/**
 * Get the IP address of the client sending a request.
 *
 * It receives the Request object or the headers object and use it to get the
 * IP address from one of the following headers in order.
 *
 * - X-Client-IP
 * - X-Forwarded-For
 * - HTTP-X-Forwarded-For
 * - Fly-Client-IP
 * - CF-Connecting-IP
 * - Fastly-Client-Ip
 * - True-Client-Ip
 * - X-Real-IP
 * - X-Cluster-Client-IP
 * - X-Forwarded
 * - Forwarded-For
 * - Forwarded
 * - DO-Connecting-IP
 * - oxygen-buyer-ip
 *
 * If the IP address is valid, it will be returned. Otherwise, null will be
 * returned.
 *
 * If the header values contains more than one IP address, the first valid one
 * will be returned.
 */
export declare function getClientIPAddress(headers: Headers): string | null;
export declare function getClientIPAddress(request: Request): string | null;