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1#!/usr/bin/env python2.7
2# Copyright 2015 gRPC authors.
3#
4# Licensed under the Apache License, Version 2.0 (the "License");
5# you may not use this file except in compliance with the License.
6# You may obtain a copy of the License at
7#
8#     http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS,
12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15"""Makes DNS queries for A records to specified servers"""
16
17import argparse
18import threading
19import time
20import twisted.internet.task as task
21import twisted.names.client as client
22import twisted.internet.reactor as reactor
23
24
25def main():
26    argp = argparse.ArgumentParser(description='Make DNS queries for A records')
27    argp.add_argument('-s',
28                      '--server_host',
29                      default='127.0.0.1',
30                      type=str,
31                      help='Host for DNS server to listen on for TCP and UDP.')
32    argp.add_argument('-p',
33                      '--server_port',
34                      default=53,
35                      type=int,
36                      help='Port that the DNS server is listening on.')
37    argp.add_argument('-n',
38                      '--qname',
39                      default=None,
40                      type=str,
41                      help=('Name of the record to query for. '))
42    argp.add_argument('-t',
43                      '--timeout',
44                      default=1,
45                      type=int,
46                      help=('Force process exit after this number of seconds.'))
47    args = argp.parse_args()
48
49    def OnResolverResultAvailable(result):
50        answers, authority, additional = result
51        for a in answers:
52            print(a.payload)
53
54    def BeginQuery(reactor, qname):
55        servers = [(args.server_host, args.server_port)]
56        resolver = client.Resolver(servers=servers)
57        deferred_result = resolver.lookupAddress(args.qname)
58        deferred_result.addCallback(OnResolverResultAvailable)
59        return deferred_result
60
61    task.react(BeginQuery, [args.qname])
62
63
64if __name__ == '__main__':
65    main()
66