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/core/dbus.c b/src/core/dbus.c
index b6124b3b22..3d8da1e6ad 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -71,7 +71,7 @@ int bus_send_queued_message(Manager *m) {
         return 0;
 }
 
-static int signal_agent_released(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int signal_agent_released(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Manager *m = userdata;
         const char *cgroup;
         int r;
@@ -100,7 +100,7 @@ static int signal_agent_released(sd_bus *bus, sd_bus_message *message, void *use
         return 0;
 }
 
-static int signal_disconnected(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int signal_disconnected(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Manager *m = userdata;
 
         assert(bus);
@@ -119,7 +119,7 @@ static int signal_disconnected(sd_bus *bus, sd_bus_message *message, void *userd
         return 0;
 }
 
-static int signal_name_owner_changed(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int signal_name_owner_changed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         const char *name, *old_owner, *new_owner;
         Manager *m = userdata;
         int r;
@@ -142,7 +142,7 @@ static int signal_name_owner_changed(sd_bus *bus, sd_bus_message *message, void
         return 0;
 }
 
-static int signal_activation_request(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int signal_activation_request(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *ret_error) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
         Manager *m = userdata;