samba-mirror/source4/scripting/bin/samba_dnsupdate

#!/usr/bin/env python3
# vim: expandtab
#
# update our DNS names using TSIG-GSS
#
# Copyright (C) Andrew Tridgell 2010
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


import os
import fcntl
import sys
import tempfile
import subprocess

# ensure we get messages out immediately, so they get in the samba logs,
# and don't get swallowed by a timeout
os.environ['PYTHONUNBUFFERED'] = '1'

# forcing GMT avoids a problem in some timezones with kerberos. Both MIT and
# heimdal can get mutual authentication errors due to the 24 second difference
# between UTC and GMT when using some zone files (eg. the PDT zone from
# the US)
os.environ["TZ"] = "GMT"

# Find right directory when running from source tree
sys.path.insert(0, "bin/python")

import samba
import optparse
from samba import getopt as options
from ldb import SCOPE_BASE
from samba import dsdb
from samba.auth import system_session
from samba.samdb import SamDB
from samba.dcerpc import netlogon, winbind
from samba.netcmd.dns import cmd_dns
from samba import gensec
from samba.kcc import kcc_utils
from samba.common import get_string
import ldb

from samba.dnsresolver import DNSResolver
import dns.resolver
import dns.exception

default_ttl = 900
am_rodc = False
error_count = 0

parser = optparse.OptionParser("samba_dnsupdate [options]")
sambaopts = options.SambaOptions(parser)
parser.add_option_group(sambaopts)
parser.add_option_group(options.VersionOptions(parser))
parser.add_option("--verbose", action="store_true")
parser.add_option("--use-samba-tool", action="store_true", help="Use samba-tool to make updates over RPC, rather than over DNS")
parser.add_option("--use-nsupdate", action="store_true", help="Use nsupdate command to make updates over DNS (default, if kinit successful)")
parser.add_option("--all-names", action="store_true")
parser.add_option("--all-interfaces", action="store_true")
parser.add_option("--current-ip", action="append", help="IP address to update DNS to match (helpful if behind NAT, valid multiple times, defaults to values from interfaces=)")
parser.add_option("--rpc-server-ip", type="string", help="IP address of server to use with samba-tool (defaults to first --current-ip)")
parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
parser.add_option("--update-list", type="string", help="Add DNS names from the given file")
parser.add_option("--update-cache", type="string", help="Cache database of already registered records")
parser.add_option("--fail-immediately", action='store_true', help="Exit on first failure")
parser.add_option("--no-credentials", dest='nocreds', action='store_true', help="don't try and get credentials")
parser.add_option("--no-substitutions", dest='nosubs', action='store_true', help="don't try and expands variables in file specified by --update-list")

creds = None
ccachename = None

opts, args = parser.parse_args()

if len(args) != 0:
    parser.print_usage()
    sys.exit(1)

lp = sambaopts.get_loadparm()

domain = lp.get("realm")
host = lp.get("netbios name")
all_interfaces = opts.all_interfaces

IPs = opts.current_ip or samba.interface_ips(lp, bool(all_interfaces)) or []

nsupdate_cmd = lp.get('nsupdate command')
dns_zone_scavenging = lp.get("dns zone scavenging")

if len(IPs) == 0:
    print("No IP interfaces - skipping DNS updates\n")
    parser.print_usage()
    sys.exit(0)

rpc_server_ip = opts.rpc_server_ip or IPs[0]

IP6s = [ip for ip in IPs if ':' in ip]
IP4s = [ip for ip in IPs if ':' not in ip]

smb_conf = sambaopts.get_loadparm_path()

if opts.verbose:
    print("IPs: %s" % IPs)

def get_possible_rw_dns_server(creds, domain):
    """Get a list of possible read-write DNS servers, starting with
       the SOA.  The SOA is the correct answer, but old Samba domains
       (4.6 and prior) do not maintain this value, so add NS servers
       as well"""

    ans_soa = check_one_dns_name(domain, 'SOA')
    # Actually there is only one
    hosts_soa = [str(a.mname).rstrip('.') for a in ans_soa]

