Message handler callbacks can be simplified drastically if the
dispatcher automatically replies to method calls if errors are returned.
Thus: add an sd_bus_error argument to all message handlers. When we
dispatch a message handler and it returns negative or a set sd_bus_error
we send this as message error back to the client. This means errors
returned by handlers by default are given back to clients instead of
rippling all the way up to the event loop, which is desirable to make
things robust.
As a side-effect we can now easily turn the SELinux checks into normal
function calls, since the method call dispatcher will generate the right
error replies automatically now.
Also, make sure we always pass the error structure to all property and
method handlers as last argument to follow the usual style of passing
variables for return values as last argument.
This patch converts PID 1 to libsystemd-bus and thus drops the
dependency on libdbus. The only remaining code using libdbus is a test
case that validates our bus marshalling against libdbus' marshalling,
and this dependency can be turned off.
This patch also adds a couple of things to libsystem-bus, that are
necessary to make the port work:
- Synthesizing of "Disconnected" messages when bus connections are
severed.
- Support for attaching multiple vtables for the same interface on the
same path.
This patch also fixes the SetDefaultTarget() and GetDefaultTarget() bus
calls which used an inappropriate signature.
As a side effect we will now generate PropertiesChanged messages which
carry property contents, rather than just invalidation information.
If a timer fires and is marked pending, but an application re-arms it
before it is dispatched, we now clear the pending state.
This fixes a bug where an application arms a timer, which fires and is
marked pending. But before it is dispatched, the application loses
interest in it and disables it. Now if the timer is re-armed and
re-enabled later, it will be immediately dispatched as it is still marked
pending.
This behavior is unexpected, so avoid it by clearing pending state when
re-arming timers. Note that applications have no way to clear pending
state themselves, so there's no current workaround.
I know that this is a pretty big net to catch some small fish,
but we *do* regularly forget to properly export symbols that
were supposed to be exported.
This time sd_bus_get_current and some renamed symbols are caught.
We want to emphasize bus connections as per-thread communication
primitives, hence introduce a concept of a per-thread default bus, and
make use of it everywhere.
Try to emphasize a bit that there should be a mapping between event
loops and threads, hence introduce a logic that there's one "default"
event loop for each thread, that can be queried via
"sd_event_default()".
So far we used ENXIO whenever the user tried to read something from a
function that didn't carry the right type, and hence use the same error
here to indicate that what the user expected and what was in the message
didn't match up.
When issuing a synchronous "systemctl daemon-reload" requests this will
send out a tonload of UnitRemoved+UnitNew signals, that we will queue
locally. When we wait for the message reply, we should be able to queue
those, hence bump the limits on locally queuing messages.
