+ hello = alloca0(sizeof(struct kdbus_cmd_hello));
+ hello->size = sizeof(struct kdbus_cmd_hello);
+ hello->conn_flags = KDBUS_HELLO_ACTIVATOR;
+ hello->pool_size = KDBUS_POOL_SIZE;
+
+ if (ioctl(fd, KDBUS_CMD_HELLO, hello) < 0) {
+ close_nointr_nofail(fd);
+ return -errno;
+ }
+
+ /* The higher 32bit of both flags fields are considered
+ * 'incompatible flags'. Refuse them all for now. */
+ if (hello->bus_flags > 0xFFFFFFFFULL ||
+ hello->conn_flags > 0xFFFFFFFFULL) {
+ close_nointr_nofail(fd);
+ return -ENOTSUP;
+ }
+
+ return fd;