path: root/source4/scripting/bin/samba_kcc

#!/usr/bin/env python
#
# Compute our KCC topology
#
# Copyright (C) Dave Craft 2011
#
# 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 sys
import random

# 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
# 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 optparse
import logging

from samba import (
    getopt as options,
    Ldb,
    ldb,
    dsdb,
    read_and_sub_file)
from samba.auth import system_session
from samba.samdb import SamDB
from samba.dcerpc import drsuapi
from samba.kcc_utils import *

class KCC(object):
    """The Knowledge Consistency Checker class.

    A container for objects and methods allowing a run of the KCC.  Produces a
    set of connections in the samdb for which the Distributed Replication
    Service can then utilize to replicate naming contexts
    """
    def __init__(self):
        """Initializes the partitions class which can hold
        our local DCs partitions or all the partitions in
        the forest
        """
        self.part_table = {}    # partition objects
        self.site_table = {}
        self.transport_table = {}
        self.sitelink_table = {}

        # Used in inter-site topology computation.  A list
        # of connections (by NTDSConnection object) that are
        # to be kept when pruning un-needed NTDS Connections
        self.keep_connection_list = []

        self.my_dsa_dnstr = None  # My dsa DN
        self.my_dsa = None  # My dsa object

        self.my_site_dnstr = None
        self.my_site = None

        self.samdb = None

    def load_all_transports(self):
        """Loads the inter-site transport objects for Sites

        ::returns: Raises an Exception on error
        """
        try:
            res = self.samdb.search("CN=Inter-Site Transports,CN=Sites,%s" %
                                    self.samdb.get_config_basedn(),
                                    scope=ldb.SCOPE_SUBTREE,
                                    expression="(objectClass=interSiteTransport)")
        except ldb.LdbError, (enum, estr):
            raise Exception("Unable to find inter-site transports - (%s)" %
                    estr)

        for msg in res:
            dnstr = str(msg.dn)

            # already loaded
            if dnstr in self.transport_table.keys():
                continue

            transport = Transport(dnstr)

            transport.load_transport(self.samdb)

            # Assign this transport to table
            # and index by dn
            self.transport_table[dnstr] = transport

    def load_all_sitelinks(self):
        """Loads the inter-site siteLink objects

        ::returns: Raises an Exception on error
        """
        try:
            res = self.samdb.search("CN=Inter-Site Transports,CN=Sites,%s" %
                                    self.samdb.get_config_basedn(),
                                    scope=ldb.SCOPE_SUBTREE,
                                    expression="(objectClass=siteLink)")
        except ldb.LdbError, (enum, estr):
            raise Exception("Unable to find inter-site siteLinks - (%s)" % estr)

        for msg in res:
            dnstr = str(msg.dn)

            # already loaded
            if dnstr in self.sitelink_table.keys():
                continue

            sitelink = SiteLink(dnstr)

            sitelink.load_sitelink(self.samdb)

            # Assign this siteLink to table
            # and index by dn
            self.sitelink_table[dnstr] = sitelink

    def get_sitelink(self, site1_dnstr, site2_dnstr):
        """Return the siteLink (if it exists) that connects the
        two input site DNs
        """
        for sitelink in self.sitelink_table.values():
            if sitelink.is_sitelink(site1_dnstr, site2_dnstr):
                return sitelink
        return None

    def load_my_site(self):
        """Loads the Site class for the local DSA

        ::returns: Raises an Exception on error
        """
        self.my_site_dnstr = "CN=%s,CN=Sites,%s" % (
                              self.samdb.server_site_name(),
                              self.samdb.get_config_basedn())
        site = Site(self.my_site_dnstr)
        site.load_site(self.samdb)

        self.site_table[self.my_site_dnstr] = site
        self.my_site = site

    def load_all_sites(self):
        """Discover all sites and instantiate and load each
        NTDS Site settings.

        ::returns: Raises an Exception on error
        """
        try:
            res = self.samdb.search("CN=Sites,%s" %
                                    self.samdb.get_config_basedn(),
                                    scope=ldb.SCOPE_SUBTREE,
                                    expression="(objectClass=site)")
        except ldb.LdbError, (enum, estr):
            raise Exception("Unable to find sites - (%s)" % estr)

        for msg in res:
            sitestr = str(msg.dn)

            # already loaded
            if sitestr in self.site_table.keys():
                continue

            site = Site(sitestr)
            site.load_site(self.samdb)

            self.site_table[sitestr] = site

    def load_my_dsa(self):
        """Discover my nTDSDSA dn thru the rootDSE entry

        ::returns: Raises an Exception on error.
        """
        dn = ldb.Dn(self.samdb, "")
        try:
            res = self.samdb.search(base=dn, scope=ldb.SCOPE_BASE,
                                    attrs=["dsServiceName"])
        except ldb.LdbError, (enum, estr):
            raise Exception("Unable to find my nTDSDSA - (%s)" % estr)

        self.my_dsa_dnstr = res[0]["dsServiceName"][0]
        self.my_dsa = self.my_site.get_dsa(self.my_dsa_dnstr)

    def load_all_partitions(self):
        """Discover all NCs thru the Partitions dn and
        instantiate and load the NCs.

