Re: [xmpp] 3921bis: probe + unavailable

[Dave Cridland <dave at cridland.net>]

On Thu Jan 28 21:34:07 2010, Peter Saint-Andre wrote:
> a. My sense of existing implementations is that people would prefer  
> a
> definitive answer to the probe (i.e., <presence  
> type='unavailable'/>).
> Therefore I would like to change "SHOULD reply with unavailable but  
> MAY
> opt to not reply at all" to "MUST reply with unavailable".
I agree - I think it's a change that's sorely needed - but I'd note  
that this will render several servers no longer conformant. So a  
note's needed at minimum to explain that this didn't used to be a  
requirement, and clients (and servers) SHOULD cope with no response  
as meaning unavailable.

> b. Someone poked me offlist about a potential security issue here:  
> what
> if the probing user was blocked from receiving the contact's  
> presence at
> that time (e.g. via privacy lists)?

Right.

>    2.  Else, if the contact has no available resources, then the  
> server
>        MUST reply to the presence probe by sending to the user a
>        presence stanza of type "unavailable"; this presence stanza
>        SHOULD be empty but (subject to local security policies) MAY
>        include the full XML of the last unavailable presence stanza  
> that
>        the server received from the contact.

Replace SHOULD with "will typically be". You can't have SHOULD but  
MAY, I think, and it's not an interop requirement.

Also, you might stamp it with a delay, in which case it's not empty...

Dave.
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