Function

|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|

+---+---+---+---+

0|.|I| 0x02 |1| Function | Reserved | +---+---+---+---+

4|TotalAHSLength | DataSegmentLength | +---+---+---+---+

8| Logical Unit Number (LUN) or Reserved | + + 12| | +---+---+---+---+

16| Initiator Task Tag | +---+---+---+---+

20| Referenced Task Tag or 0xffffffff | +---+---+---+---+

24| CmdSN | +---+---+---+---+

28| ExpStatSN | +---+---+---+---+

32| RefCmdSN or Reserved | +---+---+---+---+

36| ExpDataSN or Reserved | +---+---+---+---+

40/ Reserved / +/ / +---+---+---+---+

48| Header-Digest (optional) | +---+---+---+---+

11.5.1. Function

The task management functions provide an initiator with a way to explicitly control the execution of one or more tasks (SCSI and iSCSI tasks). The task management function codes are listed below. For a more detailed description of SCSI task management, see [SAM2].

1 ABORT TASK - aborts the task identified by the Referenced Task Tag field.

2 ABORT TASK SET - aborts all tasks issued via this session on the LU.

3 CLEAR ACA - clears the Auto Contingent Allegiance condition.

4 CLEAR TASK SET - aborts all tasks in the appropriate task set as defined by the TST field in the Control mode page

(see [SPC3]).

5 LOGICAL UNIT RESET 6 TARGET WARM RESET 7 TARGET COLD RESET

8 TASK REASSIGN - reassigns connection allegiance for the task identified by the Initiator Task Tag field to this connection, thus resuming the iSCSI exchanges for the task.

Values 9-12 are assigned in [RFC7144]. All other possible values for the Function field are unassigned.

For all these functions, the Task Management Function Response MUST be returned as detailed in Section 11.6. All these functions apply to the referenced tasks, regardless of whether they are proper SCSI tasks or tagged iSCSI operations. Task management requests must act on all the commands from the same session having a CmdSN lower than the task management CmdSN. LOGICAL UNIT RESET, TARGET WARM RESET, and TARGET COLD RESET may affect commands from other sessions or commands from the same session, regardless of their CmdSN value.

If the task management request is marked for immediate delivery, it must be considered immediately for execution, but the operations involved (all or part of them) may be postponed to allow the target to receive all relevant tasks. According to [SAM2], for all the tasks covered by the task management response (i.e., with a CmdSN lower than the task management command CmdSN), except for the task management response to a TASK REASSIGN, additional responses MUST NOT be delivered to the SCSI layer after the task management response.

The iSCSI initiator MAY deliver to the SCSI layer all responses

received before the task management response (i.e., it is a matter of implementation if the SCSI responses that are received before the task management response but after the task management request was issued are delivered to the SCSI layer by the iSCSI layer in the initiator). The iSCSI target MUST ensure that no responses for the tasks covered by a task management function are delivered to the iSCSI initiator after the task management response, except for a task covered by a TASK REASSIGN.

For ABORT TASK SET and CLEAR TASK SET, the issuing initiator MUST continue to respond to all valid Target Transfer Tags (received via R2T, Text Response, NOP-In, or SCSI Data-In PDUs) related to the

The issuing initiator SHOULD, however, terminate (i.e., by setting the F bit to 1) these response sequences as quickly as possible. The target for its part MUST wait for responses on all affected Target Transfer Tags before acting on either of these two task management requests. If all or part of the response sequence is not received (due to digest errors) for a valid TTT, the target MAY treat it as a case of a within-command error recovery class (see Section 7.1.4.1) if it is supporting ErrorRecoveryLevel >= 1 or, alternatively, may drop the connection to complete the requested task set function.

If an ABORT TASK is issued for a task created by an immediate command, then the RefCmdSN MUST be that of the task management request itself (i.e., the CmdSN and RefCmdSN are equal); otherwise, the RefCmdSN MUST be set to the CmdSN of the task to be aborted (lower than the CmdSN).

If the connection is still active (i.e., it is not undergoing an implicit or explicit logout), an ABORT TASK MUST be issued on the same connection to which the task to be aborted is allegiant at the time the task management request is issued. If the connection is implicitly or explicitly logged out (i.e., no other request will be issued on the failing connection and no other response will be received on the failing connection), then an ABORT TASK function request may be issued on another connection. This task management request will then establish a new allegiance for the command to be aborted as well as abort it (i.e., the task to be aborted will not have to be retried or reassigned, and its status, if sent but not acknowledged, will be resent followed by the task management response).

At the target, an ABORT TASK function MUST NOT be executed on a task management request; such a request MUST result in a task management response of "Function rejected".

For the LOGICAL UNIT RESET function, the target MUST behave as dictated by the Logical Unit Reset function in [SAM2].

The implementation of the TARGET WARM RESET function and the TARGET COLD RESET function is OPTIONAL and, when implemented, should act as described below. The TARGET WARM RESET is also subject to SCSI access controls on the requesting initiator as defined in [SPC3].

When authorization fails at the target, the appropriate response as described in Section 11.6.1 MUST be returned by the target. The TARGET COLD RESET function is not subject to SCSI access controls, but its execution privileges may be managed by iSCSI mechanisms such as login authentication.

When executing the TARGET WARM RESET and TARGET COLD RESET functions, the target cancels all pending operations on all LUs known by the issuing initiator. Both functions are equivalent to the TARGET RESET function specified by [SAM2]. They can affect many other initiators logged in with the servicing SCSI target port.

Additionally, the target MUST treat the TARGET COLD RESET function as a power-on event, thus terminating all of its TCP connections to all initiators (all sessions are terminated). For this reason, the service response (defined by [SAM2]) for this SCSI task management function may not be reliably delivered to the issuing initiator port.

For the TASK REASSIGN function, the target should reassign the connection allegiance to this new connection (and thus resume iSCSI exchanges for the task). TASK REASSIGN MUST ONLY be received by the target after the connection on which the command was previously executing has been successfully logged out. The task management response MUST be issued before the reassignment becomes effective.

For additional usage semantics, see Section 7.2.

At the target, a TASK REASSIGN function request MUST NOT be executed to reassign the connection allegiance of a Task Management Function Request, an active text negotiation task, or a Logout task; such a request MUST result in a task management response of "Function rejected".

TASK REASSIGN MUST be issued as an immediate command.