        Each NC is inserted into the part_table by partition
        dn string (not the nCName dn string)

        ::returns: Raises an Exception on error
        """
        try:
            res = self.samdb.search("CN=Partitions,%s" %
                                    self.samdb.get_config_basedn(),
                                    scope=ldb.SCOPE_SUBTREE,
                                    expression="(objectClass=crossRef)")
        except ldb.LdbError, (enum, estr):
            raise Exception("Unable to find partitions - (%s)" % estr)

        for msg in res:
            partstr = str(msg.dn)

            # already loaded
            if partstr in self.part_table.keys():
                continue

            part = Partition(partstr)

            part.load_partition(self.samdb)
            self.part_table[partstr] = part

    def should_be_present_test(self):
        """Enumerate all loaded partitions and DSAs in local
        site and test if NC should be present as replica
        """
        for partdn, part in self.part_table.items():
            for dsadn, dsa in self.my_site.dsa_table.items():
               needed, ro, partial = part.should_be_present(dsa)
               logger.info("dsadn:%s\nncdn:%s\nneeded=%s:ro=%s:partial=%s\n" %
                           (dsadn, part.nc_dnstr, needed, ro, partial))

    def refresh_failed_links_connections(self):
        # XXX - not implemented yet
        pass

    def is_stale_link_connection(self, target_dsa):
        """Returns False if no tuple z exists in the kCCFailedLinks or
        kCCFailedConnections variables such that z.UUIDDsa is the
        objectGUID of the target dsa, z.FailureCount > 0, and
        the current time - z.TimeFirstFailure > 2 hours.
        """
        # XXX - not implemented yet
        return False

    def remove_unneeded_failed_links_connections(self):
        # XXX - not implemented yet
        pass

    def remove_unneeded_ntdsconn(self, all_connected):
        """Removes unneeded NTDS Connections after computation
        of KCC intra and inter-site topology has finished.
        """
        mydsa = self.my_dsa

        # Loop thru connections
        for cn_dnstr, cn_conn in mydsa.connect_table.items():

            s_dnstr = cn_conn.get_from_dnstr()
            if s_dnstr is None:
                cn_conn.to_be_deleted = True
                continue

            # Get the source DSA no matter what site
            s_dsa = self.get_dsa(s_dnstr)

            # Check if the DSA is in our site
            if self.my_site.same_site(s_dsa):
                same_site = True
            else:
                same_site = False

            # Given an nTDSConnection object cn, if the DC with the
            # nTDSDSA object dc that is the parent object of cn and
            # the DC with the nTDSDA object referenced by cn!fromServer
            # are in the same site, the KCC on dc deletes cn if all of
            # the following are true:
            #
            # Bit NTDSCONN_OPT_IS_GENERATED is clear in cn!options.
            #
            # No site settings object s exists for the local DC's site, or
            # bit NTDSSETTINGS_OPT_IS_TOPL_CLEANUP_DISABLED is clear in
            # s!options.
            #
            # Another nTDSConnection object cn2 exists such that cn and
            # cn2 have the same parent object, cn!fromServer = cn2!fromServer,
            # and either
            #
            #     cn!whenCreated < cn2!whenCreated
            #
            #     cn!whenCreated = cn2!whenCreated and
            #     cn!objectGUID < cn2!objectGUID
            #
            # Bit NTDSCONN_OPT_RODC_TOPOLOGY is clear in cn!options
            if same_site:
                if cn_conn.is_generated() == False:
                    continue

                if self.my_site.is_cleanup_ntdsconn_disabled() == True:
                    continue

                # Loop thru connections looking for a duplicate that
                # fulfills the previous criteria
                lesser = False

                for cn2_dnstr, cn2_conn in mydsa.connect_table.items():
                    if cn2_conn is cn_conn:
                        continue

                    s2_dnstr = cn2_conn.get_from_dnstr()
                    if s2_dnstr is None:
                        continue

                    # If the NTDS Connections has a different
                    # fromServer field then no match
                    if s2_dnstr != s_dnstr:
                        continue

                    lesser = (cn_conn.whenCreated < cn2_conn.whenCreated or
                              (cn_conn.whenCreated == cn2_conn.whenCreated and
                               cmp(cn_conn.guid, cn2_conn.guid) < 0))

                    if lesser == True:
                        break

                if lesser and cn_conn.is_rodc_topology() == False:
                    cn_conn.to_be_deleted = True

