[stgt] Max Sessions per Target

[ronnie sahlberg]

Hi,

Why exactly can you not use ACLs?  Maybe it is possible to tweak them
so that they will work for your use-case ?



Not tested at all, not even compile tested,  but this might do what you want :
(I doubt this kind of feature will go into mainline)

{
	int cnt = 0;
	struct list_head *tmp;
	list_for_each(tmp, &target->it_nexus_list)
		cnt++;
	if (cnt > 1)
		return -EEXIST;	
}




On Mon, Jan 21, 2013 at 8:12 PM, Bruno Condez <bcondez at riotgames.com> wrote:
> Hi Everyone,
>
> I'm looking for what I hope to be a quick help from you stgt developers.
>
> I run stgt 1.0.33 on a Centos 6.2 OS and i'm looking for a way to limit
> the number of sessions a target can have.
>
> A bit of background:
> I have a bunch of client computers booting their OS through software iSCSI
> by leveraging iPXE.
> I pxe boot iPXE which then presents a LUN to the computer as a local disk
> which then instructs such computer to boot from it.
> These computers are used by different users who need their own OS
> customized a specific way and bootable from different computers (same
> hardware through).
>
> Each user as it's own target.
> A boot menu exists that allows a user to choose his own target (OS image)
> from a list.
> Now, the reason why I need to limit the number of sessions is to prevent 2
> users from booting the same LUN. Users can make mistakes and accidentally
> (or on purpose) boot someone else's LUNs.
>
> There are reasons why setting up CHAP authentication or initiator ACLs
> will not work for this specific setup.
>
> Hence, limiting the sessions per targets is the desired effect that works
> for this setup.
>
> I have found a patch from 2008 that makes every target allow only a single
> session.
> In particular, the code below does the trick:
>
> diff --git a/usr/target.c b/usr/target.c
> index dc30c87..91085dc 100644
> --- a/usr/target.c
> +++ b/usr/target.c
> @@ -248,6 +248,9 @@ int it_nexus_create(int tid, uint64_t itn_id, int
> host_no, char *info)
>
>         target = target_lookup(tid);
>
> +       if (!list_empty(&target->it_nexus_list))
> +               return -EEXIST;
> +
>         itn = zalloc(sizeof(*itn));
>         if (!itn)
>                 return -ENOMEM;
>
>
>
> I've applied that patch to the current code (git'ed today) and it does
> work as intended.
>
> However, I actually need it to allow a max of 2 sessions per target.
> This is because, during initial boot, iPXE creates a session and presents
> the LUN to the computer.; which  then boots from that LUN and during boot
> the OS detects it's on iSCSI and takes over iSCSI handling from
>  iPXE by establishing a new session to the same target.
> When this happens, in tgtadm output I see two sessions from the same IP,
> though the original session shows 0 connections and the second session 1
> connection (the actual OS). But for tgt, there are still two sessions.
>
> So, would it be possible to have a patch similar to the above but that
> allows a max of 2 sessions? Or a user configurable value?
>
> I realize this is a very specific request. I'm ok with this patch being
> ad-hoc, not officially supported and me having to deal with it on my own.
> I would do such patch myself but my knowledge of C is zero.
>
> I do appreciate any help in getting this specific request going.
>
> Cheers,
> Bruno
>
>
> ________________________________
>
> Riot Games Ltd, Registered in Ireland No 483483. Registered Office 1st Floor, Beaux Lane House, Lower Mercer Street, Dublin 2
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