    # This is not strictly legit, but old Samba domains may have an
    # unmaintained SOA record, so go for any NS that we can get a
    # ticket to.
    ans_ns = check_one_dns_name(domain, 'NS')
    # Actually there is only one
    hosts_ns = [str(a.target).rstrip('.') for a in ans_ns]

    return hosts_soa + hosts_ns

def get_krb5_rw_dns_server(creds, domain):
    """Get a list of read-write DNS servers that we can obtain a ticket
       to, starting with the SOA.  The SOA is the correct answer, but
       old Samba domains (4.6 and prior) do not maintain this value,
       so continue with the NS servers as well until we get one that
       the KDC will issue a ticket to.
    """

    rw_dns_servers = get_possible_rw_dns_server(creds, domain)
    # Actually there is only one
    for i, target_hostname in enumerate(rw_dns_servers):
        settings = {}
        settings["lp_ctx"] = lp
        settings["target_hostname"] = target_hostname

        gensec_client = gensec.Security.start_client(settings)
        gensec_client.set_credentials(creds)
        gensec_client.set_target_service("DNS")
        gensec_client.set_target_hostname(target_hostname)
        gensec_client.want_feature(gensec.FEATURE_SEAL)
        gensec_client.start_mech_by_sasl_name("GSSAPI")
        server_to_client = b""
        try:
            (client_finished, client_to_server) = gensec_client.update(server_to_client)
            if opts.verbose:
                print("Successfully obtained Kerberos ticket to DNS/%s as %s" \
                    % (target_hostname, creds.get_username()))
            return target_hostname
        except RuntimeError:
            # Only raise an exception if they all failed
            if i == len(rw_dns_servers) - 1:
                raise

def get_credentials(lp):
    """# get credentials if we haven't got them already."""
    from samba import credentials
    global ccachename
    creds = credentials.Credentials()
    creds.guess(lp)
    creds.set_machine_account(lp)
    creds.set_krb_forwardable(credentials.NO_KRB_FORWARDABLE)
    (tmp_fd, ccachename) = tempfile.mkstemp()
    try:
        if opts.use_file is not None:
            return

        creds.get_named_ccache(lp, ccachename)

        # Now confirm we can get a ticket to the DNS server
        get_krb5_rw_dns_server(creds, sub_vars['DNSDOMAIN'] + '.')
        return creds

    except RuntimeError as e:
        os.unlink(ccachename)
        raise e


class dnsobj(object):
    """an object to hold a parsed DNS line"""

    def __init__(self, string_form):
        list = string_form.split()
        if len(list) < 3:
            raise Exception("Invalid DNS entry %r" % string_form)
        self.dest = None
        self.port = None
        self.ip = None
        self.existing_port = None
        self.existing_weight = None
        self.existing_cname_target = None
        self.rpc = False
        self.zone = None
        if list[0] == "RPC":
            self.rpc = True
            self.zone = list[1]
            list = list[2:]
        self.type = list[0]
        self.name = list[1]
        self.nameservers = []
        if self.type == 'SRV':
            if len(list) < 4:
                raise Exception("Invalid DNS entry %r" % string_form)
            self.dest = list[2]
            self.port = list[3]
        elif self.type in ['A', 'AAAA']:
            self.ip   = list[2] # usually $IP, which gets replaced
        elif self.type == 'CNAME':
            self.dest = list[2]
        elif self.type == 'NS':
            self.dest = list[2]
        else:
            raise Exception("Received unexpected DNS reply of type %s: %s" % (self.type, string_form))

    def __str__(self):
        if self.type == "A":
            return "%s %s %s" % (self.type, self.name, self.ip)
        if self.type == "AAAA":
            return "%s %s %s" % (self.type, self.name, self.ip)
        if self.type == "SRV":
            return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
        if self.type == "CNAME":
            return "%s %s %s" % (self.type, self.name, self.dest)
        if self.type == "NS":
            return "%s %s %s" % (self.type, self.name, self.dest)


def parse_dns_line(line, sub_vars):
    """parse a DNS line from."""
    if line.startswith("SRV _ldap._tcp.pdc._msdcs.") and not samdb.am_pdc():
        # We keep this as compat to the dns_update_list of 4.0/4.1
        if opts.verbose:
            print("Skipping PDC entry (%s) as we are not a PDC" % line)
        return None
    subline = samba.substitute_var(line, sub_vars)
    if subline == '' or subline[0] == "#":
        return None
    return dnsobj(subline)


def hostname_match(h1, h2):
    """see if two hostnames match."""
    h1 = str(h1)
    h2 = str(h2)
    return h1.lower().rstrip('.') == h2.lower().rstrip('.')

