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
  60         # XXX hack for the transition to two separate dev/prod clusters
  61         if 'dev.xvm.mit.edu' in self.domains and name.endswith('prod.xvm.mit.edu'):
  62             # import time, sys
  63             # print time.localtime(), 'handling prod request', name
  64             # sys.stdout.flush()
  65
  66             # Point the client in the right direction for prod requests.
  67             authority = dns.RRHeader('prod.xvm.mit.edu', dns.NS, dns.IN, 3600,
  68                     dns.Record_NS(name='ns1.prod.xvm.mit.edu', ttl=3600), auth=True)
  69             additional = dns.RRHeader('ns1.prod.xvm.mit.edu', dns.A, dns.IN, 3600,
  70                     dns.Record_A(address='18.181.0.221', ttl=3600), auth=True)
  71             return defer.succeed(([], [authority], [additional]))
  72
  73         if name in self.domains:
  74             domain = name
  75         else:
  76             # Look for the longest-matching domain.  (This works because domain
  77             # will remain bound after breaking out of the loop.)
  78             best_domain = ''
  79             for domain in self.domains:
  80                 if name.endswith('.'+domain) and len(domain) > len(best_domain):
  81                     best_domain = domain
  82             if best_domain == '':
  83                 return defer.fail(failure.Failure(dns.DomainError(name)))
  84             domain = best_domain
  85         results = []
  86         authority = []
  87         additional = [self.ns1]
  88         authority.append(dns.RRHeader(domain, dns.NS, dns.IN,
  89                                       3600, self.ns, auth=True))
  90
  91         if cls == dns.IN:
  92             host = name[:-len(domain)-1]
  93             if not host: # Request for the domain itself.
  94                 if type in (dns.A, dns.ALL_RECORDS):
  95                     record = dns.Record_A(config.dns.nameservers[0].ip, ttl)
  96                     results.append(dns.RRHeader(name, dns.A, dns.IN,
  97                                                 ttl, record, auth=True))
  98                 elif type == dns.NS:
  99                     results.append(dns.RRHeader(domain, dns.NS, dns.IN,
 100                                                 ttl, self.ns, auth=True))
 101                     authority = []
 102                 elif type == dns.SOA:
 103                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 104                                                 ttl, self.soa, auth=True))
 105             else: # Request for a subdomain.
 106                 if 'passup' in dir(config.dns) and host in config.dns.passup:
 107                     record = dns.Record_CNAME('%s.%s' % (host, config.dns.parent), ttl)
 108                     return defer.succeed((
 109                         [dns.RRHeader(name, dns.CNAME, dns.IN, ttl, record, auth=True)],
 110                         [], []))
 111
 112                 value = invirt.database.Machine.get_by(name=host)
 113                 if value is None or not value.nics:
 114                     return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 115                 ip = value.nics[0].ip
 116                 if ip is None:  #Deactivated?
 117                     return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 118
 119                 if type in (dns.A, dns.ALL_RECORDS):
 120                     record = dns.Record_A(ip, ttl)
 121                     results.append(dns.RRHeader(name, dns.A, dns.IN,
 122                                                 ttl, record, auth=True))
 123                 elif type == dns.SOA:
 124                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 125                                                 ttl, self.soa, auth=True))
 126             if len(results) == 0:
 127                 authority = []
 128                 additional = []
 129             return defer.succeed((results, authority, additional))
 130         else:
 131             #Doesn't exist
 132             return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 133
 134 if '__main__' == __name__:
 135     resolver = DatabaseAuthority()
 136
 137     verbosity = 0
 138     f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity)
 139     p = dns.DNSDatagramProtocol(f)
 140     f.noisy = p.noisy = verbosity
 141
 142     reactor.listenUDP(53, p)
 143     reactor.listenTCP(53, f)
 144     reactor.run()