            # Given an nTDSConnection object cn, if the DC with the nTDSDSA
            # object dc that is the parent object of cn and the DC with
            # the nTDSDSA object referenced by cn!fromServer are in
            # different sites, a KCC acting as an ISTG in dc's site
            # deletes cn if all of the following are true:
            #
            #     Bit NTDSCONN_OPT_IS_GENERATED is clear in cn!options.
            #
            #     cn!fromServer references an nTDSDSA object for a DC
            #     in a site other than the local DC's site.
            #
            #     The keepConnections sequence returned by
            #     CreateIntersiteConnections() does not contain
            #     cn!objectGUID, or cn is "superseded by" (see below)
            #     another nTDSConnection cn2 and keepConnections
            #     contains cn2!objectGUID.
            #
            #     The return value of CreateIntersiteConnections()
            #     was true.
            #
            #     Bit NTDSCONN_OPT_RODC_TOPOLOGY is clear in
            #     cn!options
            #
            else: # different site

                if mydsa.is_istg() == False:
                    continue

                if cn_conn.is_generated() == False:
                    continue

                if self.keep_connection(cn_conn) == True:
                    continue

                # XXX - To be implemented

                if all_connected == False:
                    continue

                if cn_conn.is_rodc_topology() == False:
                    cn_conn.to_be_deleted = True


        if opts.readonly:
            for dnstr, connect in mydsa.connect_table.items():
                if connect.to_be_deleted == True:
                    logger.info("TO BE DELETED:\n%s" % connect)
                if connect.to_be_added == True:
                    logger.info("TO BE ADDED:\n%s" % connect)

            # Peform deletion from our tables but perform
            # no database modification
            mydsa.commit_connections(self.samdb, ro=True)
        else:
            # Commit any modified connections
            mydsa.commit_connections(self.samdb)

    def get_dsa_by_guidstr(self, guidstr):
        """Given a DSA guid string, consule all sites looking
        for the corresponding DSA and return it.
        """
        for site in self.site_table.values():
            dsa = site.get_dsa_by_guidstr(guidstr)
            if dsa is not None:
                return dsa
        return None

    def get_dsa(self, dnstr):
        """Given a DSA dn string, consule all sites looking
        for the corresponding DSA and return it.
        """
        for site in self.site_table.values():
            dsa = site.get_dsa(dnstr)
            if dsa is not None:
                return dsa
        return None

    def modify_repsFrom(self, n_rep, t_repsFrom, s_rep, s_dsa, cn_conn):
        """Update t_repsFrom if necessary to satisfy requirements. Such
        updates are typically required when the IDL_DRSGetNCChanges
        server has moved from one site to another--for example, to
        enable compression when the server is moved from the
        client's site to another site.

        :param n_rep: NC replica we need
        :param t_repsFrom: repsFrom tuple to modify
        :param s_rep: NC replica at source DSA
        :param s_dsa: source DSA
        :param cn_conn: Local DSA NTDSConnection child

        ::returns: (update) bit field containing which portion of the
           repsFrom was modified.  This bit field is suitable as input
           to IDL_DRSReplicaModify ulModifyFields element, as it consists
           of these bits:
               drsuapi.DRSUAPI_DRS_UPDATE_SCHEDULE
               drsuapi.DRSUAPI_DRS_UPDATE_FLAGS
               drsuapi.DRSUAPI_DRS_UPDATE_ADDRESS
        """
        s_dnstr = s_dsa.dsa_dnstr
        update = 0x0

        if self.my_site.same_site(s_dsa):
            same_site = True
        else:
            same_site = False

        times = cn_conn.convert_schedule_to_repltimes()

        # if schedule doesn't match then update and modify
        if times != t_repsFrom.schedule:
            t_repsFrom.schedule = times

        # Bit DRS_PER_SYNC is set in replicaFlags if and only
        # if nTDSConnection schedule has a value v that specifies
        # scheduled replication is to be performed at least once
        # per week.
        if cn_conn.is_schedule_minimum_once_per_week():

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_PER_SYNC) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_PER_SYNC

        # Bit DRS_INIT_SYNC is set in t.replicaFlags if and only
        # if the source DSA and the local DC's nTDSDSA object are
        # in the same site or source dsa is the FSMO role owner
        # of one or more FSMO roles in the NC replica.
        if same_site or n_rep.is_fsmo_role_owner(s_dnstr):

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_INIT_SYNC) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_INIT_SYNC

        # If bit NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT is set in
        # cn!options, bit DRS_NEVER_NOTIFY is set in t.replicaFlags
        # if and only if bit NTDSCONN_OPT_USE_NOTIFY is clear in
        # cn!options. Otherwise, bit DRS_NEVER_NOTIFY is set in
        # t.replicaFlags if and only if s and the local DC's
        # nTDSDSA object are in different sites.
        if (cn_conn.options & dsdb.NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT) != 0x0:

            if (cn_conn.option & dsdb.NTDSCONN_OPT_USE_NOTIFY) == 0x0:

                if (t_repsFrom.replica_flags &
                    drsuapi.DRSUAPI_DRS_NEVER_NOTIFY) == 0x0:
                    t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_NEVER_NOTIFY

        elif same_site == False:

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_NEVER_NOTIFY) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_NEVER_NOTIFY