def get_resolver(d=None):
    resolv_conf = os.getenv('RESOLV_CONF', default='/etc/resolv.conf')
    resolver = DNSResolver(filename=resolv_conf, configure=True)

    if d is not None and d.nameservers != []:
        resolver.nameservers = d.nameservers

    return resolver

def check_one_dns_name(name, name_type, d=None):
    resolver = get_resolver(d)
    if d and not d.nameservers:
        d.nameservers = resolver.nameservers
    # dns.resolver.Answer
    return resolver.resolve(name, name_type)

def check_dns_name(d):
    """check that a DNS entry exists."""
    normalised_name = d.name.rstrip('.') + '.'
    if opts.verbose:
        print("Looking for DNS entry %s as %s" % (d, normalised_name))

    if opts.use_file is not None:
        try:
            dns_file = open(opts.use_file, "r")
        except IOError:
            return False

        with dns_file:
            for line in dns_file:
                line = line.strip()
                if line == '' or line[0] == "#":
                    continue
                if line.lower() == str(d).lower():
                    return True
        return False

    try:
        ans = check_one_dns_name(normalised_name, d.type, d)
    except dns.exception.Timeout:
        raise Exception("Timeout while waiting to contact a working DNS server while looking for %s as %s" % (d, normalised_name))
    except dns.resolver.NoNameservers:
        raise Exception("Unable to contact a working DNS server while looking for %s as %s" % (d, normalised_name))
    except dns.resolver.NXDOMAIN:
        if opts.verbose:
            print("The DNS entry %s, queried as %s does not exist" % (d, normalised_name))
        return False
    except dns.resolver.NoAnswer:
        if opts.verbose:
            print("The DNS entry %s, queried as %s does not hold this record type" % (d, normalised_name))
        return False
    except dns.exception.DNSException:
        raise Exception("Failure while trying to resolve %s as %s" % (d, normalised_name))
    if d.type in ['A', 'AAAA']:
        # we need to be sure that our IP is there
        for rdata in ans:
            if str(rdata) == str(d.ip):
                return True
    elif d.type == 'CNAME':
        for i in range(len(ans)):
            if hostname_match(ans[i].target, d.dest):
                return True
            else:
                d.existing_cname_target = str(ans[i].target)
    elif d.type == 'NS':
        for i in range(len(ans)):
            if hostname_match(ans[i].target, d.dest):
                return True
    elif d.type == 'SRV':
        for rdata in ans:
            if opts.verbose:
                print("Checking %s against %s" % (rdata, d))
            if hostname_match(rdata.target, d.dest):
                if str(rdata.port) == str(d.port):
                    return True
                else:
                    d.existing_port     = str(rdata.port)
                    d.existing_weight = str(rdata.weight)

    if opts.verbose:
        print("Lookup of %s succeeded, but we failed to find a matching DNS entry for %s" % (normalised_name, d))

    return False


def get_subst_vars(samdb):
    """get the list of substitution vars."""
    global lp, am_rodc
    vars = {}

    vars['DNSDOMAIN'] = samdb.domain_dns_name()
    vars['DNSFOREST'] = samdb.forest_dns_name()
    vars['HOSTNAME']  = samdb.host_dns_name()
    vars['NTDSGUID']  = samdb.get_ntds_GUID()
    vars['SITE']      = samdb.server_site_name()
    res = samdb.search(base=samdb.get_default_basedn(), scope=SCOPE_BASE, attrs=["objectGUID"])
    guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
    vars['DOMAINGUID'] = get_string(guid)

    vars['IF_DC'] = ""
    vars['IF_RWDC'] = "# "
    vars['IF_RODC'] = "# "
    vars['IF_PDC'] = "# "
    vars['IF_GC'] = "# "
    vars['IF_RWGC'] = "# "
    vars['IF_ROGC'] = "# "
    vars['IF_DNS_DOMAIN'] = "# "
    vars['IF_RWDNS_DOMAIN'] = "# "
    vars['IF_RODNS_DOMAIN'] = "# "
    vars['IF_DNS_FOREST'] = "# "
    vars['IF_RWDNS_FOREST'] = "# "
    vars['IF_R0DNS_FOREST'] = "# "

    am_rodc = samdb.am_rodc()
    if am_rodc:
        vars['IF_RODC'] = ""
    else:
        vars['IF_RWDC'] = ""

    if samdb.am_pdc():
        vars['IF_PDC'] = ""

