bus: rework message handlers to always take an error argument

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.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/machine/machined.h b/src/machine/machined.h
index 3f07d4dd8e..0b074c4e8a 100644
--- a/src/machine/machined.h
+++ b/src/machine/machined.h
@@ -62,10 +62,10 @@ extern const sd_bus_vtable manager_vtable[];
 
 int machine_node_enumerator(sd_bus *bus, const char *path, char ***nodes, void *userdata);
 
-int match_reloading(sd_bus *bus, sd_bus_message *message, void *userdata);
-int match_unit_removed(sd_bus *bus, sd_bus_message *message, void *userdata);
-int match_properties_changed(sd_bus *bus, sd_bus_message *message, void *userdata);
-int match_job_removed(sd_bus *bus, sd_bus_message *message, void *userdata);
+int match_reloading(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
+int match_unit_removed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
+int match_properties_changed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
+int match_job_removed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error);
 
 int manager_start_scope(Manager *manager, const char *scope, pid_t pid, const char *slice, const char *description, sd_bus_message *more_properties, sd_bus_error *error, char **job);
 int manager_stop_unit(Manager *manager, const char *unit, sd_bus_error *error, char **job);