net.ParseIP(host) != nil {
		return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
	}

	return matchDomainConstraint(host, constraint)
}

func matchIPConstraint(ip net.IP, constraint *net.IPNet) (bool, error) {
	if len(ip) != len(constraint.IP) {
		return false, nil
	}

	for i := range ip {
		if mask := constraint.Mask[i]; ip[i]&mask != constraint.IP[i]&mask {