iucv_send_ctrl
err = iucv_send_ctrl(sk, AF_IUCV_FLAG_WIN);
iucv_send_ctrl(sk, AF_IUCV_FLAG_SHT);
iucv_send_ctrl(sk, AF_IUCV_FLAG_FIN);
err = iucv_send_ctrl(sk, AF_IUCV_FLAG_FIN);
err = iucv_send_ctrl(sock->sk, AF_IUCV_FLAG_SYN);