[libvirt] [PATCH] DBus: introduce virDBusIsServiceEnabled

[Daniel P. Berrange]

On Tue, Sep 10, 2013 at 11:34:32AM +0800, Gao feng wrote:
> This patch introduces virDBusIsServiceEnabled, we can use
> this method to get if the service is supported.
> 
> In one case, if org.freedesktop.machine1 is unavailable on
> host, we should skip creating machine through systemd.
> 
> Signed-off-by: Gao feng <gaofeng at cn.fujitsu.com>
> ---
>  src/util/virdbus.c    | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  src/util/virdbus.h    |  1 +
>  src/util/virsystemd.c | 11 ++--------
>  3 files changed, 62 insertions(+), 9 deletions(-)
> 
> diff --git a/src/util/virdbus.c b/src/util/virdbus.c
> index 62c31be..29068b0 100644
> --- a/src/util/virdbus.c
> +++ b/src/util/virdbus.c
> @@ -1207,6 +1207,58 @@ int virDBusMessageRead(DBusMessage *msg,
>      return ret;
>  }
>  
> +/**
> + * virDBusIsServiceEnabled:
> + * @name: service name
> + */
> +bool virDBusIsServiceEnabled(const char *name)

IMHO this should be a tri-state so we can distinguish
actual 'service not available' from other fatal errors.

> +{
> +    DBusConnection *conn;
> +    DBusMessage *reply = NULL;
> +    DBusMessageIter iter, sub;
> +    bool ret = false;
> +
> +    if (!virDBusHasSystemBus())
> +        return ret;
> +
> +    conn = virDBusGetSystemBus();
> +
> +    if (virDBusCallMethod(conn,
> +                          &reply,
> +                          "org.freedesktop.DBus",
> +                          "/org/freedesktop/DBus",
> +                          "org.freedesktop.DBus",
> +                          "ListActivatableNames",
> +                          DBUS_TYPE_INVALID) < 0) {
> +        VIR_DEBUG("ListActivatableNames failed.");
> +        return ret;

In particular this is a fatal error condition that
should be treated as such.

> +    }
> +
> +    if (!dbus_message_iter_init(reply, &iter) ||
> +        dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_ARRAY) {
> +        VIR_DEBUG("Reply message incorrect.");
> +        goto cleanup;
> +    }
> +
> +    dbus_message_iter_recurse(&iter, &sub);
> +    while (dbus_message_iter_get_arg_type(&sub) == DBUS_TYPE_STRING) {
> +        const char *service = NULL;
> +
> +        dbus_message_iter_get_basic(&sub, &service);
> +        dbus_message_iter_next(&sub);
> +
> +        if (STREQ(service, name)) {
> +            ret = true;
> +            goto cleanup;
> +        }
> +    }
> +
> + cleanup:
> +    VIR_DEBUG("Service %s is %s", name, ret ? "available" : "unavailable");
> +    dbus_message_unref(reply);
> +    return false;
> +}
> 


Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|