Signal handlers can get called for the wrong proxy
If we've the same proxy connected to different services over the same connection, the handlers for all the proxies are getting called for this signal if only one of the services emit the signal. This can lead to very bad consequences.
The reason is that we don't compare the sender
of the signal to the proxy's destination
. However, we don't do that because proxy's destination
could be (and is most often) the well-known name of the service, and dbus-daemon (maybe bus broker does different?) sets the unique name of the sender as the sender
. So we need to make a bus call to find the unique name for a destination and we need to store it around so we don't have to keep making the call each time.