python_dns.py

#!/usr/bin/env python2
# coding=utf-8

import json
from twisted.internet import reactor, defer
from twisted.names import client, dns, error, server

class MyResolver(object):
    def __init__ (self, resource_path):
        with open(resource_path) as f:            
            self.table = json.load(f)

            
    def _ResponseRequired(self, query):
        if query.type == dns.A:
            return query.name.name in self.table
        return False


    def _Response(self, query):
        name = query.name.name
        answer = dns.RRHeader(
            name=name,
            payload=dns.Record_A(address=b'%s' % self.table[name]))
        answers = [answer]
        authority = []
        additional = []
        return answers, authority, additional


    def query(self, query, timeout=None):
        if self._ResponseRequired(query):
            return defer.succeed(self._Response(query))
        else:
            return defer.fail(error.DomainError())



def main():
    factory = server.DNSServerFactory(
        #clients=[MyResolver(), client.Resolver(resolv='/etc/resolv.conf')]
        clients=[MyResolver('config.json'), client.Resolver(servers=[('8.8.8.8',53), ('8.8.4.4',53)])]
    )
    protocol = dns.DNSDatagramProtocol(controller=factory)
    reactor.listenUDP(53, protocol)
    reactor.listenTCP(53, factory)
    reactor.run()


if __name__ == '__main__':
    raise SystemExit(main())