source4/scripting/bin/samba_dnsupdate

   1 #!/usr/bin/env python
   2 # vim: expandtab
   3 #
   4 # update our DNS names using TSIG-GSS
   5 #
   6 # Copyright (C) Andrew Tridgell 2010
   7 #
   8 # This program is free software; you can redistribute it and/or modify
   9 # it under the terms of the GNU General Public License as published by
  10 # the Free Software Foundation; either version 3 of the License, or
  11 # (at your option) any later version.
  12 #
  13 # This program is distributed in the hope that it will be useful,
  14 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 # GNU General Public License for more details.
  17 #
  18 # You should have received a copy of the GNU General Public License
  19 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20
  21
  22 import os
  23 import fcntl
  24 import sys
  25 import tempfile
  26 import subprocess
  27
  28 # ensure we get messages out immediately, so they get in the samba logs,
  29 # and don't get swallowed by a timeout
  30 os.environ['PYTHONUNBUFFERED'] = '1'
  31
  32 # forcing GMT avoids a problem in some timezones with kerberos. Both MIT
  33 # heimdal can get mutual authentication errors due to the 24 second difference
  34 # between UTC and GMT when using some zone files (eg. the PDT zone from
  35 # the US)
  36 os.environ["TZ"] = "GMT"
  37
  38 # Find right directory when running from source tree
  39 sys.path.insert(0, "bin/python")
  40
  41 import samba
  42 import optparse
  43 from samba import getopt as options
  44 from ldb import SCOPE_BASE
  45 from samba import dsdb
  46 from samba.auth import system_session
  47 from samba.samdb import SamDB
  48 from samba.dcerpc import netlogon, winbind
  49
  50 samba.ensure_third_party_module("dns", "dnspython")
  51 import dns.resolver
  52 import dns.exception
  53
  54 default_ttl = 900
  55 am_rodc = False
  56 error_count = 0
  57
  58 parser = optparse.OptionParser("samba_dnsupdate")
  59 sambaopts = options.SambaOptions(parser)
  60 parser.add_option_group(sambaopts)
  61 parser.add_option_group(options.VersionOptions(parser))
  62 parser.add_option("--verbose", action="store_true")
  63 parser.add_option("--all-names", action="store_true")
  64 parser.add_option("--all-interfaces", action="store_true")
  65 parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
  66 parser.add_option("--update-list", type="string", help="Add DNS names from the given file")
  67 parser.add_option("--update-cache", type="string", help="Cache database of already registered records")
  68 parser.add_option("--fail-immediately", action='store_true', help="Exit on first failure")
  69 parser.add_option("--no-credentials", dest='nocreds', action='store_true', help="don't try and get credentials")
  70 parser.add_option("--no-substiutions", dest='nosubs', action='store_true', help="don't try and expands variables in file specified by --update-list")
  71
  72 creds = None
  73 ccachename = None
  74
  75 opts, args = parser.parse_args()
  76
  77 if len(args) != 0:
  78     parser.print_usage()
  79     sys.exit(1)
  80
  81 lp = sambaopts.get_loadparm()
  82
  83 domain = lp.get("realm")
  84 host = lp.get("netbios name")
  85 if opts.all_interfaces:
  86     all_interfaces = True
  87 else:
  88     all_interfaces = False
  89
  90 IPs = samba.interface_ips(lp, all_interfaces)
  91 nsupdate_cmd = lp.get('nsupdate command')
  92
  93 if len(IPs) == 0:
  94     print "No IP interfaces - skipping DNS updates"
  95     sys.exit(0)
  96
  97 IP6s = []
  98 IP4s = []
  99 for i in IPs:
 100     if i.find(':') != -1:
 101         IP6s.append(i)
 102     else:
 103         IP4s.append(i)
 104
 105
 106 if opts.verbose:
 107     print "IPs: %s" % IPs
 108
 109
 110 def get_credentials(lp):
 111     """# get credentials if we haven't got them already."""
