invirt-dns

   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.names import authority
   7 from twisted.internet import defer
   8 from twisted.python import failure
   9
  10 from invirt.config import structs as config
  11 import invirt.database
  12 import psycopg2
  13 import sqlalchemy
  14 import time
  15 import re
  16
  17 class DatabaseAuthority(common.ResolverBase):
  18     """An Authority that is loaded from a file."""
  19
  20     soa = None
  21
  22     def __init__(self, domains=None, database=None):
  23         common.ResolverBase.__init__(self)
  24         if database is not None:
  25             invirt.database.connect(database)
  26         else:
  27             invirt.database.connect()
  28         if domains is not None:
  29             self.domains = domains
  30         else:
  31             self.domains = config.dns.domains
  32         ns = config.dns.nameservers[0]
  33         self.soa = dns.Record_SOA(mname=ns.hostname,
  34                                   rname=config.dns.contact.replace('@','.',1),
  35                                   serial=1, refresh=3600, retry=900,
  36                                   expire=3600000, minimum=21600, ttl=3600)
  37         self.ns = dns.Record_NS(name=ns.hostname, ttl=3600)
  38         record = dns.Record_A(address=ns.ip, ttl=3600)
  39         self.ns1 = dns.RRHeader(ns.hostname, dns.A, dns.IN,
  40                                 3600, record, auth=True)
  41
  42
  43     def _lookup(self, name, cls, type, timeout = None):
  44         for i in range(3):
  45             try:
  46                 value = self._lookup_unsafe(name, cls, type, timeout = None)
  47             except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError):
  48                 if i == 2:
  49                     raise
  50                 print "Reloading database"
  51                 time.sleep(0.5)
  52                 continue
  53             else:
  54                 return value
  55
  56     def _lookup_unsafe(self, name, cls, type, timeout):
  57         invirt.database.clear_cache()
  58
  59         ttl = 900
  60         name = name.lower()
  61
  62         if name in self.domains:
  63             domain = name
  64         else:
  65             # Look for the longest-matching domain.  (This works because domain
  66             # will remain bound after breaking out of the loop.)
  67             best_domain = ''
  68             for domain in self.domains:
  69                 if name.endswith('.'+domain) and len(domain) > len(best_domain):
  70                     best_domain = domain
  71             if best_domain == '':
  72                 return defer.fail(failure.Failure(dns.DomainError(name)))
  73             domain = best_domain
  74         results = []
  75         authority = []
  76         additional = [self.ns1]
  77         authority.append(dns.RRHeader(domain, dns.NS, dns.IN,
  78                                       3600, self.ns, auth=True))
  79
  80         if cls == dns.IN:
  81             host = name[:-len(domain)-1]
  82             if not host: # Request for the domain itself.
  83                 if type in (dns.A, dns.ALL_RECORDS):
  84                     record = dns.Record_A(config.dns.nameservers[0].ip, ttl)
  85                     results.append(dns.RRHeader(name, dns.A, dns.IN,
  86                                                 ttl, record, auth=True))
  87                 elif type == dns.NS:
  88                     results.append(dns.RRHeader(domain, dns.NS, dns.IN,
  89                                                 ttl, self.ns, auth=True))
  90                     authority = []
  91                 elif type == dns.SOA:
  92                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
  93                                                 ttl, self.soa, auth=True))
  94             else: # Request for a subdomain.
  95                 value = invirt.database.Machine.query().filter_by(name=host).first()
  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
 102                 if type in (dns.A, dns.ALL_RECORDS):
 103                     record = dns.Record_A(ip, ttl)
 104                     results.append(dns.RRHeader(name, dns.A, dns.IN,
 105                                                 ttl, record, auth=True))
 106                 elif type == dns.SOA:
 107                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 108                                                 ttl, self.soa, auth=True))
 109             if len(results) == 0:
 110                 authority = []
 111                 additional = []
 112             return defer.succeed((results, authority, additional))
 113         else:
 114             #Doesn't exist
 115             return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 116
 117 class QuotingBindAuthority(authority.BindAuthority):
 118     """
 119     A BindAuthority that (almost) deals with quoting correctly
 120
 121     This will catch double quotes as marking the start or end of a
 122     quoted phrase, unless the double quote is escaped by a backslash
 123     """
 124     # Match either a quoted or unquoted string literal followed by
 125     # whitespace or the end of line.  This yields two groups, one of
 126     # which has a match, and the other of which is None, depending on
 127     # whether the string literal was quoted or unquoted; this is what
 128     # necessitates the subsequent filtering out of groups that are
 129     # None.
 130     string_pat = \
 131             re.compile(r'"((?:[^"\\]|\\.)*)"|((?:[^\\\s]|\\.)+)(?:\s+|\s*$)')
 132
 133     # For interpreting escapes.
 134     escape_pat = re.compile(r'\\(.)')
 135
 136     def collapseContinuations(self, lines):
 137         L = []
 138         state = 0
 139         for line in lines:
 140             if state == 0:
 141                 if line.find('(') == -1:
 142                     L.append(line)
 143                 else:
 144                     L.append(line[:line.find('(')])
 145                     state = 1
 146             else:
 147                 if line.find(')') != -1:
 148                     L[-1] += ' ' + line[:line.find(')')]
 149                     state = 0
 150                 else:
 151                     L[-1] += ' ' + line
 152         lines = L
 153         L = []
 154
 155         for line in lines:
 156             in_quote = False
 157             split_line = []
 158             for m in self.string_pat.finditer(line):
 159                 [x] = [x for x in m.groups() if x is not None]
 160                 split_line.append(self.escape_pat.sub(r'\1', x))
 161             L.append(split_line)
 162         return filter(None, L)
 163
 164 if '__main__' == __name__:
 165     resolvers = []
 166     for zone in config.dns.zone_files:
 167         for origin in config.dns.domains:
 168             r = QuotingBindAuthority(zone)
 169             # This sucks, but if I want a generic zone file, I have to
 170             # reload the information by hand
 171             r.origin = origin
 172             lines = open(zone).readlines()
 173             lines = r.collapseContinuations(r.stripComments(lines))
 174             r.parseLines(lines)
 175
 176             resolvers.append(r)
 177     resolvers.append(DatabaseAuthority())
 178
 179     verbosity = 0
 180     f = server.DNSServerFactory(authorities=resolvers, verbose=verbosity)
 181     p = dns.DNSDatagramProtocol(f)
 182     f.noisy = p.noisy = verbosity
 183
 184     reactor.listenUDP(53, p)
 185     reactor.listenTCP(53, f)
 186     reactor.run()