        # Bit DRS_USE_COMPRESSION is set in t.replicaFlags if
        # and only if s and the local DC's nTDSDSA object are
        # not in the same site and the
        # NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION bit is
        # clear in cn!options
        if (same_site == False and
           (cn_conn.options &
            dsdb.NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION) == 0x0):

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_USE_COMPRESSION) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_USE_COMPRESSION

        # Bit DRS_TWOWAY_SYNC is set in t.replicaFlags if and only
        # if bit NTDSCONN_OPT_TWOWAY_SYNC is set in cn!options.
        if (cn_conn.options & dsdb.NTDSCONN_OPT_TWOWAY_SYNC) != 0x0:

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_TWOWAY_SYNC) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_TWOWAY_SYNC

        # Bits DRS_DISABLE_AUTO_SYNC and DRS_DISABLE_PERIODIC_SYNC are
        # set in t.replicaFlags if and only if cn!enabledConnection = false.
        if cn_conn.is_enabled() == False:

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_DISABLE_AUTO_SYNC) == 0x0:
                t_repsFrom.replica_flags |= \
                    drsuapi.DRSUAPI_DRS_DISABLE_AUTO_SYNC

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_DISABLE_PERIODIC_SYNC) == 0x0:
                t_repsFrom.replica_flags |= \
                    drsuapi.DRSUAPI_DRS_DISABLE_PERIODIC_SYNC

        # If s and the local DC's nTDSDSA object are in the same site,
        # cn!transportType has no value, or the RDN of cn!transportType
        # is CN=IP:
        #
        #     Bit DRS_MAIL_REP in t.replicaFlags is clear.
        #
        #     t.uuidTransport = NULL GUID.
        #
        #     t.uuidDsa = The GUID-based DNS name of s.
        #
        # Otherwise:
        #
        #     Bit DRS_MAIL_REP in t.replicaFlags is set.
        #
        #     If x is the object with dsname cn!transportType,
        #     t.uuidTransport = x!objectGUID.
        #
        #     Let a be the attribute identified by
        #     x!transportAddressAttribute. If a is
        #     the dNSHostName attribute, t.uuidDsa = the GUID-based
        #      DNS name of s. Otherwise, t.uuidDsa = (s!parent)!a.
        #
        # It appears that the first statement i.e.
        #
        #     "If s and the local DC's nTDSDSA object are in the same
        #      site, cn!transportType has no value, or the RDN of
        #      cn!transportType is CN=IP:"
        #
        # could be a slightly tighter statement if it had an "or"
        # between each condition.  I believe this should
        # be interpreted as:
        #
        #     IF (same-site) OR (no-value) OR (type-ip)
        #
        # because IP should be the primary transport mechanism
        # (even in inter-site) and the absense of the transportType
        # attribute should always imply IP no matter if its multi-site
        #
        # NOTE MS-TECH INCORRECT:
        #
        #     All indications point to these statements above being
        #     incorrectly stated:
        #
        #         t.uuidDsa = The GUID-based DNS name of s.
        #
        #         Let a be the attribute identified by
        #         x!transportAddressAttribute. If a is
        #         the dNSHostName attribute, t.uuidDsa = the GUID-based
        #         DNS name of s. Otherwise, t.uuidDsa = (s!parent)!a.
        #
        #     because the uuidDSA is a GUID and not a GUID-base DNS
        #     name.  Nor can uuidDsa hold (s!parent)!a if not
        #     dNSHostName.  What should have been said is:
        #
        #         t.naDsa = The GUID-based DNS name of s
        #
        #     That would also be correct if transportAddressAttribute
        #     were "mailAddress" because (naDsa) can also correctly
        #     hold the SMTP ISM service address.
        #
        nastr = "%s._msdcs.%s" % (s_dsa.dsa_guid, self.samdb.forest_dns_name())

        # We're not currently supporting SMTP replication
        # so is_smtp_replication_available() is currently
        # always returning False
        if (same_site == True or
            cn_conn.transport_dnstr == None or
            cn_conn.transport_dnstr.find("CN=IP") == 0 or
            is_smtp_replication_available() == False):

            if (t_repsFrom.replica_flags &
                drsuapi.DRSUAPI_DRS_MAIL_REP) != 0x0:
                t_repsFrom.replica_flags &= ~drsuapi.DRSUAPI_DRS_MAIL_REP

            null_guid = misc.GUID()
            if (t_repsFrom.transport_guid is None or
                t_repsFrom.transport_guid != null_guid):
                t_repsFrom.transport_guid = null_guid

            # See (NOTE MS-TECH INCORRECT) above
            if t_repsFrom.version == 0x1:
                if t_repsFrom.dns_name1 is None or \
                   t_repsFrom.dns_name1 != nastr:
                    t_repsFrom.dns_name1 = nastr
            else:
                if t_repsFrom.dns_name1 is None or \
                   t_repsFrom.dns_name2 is None or \
                   t_repsFrom.dns_name1 != nastr or \
                   t_repsFrom.dns_name2 != nastr:
                    t_repsFrom.dns_name1 = nastr
                    t_repsFrom.dns_name2 = nastr

        else:
            if (t_repsFrom.replica_flags & \
                drsuapi.DRSUAPI_DRS_MAIL_REP) == 0x0:
                t_repsFrom.replica_flags |= drsuapi.DRSUAPI_DRS_MAIL_REP