 112     from samba import credentials
 113     global ccachename, creds
 114     if creds is not None:
 115         return
 116     creds = credentials.Credentials()
 117     creds.guess(lp)
 118     creds.set_machine_account(lp)
 119     creds.set_krb_forwardable(credentials.NO_KRB_FORWARDABLE)
 120     (tmp_fd, ccachename) = tempfile.mkstemp()
 121     try:
 122         creds.get_named_ccache(lp, ccachename)
 123     except RuntimeError as e:
 124         os.unlink(ccachename)
 125         raise e
 126
 127
 128 class dnsobj(object):
 129     """an object to hold a parsed DNS line"""
 130
 131     def __init__(self, string_form):
 132         list = string_form.split()
 133         if len(list) < 3:
 134             raise Exception("Invalid DNS entry %r" % string_form)
 135         self.dest = None
 136         self.port = None
 137         self.ip = None
 138         self.existing_port = None
 139         self.existing_weight = None
 140         self.type = list[0]
 141         self.name = list[1]
 142         self.nameservers = []
 143         if self.type == 'SRV':
 144             if len(list) < 4:
 145                 raise Exception("Invalid DNS entry %r" % string_form)
 146             self.dest = list[2]
 147             self.port = list[3]
 148         elif self.type in ['A', 'AAAA']:
 149             self.ip   = list[2] # usually $IP, which gets replaced
 150         elif self.type == 'CNAME':
 151             self.dest = list[2]
 152         elif self.type == 'NS':
 153             self.dest = list[2]
 154         else:
 155             raise Exception("Received unexpected DNS reply of type %s: %s" % (self.type, string_form))
 156
 157     def __str__(self):
 158         if self.type == "A":
 159             return "%s %s %s" % (self.type, self.name, self.ip)
 160         if self.type == "AAAA":
 161             return "%s %s %s" % (self.type, self.name, self.ip)
 162         if self.type == "SRV":
 163             return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
 164         if self.type == "CNAME":
 165             return "%s %s %s" % (self.type, self.name, self.dest)
 166         if self.type == "NS":
 167             return "%s %s %s" % (self.type, self.name, self.dest)
 168
 169
 170 def parse_dns_line(line, sub_vars):
 171     """parse a DNS line from."""
 172     if line.startswith("SRV _ldap._tcp.pdc._msdcs.") and not samdb.am_pdc():
 173         # We keep this as compat to the dns_update_list of 4.0/4.1
 174         if opts.verbose:
 175             print "Skipping PDC entry (%s) as we are not a PDC" % line
 176         return None
 177     subline = samba.substitute_var(line, sub_vars)
 178     if subline == '' or subline[0] == "#":
 179         return None
 180     return dnsobj(subline)
 181
 182
 183 def hostname_match(h1, h2):
 184     """see if two hostnames match."""
 185     h1 = str(h1)
 186     h2 = str(h2)
 187     return h1.lower().rstrip('.') == h2.lower().rstrip('.')
 188
 189
 190 def check_dns_name(d):
 191     """check that a DNS entry exists."""
 192     normalised_name = d.name.rstrip('.') + '.'
 193     if opts.verbose:
 194         print "Looking for DNS entry %s as %s" % (d, normalised_name)
 195
 196     if opts.use_file is not None:
 197         try:
 198             dns_file = open(opts.use_file, "r")
 199         except IOError:
 200             return False
 201
 202         for line in dns_file:
 203             line = line.strip()
 204             if line == '' or line[0] == "#":
 205                 continue
 206             if line.lower() == str(d).lower():
 207                 return True
 208         return False
 209
 210     resolv_conf = os.getenv('RESOLV_WRAPPER_CONF')
 211     if not resolv_conf:
 212         resolv_conf = '/etc/resolv.conf'
 213     resolver = dns.resolver.Resolver(filename=resolv_conf, configure=True)
 214
 215     if d.nameservers != []:
 216         resolver.nameservers = d.nameservers
 217     else:
 218         d.nameservers = resolver.nameservers
 219
 220     try:
 221         ans = resolver.query(normalised_name, d.type)
 222     except dns.exception.DNSException:
 223         if opts.verbose:
 224             print "Failed to find DNS entry %s" % d
 225         return False
 226     if d.type in ['A', 'AAAA']:
 227         # we need to be sure that our IP is there
 228         for rdata in ans:
 229             if str(rdata) == str(d.ip):
 230                 return True
 231     elif d.type == 'CNAME':
 232         for i in range(len(ans)):
 233             if hostname_match(ans[i].target, d.dest):
 234                 return True
 235     elif d.type == 'NS':
 236         for i in range(len(ans)):
 237             if hostname_match(ans[i].target, d.dest):
 238                 return True
 239     elif d.type == 'SRV':
 240         for rdata in ans:
 241             if opts.verbose:
 242                 print "Checking %s against %s" % (rdata, d)
 243             if hostname_match(rdata.target, d.dest):
 244                 if str(rdata.port) == str(d.port):
 245                     return True
 246                 else:
 247                     d.existing_port     = str(rdata.port)
 248                     d.existing_weight = str(rdata.weight)
 249
 250     if opts.verbose:
 251         print "Failed to find matching DNS entry %s" % d
 252
 253     return False
 254
 255
 256 def get_subst_vars(samdb):
 257     """get the list of substitution vars."""
