempt to recover the file transfer.
  The transfer ID is: <transfer identifier>. The error message is:
  BFGBR0104E: Bridge agent failed to connect to host <file server
  host> with credentials of <credentials> because connection is
  closed by foreign host
  
  BFGTR0062I: Transfer ID: <transfer identifier>, from source
  agent <source agent>, is entering recovery, after a short pause,
  due to recoverable error: BFGTR0058I: The transfer frame had a
  recoverable I/O error while attempting to write to a destination
  file. The reason is: BFGBR0104E: Bridge agent failed to connect
  to host <file server host> with credentials of <credentials>
  because connection is closed by foreign host
  
  and put the managed transfer into recovery. However, when the
  managed transfer resumes, the destination agent fails to connect
  to the file server again, writes the two messages shown above
  into its event log, and puts the managed transfer into recovery
  for a second time.
  
  This sequence of events continues to occur until the managed
  transfer is cancelled.
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users of IBM MQ 9.2 Managed File Transfer who
  have protocol bridge agents (PBAs) that connect to a file server
  using the SFTP protocol.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  IBM MQ Managed File Transfer protocol bridge agents (PBAs) use a
  fork of the third-party JSch library to communicate with file
  servers using the SFTP protocol. If a protocol bridge agent
  fails to connect to a file server using this protocol while
  processing a managed transfer, an internal exception is
  generated within the fork of the JSch library. The protocol
  bridge agent will then look at the exception to determine if it
  represents:
  
  - Either a transient, recoverable error.
  - Or a more permanent, non-recoverable error.
  
  If the exception represents a transient, recoverable error, then
  the protocol bridge agent will put the managed transfer into
  recovery. However, if the failure to connect to the file server
  is due to a more permanent reason (such as invalid credentials),
  then the managed transfer will be marked as "Failed".
  
  
  Now, the logic within the protocol bridge agent which performed
  this determination always treated java.net.ConnectExceptions and
  exceptions containing the message:
  
    "connection is closed by foreign host"
  
  as recoverable errors. However, this was incorrect.
  java.net.ConnectExceptions or exceptions containing the text:
  
    "connection is closed by foreign host"
  
   represented non-recoverable errors, and so if they were
  encountered during the processing of a managed transfer, then
  that managed transfer should have been marked as "Failed".
  

Problem conclusion

• To resolve this issue, IBM MQ Managed File Transfer protocol
  bridge agents have been updated so that to treat
  java.net.ConnectExceptions and exceptions containing the
  message:
  
    "connection is closed by foreign host"
  
  as non-recoverable errors when connecting to a file server using
  the SFTP protocol. This means that:
  
  - If a protocol bridge agent is acting as the source agent for a
  managed transfer and encounters either a
  java.net.ConnectException or an exception containing the text
  "connection is closed by foreign host" while trying to connect
  to the file server, it will mark the managed transfer as
  "Failed" with the one of the following messages:
  
  BFGRP0038I: The file transfer request failed due to :
  BFGBR0221E: An attempt to connect to the file server on host
  <hostname> using the SFTP protocol failed as the connection was
  closed by the foreign host.
  
  BFGRP0038I: The file transfer request failed due to :
  BFGBR0222E: An attempt to connect to the file server on host
  <hostname> using the SFTP protocol failed with exception
  <exception details>.
  
  
  - If the protocol bridge agent is acting as the destination
  agent for a managed transfer, and fails to connect to the file
  server due to either a java.net.ConnectException or an exception
  containing the text   "connection is closed by foreign host",
  then the current transfer item will be marked as "Failed" with
  one of the following supplementary messages:
  
  BFGTR0072E: The transfer failed to complete due to the exception
  : BFGBR0221E: An attempt to connect to the file server on host
  <hostname> using the SFTP protocol failed as the connection was
  closed by the foreign host.
  
  BFGTR0072E: The transfer failed to complete due to the exception
  : BFGBR0222E: An attempt to connect to the file server on host
  <hostname> using the SFTP protocol failed with exception
  <exception details>.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.2 LTS   9.2.0.5
  v9.x CD    9.2.5
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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

  MQ BASE V9.2

• Fixed component ID

  5724H7281

Applicable component levels