iSCSI: Reject reason codes

["Mallikarjun C." <cbm@rose.hp.com>]

Julian,

The following Reject reason codes are defined in 
rev07 that are related to retry -

4 - Command-Retry Reject
6 - Command-in-progress
7 - Command Replay Not Supported
9 - Immediate Command Retry Reject - task not found

Since what we generically refer to as "retry" 
can be (section 7.1) one of 
	(a) command plugging, or
	(b) command failover, or
	(c) command replay,
I suggest that we define the Reject codes to 
specifically identify each of these three usages of 
retry bit.  With that said, I propose to -

   - define a new reason code "Command failover not
     supported" specifically for (b). (see NOTE below)

   - drop "Command-Retry Reject" since it is too
     generic and can be inadvertently used for all 
     flavors of retry rejects (which have separate
     codes, but are all technically retries).

   - drop "Immediate Command Retry Reject" since it
     could use 
	o "Command-in-progress" for "proactive" retries
          (since command plugging is not really valid for an 
          immediate command as it doesn't consume a CmdSN).
        o "Command failover not supported" for (b)
        o "Command Replay Not Supported" for (c)

     I am not sure about the current "task not found"
     qualifier - I assume that if the task is not found,
     it would be treated as a new immediate command and
     appropriately dealt with (reject-"too many immediate 
     commands"/execute).


NOTE: I also propose that a target that does not support command 
failover (CommandFailoverSupport=no) should fail the Logout Command
with reason code "2" (recovery), with a TBD Logout Response
code meaning "Connection recovery not supported.".  

Once this is done, the "Command failover not supported" Reject 
reason code (that I am proposing) is useful only for a 
transient period while the tasks are in the process of being
cleaned up on target - though one could arguably use "Protocol
Error" for those cases.  My preference is to define the new
Reject reason code for uniformity.
--
Mallikarjun 


Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668	Hewlett-Packard, Roseville.
cbm@rose.hp.com