    # check if we "are DNS server"
    res = samdb.search(base=samdb.get_config_basedn(),
                   expression='(objectguid=%s)' % vars['NTDSGUID'],
                   attrs=["options", "msDS-hasMasterNCs"])

    if len(res) == 1:
        if "options" in res[0]:
            options = int(res[0]["options"][0])
            if (options & dsdb.DS_NTDSDSA_OPT_IS_GC) != 0:
                vars['IF_GC'] = ""
                if am_rodc:
                    vars['IF_ROGC'] = ""
                else:
                    vars['IF_RWGC'] = ""

        basedn = str(samdb.get_default_basedn())
        forestdn = str(samdb.get_root_basedn())

        if "msDS-hasMasterNCs" in res[0]:
            for e in res[0]["msDS-hasMasterNCs"]:
                if str(e) == "DC=DomainDnsZones,%s" % basedn:
                    vars['IF_DNS_DOMAIN'] = ""
                    if am_rodc:
                        vars['IF_RODNS_DOMAIN'] = ""
                    else:
                        vars['IF_RWDNS_DOMAIN'] = ""
                if str(e) == "DC=ForestDnsZones,%s" % forestdn:
                    vars['IF_DNS_FOREST'] = ""
                    if am_rodc:
                        vars['IF_RODNS_FOREST'] = ""
                    else:
                        vars['IF_RWDNS_FOREST'] = ""

    return vars


def call_nsupdate(d, op="add"):
    """call nsupdate for an entry."""
    global ccachename, nsupdate_cmd, krb5conf

    assert(op in ["add", "delete"])

    if opts.use_file is not None:
        if opts.verbose:
            print("Use File instead of nsupdate for %s (%s)" % (d, op))

        try:
            rfile = open(opts.use_file, 'r+')
        except IOError:
            # Perhaps create it
            open(opts.use_file, 'w+').close()
            # Open it for reading again, in case someone else got to it first
            rfile = open(opts.use_file, 'r+')
        fcntl.lockf(rfile, fcntl.LOCK_EX)
        (file_dir, file_name) = os.path.split(opts.use_file)
        (tmp_fd, tmpfile) = tempfile.mkstemp(dir=file_dir, prefix=file_name, suffix="XXXXXX")
        wfile = os.fdopen(tmp_fd, 'a')
        for line in rfile:
            if op == "delete":
                l = parse_dns_line(line, {})
                if str(l).lower() == str(d).lower():
                    continue
            wfile.write(line)
        if op == "add":
            wfile.write(str(d)+"\n")
        rfile.close()
        wfile.close()
        os.rename(tmpfile, opts.use_file)
        return

    if opts.verbose:
        print("Calling nsupdate for %s (%s)" % (d, op))

    normalised_name = d.name.rstrip('.') + '.'

    (tmp_fd, tmpfile) = tempfile.mkstemp()
    f = os.fdopen(tmp_fd, 'w')

    resolver = get_resolver(d)

    # Local the zone for this name
    zone = dns.resolver.zone_for_name(normalised_name,
                                      resolver=resolver)

    # Now find the SOA, or if we can't get a ticket to the SOA,
    # any server with an NS record we can get a ticket for.
    #
    # Thanks to the Kerberos Credentials cache this is not
    # expensive inside the loop
    server = get_krb5_rw_dns_server(creds, zone)
    f.write('server %s\n' % server)

    if d.type == "A":
        f.write("update %s %s %u A %s\n" % (op, normalised_name, default_ttl, d.ip))
    if d.type == "AAAA":
        f.write("update %s %s %u AAAA %s\n" % (op, normalised_name, default_ttl, d.ip))
    if d.type == "SRV":
        if op == "add" and d.existing_port is not None:
            f.write("update delete %s SRV 0 %s %s %s\n" % (normalised_name, d.existing_weight,
                                                           d.existing_port, d.dest))
        f.write("update %s %s %u SRV 0 100 %s %s\n" % (op, normalised_name, default_ttl, d.port, d.dest))
    if d.type == "CNAME":
        f.write("update %s %s %u CNAME %s\n" % (op, normalised_name, default_ttl, d.dest))
    if d.type == "NS":
        f.write("update %s %s %u NS %s\n" % (op, normalised_name, default_ttl, d.dest))
    if opts.verbose:
        f.write("show\n")
    f.write("send\n")
    f.close()