 258     global lp, am_rodc
 259     vars = {}
 260
 261     vars['DNSDOMAIN'] = samdb.domain_dns_name()
 262     vars['DNSFOREST'] = samdb.forest_dns_name()
 263     vars['HOSTNAME']  = samdb.host_dns_name()
 264     vars['NTDSGUID']  = samdb.get_ntds_GUID()
 265     vars['SITE']      = samdb.server_site_name()
 266     res = samdb.search(base=samdb.get_default_basedn(), scope=SCOPE_BASE, attrs=["objectGUID"])
 267     guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
 268     vars['DOMAINGUID'] = guid
 269
 270     vars['IF_DC'] = ""
 271     vars['IF_RWDC'] = "# "
 272     vars['IF_RODC'] = "# "
 273     vars['IF_PDC'] = "# "
 274     vars['IF_GC'] = "# "
 275     vars['IF_RWGC'] = "# "
 276     vars['IF_ROGC'] = "# "
 277     vars['IF_DNS_DOMAIN'] = "# "
 278     vars['IF_RWDNS_DOMAIN'] = "# "
 279     vars['IF_RODNS_DOMAIN'] = "# "
 280     vars['IF_DNS_FOREST'] = "# "
 281     vars['IF_RWDNS_FOREST'] = "# "
 282     vars['IF_R0DNS_FOREST'] = "# "
 283
 284     am_rodc = samdb.am_rodc()
 285     if am_rodc:
 286         vars['IF_RODC'] = ""
 287     else:
 288         vars['IF_RWDC'] = ""
 289
 290     if samdb.am_pdc():
 291         vars['IF_PDC'] = ""
 292
 293     # check if we "are DNS server"
 294     res = samdb.search(base=samdb.get_config_basedn(),
 295                    expression='(objectguid=%s)' % vars['NTDSGUID'],
 296                    attrs=["options", "msDS-hasMasterNCs"])
 297
 298     if len(res) == 1:
 299         if "options" in res[0]:
 300             options = int(res[0]["options"][0])
 301             if (options & dsdb.DS_NTDSDSA_OPT_IS_GC) != 0:
 302                 vars['IF_GC'] = ""
 303                 if am_rodc:
 304                     vars['IF_ROGC'] = ""
 305                 else:
 306                     vars['IF_RWGC'] = ""
 307
 308         basedn = str(samdb.get_default_basedn())
 309         forestdn = str(samdb.get_root_basedn())
 310
 311         if "msDS-hasMasterNCs" in res[0]:
 312             for e in res[0]["msDS-hasMasterNCs"]:
 313                 if str(e) == "DC=DomainDnsZones,%s" % basedn:
 314                     vars['IF_DNS_DOMAIN'] = ""
 315                     if am_rodc:
 316                         vars['IF_RODNS_DOMAIN'] = ""
 317                     else:
 318                         vars['IF_RWDNS_DOMAIN'] = ""
 319                 if str(e) == "DC=ForestDnsZones,%s" % forestdn:
 320                     vars['IF_DNS_FOREST'] = ""
 321                     if am_rodc:
 322                         vars['IF_RODNS_FOREST'] = ""
 323                     else:
 324                         vars['IF_RWDNS_FOREST'] = ""
 325
 326     return vars
 327
 328
 329 def call_nsupdate(d, op="add"):
 330     """call nsupdate for an entry."""
