func GetsockoptUcred(fd, level, opt int) (*Ucred, error) {
	var value Ucred
	vallen := _Socklen(SizeofUcred)
	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
	return &value, err
}

func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
}