How to use the haraka-net-utils.ip_to_long function in haraka-net-utils

const decoupled = tlds.split_hostname(rdns, 3);
    const vardom = decoupled[0]; // "variable" portion of domain
    const dom = decoupled[1]; // "static" portion of domain

    // we check for special cases where rdns looks custom/static, but really is dynamic
    const special_case_info = plugin.check_rdns_for_special_cases(rdns, vardom);
    if (special_case_info) {
        return chsit(null, special_case_info.why);
    }

    let stripped_dom = dom;

    if (vardom) {

        // check for decimal IP in rDNS
        if (vardom.match(String(net_utils.ip_to_long(ip))))
            return chsit(null, 'decimal IP');

        // craft the +hostid+
        const label = vardom.split('.').slice(1).join('.');
        if (label)
            stripped_dom = `${label}.${stripped_dom}`;
    }

    return chsit(stripped_dom);
}