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

[David Herrmann]

Hey

On Thu, Apr 20, 2017 at 12:06 PM, David Härdeman <david at hardeman.nu> wrote:
> Hi,
>
> I'm implementing a server which creates an ObjectManager using the
> sd-bus API and there seems to be some differences between how gdbus and
> sd-bus implements the API.
>
> I implemented a simple ObjectManager at /org/gnome/TestManager which
> exports objects /org/gnome/TestManager/fooX with interface
> org.gnome.TestManager.Device.
>
> Under sd-bus, if an object is removed, the following signal is
> generated:
>
> signal time=1492642227.714223 sender=:1.104 -> destination=(null destination)
>         serial=90 path=/org/gnome/TestManager;
>         interface=org.freedesktop.DBus.ObjectManager;
>         member=InterfacesRemoved
>    object path "/org/gnome/TestManager/foo0"
>    array [
>       string "org.freedesktop.DBus.Peer"
>       string "org.freedesktop.DBus.Introspectable"
>       string "org.freedesktop.DBus.Properties"
>       string "org.freedesktop.DBus.ObjectManager"
>       string "org.gnome.TestManager.Device"
>    ]
>
> If I implement the same simple server in gdbus, the signal is instead:
>
> signal time=1492642227.714223 sender=:1.104 -> destination=(null destination)
>         serial=90 path=/org/gnome/TestManager;
>         interface=org.freedesktop.DBus.ObjectManager;
>         member=InterfacesRemoved
>    object path "/org/gnome/TestManager/foo0"
>    array [
>       string "org.gnome.TestManager.Device"
>    ]
>
> The corresponding signals are also generated when an object is added.
>
> Beside simply being different, this difference seems to confuse gdbus.
> If I create a test client, it will report that any object which is
> already existing when I start the client has 1 interface and any object
> which is added/removed subsequently is reported as having 5 interfaces,
> 4 of which are nameless (this would appear to be one or more gdbus
> bug(s)).
>
> This bug in gdbus also means that it doesn't correctly catch the removal
> of an object which existed at the time the client was started (because
> of the interface count mismatch).
>
> Anyway, gdbus bugs aside, it seems that the interfaces reported by
> sd-bus should match what gdbus does? (assuming, of course, that gdbus
> can be considered the "reference" implementation).

Does the appended patch fix your issue?
(line-breaks might be screwed, sorry)

Thanks
David


diff --git a/src/libsystemd/sd-bus/bus-objects.c
b/src/libsystemd/sd-bus/bus-objects.c
index 9bd07ffca..b6f5afe1b 100644
--- a/src/libsystemd/sd-bus/bus-objects.c
+++ b/src/libsystemd/sd-bus/bus-objects.c
@@ -1057,6 +1057,22 @@ static int object_manager_serialize_path(
                         if (r < 0)
                                 return r;

+                        r = sd_bus_message_append(reply, "{sa{sv}}",
"org.freedesktop.DBus.Peer", 0);
+                        if (r < 0)
+                                return r;
+
+                        r = sd_bus_message_append(reply, "{sa{sv}}",
"org.freedesktop.DBus.Introspectable", 0);
+                        if (r < 0)
+                                return r;
+
+                        r = sd_bus_message_append(reply, "{sa{sv}}",
"org.freedesktop.DBus.Properties", 0);
+                        if (r < 0)
+                                return r;
+
+                        r = sd_bus_message_append(reply, "{sa{sv}}",
"org.freedesktop.DBus.ObjectManager", 0);
+                        if (r < 0)
+                                return r;
+
                         found_something = true;
                 }