Examples of org.jscsi.parser.logout.LogoutRequestParser

• org.jscsi.parser.logout.LogoutRequestParser

  LogoutRequestParser

  This class parses a Logout Request message defined in the iSCSI Standard (RFC3720).

  The Logout Request is used to perform a controlled closing of a connection.

  An initiator MAY use a Logout Request to remove a connection from a session or to close an entire session.

  After sending the Logout Request PDU, an initiator MUST NOT send any new iSCSI requests on the closing connection. If the Logout Request is intended to close the session, new iSCSI requests MUST NOT be sent on any of the connections participating in the session.

  When receiving a Logout Request with the reason code of "close the connection" or "close the session", the target MUST terminate all pending commands, whether acknowledged via ExpCmdSN or not, on that connection or session respectively.

  When receiving a Logout Request with the reason code "remove connection for recovery", the target MUST discard all requests not yet acknowledged via ExpCmdSN that were issued on the specified connection, and suspend all data/status/R2T transfers on behalf of pending commands on the specified connection.

  The target then issues the Logout Response and half-closes the TCP connection (sends FIN). After receiving the Logout Response and attempting to receive the FIN (if still possible), the initiator MUST completely close the logging-out connection. For the terminated commands, no additional responses should be expected.

  A Logout for a CID may be performed on a different transport connection when the TCP connection for the CID has already been terminated. In such a case, only a logical "closing" of the iSCSI connection for the CID is implied with a Logout.

  All commands that were not terminated or not completed (with status) and acknowledged when the connection is closed completely can be reassigned to a new connection if the target supports connection recovery.

  If an initiator intends to start recovery for a failing connection, it MUST use the Logout Request to "clean-up" the target end of a failing connection and enable recovery to start, or the Login Request with a non-zero TSIH and the same CID on a new connection for the same effect (see Section 10.14.3 CID). In sessions with a single connection, the connection can be closed and then a new connection reopened. A connection reinstatement login can be used for recovery (see Section 5.3.4 Connection Reinstatement).

  A successful completion of a Logout Request with the reason code of "close the connection" or "remove the connection for recovery" results at the target in the discarding of unacknowledged commands received on the connection being logged out. These are commands that have arrived on the connection being logged out, but have not been delivered to SCSI because one or more commands with a smaller CmdSN has not been received by iSCSI. See Section 3.2.2.1 Command Numbering and Acknowledging. The resulting holes the in command sequence numbers will have to be handled by appropriate recovery (see Chapter 6) unless the session is also closed.

  The entire logout discussion in this section is also applicable for an implicit Logout realized via a connection reinstatement or session reinstatement. When a Login Request performs an implicit Logout, the implicit Logout is performed as if having the reason codes specified below:

  Reason code	Type of implicit Logout
  0	session reinstatement
  1	connection reinstatement when the operational ErrorRecoveryLevel < 2
  2	connection reinstatement when the operational ErrorRecoveryLevel = 2

  TotalAHSLength and DataSegmentLength

  For this PDU TotalAHSLength and DataSegmentLength MUST be 0.

  ExpStatSN

  This is the last ExpStatSN value for the connection to be closed.

  Implicit termination of tasks

  A target implicitly terminates the active tasks due to the iSCSI protocol in the following cases:

  1. When a connection is implicitly or explicitly logged out with the reason code of "Close the connection" and there are active tasks allegiant to that connection.
  2. When a connection fails and eventually the connection state times out (state transition M1 in Section 7.2.2 State Transition Descriptions for Initiators and Targets) and there are active tasks allegiant to that connection.
  3. When a successful recovery Logout is performed while there are active tasks allegiant to that connection, and those tasks eventually time out after the Time2Wait and Time2Retain periods without allegiance reassignment.
  4. When a connection is implicitly or explicitly logged out with the reason code of "Close the session" and there are active tasks in that session.

  If the tasks terminated in any of the above cases are SCSI tasks, they must be internally terminated as if with CHECK CONDITION status. This status is only meaningful for appropriately handling the internal SCSI state and SCSI side effects with respect to ordering because this status is never communicated back as a terminating status to the initiator. However additional actions may have to be taken at SCSI level depending on the SCSI context as defined by the SCSI standards (e.g., queued commands and ACA, in cases a), b), and c), after the tasks are terminated, the target MUST report a Unit Attention condition on the next command processed on any connection for each affected I_T_L nexus with the status of CHECK CONDITION, and the ASC/ASCQ value of 47h/7Fh - "SOME COMMANDS CLEARED BY ISCSI PROTOCOL EVENT" - etc. - see [SAM2] and [SPC3]).

  @author Volker Wildi

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