    # Set a bigger MTU size to work around a bug in nsupdate's doio_send()
    os.environ["SOCKET_WRAPPER_MTU"] = "2000"

    global error_count
    if ccachename:
        os.environ["KRB5CCNAME"] = ccachename
    try:
        cmd = nsupdate_cmd[:]
        cmd.append(tmpfile)
        env = os.environ
        if krb5conf:
            env["KRB5_CONFIG"] = krb5conf
        if ccachename:
            env["KRB5CCNAME"] = ccachename
        ret = subprocess.call(cmd, shell=False, env=env)
        if ret != 0:
            if opts.fail_immediately:
                if opts.verbose:
                    print("Failed update with %s" % tmpfile)
                sys.exit(1)
            error_count = error_count + 1
            if opts.verbose:
                print("Failed nsupdate: %d" % ret)
    except Exception as estr:
        if opts.fail_immediately:
            sys.exit(1)
        error_count = error_count + 1
        if opts.verbose:
            print("Failed nsupdate: %s : %s" % (str(d), estr))
    os.unlink(tmpfile)

    # Let socket_wrapper set the default MTU size
    os.environ["SOCKET_WRAPPER_MTU"] = "0"


def call_samba_tool(d, op="add", zone=None):
    """call samba-tool dns to update an entry."""

    assert(op in ["add", "delete"])

    if (sub_vars['DNSFOREST'] != sub_vars['DNSDOMAIN']) and \
       sub_vars['DNSFOREST'].endswith('.' + sub_vars['DNSDOMAIN']):
        print("Refusing to use samba-tool when forest %s is under domain %s" \
            % (sub_vars['DNSFOREST'], sub_vars['DNSDOMAIN']))

    if opts.verbose:
        print("Calling samba-tool dns for %s (%s)" % (d, op))

    normalised_name = d.name.rstrip('.') + '.'
    if zone is None:
        if normalised_name == (sub_vars['DNSDOMAIN'] + '.'):
            short_name = '@'
            zone = sub_vars['DNSDOMAIN']
        elif normalised_name == (sub_vars['DNSFOREST'] + '.'):
            short_name = '@'
            zone = sub_vars['DNSFOREST']
        elif normalised_name == ('_msdcs.' + sub_vars['DNSFOREST'] + '.'):
            short_name = '@'
            zone = '_msdcs.' + sub_vars['DNSFOREST']
        else:
            if not normalised_name.endswith('.' + sub_vars['DNSDOMAIN'] + '.'):
                print("Not Calling samba-tool dns for %s (%s), %s not in %s" % (d, op, normalised_name, sub_vars['DNSDOMAIN'] + '.'))
                return False
            elif normalised_name.endswith('._msdcs.' + sub_vars['DNSFOREST'] + '.'):
                zone = '_msdcs.' + sub_vars['DNSFOREST']
            else:
                zone = sub_vars['DNSDOMAIN']
            len_zone = len(zone)+2
            short_name = normalised_name[:-len_zone]
    else:
        len_zone = len(zone)+2
        short_name = normalised_name[:-len_zone]

    if d.type == "A":
        args = [rpc_server_ip, zone, short_name, "A", d.ip]
    if d.type == "AAAA":
        args = [rpc_server_ip, zone, short_name, "AAAA", d.ip]
    if d.type == "SRV":
        if op == "add" and d.existing_port is not None:
            print("Not handling modify of existing SRV %s using samba-tool" % d)
            return False
        args = [rpc_server_ip, zone, short_name, "SRV",
                "%s %s %s %s" % (d.dest, d.port, "0", "100")]
    if d.type == "CNAME":
        if d.existing_cname_target is None:
            args = [rpc_server_ip, zone, short_name, "CNAME", d.dest]
        else:
            op = "update"
            args = [rpc_server_ip, zone, short_name, "CNAME",
                    d.existing_cname_target.rstrip('.'), d.dest]

