grpc/test/cpp/naming/utils/dns_resolver.py

#!/usr/bin/env python3
# Copyright 2015 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Makes DNS queries for A records to specified servers"""

import argparse
import threading
import time

import twisted.internet.reactor as reactor
import twisted.internet.task as task
import twisted.names.client as client


def main():
    argp = argparse.ArgumentParser(description="Make DNS queries for A records")
    argp.add_argument(
        "-s",
        "--server_host",
        default="127.0.0.1",
        type=str,
        help="Host for DNS server to listen on for TCP and UDP.",
    )
    argp.add_argument(
        "-p",
        "--server_port",
        default=53,
        type=int,
        help="Port that the DNS server is listening on.",
    )
    argp.add_argument(
        "-n",
        "--qname",
        default=None,
        type=str,
        help="Name of the record to query for. ",
    )
    argp.add_argument(
        "-t",
        "--timeout",
        default=1,
        type=int,
        help="Force process exit after this number of seconds.",
    )
    args = argp.parse_args()

    def OnResolverResultAvailable(result):
        answers, authority, additional = result
        for a in answers:
            print(a.payload)

    def BeginQuery(reactor, qname):
        servers = [(args.server_host, args.server_port)]
        resolver = client.Resolver(servers=servers)
        deferred_result = resolver.lookupAddress(args.qname)
        deferred_result.addCallback(OnResolverResultAvailable)
        return deferred_result

    task.react(BeginQuery, [args.qname])


if __name__ == "__main__":
    main()