            # We have a transport type but its not an
            # object in the database
            if cn_conn.transport_dnstr not in self.transport_table.keys():
                raise Exception("Missing inter-site transport - (%s)" % \
                                cn_conn.transport_dnstr)

            x_transport = self.transport_table[cn_conn.transport_dnstr]

            if t_repsFrom.transport_guid != x_transport.guid:
                t_repsFrom.transport_guid = x_transport.guid

            # See (NOTE MS-TECH INCORRECT) above
            if x_transport.address_attr == "dNSHostName":

                if t_repsFrom.version == 0x1:
                    if t_repsFrom.dns_name1 is None or \
                       t_repsFrom.dns_name1 != nastr:
                        t_repsFrom.dns_name1 = nastr
                else:
                    if t_repsFrom.dns_name1 is None or \
                       t_repsFrom.dns_name2 is None or \
                       t_repsFrom.dns_name1 != nastr or \
                       t_repsFrom.dns_name2 != nastr:
                        t_repsFrom.dns_name1 = nastr
                        t_repsFrom.dns_name2 = nastr

            else:
                # MS tech specification says we retrieve the named
                # attribute in "transportAddressAttribute" from the parent of
                # the DSA object
                try:
                    pdnstr = s_dsa.get_parent_dnstr()
                    attrs = [ x_transport.address_attr ]

                    res = self.samdb.search(base=pdnstr, scope=ldb.SCOPE_BASE,
                                            attrs=attrs)
                except ldb.ldbError, (enum, estr):
                    raise Exception \
                        ("Unable to find attr (%s) for (%s) - (%s)" % \
                         (x_transport.address_attr, pdnstr, estr))

                msg = res[0]
                nastr = str(msg[x_transport.address_attr][0])

                # See (NOTE MS-TECH INCORRECT) above
                if t_repsFrom.version == 0x1:
                    if t_repsFrom.dns_name1 is None or \
                       t_repsFrom.dns_name1 != nastr:
                        t_repsFrom.dns_name1 = nastr
                else:
                    if t_repsFrom.dns_name1 is None or \
                       t_repsFrom.dns_name2 is None or \
                       t_repsFrom.dns_name1 != nastr or \
                       t_repsFrom.dns_name2 != nastr:

                        t_repsFrom.dns_name1 = nastr
                        t_repsFrom.dns_name2 = nastr

        if t_repsFrom.is_modified():
            logger.debug("modify_repsFrom(): %s" % t_repsFrom)

    def is_repsFrom_implied(self, n_rep, cn_conn):
        """Given a NC replica and NTDS Connection, determine if the connection
        implies a repsFrom tuple should be present from the source DSA listed
        in the connection to the naming context

        :param n_rep: NC replica
        :param conn: NTDS Connection
        ::returns (True || False), source DSA:
        """
        # NTDS Connection must satisfy all the following criteria
        # to imply a repsFrom tuple is needed:
        #
        #    cn!enabledConnection = true.
        #    cn!options does not contain NTDSCONN_OPT_RODC_TOPOLOGY.
        #    cn!fromServer references an nTDSDSA object.
        s_dsa = None

        if cn_conn.is_enabled() == True and \
            cn_conn.is_rodc_topology() == False:

            s_dnstr = cn_conn.get_from_dnstr()
            if s_dnstr is not None:
                s_dsa = self.get_dsa(s_dnstr)

            # No DSA matching this source DN string?
            if s_dsa == None:
                return False, None

        # To imply a repsFrom tuple is needed, each of these
        # must be True:
        #
        #     An NC replica of the NC "is present" on the DC to
        #     which the nTDSDSA object referenced by cn!fromServer
        #     corresponds.
        #
        #     An NC replica of the NC "should be present" on
        #     the local DC
        s_rep = s_dsa.get_current_replica(n_rep.nc_dnstr)

        if s_rep is None or s_rep.is_present() == False:
            return False, None

        # To imply a repsFrom tuple is needed, each of these
        # must be True:
        #
        #     The NC replica on the DC referenced by cn!fromServer is
        #     a writable replica or the NC replica that "should be
        #     present" on the local DC is a partial replica.
        #
        #     The NC is not a domain NC, the NC replica that
        #     "should be present" on the local DC is a partial
        #     replica, cn!transportType has no value, or
        #     cn!transportType has an RDN of CN=IP.
        #
        implied = (s_rep.is_ro() == False or n_rep.is_partial() == True) and \
                  (n_rep.is_domain() == False or
                   n_rep.is_partial() == True or
                   cn_conn.transport_dnstr == None or
                   cn_conn.transport_dnstr.find("CN=IP") == 0)

        if implied:
            return True, s_dsa
        else:
            return False, None

    def translate_ntdsconn(self):
        """This function adjusts values of repsFrom abstract attributes of NC
        replicas on the local DC to match those implied by
        nTDSConnection objects.
        """
        logger.debug("translate_ntdsconn(): enter")

        if self.my_dsa.is_translate_ntdsconn_disabled():
            return

        current_rep_table, needed_rep_table = self.my_dsa.get_rep_tables()