    if d.type == "NS":
        args = [rpc_server_ip, zone, short_name, "NS", d.dest]

    if smb_conf and args:
        args += ["--configfile=" + smb_conf]

    global error_count
    try:
        cmd = cmd_dns()
        if opts.verbose:
            print(f'Calling samba-tool dns {op} --use-kerberos off -P {args}')
        command, args = cmd._resolve("dns", op, "--use-kerberos", "off", "-P", *args)
        ret = command._run(*args)
        if ret == -1:
            if opts.fail_immediately:
                sys.exit(1)
            error_count = error_count + 1
            if opts.verbose:
                print("Failed 'samba-tool dns' based update of %s" % (str(d)))
    except Exception as estr:
        if opts.fail_immediately:
            sys.exit(1)
        error_count = error_count + 1
        if opts.verbose:
            print("Failed 'samba-tool dns' based update: %s : %s" % (str(d), estr))
        raise

irpc_wb = None
def cached_irpc_wb(lp):
    global irpc_wb
    if irpc_wb is not None:
        return irpc_wb
    irpc_wb = winbind.winbind("irpc:winbind_server", lp)
    return irpc_wb

def rodc_dns_update(d, t, op):
    '''a single DNS update via the RODC netlogon call'''
    global sub_vars

    assert(op in ["add", "delete"])

    if opts.verbose:
        print("Calling netlogon RODC update for %s" % d)

    typemap = {
        netlogon.NlDnsLdapAtSite       : netlogon.NlDnsInfoTypeNone,
        netlogon.NlDnsGcAtSite         : netlogon.NlDnsDomainNameAlias,
        netlogon.NlDnsDsaCname         : netlogon.NlDnsDomainNameAlias,
        netlogon.NlDnsKdcAtSite        : netlogon.NlDnsInfoTypeNone,
        netlogon.NlDnsDcAtSite         : netlogon.NlDnsInfoTypeNone,
        netlogon.NlDnsRfc1510KdcAtSite : netlogon.NlDnsInfoTypeNone,
        netlogon.NlDnsGenericGcAtSite  : netlogon.NlDnsDomainNameAlias
        }

    w = cached_irpc_wb(lp)
    dns_names = netlogon.NL_DNS_NAME_INFO_ARRAY()
    dns_names.count = 1
    name = netlogon.NL_DNS_NAME_INFO()
    name.type = t
    name.dns_domain_info_type = typemap[t]
    name.priority = 0
    name.weight   = 0
    if d.port is not None:
        name.port = int(d.port)
    if op == "add":
        name.dns_register = True
    else:
        name.dns_register = False
    dns_names.names = [ name ]
    site_name = sub_vars['SITE']

    global error_count

    try:
        ret_names = w.DsrUpdateReadOnlyServerDnsRecords(site_name, default_ttl, dns_names)
        if ret_names.names[0].status != 0:
            print("Failed to set DNS entry: %s (status %u)" % (d, ret_names.names[0].status))
            error_count = error_count + 1
    except RuntimeError as reason:
        print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason))
        error_count = error_count + 1

    if opts.verbose:
        print("Called netlogon RODC update for %s" % d)

    if error_count != 0 and opts.fail_immediately:
        sys.exit(1)


def call_rodc_update(d, op="add"):
    '''RODCs need to use the netlogon API for nsupdate'''
    global lp, sub_vars

    assert(op in ["add", "delete"])

    # we expect failure for 3268 if we aren't a GC
    if d.port is not None and int(d.port) == 3268:
        return

    # map the DNS request to a netlogon update type
    map = {
        netlogon.NlDnsLdapAtSite       : '_ldap._tcp.${SITE}._sites.${DNSDOMAIN}',
        netlogon.NlDnsGcAtSite         : '_ldap._tcp.${SITE}._sites.gc._msdcs.${DNSDOMAIN}',
        netlogon.NlDnsDsaCname         : '${NTDSGUID}._msdcs.${DNSFOREST}',
        netlogon.NlDnsKdcAtSite        : '_kerberos._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
        netlogon.NlDnsDcAtSite         : '_ldap._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
        netlogon.NlDnsRfc1510KdcAtSite : '_kerberos._tcp.${SITE}._sites.${DNSDOMAIN}',
        netlogon.NlDnsGenericGcAtSite  : '_gc._tcp.${SITE}._sites.${DNSFOREST}'
        }

    for t in map:
        subname = samba.substitute_var(map[t], sub_vars)
        if subname.lower() == d.name.lower():
            # found a match - do the update
            rodc_dns_update(d, t, op)
            return
    if opts.verbose:
        print("Unable to map to netlogon DNS update: %s" % d)


