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, 11 insertions, 11 deletions

diff --git a/src/machine/machine-dbus.c b/src/machine/machine-dbus.c
index 8e671edba..2c7f3a798 100644
--- a/src/machine/machine-dbus.c
+++ b/src/machine/machine-dbus.c
@@ -32,8 +32,8 @@ static int property_get_id(
                 const char *interface,
                 const char *property,
                 sd_bus_message *reply,
-                sd_bus_error *error,
-                void *userdata) {
+                void *userdata,
+                sd_bus_error *error) {
 
         Machine *m = userdata;
         int r;
@@ -55,8 +55,8 @@ static int property_get_state(
                 const char *interface,
                 const char *property,
                 sd_bus_message *reply,
-                sd_bus_error *error,
-                void *userdata) {
+                void *userdata,
+                sd_bus_error *error) {
 
         Machine *m = userdata;
         const char *state;
@@ -77,7 +77,7 @@ static int property_get_state(
 
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_class, machine_class, MachineClass);
 
-static int method_terminate(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int method_terminate(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Machine *m = userdata;
         int r;
 
@@ -87,12 +87,12 @@ static int method_terminate(sd_bus *bus, sd_bus_message *message, void *userdata
 
         r = machine_stop(m);
         if (r < 0)
-                return sd_bus_reply_method_errno(message, r, NULL);
+                return r;
 
         return sd_bus_reply_method_return(message, NULL);
 }
 
-static int method_kill(sd_bus *bus, sd_bus_message *message, void *userdata) {
+static int method_kill(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Machine *m = userdata;
         const char *swho;
         int32_t signo;
@@ -105,22 +105,22 @@ static int method_kill(sd_bus *bus, sd_bus_message *message, void *userdata) {
 
         r = sd_bus_message_read(message, "si", &swho, &signo);
         if (r < 0)
-                return sd_bus_reply_method_errno(message, r, NULL);
+                return r;
 
         if (isempty(swho))
                 who = KILL_ALL;
         else {
                 who = kill_who_from_string(swho);
                 if (who < 0)
-                        return sd_bus_reply_method_errorf(message, SD_BUS_ERROR_INVALID_ARGS, "Invalid kill parameter '%s'", swho);
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid kill parameter '%s'", swho);
         }
 
         if (signo <= 0 || signo >= _NSIG)
-                return sd_bus_reply_method_errorf(message, SD_BUS_ERROR_INVALID_ARGS, "Invalid signal %i", signo);
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid signal %i", signo);
 
         r = machine_kill(m, who, signo);
         if (r < 0)
-                return sd_bus_reply_method_errno(message, r, NULL);
+                return r;
 
         return sd_bus_reply_method_return(message, NULL);
 }