        # Filled in with replicas we currently have that need deleting
        delete_rep_table = {}

        # We're using the MS notation names here to allow
        # correlation back to the published algorithm.
        #
        # n_rep      - NC replica (n)
        # t_repsFrom - tuple (t) in n!repsFrom
        # s_dsa      - Source DSA of the replica. Defined as nTDSDSA
        #              object (s) such that (s!objectGUID = t.uuidDsa)
        #              In our IDL representation of repsFrom the (uuidDsa)
        #              attribute is called (source_dsa_obj_guid)
        # cn_conn    - (cn) is nTDSConnection object and child of the local DC's
        #              nTDSDSA object and (cn!fromServer = s)
        # s_rep      - source DSA replica of n
        #
        # If we have the replica and its not needed
        # then we add it to the "to be deleted" list.
        for dnstr, n_rep in current_rep_table.items():
            if dnstr not in needed_rep_table.keys():
                delete_rep_table[dnstr] = n_rep

        # Now perform the scan of replicas we'll need
        # and compare any current repsFrom against the
        # connections
        for dnstr, n_rep in needed_rep_table.items():

            # load any repsFrom and fsmo roles as we'll
            # need them during connection translation
            n_rep.load_repsFrom(self.samdb)
            n_rep.load_fsmo_roles(self.samdb)

            # Loop thru the existing repsFrom tupples (if any)
            for i, t_repsFrom in enumerate(n_rep.rep_repsFrom):

                # for each tuple t in n!repsFrom, let s be the nTDSDSA
                # object such that s!objectGUID = t.uuidDsa
                guidstr = str(t_repsFrom.source_dsa_obj_guid)
                s_dsa = self.get_dsa_by_guidstr(guidstr)

                # Source dsa is gone from config (strange)
                # so cleanup stale repsFrom for unlisted DSA
                if s_dsa is None:
                    logger.debug("repsFrom source DSA guid (%s) not found" %
                                 guidstr)
                    t_repsFrom.to_be_deleted = True
                    continue

                s_dnstr = s_dsa.dsa_dnstr

                # Retrieve my DSAs connection object (if it exists)
                # that specifies the fromServer equivalent to
                # the DSA that is specified in the repsFrom source
                cn_conn = self.my_dsa.get_connection_by_from_dnstr(s_dnstr)

                # Let (cn) be the nTDSConnection object such that (cn)
                # is a child of the local DC's nTDSDSA object and
                # (cn!fromServer = s) and (cn!options) does not contain
                # NTDSCONN_OPT_RODC_TOPOLOGY or NULL if no such (cn) exists.
                if cn_conn and cn_conn.is_rodc_topology() == True:
                    cn_conn = None

                # KCC removes this repsFrom tuple if any of the following
                # is true:
                #     cn = NULL.
                #
                #     No NC replica of the NC "is present" on DSA that
                #     would be source of replica
                #
                #     A writable replica of the NC "should be present" on
                #     the local DC, but a partial replica "is present" on
                #     the source DSA
                s_rep = s_dsa.get_current_replica(n_rep.nc_dnstr)

                if cn_conn is None or \
                   s_rep is None or s_rep.is_present() == False or \
                   (n_rep.is_ro() == False and s_rep.is_partial() == True):

                    t_repsFrom.to_be_deleted = True
                    continue

                # If the KCC did not remove t from n!repsFrom, it updates t
                self.modify_repsFrom(n_rep, t_repsFrom, s_rep, s_dsa, cn_conn)

            # Loop thru connections and add implied repsFrom tuples
            # for each NTDSConnection under our local DSA if the
            # repsFrom is not already present
            for cn_dnstr, cn_conn in self.my_dsa.connect_table.items():

                implied, s_dsa = self.is_repsFrom_implied(n_rep, cn_conn)
                if implied == False:
                    continue

                # Loop thru the existing repsFrom tupples (if any) and
                # if we already have a tuple for this connection then
                # no need to proceed to add.  It will have been changed
                # to have the correct attributes above
                for i, t_repsFrom in enumerate(n_rep.rep_repsFrom):

                     guidstr = str(t_repsFrom.source_dsa_obj_guid)
                     if s_dsa is self.get_dsa_by_guidstr(guidstr):
                         s_dsa = None
                         break

                if s_dsa == None:
                    continue

                # Create a new RepsFromTo and proceed to modify
                # it according to specification
                t_repsFrom = RepsFromTo(n_rep.nc_dnstr)

                t_repsFrom.source_dsa_obj_guid = s_dsa.dsa_guid

                self.modify_repsFrom(n_rep, t_repsFrom, s_rep, s_dsa, cn_conn)

