        def _callback() -> None:
            has_bad_ip = False
            for address in addresses:
                # We only expect IPv4 and IPv6 addresses since only A/AAAA lookups
                # should go through this path.
                if not isinstance(address, (IPv4Address, IPv6Address)):
                    continue

                ip_address = IPAddress(address.host)

                if check_against_blacklist(
                    ip_address, self._ip_whitelist, self._ip_blacklist
                ):
                    logger.info(
                        "Dropped %s from DNS resolution to %s due to blacklist"
                        % (ip_address, hostname)
                    )
                    has_bad_ip = True

            # if we have a blacklisted IP, we'd like to raise an error to block the
            # request, but all we can really do from here is claim that there were no
            # valid results.
            if not has_bad_ip:
                for address in addresses:
                    recv.addressResolved(address)
            recv.resolutionComplete()
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.