 331     global ccachename, nsupdate_cmd, krb5conf
 332
 333     assert(op in ["add", "delete"])
 334
 335     if opts.verbose:
 336         print "Calling nsupdate for %s (%s)" % (d, op)
 337
 338     if opts.use_file is not None:
 339         try:
 340             rfile = open(opts.use_file, 'r+')
 341         except IOError:
 342             # Perhaps create it
 343             rfile = open(opts.use_file, 'w+')
 344             # Open it for reading again, in case someone else got to it first
 345             rfile = open(opts.use_file, 'r+')
 346         fcntl.lockf(rfile, fcntl.LOCK_EX)
 347         (file_dir, file_name) = os.path.split(opts.use_file)
 348         (tmp_fd, tmpfile) = tempfile.mkstemp(dir=file_dir, prefix=file_name, suffix="XXXXXX")
 349         wfile = os.fdopen(tmp_fd, 'a')
 350         rfile.seek(0)
 351         for line in rfile:
 352             if op == "delete":
 353                 l = parse_dns_line(line, {})
 354                 if str(l).lower() == str(d).lower():
 355                     continue
 356             wfile.write(line)
 357         if op == "add":
 358             wfile.write(str(d)+"\n")
 359         os.rename(tmpfile, opts.use_file)
 360         fcntl.lockf(rfile, fcntl.LOCK_UN)
 361         return
 362
 363     normalised_name = d.name.rstrip('.') + '.'
 364
 365     (tmp_fd, tmpfile) = tempfile.mkstemp()
 366     f = os.fdopen(tmp_fd, 'w')
 367     if d.nameservers != []:
 368         f.write('server %s\n' % d.nameservers[0])
 369     if d.type == "A":
 370         f.write("update %s %s %u A %s\n" % (op, normalised_name, default_ttl, d.ip))
 371     if d.type == "AAAA":
 372         f.write("update %s %s %u AAAA %s\n" % (op, normalised_name, default_ttl, d.ip))
 373     if d.type == "SRV":
 374         if op == "add" and d.existing_port is not None:
 375             f.write("update delete %s SRV 0 %s %s %s\n" % (normalised_name, d.existing_weight,
 376                                                            d.existing_port, d.dest))
 377         f.write("update %s %s %u SRV 0 100 %s %s\n" % (op, normalised_name, default_ttl, d.port, d.dest))
 378     if d.type == "CNAME":
 379         f.write("update %s %s %u CNAME %s\n" % (op, normalised_name, default_ttl, d.dest))
 380     if d.type == "NS":
 381         f.write("update %s %s %u NS %s\n" % (op, normalised_name, default_ttl, d.dest))
 382     if opts.verbose:
 383         f.write("show\n")
 384     f.write("send\n")
 385     f.close()
 386
 387     global error_count
 388     if ccachename:
 389         os.environ["KRB5CCNAME"] = ccachename
 390     try:
 391         cmd = nsupdate_cmd[:]
 392         cmd.append(tmpfile)
 393         env = os.environ
 394         if krb5conf:
 395             env["KRB5_CONFIG"] = krb5conf
 396         if ccachename:
 397             env["KRB5CCNAME"] = ccachename
 398         ret = subprocess.call(cmd, shell=False, env=env)
 399         if ret != 0:
 400             if opts.fail_immediately:
 401                 if opts.verbose:
 402                     print("Failed update with %s" % tmpfile)
 403                 sys.exit(1)
 404             error_count = error_count + 1
 405             if opts.verbose:
 406                 print("Failed nsupdate: %d" % ret)
 407     except Exception, estr:
 408         if opts.fail_immediately:
 409             sys.exit(1)
 410         error_count = error_count + 1
 411         if opts.verbose:
 412             print("Failed nsupdate: %s : %s" % (str(d), estr))
 413     os.unlink(tmpfile)
 414
 415
 416
 417 def rodc_dns_update(d, t, op):
 418     '''a single DNS update via the RODC netlogon call'''
 419     global sub_vars
 420
 421     assert(op in ["add", "delete"])
 422
 423     if opts.verbose:
 424         print "Calling netlogon RODC update for %s" % d
 425
 426     typemap = {
 427         netlogon.NlDnsLdapAtSite       : netlogon.NlDnsInfoTypeNone,
 428         netlogon.NlDnsGcAtSite         : netlogon.NlDnsDomainNameAlias,
 429         netlogon.NlDnsDsaCname         : netlogon.NlDnsDomainNameAlias,
