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.
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.
Old static libsystemd-bus.la becomes libsystemd-bus-internal.la.
memfd functions are also exported in the same library.
(Best viewed with --color-words -U0).
Among other things this also adds a few things necessary for the change:
- Considerably more powerful error returning APIs in libsystemd-bus
- Adapter for connecting an sd_bus to an sd_event
- As I reworked the PolicyKit logic to the new library I also made it
asynchronous, so that PolicyKit requests of one user cannot block out
another user anymore.
- We always use the macro names for common bus error. That way it is
harder to mistype them since the compiler will notice
This way they are nicer to use from method dispatch callbacks as last
call, since method dispatch callbacks expect > 0 return if the message
got handled.
This adds a lightweight scheme how to define interfaces in static fixed
arrays which then can be easily registered on a bus connection. This
makes it much easier to write bus services.
This automatically handles implementation of the Properties,
ObjectManager, and Introspection bus interfaces.
We want to allow clients to process an sd_bus_message on a different
thread than it was received on. Since unreffing a bus message might
readd some of its memfds to the memfd cache add some minimal locking
around the cache.
We need this since we might need to invoke the release ioctl for
messages. Since we don't want to add any locking for that we simply keep
a reference to the bus and then rely that the fd stays valid all the
time.