# get the list of DNS entries we should have
dns_update_list = opts.update_list or lp.private_path('dns_update_list')

dns_update_cache = opts.update_cache or lp.private_path('dns_update_cache')

krb5conf = None
# only change the krb5.conf if we are not in selftest
if 'SOCKET_WRAPPER_DIR' not in os.environ:
    # use our private krb5.conf to avoid problems with the wrong domain
    # bind9 nsupdate wants the default domain set
    krb5conf = lp.private_path('krb5.conf')
    os.environ['KRB5_CONFIG'] = krb5conf

try:
    file = open(dns_update_list, "r")
except OSError as e:
    if opts.update_list:
        print("The specified update list does not exist")
    else:
        print("The server update list was not found, "
              "and --update-list was not provided.")
    print(e)
    print()
    parser.print_usage()
    sys.exit(1)

if opts.nosubs:
    sub_vars = {}
else:
    samdb = SamDB(url=lp.samdb_url(), session_info=system_session(), lp=lp)

    # get the substitution dictionary
    sub_vars = get_subst_vars(samdb)

# build up a list of update commands to pass to nsupdate
update_list = []
dns_list = []
cache_list = []
delete_list = []

dup_set = set()
cache_set = set()

rebuild_cache = False
try:
    cfile = open(dns_update_cache, 'r+')
except IOError:
    # Perhaps create it
    open(dns_update_cache, 'w+').close()
    # Open it for reading again, in case someone else got to it first
    cfile = open(dns_update_cache, 'r+')
fcntl.lockf(cfile, fcntl.LOCK_EX)
for line in cfile:
    line = line.strip()
    if line == '' or line[0] == "#":
        continue
    c = parse_dns_line(line, {})
    if c is None:
        continue
    if str(c) not in cache_set:
        cache_list.append(c)
        cache_set.add(str(c))

cfile.close()

site_specific_rec = []

# read each line, and check that the DNS name exists
for line in file:
    line = line.strip()

    if '${SITE}' in line:
        site_specific_rec.append(line)

    if line == '' or line[0] == "#":
        continue
    d = parse_dns_line(line, sub_vars)
    if d is None:
        continue
    if d.type == 'A' and len(IP4s) == 0:
        continue
    if d.type == 'AAAA' and len(IP6s) == 0:
        continue
    if str(d) not in dup_set:
        dns_list.append(d)
        dup_set.add(str(d))

file.close()

# Perform automatic site coverage by default
auto_coverage = True

if not am_rodc and auto_coverage:
    site_names = kcc_utils.uncovered_sites_to_cover(samdb,
                                                    samdb.server_site_name())

    # Duplicate all site specific records for the uncovered site
    for site in site_names:
        to_add = [samba.substitute_var(line, {'SITE': site})
                  for line in site_specific_rec]

        for site_line in to_add:
            d = parse_dns_line(site_line,
                               sub_vars=sub_vars)
            if d is not None and str(d) not in dup_set:
                dns_list.append(d)
                dup_set.add(str(d))

# now expand the entries, if any are A record with ip set to $IP
# then replace with multiple entries, one for each interface IP
for d in dns_list:
    if d.ip != "$IP":
        continue
    if d.type == 'A':
        d.ip = IP4s[0]
        for i in range(len(IP4s)-1):
            d2 = dnsobj(str(d))
            d2.ip = IP4s[i+1]
            dns_list.append(d2)
    if d.type == 'AAAA':
        d.ip = IP6s[0]
        for i in range(len(IP6s)-1):
            d2 = dnsobj(str(d))
            d2.ip = IP6s[i+1]
            dns_list.append(d2)

