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iSCSI - last change for 2001!
Dear colleagues,
According to the agreement reached in SLC here is the new text for the Task Management Request/Response (with all synchronization functions delegated to the target). The impementer's notes - subsection 4 is out.
Task Management Function Request
Byte / 0 | 1 | 2 | 3 |
/ | | | |
|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
+---------------+---------------+---------------+---------------+
0|0|I| x02 |0| Function | Reserved |
+---------------+---------------+---------------+---------------+
4| Reserved |
+---------------+---------------+---------------+---------------+
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 ExpDataSN |
+---------------+---------------+---------------+---------------+
36/ Reserved /
+/ /
+---------------+---------------+---------------+---------------+
48
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 functions 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 logical unit.
3 CLEAR ACA - clears the Auto Contingent Allegiance condi-tion.
4 CLEAR TASK SET - aborts all Tasks for the Logical Unit.
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 on this con-nection, thus resuming the iSCSI exchanges for the task.
For all these functions, if executed, the Task Management Function Response MUST be returned using the Initiator Task Tag to identify the operation for which it is responding. All these functions apply to the referenced tasks regardless of whether they are proper SCSI tasks or tagged iSCSI operations. Task management commands must be executed as if all the commands having a CmdSN lower or equal to the task manage-ment CmdSN have been received by the target (i.e., have to be executed as if received for ordered delivery even when marked for immediate delivery). For all the tasks covered by the task management response (i.e., with CmdSN not higher than the task management command CmdSN), 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 received before the task mangement response but after the task management request are delivered to the SCSI layer by the iSCSI layer in the ini-tiator). The iSCSI target MUST ensure that no responses for the tasks covered by a task management function are delivered to the iSCSI ini-tiator after the task management response.
If the connection is still active (it is not undergoing an implicit or explicit logout), ABORT TASK MUST be issued on the same connection to which the task to be aborted is allegiant at the time the Task Manage-ment Request is issued. If the connection is being 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 fail-ing 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 reas-signed, and its status, if issued, but not acknowledged will be reis-sued). For the LOGICAL UNIT RESET function, the target MUST behave as dictated by the Logical Unit Reset function in [SAM2].
The TARGET RESET function (WARM and COLD) implementation is OPTIONAL and when implemented, should act as described below. Target Reset MAY also be subject to SCSI access controls for the requesting initiator. When not implemented or when authorization fails at target, Target Reset functions should end as if the function was executed success-fully and the response qualifier will detail what was executed.
For the TARGET WARM RESET and TARGET COLD RESET functions, the target cancels all pending operations. Both functions are equivalent to the Target Reset function specified by [SAM2]. They can affect many other initiators.
In addition, for the TARGET COLD RESET, the target MUST then terminate all of its TCP connections to all initiators (all sessions are termi-nated).
For the TASK REASSIGN function, the target should reassign the connec-tion allegiance to this new connection (and thus resume iSCSI exchanges for the task). TASK REASSIGN MUST be received by the target ONLY after the connection on which the command was previously execut-ing has been successfully logged-out. For additional usage semantics see Section 7.1 Retry and Reassign in Recovery.
TASK REASSIGN MUST be issued as an immediate command.
LUN
This field is required for functions that address a specific LU (ABORT TASK, CLEAR TASK SET, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT RESET) and is reserved in all others.
Referenced Task Tag
The Initiator Task Tag of the task to be aborted or reassigned.
RefCmdSN or ExpDataSN
For ABORT TASK, the task CmdSN to enable task removal. If RefCmdSN does not match the CmdSN of the command to be aborted at the target,
the abort action MUST NOT be performed and the response MUST be func-tion rejected.
If the function is TASK REASSIGN, which establishes a new connection allegiance for a previously issued Read or Bidirectional command, this field will contain the next consecutive input DataSN number expected by the initiator (no gaps) for the referenced command in a previous execution.
Otherwise, this field is reserved.
Task Management Function Response
Byte / 0 | 1 | 2 | 3 |
/ | | | |
|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
+---------------+---------------+---------------+---------------+
0|0|1| 0x22 |1| Reserved | Response | Qualifier |
+---------------+---------------+---------------+---------------+
4/ Reserved /
/ /
+---------------+---------------+---------------+---------------+
16| Initiator Task Tag |
+---------------+---------------+---------------+---------------+
20| Referenced Task Tag or 0xffffffff |
+---------------+---------------+---------------+---------------+
24| StatSN |
+---------------+---------------+---------------+---------------+
28| ExpCmdSN |
+---------------+---------------+---------------+---------------+
32| MaxCmdSN |
+---------------+---------------+---------------+---------------+
36/ Reserved /
+/ /
+---------------+---------------+---------------+---------------+
48| Digest (if any) |
+---------------------------------------------------------------+
For the functions ABORT TASK, ABORT TASK SET, CLEAR ACA, CLEAR TASK SET, LOGICAL UNIT RESET, and TARGET WARM RESET, the target performs the requested Task Management function and sends a Task Management Response back to the initiator.
Response and Qualifier
The target provides a Response, which may take on the following val-ues:
0 - Function Complete
1 - Task specified in the Referenced Task Tag field was not in task set.
2 - LUN does not exist.
3 - Task still allegiant.
4 - Task failover not supported.
5 - Task management function not supported.
255 Function Rejected
All other values are reserved.
The Qualifier field provides additional information about the Response.
For a Response of "Function Complete" the valid Qualifiers are:
0 - Function Executed
1 - Not Authorized
For a discussion on usage of response codes 3 and 4, see Section 7.1.2 Allegiance Reassignment.
For the TARGET COLD RESET and TARGET WARM RESET functions, the target cancels all pending operations. For the TARGET COLD RESET function, the target MUST then close all of its TCP connections to all initia-tors (terminates all sessions).
The mapping of the response code into a SCSI service response code, if needed, is outside the scope of this document.
The response to ABORT TASK SET and CLEAR TASK SET MUST be issued by the target only after all the commands affected have been received by the target the corresponding task management functions functions have been executed by the SCSI target and the delivery of all previous responses has been confirmed (acknowledged through ExpStatSN) by the initiator on all connections of this session.
Referenced Task Tag
If the Request was ABORT TASK and the Response is "task not found", THE Referenced Task Tag contains the Initiator Task Tag of the task that had to be aborted. In other cases, it MUST be set to 0xffffffff.
Your comments please.
Julo
