Re: [Scst-devel] Problem with registering Microsoft isns server

[Vladislav B. <vs...@vl...>]

Hi,

Bag...@em..., on 08/08/2011 12:47 PM wrote:
> Hi All,
>  
> My name is kumar,i am a developer and basically using the iscsi-scst 2.0.0 
> stack with mutli target configuration. On my experimentation when I register 
> the stack to an external microsoft(2008) isns server. The server is discovering
> only one iscsi target (though my config has many).
>  
> When i back traced the issue,i am able to figured out that the isns device
> registeration is having a problem.The DevAttributeReg request from iscsi-scst is
> failing with a response code "source unknown" from the Microsoft isns server.
>  
> Issue:
> ------------
> The DevRegAttribute is sending a different Source Attribute (ISCSI name) which
> represents the Storage Node for each target. So Microsoft isns server considers
> the last request as the storage node and doesn't discover the previous targets.
>  
> Root Cause
> ----------------
> Function ISNS_FUNC_DEV_ATTR_REG
>  
> Target A
> Source attribute 
>             ISCSI-Name = <IQN A Name>
> Operating Attribute 
>             ISCSI-Name  = <IQN A Name>
> Flags
> Replace Access = 1
>  
> Target B 
> Source attribute 
>                ISCSI-Name = <IQN B Name>
> Operating Attribute 
>                ISCSI-Name  = <IQN B Name>
> Replace Access = 1
>  
> So as per the request format Microsoft isns Server always takes the last target
> as the source node. and register the same. Hence it doesn't discover the
> targets other than last one. The Source Attribute has to be fixed for all targets. It
> would be better if we use the first target iscsi name (rather than the last target
> iscsi name) as source attribute iscsi name to represent the storage node.
>  
> Patch
> -------
>  
> +diff -Naur iscsi-scst-2.0.0-3461.old/usr/isns.c iscsi-scst-2.0.0-3461/usr/isns.c
> +--- iscsi-scst-2.0.0-3461.old/usr/isns.c 2011-04-14 23:13:04.000000000 -0400
> ++++ iscsi-scst-2.0.0-3461/usr/isns.c 2011-08-03 09:40:04.000000000 -0400
> +@@ -502,7 +502,7 @@
> +  tlv = (struct isns_tlv *)hdr->pdu;
> +  max_buf = sizeof(buf) - offsetof(struct isns_hdr, pdu);
> + 
> +-        target = list_entry(targets_list.q_back, struct target, tlist);
> ++        target = list_entry(targets_list.q_forw, struct target, tlist);
> + 
> +  err = isns_tlv_set(&tlv, max_buf - length, ISNS_ATTR_ISCSI_NAME,
> +     strlen(target->name) + 1, target->name);
>  
>  
> Please let me know your inputs on the above issue.

It looks reasonable, but it's rather a workaround. For instance, what would
happen, if the first target was removed?

Therefore, I'd suggest instead to create a new sysfs attribute isns_entity_name
and by default set it in the name of the first registered target, if
isns_entity_name was not yet manually set using sysfs before. Then we will have
persistent iSNS entity name in all circumstances as required.

Thanks,
Vlad