Hi Andrew,

On 03/14/2016 05:15 PM, Andrzej Zaborowski wrote:
> Hi Denis,
>
> On 14 March 2016 at 18:11, Denis Kenzior <denkenz@gmail.com> wrote:
>> Hi Andrew,
>>
>> On 03/13/2016 10:41 PM, Andrew Zaborowski wrote:
>>>
>>> Kdbus doesn't store the cookies for messages that have the no reply flag
>>> and throws error when a reply is sent with reply_cookie that it doesn't
>>> know.  It's not fatal, but we also save some cycles by not sending the
>>> message.  A further change could be made to not even let users create a
>>> message as a return from a method call but that may be confusing.
>>> ---
>>>    ell/dbus-service.c | 8 ++++++--
>>>    1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/ell/dbus-service.c b/ell/dbus-service.c
>>> index b4e0b60..c1ed9ec 100644
>>> --- a/ell/dbus-service.c
>>> +++ b/ell/dbus-service.c
>>> @@ -1624,8 +1624,12 @@ bool _dbus_object_tree_dispatch(struct
>>> _dbus_object_tree *tree,
>>>                  return false;
>>>
>>>          reply = method->cb(dbus, message, instance->user_data);
>>> -       if (reply)
>>> -               l_dbus_send(dbus, reply);
>>> +       if (reply) {
>>> +               if (l_dbus_message_get_no_reply(message))
>>> +                       l_dbus_message_unref(reply);
>>> +               else
>>> +                       l_dbus_send(dbus, reply);
>>> +       }
>>
>>
>> Okay, but this doesn't solve the issue for async method returns.
>>
>
> True, I forgot about that.
>
>> Should we
>> save the no_reply flag inside l_dbus_message_new_method_return &
>> l_dbus_message_new_error and then take care of this inside l_dbus_send?
>
> I was thinking of modifying l_dbus_message_new_method_return to set
> message->destination to NULL or returning an error.
>

Returning an error is bad, since the code might not be setup to handle 
noreply messages.  Any client can call any method call on the service 
and just randomly set the noreply flag.  If we return an error, then 
half our method handlers might crash.  And I don't necessarily want to 
check for the noreply flag in every method handler.

I think the easiest way would be to just add a noreply flag inside 
l_dbus_message (similar to bool sealed) and just not put the message on 
the wire if that flag is set.

Regards,
-Denis