split-brain-dns.py

# Split Brain DNS Stupidly Simple
# Edit the script and run it, point your DNS client to 127.0.0.1 or whatever

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

class DynamicResolver(object):

    #List of custom domain names and their associated DNS server
    _custom = [ ('yourdomain.local', '1.2.3.4'),
                ('anotherdomain.com', '192.168.1.1'),
                ('sub.domain.yours', '10.0.0.1')
              ]

    def query(self, query, timeout=None):
        for o in self._custom:
            if o[0] in query.name.name:
                print "Using custom DNS for", query.name.name
                customClient = client.Resolver(servers=[ ( o[1], 53 ) ])
                return customClient.query(query)

        return defer.fail(error.DomainError())

def main():

    #Fallback DNS server is 8.8.8.8
    factory = server.DNSServerFactory(
            clients=[DynamicResolver(), client.Resolver(servers=[ ("8.8.8.8",53) ])]
    )

    protocol = dns.DNSDatagramProtocol(controller=factory)
    
    reactor.listenUDP(53, protocol)
    reactor.listenTCP(53, factory)

    reactor.run()

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