CMSG_ALIGN
control->m_len = CMSG_ALIGN(newlen);
control->m_data += CMSG_ALIGN(cm->cmsg_len),
control->m_len -= CMSG_ALIGN(cm->cmsg_len)) {
if (CMSG_ALIGN(cm->cmsg_len) >= control->m_len) {
control->m_data += CMSG_ALIGN(cm->cmsg_len);
control->m_len -= CMSG_ALIGN(cm->cmsg_len);