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.common import InvirtConfigError
  11 from invirt.config import structs as config
  12 import invirt.database
  13 import psycopg2
  14 import sqlalchemy
  15 import time
  16 import re
  17
  18 class DatabaseAuthority(common.ResolverBase):
  19     """An Authority that is loaded from a file."""
  20
  21     soa = None
  22
  23     def __init__(self, domains=None, database=None):
  24         common.ResolverBase.__init__(self)
  25         if database is not None:
  26             invirt.database.connect(database)
  27         else:
  28             invirt.database.connect()
  29         if domains is not None:
  30             self.domains = domains
  31         else:
  32             self.domains = config.dns.domains
  33         ns = config.dns.nameservers[0]
  34         self.soa = dns.Record_SOA(mname=ns.hostname,
  35                                   rname=config.dns.contact.replace('@','.',1),
  36                                   serial=1, refresh=3600, retry=900,
  37                                   expire=3600000, minimum=21600, ttl=3600)
  38         self.ns = dns.Record_NS(name=ns.hostname, ttl=3600)
  39         record = dns.Record_A(address=ns.ip, ttl=3600)
  40         self.ns1 = dns.RRHeader(ns.hostname, dns.A, dns.IN,
  41                                 3600, record, auth=True)
  42
  43
  44     def _lookup(self, name, cls, type, timeout = None):
  45         for i in range(3):
  46             try:
  47                 value = self._lookup_unsafe(name, cls, type, timeout = None)
  48             except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError):
  49                 if i == 2:
  50                     raise
  51                 print "Reloading database"
  52                 time.sleep(0.5)
  53                 continue
  54             else:
  55                 return value
  56
  57     def _lookup_unsafe(self, name, cls, type, timeout):
  58         invirt.database.clear_cache()
  59
  60         ttl = 900
  61         name = name.lower()
  62
  63         if name in self.domains:
  64             domain = name
  65         else:
  66             # Look for the longest-matching domain.  (This works because domain
  67             # will remain bound after breaking out of the loop.)
  68             best_domain = ''
  69             for domain in self.domains:
  70                 if name.endswith('.'+domain) and len(domain) > len(best_domain):
  71                     best_domain = domain
  72             if best_domain == '':
  73                 return defer.fail(failure.Failure(dns.DomainError(name)))
  74             domain = best_domain
  75         results = []
  76         authority = []
  77         additional = [self.ns1]
  78         authority.append(dns.RRHeader(domain, dns.NS, dns.IN,
  79                                       3600, self.ns, auth=True))
  80
  81         if cls == dns.IN:
  82             host = name[:-len(domain)-1]
  83             if not host: # Request for the domain itself.
  84                 if type in (dns.A, dns.ALL_RECORDS):
  85                     record = dns.Record_A(config.dns.nameservers[0].ip, ttl)
  86                     results.append(dns.RRHeader(name, dns.A, dns.IN,
  87                                                 ttl, record, auth=True))
  88                 elif type == dns.NS:
  89                     results.append(dns.RRHeader(domain, dns.NS, dns.IN,
  90                                                 ttl, self.ns, auth=True))
  91                     authority = []
  92                 elif type == dns.SOA:
  93                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
  94                                                 ttl, self.soa, auth=True))
  95             else: # Request for a subdomain.
  96                 value = invirt.database.NIC.query.filter_by(hostname=host).first()
  97                 if value:
  98                     ip = value.ip
  99                 else:
 100                     value = invirt.database.Machine.query().filter_by(name=host).first()
 101                     if value:
 102                         ip = value.nics[0].ip
 103                     else:
 104                         return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 105
 106                 if ip is None:
 107                     return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 108
 109                 if type in (dns.A, dns.ALL_RECORDS):
 110                     record = dns.Record_A(ip, ttl)
 111                     results.append(dns.RRHeader(name, dns.A, dns.IN,
 112                                                 ttl, record, auth=True))
 113                 elif type == dns.SOA:
 114                     results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 115                                                 ttl, self.soa, auth=True))
 116             if len(results) == 0:
 117                 authority = []
 118                 additional = []
 119             return defer.succeed((results, authority, additional))
 120         else:
 121             #Doesn't exist
 122             return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 123
 124 class QuotingBindAuthority(authority.BindAuthority):
 125     """
 126     A BindAuthority that (almost) deals with quoting correctly
 127
 128     This will catch double quotes as marking the start or end of a
 129     quoted phrase, unless the double quote is escaped by a backslash
 130     """
 131     # Match either a quoted or unquoted string literal followed by
 132     # whitespace or the end of line.  This yields two groups, one of
 133     # which has a match, and the other of which is None, depending on
 134     # whether the string literal was quoted or unquoted; this is what
 135     # necessitates the subsequent filtering out of groups that are
 136     # None.
 137     string_pat = \
 138             re.compile(r'"((?:[^"\\]|\\.)*)"|((?:[^\\\s]|\\.)+)(?:\s+|\s*$)')
 139
 140     # For interpreting escapes.
 141     escape_pat = re.compile(r'\\(.)')
 142
 143     def collapseContinuations(self, lines):
 144         L = []
 145         state = 0
 146         for line in lines:
 147             if state == 0:
 148                 if line.find('(') == -1:
 149                     L.append(line)
 150                 else:
 151                     L.append(line[:line.find('(')])
 152                     state = 1
 153             else:
 154                 if line.find(')') != -1:
 155                     L[-1] += ' ' + line[:line.find(')')]
 156                     state = 0
 157                 else:
 158                     L[-1] += ' ' + line
 159         lines = L
 160         L = []
 161
 162         for line in lines:
 163             in_quote = False
 164             split_line = []
 165             for m in self.string_pat.finditer(line):
 166                 [x] = [x for x in m.groups() if x is not None]
 167                 split_line.append(self.escape_pat.sub(r'\1', x))
 168             L.append(split_line)
 169         return filter(None, L)
 170
 171 if '__main__' == __name__:
 172     resolvers = []
 173     try:
 174         for zone in config.dns.zone_files:
 175             for origin in config.dns.domains:
 176                 r = QuotingBindAuthority(zone)
 177                 # This sucks, but if I want a generic zone file, I have to
 178                 # reload the information by hand
 179                 r.origin = origin
 180                 lines = open(zone).readlines()
 181                 lines = r.collapseContinuations(r.stripComments(lines))
 182                 r.parseLines(lines)
 183
 184                 resolvers.append(r)
 185     except InvirtConfigError:
 186         # Don't care if zone_files isn't defined
 187         pass
 188     resolvers.append(DatabaseAuthority())
 189
 190     verbosity = 0
 191     f = server.DNSServerFactory(authorities=resolvers, verbose=verbosity)
 192     p = dns.DNSDatagramProtocol(f)
 193     f.noisy = p.noisy = verbosity
 194
 195     reactor.listenUDP(53, p)
 196     reactor.listenTCP(53, f)
 197     reactor.run()