[Standards] Removal of GC1.0 from MUC / XEP-0045

Georg Lukas georg at op-co.de
Tue Apr 10 08:29:36 UTC 2018

It is this time of the month again. Georg is trying to fix MUC.
This time, I'm asking the Council to remove GC1.0 support from XEP-0045.

In case this motion is approved, I'd prepare a PR against 0045 where the
respective section will be replaced by a stub, and where servers will be
advised to respond to join-less presence with either <not-acceptable/>
or a <status code='307'/> presence (I think the former is more elegant).

The last time this was brought up, concerns were raised that we do not
know how many clients / users still rely on this behavior. Therefore,
Kim kindly created https://modules.prosody.im/mod_muc_gc10.html which
logs GC1.0 joins and asks the joining client for their version.

I've been running this module on yax.im for the last two weeks, and
ngathered additional feedback from other server operators. Almost all of
the GC1.0 joins were traced back to clients that _do_ support proper MUC
joins, and therefore are symptoms of c2s/s2s desynchronizations.

The two instances of GC1.0 joins that most probably are actual GC1.0
joins are:

* the prosody webchat client (unmaintained, semi-abandoned, but I have
  an idea who's the non-maintainer and maybe they'd fix it if we ask
  very nicely)

* Sawim for Android which I tested myself and failed to join any MUCs
  beacuse of its awesome UI. But it makes it easy to add a MUC as a
  roster item, obviously leading to user confusion and GC1.0-induced
  failure. So I ended up reverse engineering the APK, which indeed
  seemed to support the proper MUC protocol.

Because of this obvious lack of GC1.0 usage in the field, the fact that
adding a MUC to your roster will induce GC1.0 behavior that most
probably won't be comprehended by clients, and the desync problems of
GC1.0 that I outlined in [0] and at the Summit, I motion for permanent
deactivation of GC1.0 support.

Kind regards,


[0] https://mail.jabber.org/pipermail/standards/2017-October/033501.html
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