[avahi] Running avahi-daemon on-demand

[Till Kamppeter]

I am responsible for Ubuntu's printing stack and for Ubuntu Touch (the 
phone OS from Ubuntu) I would like to run the three daemons 
avahi-daemon, cupsd, and cups-browsed on-demend.

cups-browsed is accessing avahi-daemon via the library functions 
avahi_glib_poll_new(), avahi_client_new(), avahi_service_browser_new(), 
which is probably using the D-Bus interface (am I right?). Can I have 
avahi-daemon not started and the start it D-Bus triggered, for example 
through the D-Bus bridge of Upstart?

In Upstart I would need to set a rule like (see dbus-event(7) man page 
on Upstart-enabled distros like Ubuntu):

start on dbus   [BUS=BUS_NAME]  SIGNAL=SIGNAL  INTERFACE=INTERFACE 
OBJPATH=PATH SENDER=SENDER DESTINATION=DESTINATION ARG0=VALUE ARGN=VALUE

How do I have to fill in these fields so that the rule gets matched by 
the first D-Bus call sent by above library functions?

    Till