                # Add to our NC repsFrom as this is newly computed
                if t_repsFrom.is_modified():
                    n_rep.rep_repsFrom.append(t_repsFrom)

            if opts.readonly:
                # Display any to be deleted or modified repsFrom
                text = n_rep.dumpstr_to_be_deleted()
                if text:
                    logger.info("TO BE DELETED:\n%s" % text)
                text = n_rep.dumpstr_to_be_modified()
                if text:
                    logger.info("TO BE MODIFIED:\n%s" % text)

                # Peform deletion from our tables but perform
                # no database modification
                n_rep.commit_repsFrom(self.samdb, ro=True)
            else:
                # Commit any modified repsFrom to the NC replica
                n_rep.commit_repsFrom(self.samdb)

    def keep_connection(self, cn_conn):
        """Determines if the connection is meant to be kept during the
        pruning of unneeded connections operation.

        Consults the keep_connection_list[] which was built during
        intersite NC replica graph computation.

        ::returns (True or False): if (True) connection should not be pruned
        """
        if cn_conn in self.keep_connection_list:
            return True
        return False

    def merge_failed_links(self):
        """Merge of kCCFailedLinks and kCCFailedLinks from bridgeheads.
        The KCC on a writable DC attempts to merge the link and connection
        failure information from bridgehead DCs in its own site to help it
        identify failed bridgehead DCs.
        """
        # MS-TECH Ref 6.2.2.3.2 Merge of kCCFailedLinks and kCCFailedLinks
        #     from Bridgeheads

        # XXX - not implemented yet

    def setup_graph(self):
        """Set up a GRAPH, populated with a VERTEX for each site
        object, a MULTIEDGE for each siteLink object, and a
        MUTLIEDGESET for each siteLinkBridge object (or implied
        siteLinkBridge).

        ::returns: a new graph
        """
        # XXX - not implemented yet
        return None

    def get_bridgehead(self, site, part, transport, partial_ok, detect_failed):
        """Get a bridghead DC.

        :param site: site object representing for which a bridgehead
            DC is desired.
        :param part: crossRef for NC to replicate.
        :param transport: interSiteTransport object for replication
            traffic.
        :param partial_ok: True if a DC containing a partial
            replica or a full replica will suffice, False if only
            a full replica will suffice.
        :param detect_failed: True to detect failed DCs and route
            replication traffic around them, False to assume no DC
            has failed.
        ::returns: dsa object for the bridgehead DC or None
        """

        bhs = self.get_all_bridgeheads(site, part, transport,
                                       partial_ok, detect_failed)
        if len(bhs) == 0:
            logger.debug("get_bridgehead: exit\n\tsitedn=%s\n\tbhdn=None" %
                         site.site_dnstr)
            return None
        else:
            logger.debug("get_bridgehead: exit\n\tsitedn=%s\n\tbhdn=%s" %
                         (site.site_dnstr, bhs[0].dsa_dnstr))
            return bhs[0]

    def get_all_bridgeheads(self, site, part, transport,
                            partial_ok, detect_failed):
        """Get all bridghead DCs satisfying the given criteria

        :param site: site object representing the site for which
            bridgehead DCs are desired.
        :param part: partition for NC to replicate.
        :param transport: interSiteTransport object for
            replication traffic.
        :param partial_ok: True if a DC containing a partial
            replica or a full replica will suffice, False if
            only a full replica will suffice.
        :param detect_ok: True to detect failed DCs and route
            replication traffic around them, FALSE to assume
            no DC has failed.
        ::returns: list of dsa object for available bridgehead
            DCs or None
        """

        bhs = []

        logger.debug("get_all_bridgeheads: %s" % transport)

        for key, dsa in site.dsa_table.items():

            pdnstr = dsa.get_parent_dnstr()

            # IF t!bridgeheadServerListBL has one or more values and
            # t!bridgeheadServerListBL does not contain a reference
            # to the parent object of dc then skip dc
            if (len(transport.bridgehead_list) != 0 and
                pdnstr not in transport.bridgehead_list):
                continue

            # IF dc is in the same site as the local DC
            #    IF a replica of cr!nCName is not in the set of NC replicas
            #    that "should be present" on dc or a partial replica of the
            #    NC "should be present" but partialReplicasOkay = FALSE
            #        Skip dc
            if self.my_site.same_site(dsa):
                needed, ro, partial = part.should_be_present(dsa)
                if needed == False or (partial == True and partial_ok == False):
                    continue

            # ELSE
            #     IF an NC replica of cr!nCName is not in the set of NC
            #     replicas that "are present" on dc or a partial replica of
            #     the NC "is present" but partialReplicasOkay = FALSE
            #          Skip dc
            else:
                rep = dsa.get_current_replica(part.nc_dnstr)
                if rep is None or (rep.is_partial() and partial_ok == False):
                    continue