# now check if the entries already exist on the DNS server
for d in dns_list:
    found = False
    for c in cache_list:
        if str(c).lower() == str(d).lower():
            found = True
            break
    if not found:
        rebuild_cache = True
        if opts.verbose:
            print("need cache add: %s" % d)
    if dns_zone_scavenging:
        update_list.append(d)
        if opts.verbose:
            print("scavenging requires update: %s" % d)
    elif opts.all_names:
        update_list.append(d)
        if opts.verbose:
            print("force update: %s" % d)
    elif not check_dns_name(d):
        update_list.append(d)
        if opts.verbose:
            print("need update: %s" % d)

for c in cache_list:
    found = False
    for d in dns_list:
        if str(c).lower() == str(d).lower():
            found = True
            break
    if found:
        continue
    rebuild_cache = True
    if opts.verbose:
        print("need cache remove: %s" % c)
    if not opts.all_names and not check_dns_name(c):
        continue
    delete_list.append(c)
    if opts.verbose:
        print("need delete: %s" % c)

if len(delete_list) == 0 and len(update_list) == 0 and not rebuild_cache:
    if opts.verbose:
        print("No DNS updates needed")
    sys.exit(0)
else:
    if opts.verbose:
        print("%d DNS updates and %d DNS deletes needed" % (len(update_list), len(delete_list)))

use_samba_tool = opts.use_samba_tool
use_nsupdate = opts.use_nsupdate
# get our krb5 creds
if (delete_list or update_list) and not opts.nocreds:
    try:
        creds = get_credentials(lp)
    except RuntimeError as e:
        ccachename = None

        if sub_vars['IF_RWDNS_DOMAIN'] == "# ":
            raise

        if use_nsupdate:
            raise

        print("Failed to get Kerberos credentials, falling back to samba-tool: %s" % e)
        use_samba_tool = True


# ask nsupdate to delete entries as needed
for d in delete_list:
    if d.rpc or (not use_nsupdate and use_samba_tool):
        if opts.verbose:
            print("delete (samba-tool): %s" % d)
        call_samba_tool(d, op="delete", zone=d.zone)

    elif am_rodc:
        if d.name.lower() == domain.lower():
            if opts.verbose:
                print("skip delete (rodc): %s" % d)
            continue
        if d.type not in [ 'A', 'AAAA' ]:
            if opts.verbose:
                print("delete (rodc): %s" % d)
            call_rodc_update(d, op="delete")
        else:
            if opts.verbose:
                print("delete (nsupdate): %s" % d)
            call_nsupdate(d, op="delete")
    else:
        if opts.verbose:
            print("delete (nsupdate): %s" % d)
        call_nsupdate(d, op="delete")

# ask nsupdate to add entries as needed
for d in update_list:
    if d.rpc or (not use_nsupdate and use_samba_tool):
        if opts.verbose:
            print("update (samba-tool): %s" % d)
        call_samba_tool(d, zone=d.zone)

    elif am_rodc:
        if d.name.lower() == domain.lower():
            if opts.verbose:
                print("skip (rodc): %s" % d)
            continue
        if d.type not in [ 'A', 'AAAA' ]:
            if opts.verbose:
                print("update (rodc): %s" % d)
            call_rodc_update(d)
        else:
            if opts.verbose:
                print("update (nsupdate): %s" % d)
            call_nsupdate(d)
    else:
        if opts.verbose:
            print("update(nsupdate): %s" % d)
        call_nsupdate(d)

if rebuild_cache:
    print("Rebuilding cache at %s" % dns_update_cache)
    (file_dir, file_name) = os.path.split(dns_update_cache)
    (tmp_fd, tmpfile) = tempfile.mkstemp(dir=file_dir, prefix=file_name, suffix="XXXXXX")
    wfile = os.fdopen(tmp_fd, 'a')
    for d in dns_list:
        if opts.verbose:
            print("Adding %s to %s" % (str(d), file_name))
        wfile.write(str(d)+"\n")
    wfile.close()
    os.rename(tmpfile, dns_update_cache)

# delete the ccache if we created it
if ccachename is not None:
    os.unlink(ccachename)

if error_count != 0:
    print("Failed update of %u entries" % error_count)
sys.exit(error_count)