RE: iSCSI ABORT TASK RefCmdSN question

[Black_David@emc.com]

> Suppose an iSCSI target receives an ABORT TASK Task Management Function
that
> does not refer to a valid task (i.e. the Referenced Task Tag does not
match
> any task at the target) but the CmdSN is inside the valid window and
matches
> a non-immediate command that has not yet been delivered for execution.
For
> example,
> 
> Target's ExpCmdSN is 10.
> Target has a queued non-immediate command with CmdSN 11 and 
> Initiator Task Tag of 55 which has not been delivered for execution
> because the target is waiting for a non-immediate command with CmdSN 10
> first.  Target receives an immediate ABORT TASK Task Management Function
> with Referenced Task Tag of 66 and RefCmdSN of 11.

This is an error.  The initiator has violated the following MUST:

9.5.5  RefCmdSN

   For the ABORT TASK function, initiators MUST always set this to the 
   CmdSN of the task identified by the Referenced Task Tag field. Tar-
   gets must use this field as described in section 9.6.1 when the task 
   identified by the Referenced Task Tag field is not with the target.

A Reject PDU with Reason 0x09 will do nicely to tell the Initiator that
it screwed up.  Processing an erroneous task management function
request by trying to infer what the initiator might have intended is
not a good idea.

Thanks,
--David
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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
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