dns_resolver.py

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#!/usr/bin/env python2.7
# 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()