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, 9 insertions, 7 deletions

diff --git a/src/libsystemd-bus/bus-util.h b/src/libsystemd-bus/bus-util.h
index c8d5dd982e..38533be66d 100644
--- a/src/libsystemd-bus/bus-util.h
+++ b/src/libsystemd-bus/bus-util.h
@@ -72,8 +72,8 @@ int bus_open_transport_systemd(BusTransport transport, const char *host, bool us
 int bus_print_property(const char *name, sd_bus_message *property, bool all);
 int bus_print_all_properties(sd_bus *bus, const char *dest, const char *path, char **filter, bool all);
 
-int bus_property_get_tristate(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata);
-int bus_property_get_bool(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata);
+int bus_property_get_tristate(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
+int bus_property_get_bool(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
 
 #define bus_property_get_usec ((sd_bus_property_get_t) NULL)
 #define bus_property_set_usec ((sd_bus_property_set_t) NULL)
@@ -89,15 +89,15 @@ assert_cc(sizeof(unsigned) == sizeof(unsigned));
 #if __SIZEOF_SIZE_T__ == 8
 #define bus_property_get_size ((sd_bus_property_get_t) NULL)
 #else
-int bus_property_get_size(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata);
+int bus_property_get_size(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
 #endif
 
 #if __SIZEOF_LONG__ == 8
 #define bus_property_get_long ((sd_bus_property_get_t) NULL)
 #define bus_property_get_ulong ((sd_bus_property_get_t) NULL)
 #else
-int bus_property_get_long(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata);
-int bus_property_get_ulong(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata);
+int bus_property_get_long(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
+int bus_property_get_ulong(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
 #endif
 
 /* uid_t and friends on Linux 32 bit. This means we can just use the
@@ -146,8 +146,8 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_message*, sd_bus_message_unref);
                      const char *interface,                             \
                      const char *property,                              \
                      sd_bus_message *reply,                             \
-                     sd_bus_error *error,                               \
-                     void *userdata) {                                  \
+                     void *userdata,                                    \
+                     sd_bus_error *error) {                             \
                                                                         \
                 const char *value;                                      \
                 type *field = userdata;                                 \
@@ -170,3 +170,5 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_message*, sd_bus_message_unref);
 #define BUS_PROPERTY_DUAL_TIMESTAMP(name, offset, flags) \
         SD_BUS_PROPERTY(name, "t", bus_property_get_usec, offset + offsetof(struct dual_timestamp, realtime), flags), \
         SD_BUS_PROPERTY(name "Monotonic", "t", bus_property_get_usec, offset + offsetof(struct dual_timestamp, monotonic), flags)
+
+int bus_maybe_reply_error(sd_bus_message *m, int r, sd_bus_error *error);