 430         netlogon.NlDnsKdcAtSite        : netlogon.NlDnsInfoTypeNone,
 431         netlogon.NlDnsDcAtSite         : netlogon.NlDnsInfoTypeNone,
 432         netlogon.NlDnsRfc1510KdcAtSite : netlogon.NlDnsInfoTypeNone,
 433         netlogon.NlDnsGenericGcAtSite  : netlogon.NlDnsDomainNameAlias
 434         }
 435
 436     w = winbind.winbind("irpc:winbind_server", lp)
 437     dns_names = netlogon.NL_DNS_NAME_INFO_ARRAY()
 438     dns_names.count = 1
 439     name = netlogon.NL_DNS_NAME_INFO()
 440     name.type = t
 441     name.dns_domain_info_type = typemap[t]
 442     name.priority = 0
 443     name.weight   = 0
 444     if d.port is not None:
 445         name.port = int(d.port)
 446     if op == "add":
 447         name.dns_register = True
 448     else:
 449         name.dns_register = False
 450     dns_names.names = [ name ]
 451     site_name = sub_vars['SITE'].decode('utf-8')
 452
 453     global error_count
 454
 455     try:
 456         ret_names = w.DsrUpdateReadOnlyServerDnsRecords(site_name, default_ttl, dns_names)
 457         if ret_names.names[0].status != 0:
 458             print("Failed to set DNS entry: %s (status %u)" % (d, ret_names.names[0].status))
 459             error_count = error_count + 1
 460     except RuntimeError, reason:
 461         print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason))
 462         error_count = error_count + 1
 463
 464     if error_count != 0 and opts.fail_immediately:
 465         sys.exit(1)
 466
 467
 468 def call_rodc_update(d, op="add"):
 469     '''RODCs need to use the netlogon API for nsupdate'''
 470     global lp, sub_vars
 471
 472     assert(op in ["add", "delete"])
 473
 474     # we expect failure for 3268 if we aren't a GC
 475     if d.port is not None and int(d.port) == 3268:
 476         return
 477
 478     # map the DNS request to a netlogon update type
 479     map = {
 480         netlogon.NlDnsLdapAtSite       : '_ldap._tcp.${SITE}._sites.${DNSDOMAIN}',
 481         netlogon.NlDnsGcAtSite         : '_ldap._tcp.${SITE}._sites.gc._msdcs.${DNSDOMAIN}',
 482         netlogon.NlDnsDsaCname         : '${NTDSGUID}._msdcs.${DNSFOREST}',
 483         netlogon.NlDnsKdcAtSite        : '_kerberos._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
 484         netlogon.NlDnsDcAtSite         : '_ldap._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
 485         netlogon.NlDnsRfc1510KdcAtSite : '_kerberos._tcp.${SITE}._sites.${DNSDOMAIN}',
 486         netlogon.NlDnsGenericGcAtSite  : '_gc._tcp.${SITE}._sites.${DNSFOREST}'
 487         }
 488
 489     for t in map:
 490         subname = samba.substitute_var(map[t], sub_vars)
 491         if subname.lower() == d.name.lower():
 492             # found a match - do the update
 493             rodc_dns_update(d, t, op)
 494             return
 495     if opts.verbose:
 496         print("Unable to map to netlogon DNS update: %s" % d)
 497
 498
 499 # get the list of DNS entries we should have
 500 if opts.update_list:
 501     dns_update_list = opts.update_list
 502 else:
 503     dns_update_list = lp.private_path('dns_update_list')
 504
 505 if opts.update_cache:
 506     dns_update_cache = opts.update_cache
 507 else:
 508     dns_update_cache = lp.private_path('dns_update_cache')
 509
 510 # use our private krb5.conf to avoid problems with the wrong domain
 511 # bind9 nsupdate wants the default domain set
 512 krb5conf = lp.private_path('krb5.conf')
 513 os.environ['KRB5_CONFIG'] = krb5conf
 514
 515 file = open(dns_update_list, "r")
 516
 517 if opts.nosubs:
 518     sub_vars = {}
 519 else:
 520     samdb = SamDB(url=lp.samdb_url(), session_info=system_session(), lp=lp)
 521
 522     # get the substitution dictionary
 523     sub_vars = get_subst_vars(samdb)
 524
 525 # build up a list of update commands to pass to nsupdate
 526 update_list = []
 527 dns_list = []
 528 cache_list = []
 529 delete_list = []
 530
 531 dup_set = set()
 532 cache_set = set()
 533
 534 rebuild_cache = False
 535 try:
 536     cfile = open(dns_update_cache, 'r+')
 537 except IOError:
 538     # Perhaps create it
