D-Bus User Bus

Thiago Macieira thiago at kde.org
Wed May 19 11:18:40 PDT 2010

Em Quarta-feira 19. Maio 2010, às 19.50.57, Colin Walters escreveu:
> 2010/5/17 Havoc Pennington <hp at pobox.com>:
> > The longstanding issue with a user bus is that it doesn't really solve
> > anything,
> It makes things work for people who want to use cron to schedule jobs
> that need to access e.g. gnome-keyring.  (Though really, we should
> also have DISPLAY set).  Also logging in via ssh.

I think what we're looking for here is an "all-sessions user overlay".

That is, there's this special bus that belongs to a user and the session 
busses connect to. One session does not see services in another and cannot 
communicate with it. However, services in the session do see the services in 
the user bus overlay.

This would require that session buses coordinate the assignment of unique 
connection IDs, so that they are globally unique.

This way, we could move services that are supposed to be singletons into the 
user bus, but no client would require code changes.

At an extreme, this could be implemented entirely in the client (binding) 
code, by connecting to two buses and hiding the fact that there are two, but 
I'm pretty sure it wouldn't be long until a three-way communication situation 
is found and it breaks (A tells B to talk to C, but B and C can't talk).

Another way to look at this is to have only a user bus, but introduce a 
session or domain concept inside it. Connections in one domain can only see 
connections in that domain, plus the global domain. Access to a domain is 
granted by knowing the domain's "secret" at connection time (like an ID at 
handshake or by connecting to a special Unix socket whose name is random and 
is saved in an environment variable).

Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
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