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, 10 insertions, 10 deletions

diff --git a/src/libsystemd-bus/test-bus-objects.c b/src/libsystemd-bus/test-bus-objects.c
index 0e9ef57da1..043aa90b3c 100644
--- a/src/libsystemd-bus/test-bus-objects.c
+++ b/src/libsystemd-bus/test-bus-objects.c
@@ -44,7 +44,7 @@ struct context {
         uint32_t automatic_integer_property;
 };
 
-static int something_handler(sd_bus *bus, sd_bus_message *m, void *userdata) {
+static int something_handler(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
         struct context *c = userdata;
         const char *s;
         char *n = NULL;
@@ -67,7 +67,7 @@ static int something_handler(sd_bus *bus, sd_bus_message *m, void *userdata) {
         return 1;
 }
 
-static int exit_handler(sd_bus *bus, sd_bus_message *m, void *userdata) {
+static int exit_handler(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
         struct context *c = userdata;
         int r;
 
@@ -81,11 +81,11 @@ static int exit_handler(sd_bus *bus, sd_bus_message *m, void *userdata) {
         return 1;
 }
 
-static int get_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata) {
+static int get_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error) {
         struct context *c = userdata;
         int r;
 
-        log_info("property get for %s called", property);
+        log_info("property get for %s called, returning \"%s\".", property, c->something);
 
         r = sd_bus_message_append(reply, "s", c->something);
         assert_se(r >= 0);
@@ -93,7 +93,7 @@ static int get_handler(sd_bus *bus, const char *path, const char *interface, con
         return 1;
 }
 
-static int set_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *value, sd_bus_error *error, void *userdata) {
+static int set_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *value, void *userdata, sd_bus_error *error) {
         struct context *c = userdata;
         const char *s;
         char *n;
@@ -113,7 +113,7 @@ static int set_handler(sd_bus *bus, const char *path, const char *interface, con
         return 1;
 }
 
-static int value_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, sd_bus_error *error, void *userdata) {
+static int value_handler(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error) {
         _cleanup_free_ char *s = NULL;
         const char *x;
         int r;
@@ -129,7 +129,7 @@ static int value_handler(sd_bus *bus, const char *path, const char *interface, c
         return 1;
 }
 
-static int notify_test(sd_bus *bus, sd_bus_message *m, void *userdata) {
+static int notify_test(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
         int r;
 
         assert_se(sd_bus_emit_properties_changed(bus, m->path, "org.freedesktop.systemd.ValueTest", "Value", NULL) >= 0);
@@ -140,7 +140,7 @@ static int notify_test(sd_bus *bus, sd_bus_message *m, void *userdata) {
         return 1;
 }
 
-static int emit_interfaces_added(sd_bus *bus, sd_bus_message *m, void *userdata) {
+static int emit_interfaces_added(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
         int r;
 
         assert_se(sd_bus_emit_interfaces_added(bus, m->path, "org.freedesktop.systemd.test", NULL) >= 0);
@@ -151,7 +151,7 @@ static int emit_interfaces_added(sd_bus *bus, sd_bus_message *m, void *userdata)
         return 1;
 }
 
-static int emit_interfaces_removed(sd_bus *bus, sd_bus_message *m, void *userdata) {
+static int emit_interfaces_removed(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
         int r;
 
         assert_se(sd_bus_emit_interfaces_removed(bus, m->path, "org.freedesktop.systemd.test", NULL) >= 0);
@@ -435,7 +435,7 @@ static int client(struct context *c) {
 }
 
 int main(int argc, char *argv[]) {
-        struct context c;
+        struct context c = {};
         pthread_t s;
         void *p;
         int r, q;