[systemd-devel] sd-bus: ObjectManager difference with gdbus

[David Härdeman]

On Tue, Apr 25, 2017 at 09:54:45AM +0200, David Herrmann wrote:
>On Tue, Apr 25, 2017 at 9:40 AM, David Härdeman <david at hardeman.nu> wrote:
>> April 21, 2017 1:22 PM, "David Herrmann" <dh.herrmann at gmail.com> wrote:
>>> This change makes sure all objects have the built-in interfaces
>>> reported at all times. The GetManagedObjects() call didn't report them
>>> so far.
>>
>> Quite the contrary? If you look at the output from dbus-monitor above, you'll see that it is sd-bus that already *does* report all interfaces while gdbus doesnt?
>
>No, it does not. sd-bus was inconsistent. See, there are 3 things
>involved in the Object-Manager:
>
>Signal: InterfacesAdded
>Signal: InterfacesRemoved
>Call: GetManagedObjects
>
>The first two signals are used to add and remove objects (and their
>respective interfaces) at runtime. The GetManagedObjects() call is
>used to bootstrap, that is, to get the initial set of objects (and
>their respective interfaces) when starting your application.
>
>So far, sd-bus reported the builtin interfaces correctly via the
>signals, but did not return that information in the
>GetManagedObjects() call. My patch fixed this omission.
>The effect of this is that objects added/removed at runtime work fine,
>but if an object was there already when your application starts, then
>it will never be removed, since gdbus will see an interface-count
>mismatch (as you observed above).
>
>Hence, the patch I provided fixes how sd-bus provides this
>information. It does *not* change any policy.
>
>I think the 2 underlying problems you saw are bugs in both gdbus and
>sd-bus. The one in sd-bus I tried to fix above, the one in gdbus is
>only about counting interfaces and properly detecting negative
>interface-counts. The gdbus bug is non-severe, though, since it
>originates in a buggy remote client. So there is no hard reason to
>change gdbus there.

Ok, I've tried the patch. It seems to fix things insofar that
InterfacesAdded/InterfacesRemoved/GetManagedObjects all report 5
interfaces (checked with dbus-monitor).

gdbus still gets royally confused though. It seems to report 5
interfaces for objects which are added dynamically (i.e. signalled via
InterfacesAdded) and 1 interface for objects which are generated via
GetManagedObjects (even though the sd-bus server reports 5 interfaces).

I'll start working on a testcase...

-- 
David Härdeman