[Standards] presence muc element

Dave Cridland dave at cridland.net
Fri Jun 25 11:29:26 UTC 2010


On Fri Jun 25 10:55:08 2010, Matthew Wild wrote:
> On 25 June 2010 10:02, Dave Cridland <dave at cridland.net> wrote:
> > There is, in fact, a workaround in M-Link, too, in as much as  
> it's possible
> > to strip out the XEP-0045 control element on inbound presence  
> from a domain
> > before the processing code ever sees it. I'd be loathe to put  
> that into
> > production.
> >
> 
> That's not actually possible on its own, unless you know which  
> domains
> are Google and which aren't. Our "workaround" was to detect this  
> based
> on the SRV records for the domain - then we set a flag for that  
> stream
> to say that it repeats presence, and our MUC component disables the
> rejoin logic for stanzas received over that stream. That is some
> workaround, though I don't see why it wouldn't work.
> 
> 
Oh, ouch. Yes, I can see why you don't deploy that.

> > Yes, also if we ensure servers respond correctly to probes when  
> directed
> > presence is involved we can probe in various cases - that said, I  
> know
> > M-Link doesn't respond correctly in this case, although we're  
> working on
> > that. (I'm curious as to whether other servers do, as well - this  
> is a bis
> > thing we've not caught up with yet, AFAIK).
> >
> 
> No, I don't think we have that either yet - likely for the next  
> release though.
> 
> 
Probably likewise. I have not yet figured out all the various failure  
cases, nor what the behavious in the wild actually is. I supect some  
judicious id tracking would solve most problems, but still.


> I have a better idea though...
> http://matthewwild.co.uk/uploads/gc_pinger.html :)
> 
> 
Yes... I did contemplate using ping, or disco#info, but it's not  
clear this is ideal either.

> > As an aside, here, it may be required that clients send  
> unavailable to their
> > old nickname after a nick change, as suggested above as a  
> workaround to
> > Google, since the server has to track the directed presence in  
> order to send
> > unavailable and respond to pings - if the client never sends the  
> unavailable
> > to match the directed presence, then various state mismatches  
> could occur.
> >
> 
> Yes, good point - this would need clarification in XEP-0045 I think.

Yes, it would, it's a change to the wire protocol.

The issue exists in RFC 3921 based systems, it's more acute in the  
~bis systems because of increased tracking requirements, I think.

Dave.
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