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 from invirt.config import structs as config
  10 import invirt.database
  11 import psycopg2
  12 import sqlalchemy
  13 import time
  14
  15 class DatabaseAuthority(common.ResolverBase):
  16     """An Authority that is loaded from a file."""
  17
  18     soa = None
  19
  20     def __init__(self, domains=None, database=None):
  21         common.ResolverBase.__init__(self)
  22         if database is not None:
  23             invirt.database.connect(database)
  24         else:
  25             invirt.database.connect()
  26         if domains is not None:
  27             self.domains = domains
  28         else:
  29             self.domains = config.dns.domains
  30         ns = config.dns.nameservers[0]
  31         self.soa = dns.Record_SOA(mname=ns.hostname,
  32                                   rname=config.dns.contact.replace('@','.',1),
  33                                   serial=1, refresh=3600, retry=900,
  34                                   expire=3600000, minimum=21600, ttl=3600)
  35         self.ns = dns.Record_NS(name=ns.hostname, ttl=3600)
  36         record = dns.Record_A(address=ns.ip, ttl=3600)
  37         self.ns1 = dns.RRHeader(ns.hostname, dns.A, dns.IN,
  38                                 3600, record, auth=True)
  39
  40
  41     def _lookup(self, name, cls, type, timeout = None):
  42         for i in range(3):
  43             try:
  44                 value = self._lookup_unsafe(name, cls, type, timeout = None)
  45             except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError):
  46                 if i == 2:
  47                     raise
  48                 print "Reloading database"
  49                 time.sleep(0.5)
  50                 continue
  51             else:
  52                 return value
  53
  54     def _lookup_unsafe(self, name, cls, type, timeout):
  55         invirt.database.clear_cache()
  56
  57         ttl = 900
  58         name = name.lower()
  59         if name in self.domains:
  60             domain = name
  61         else:
  62             # This works because domain will remain bound after breaking out of the loop
  63             for domain in self.domains:
  64                 if name.endswith('.'+domain):
  65                     break
  66             else: #Not us
  67                 return defer.fail(failure.Failure(dns.DomainError(name)))
  68         results = []
  69         authority = []
  70         additional = [self.ns1]
  71         authority.append(dns.RRHeader(domain, dns.NS, dns.IN,
  72                                       3600, self.ns, auth=True))
  73         if cls == dns.IN:
  74             host = name[:-len(domain)-1]
  75             if not host:
  76                 if type in (dns.A, dns.ALL_RECORDS):
  77                     record = dns.Record_A(config.dns.nameservers[0].ip, ttl)
  78                     results.append(dns.RRHeader(name, dns.A, dns.IN,
  79                                                 ttl, record, auth=True))
  80                 elif type == dns.NS:
  81                     results.append(dns.RRHeader(domain, dns.NS, dns.IN,
  82                                                 ttl, self.ns, auth=True))
  83                     authority = []
  84                 elif type == dns.SOA:
  85                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
  86                                                 ttl, self.soa, auth=True))
  87             else:
  88                 if 'passup' in dir(config.dns) and host in config.dns.passup:
  89                     record = dns.Record_CNAME('%s.%s' % (host, config.dns.parent), ttl)
  90                     return defer.succeed((
  91                         [dns.RRHeader(name, dns.CNAME, dns.IN, ttl, record, auth=True)],
  92                         [], []))
  93
  94                 if host:
  95                     value = invirt.database.Machine.get_by(name=host)
  96                     if value is None or not value.nics:
  97                         return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
  98                     ip = value.nics[0].ip
  99                     if ip is None:  #Deactivated?
 100                         return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 101                 if type in (dns.A, dns.ALL_RECORDS):
 102                     record = dns.Record_A(ip, ttl)
 103                     results.append(dns.RRHeader(name, dns.A, dns.IN,
 104                                                 ttl, record, auth=True))
 105                 elif type == dns.SOA:
 106                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 107                                                 ttl, self.soa, auth=True))
 108             if len(results) == 0:
 109                 authority = []
 110                 additional = []
 111             return defer.succeed((results, authority, additional))
 112         else:
 113             #Doesn't exist
 114             return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 115
 116 if '__main__' == __name__:
 117     resolver = DatabaseAuthority()
 118
 119     verbosity = 0
 120     f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity)
 121     p = dns.DNSDatagramProtocol(f)
 122     f.noisy = p.noisy = verbosity
 123
 124     reactor.listenUDP(53, p)
 125     reactor.listenTCP(53, f)
 126     reactor.run()