timesync,shared: move logic requesting bus name to shared

Preparation for setting DynamicUser= to other services which
request bus names.

2 files changed, 123 insertions, 0 deletions

diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index 4cfe40433..a191c3a4a 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -1744,3 +1744,124 @@ int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *descri
 
         return 0;
 }
+
+struct request_name_data {
+        const char *name;
+        uint64_t flags;
+        void *userdata;
+};
+
+static int reload_dbus_handler(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
+        _cleanup_free_ struct request_name_data *data = userdata;
+        const sd_bus_error *e;
+        int r;
+
+        assert(m);
+        assert(data);
+        assert(data->name);
+
+        e = sd_bus_message_get_error(m);
+        if (e) {
+                log_error_errno(sd_bus_error_get_errno(e), "Failed to reload DBus configuration: %s", e->message);
+                return 1;
+        }
+
+        /* Here, use the default request name handler to avoid an infinite loop of reloading and requesting. */
+        r = sd_bus_request_name_async(sd_bus_message_get_bus(m), NULL, data->name, data->flags, NULL, data->userdata);
+        if (r < 0)
+                log_error_errno(r, "Failed to request name: %m");
+
+        return 1;
+}
+
+static int request_name_handler_may_reload_dbus(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
+        _cleanup_free_ struct request_name_data *data = userdata;
+        uint32_t ret;
+        int r;
+
+        assert(m);
+        assert(userdata);
+
+        if (sd_bus_message_is_method_error(m, NULL)) {
+                const sd_bus_error *e = sd_bus_message_get_error(m);
+
+                if (!sd_bus_error_has_name(e, SD_BUS_ERROR_ACCESS_DENIED)) {
+                        log_debug_errno(sd_bus_error_get_errno(e),
+                                        "Unable to request name, failing connection: %s",
+                                        e->message);
+
+                        bus_enter_closing(sd_bus_message_get_bus(m));
+                        return 1;
+                }
+
+                log_debug_errno(sd_bus_error_get_errno(e),
+                                "Unable to request name, retry after reloading DBus configuration: %s",
+                                e->message);
+
+                /* If systemd-timesyncd.service enables DynamicUser= and dbus.service
+                 * started before the dynamic user is realized, then the DBus policy
+                 * about timesyncd has not been enabled yet. So, let's try to reload
+                 * DBus configuration, and after that request name again. Note that it
+                 * seems that no privileges are necessary to call the following method. */
+
+                r = sd_bus_call_method_async(
+                                sd_bus_message_get_bus(m),
+                                NULL,
+                                "org.freedesktop.DBus",
+                                "/org/freedesktop/DBus",
+                                "org.freedesktop.DBus",
+                                "ReloadConfig",
+                                reload_dbus_handler,
+                                userdata, NULL);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to reload DBus configuration: %m");
+                        bus_enter_closing(sd_bus_message_get_bus(m));
+                        return 1;
+                }
+
+                data = NULL; /* Avoid free() */
+                return 1;
+        }
+
+        r = sd_bus_message_read(m, "u", &ret);
+        if (r < 0)
+                return r;
+
+        switch (ret) {
+
+        case BUS_NAME_ALREADY_OWNER:
+                log_debug("Already owner of requested service name, ignoring.");
+                return 1;
+
+        case BUS_NAME_IN_QUEUE:
+                log_debug("In queue for requested service name.");
+                return 1;
+
+        case BUS_NAME_PRIMARY_OWNER:
+                log_debug("Successfully acquired requested service name.");
+                return 1;
+
+        case BUS_NAME_EXISTS:
+                log_debug("Requested service name already owned, failing connection.");
+                bus_enter_closing(sd_bus_message_get_bus(m));
+                return 1;
+        }
+
+        log_debug("Unexpected response from RequestName(), failing connection.");
+        bus_enter_closing(sd_bus_message_get_bus(m));
+        return 1;
+}
+
+int bus_request_name_async_may_reload_dbus(sd_bus *bus, sd_bus_slot **ret_slot, const char *name, uint64_t flags, void *userdata) {
+        struct request_name_data *data;
+
+        data = new0(struct request_name_data, 1);
+        if (!data)
+                return -ENOMEM;
+
+        data->name = name;
+        data->flags = flags;
+        data->userdata = userdata;
+
+        return sd_bus_request_name_async(bus, ret_slot, name, flags, request_name_handler_may_reload_dbus, data);
+}
diff --git a/src/shared/bus-util.h b/src/shared/bus-util.h
index db1ce4280..4c3846969 100644
--- a/src/shared/bus-util.h
+++ b/src/shared/bus-util.h
@@ -202,3 +202,5 @@ int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *descri
 static inline int bus_open_system_watch_bind(sd_bus **ret) {
         return bus_open_system_watch_bind_with_description(ret, NULL);
 }
+
+int bus_request_name_async_may_reload_dbus(sd_bus *bus, sd_bus_slot **ret_slot, const char *name, uint64_t flags, void *userdata);