 539     cfile = open(dns_update_cache, 'w+')
 540     # Open it for reading again, in case someone else got to it first
 541     cfile = open(dns_update_cache, 'r+')
 542 fcntl.lockf(cfile, fcntl.LOCK_EX)
 543 for line in cfile:
 544     line = line.strip()
 545     if line == '' or line[0] == "#":
 546         continue
 547     c = parse_dns_line(line, {})
 548     if c is None:
 549         continue
 550     if str(c) not in cache_set:
 551         cache_list.append(c)
 552         cache_set.add(str(c))
 553
 554 # read each line, and check that the DNS name exists
 555 for line in file:
 556     line = line.strip()
 557     if line == '' or line[0] == "#":
 558         continue
 559     d = parse_dns_line(line, sub_vars)
 560     if d is None:
 561         continue
 562     if d.type == 'A' and len(IP4s) == 0:
 563         continue
 564     if d.type == 'AAAA' and len(IP6s) == 0:
 565         continue
 566     if str(d) not in dup_set:
 567         dns_list.append(d)
 568         dup_set.add(str(d))
 569
 570 # now expand the entries, if any are A record with ip set to $IP
 571 # then replace with multiple entries, one for each interface IP
 572 for d in dns_list:
 573     if d.ip != "$IP":
 574         continue
 575     if d.type == 'A':
 576         d.ip = IP4s[0]
 577         for i in range(len(IP4s)-1):
 578             d2 = dnsobj(str(d))
 579             d2.ip = IP4s[i+1]
 580             dns_list.append(d2)
 581     if d.type == 'AAAA':
 582         d.ip = IP6s[0]
 583         for i in range(len(IP6s)-1):
 584             d2 = dnsobj(str(d))
 585             d2.ip = IP6s[i+1]
 586             dns_list.append(d2)
 587
 588 # now check if the entries already exist on the DNS server
 589 for d in dns_list:
 590     found = False
 591     for c in cache_list:
 592         if str(c).lower() == str(d).lower():
 593             found = True
 594             break
 595     if not found:
 596         rebuild_cache = True
 597     if opts.all_names or not check_dns_name(d):
 598         update_list.append(d)
 599
 600 for c in cache_list:
 601     found = False
 602     for d in dns_list:
 603         if str(c).lower() == str(d).lower():
 604             found = True
 605             break
 606     if found:
 607         continue
 608     rebuild_cache = True
 609     if not opts.all_names and not check_dns_name(c):
 610         continue
 611     delete_list.append(c)
 612
 613 if len(delete_list) == 0 and len(update_list) == 0 and not rebuild_cache:
 614     if opts.verbose:
 615         print "No DNS updates needed"
 616     sys.exit(0)
 617
 618 # get our krb5 creds
 619 if len(delete_list) != 0 or len(update_list) != 0:
 620     if not opts.nocreds:
 621         get_credentials(lp)
 622
 623 # ask nsupdate to delete entries as needed
 624 for d in delete_list:
 625     if am_rodc:
 626         if d.name.lower() == domain.lower():
 627             continue
 628         if not d.type in [ 'A', 'AAAA' ]:
 629             call_rodc_update(d, op="delete")
 630         else:
 631             call_nsupdate(d, op="delete")
 632     else:
 633         call_nsupdate(d, op="delete")
 634
 635 # ask nsupdate to add entries as needed
 636 for d in update_list:
 637     if am_rodc:
 638         if d.name.lower() == domain.lower():
 639             continue
 640         if not d.type in [ 'A', 'AAAA' ]:
 641             call_rodc_update(d)
 642         else:
 643             call_nsupdate(d)
 644     else:
 645         call_nsupdate(d)
 646
 647 if rebuild_cache:
 648     (file_dir, file_name) = os.path.split(dns_update_cache)
 649     (tmp_fd, tmpfile) = tempfile.mkstemp(dir=file_dir, prefix=file_name, suffix="XXXXXX")
 650     wfile = os.fdopen(tmp_fd, 'a')
 651     for d in dns_list:
 652         wfile.write(str(d)+"\n")
 653     os.rename(tmpfile, dns_update_cache)
 654 fcntl.lockf(cfile, fcntl.LOCK_UN)
 655
 656 # delete the ccache if we created it
 657 if ccachename is not None:
 658     os.unlink(ccachename)
 659
 660 if error_count != 0:
 661     print("Failed update of %u entries" % error_count)
 662 sys.exit(error_count)