Google sending weird XMPP stuff

Fastmail’s XMPP server is receiving some bogus crap from Google at the moment. First we get a connection from a Google IP, and then a dialback challenge:

<db:result from='' to='********'>********</db:result>

All good so far. But then, before we even get chance to connect back and do the dialback validation, we get:

<nsp0:message from='' to='********' xmlns:nsp0='jabber:server'>
  <push:push channel='babel' xmlns:push='google:push'>
    <push:recipient to='********'/>

Which promptly gets the connection dropped because (a) we haven’t yet authorised send and (b) we’ve only been asked to authorise, not

Google itself knows nothing about, and only rumours and whispers of a new messaging platform called “Babel”.

Its only happening for a couple of users, but the disconnections are causing them to lose messages. I don’t know if this is an experiment gone awry, but there’s something wrong here.