code/dnsserver.py

   1 #!/usr/bin/python
   2 from twisted.internet import reactor
   3 from twisted.names import server
   4 from twisted.names import dns
   5 from twisted.names import common
   6 from twisted.internet import defer
   7 from twisted.python import failure
   8
   9 import sipb_xen_database
  10
  11 class DatabaseAuthority(common.ResolverBase):
  12     """An Authority that is loaded from a file."""
  13
  14     soa = None
  15
  16     def __init__(self, domain, database=None):
  17         common.ResolverBase.__init__(self)
  18         if database is not None:
  19             sipb_xen_database.connect(database)
  20         self.domain = domain
  21         self.soa = dns.Record_SOA(mname='sipb-xen-dev.mit.edu',
  22                                   rname='sipb-xen.mit.edu',
  23                                   serial=1, refresh=3600, retry=900,
  24                                   expire=3600000, minimum=21600, ttl=3600)
  25     def _lookup(self, name, cls, type, timeout = None):
  26         if not (name.lower() == self.domain or
  27                 name.lower().endswith('.'+self.domain)):
  28             #Not us
  29             return defer.fail(failure.Failure(dns.DomainError(name)))
  30         results = []
  31         if cls == dns.IN and type in (dns.A, dns.ALL_RECORDS):
  32             host = name[:-len(self.domain)-1]
  33             value = sipb_xen_database.Machine.get_by(name=host)
  34             if value is None or not value.nics:
  35                 return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
  36             ip = value.nics[0].ip
  37             if ip is None:  #Deactivated?
  38                 return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
  39             ttl = 900
  40             record = dns.Record_A(ip, ttl)
  41             results.append(dns.RRHeader(name, dns.A, dns.IN,
  42                                         ttl, record, auth=True))
  43         authority = []
  44         authority.append(dns.RRHeader(self.domain, dns.SOA, dns.IN, 3600,
  45                                       self.soa, auth=True))
  46         return defer.succeed((results, authority, []))
  47         #Doesn't exist
  48         return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
  49
  50 if '__main__' == __name__:
  51     resolver = DatabaseAuthority('servers.csail.mit.edu',
  52                                  'postgres://sipb-xen@sipb-xen-dev/sipb_xen')
  53
  54     verbosity = 0
  55     f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity)
  56     p = dns.DNSDatagramProtocol(f)
  57     f.noisy = p.noisy = verbosity
  58
  59     reactor.listenUDP(53, p)
  60     reactor.listenTCP(53, f)
  61     reactor.run()