IPFilterExample.scala

class IPFilter()(override implicit val mat: Materializer) extends Filter {

  def apply(f: (RequestHeader) => Future[Result])(request: RequestHeader): Future[Result] = {
    if (request.remoteAddress == "127.0.0.1") {
      Logger.info(s"from: ${request.remoteAddress}, pass")
      f(request).map(identity)
    } else {
      Logger.info(s"from: ${request.remoteAddress}, rejected")
      Future.successful(Default.BadRequest.withHeaders(
        "Access-Control-Allow-Origin" -> "NOT YOU"
      ))
    }
  }
}

object IPFilter {
  def apply()(implicit mat: Materializer) = new IPFilter()
}