            # IF AmIRODC() and cr!nCName corresponds to default NC then
            #     Let dsaobj be the nTDSDSA object of the dc
            #     IF  dsaobj.msDS-Behavior-Version < DS_BEHAVIOR_WIN2008
            #         Skip dc
            if self.my_dsa.is_ro() and part.is_default():
                if dsa.is_minimum_behavior(DS_BEHAVIOR_WIN2008) == False:
                    continue

            # IF t!name != "IP" and the parent object of dc has no value for
            # the attribute specified by t!transportAddressAttribute
            #     Skip dc
            if transport.name != "IP":
                # MS tech specification says we retrieve the named
                # attribute in "transportAddressAttribute" from the parent
                # of the DSA object
                try:
                    attrs = [ transport.address_attr ]

                    res = self.samdb.search(base=pdnstr, scope=ldb.SCOPE_BASE,
                                            attrs=attrs)
                except ldb.ldbError, (enum, estr):
                    continue

                msg = res[0]
                nastr = str(msg[transport.address_attr][0])

            # IF BridgeheadDCFailed(dc!objectGUID, detectFailedDCs) = TRUE
            #     Skip dc
            if self.is_bridgehead_failed(dsa, detect_failed) == True:
                continue

            logger.debug("get_all_bridgeheads: dsadn=%s" % dsa.dsa_dnstr)
            bhs.append(dsa)

        # IF bit NTDSSETTINGS_OPT_IS_RAND_BH_SELECTION_DISABLED is set in
        # s!options
        #    SORT bhs such that all GC servers precede DCs that are not GC
        #    servers, and otherwise by ascending objectGUID
        # ELSE
        #    SORT bhs in a random order
        if site.is_random_bridgehead_disabled() == True:
            bhs.sort(sort_dsa_by_gc_and_guid)
        else:
            random.shuffle(bhs)

        return bhs


    def is_bridgehead_failed(self, dsa, detect_failed):
        """Determine whether a given DC is known to be in a failed state
        ::returns: True if and only if the DC should be considered failed
        """
        # XXX - not implemented yet
        return False

    def create_connection(self, part, rbh, rsite, transport,
                          lbh, lsite, link_opt, link_sched,
                          partial_ok, detect_failed):
        """Create an nTDSConnection object with the given parameters
        if one does not already exist.

        :param part: crossRef object for the NC to replicate.
        :param rbh: nTDSDSA object for DC to act as the
            IDL_DRSGetNCChanges server (which is in a site other
            than the local DC's site).
        :param rsite: site of the rbh
        :param transport: interSiteTransport object for the transport
            to use for replication traffic.
        :param lbh: nTDSDSA object for DC to act as the
            IDL_DRSGetNCChanges client (which is in the local DC's site).
        :param lsite: site of the lbh
        :param link_opt: Replication parameters (aggregated siteLink options, etc.)
        :param link_sched: Schedule specifying the times at which
            to begin replicating.
        :partial_ok: True if bridgehead DCs containing partial
            replicas of the NC are acceptable.
        :param detect_failed: True to detect failed DCs and route
            replication traffic around them, FALSE to assume no DC
            has failed.
        """
        rbhs_all = self.get_all_bridgeheads(rsite, part, transport,
                                            partial_ok, False)

        # MS-TECH says to compute rbhs_avail but then doesn't use it
        # rbhs_avail = self.get_all_bridgeheads(rsite, part, transport,
        #                                        partial_ok, detect_failed)

        lbhs_all = self.get_all_bridgeheads(lsite, part, transport,
                                            partial_ok, False)

        # MS-TECH says to compute lbhs_avail but then doesn't use it
        # lbhs_avail = self.get_all_bridgeheads(lsite, part, transport,
        #                                       partial_ok, detect_failed)

        # FOR each nTDSConnection object cn such that the parent of cn is
        # a DC in lbhsAll and cn!fromServer references a DC in rbhsAll
        for ldsa in lbhs_all:
            for cn in ldsa.connect_table.values():

                rdsa = None
                for rdsa in rbhs_all:
                    if cn.from_dnstr == rdsa.dsa_dnstr:
                        break

                if rdsa is None:
                    continue

                # IF bit NTDSCONN_OPT_IS_GENERATED is set in cn!options and
                # NTDSCONN_OPT_RODC_TOPOLOGY is clear in cn!options and
                # cn!transportType references t
                if (cn.is_generated() and not cn.is_rodc_topology() and
                    cn.transport_dnstr == transport.dnstr):

                    # IF bit NTDSCONN_OPT_USER_OWNED_SCHEDULE is clear in
                    # cn!options and cn!schedule != sch
                    #     Perform an originating update to set cn!schedule to
                    #     sched
                    if (not cn.is_user_owned_schedule() and
                        not cn.is_equivalent_schedule(link_sched)):
                        cn.schedule = link_sched
                        cn.set_modified(True)

                    # IF bits NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT and
                    # NTDSCONN_OPT_USE_NOTIFY are set in cn
                    if cn.is_override_notify_default() == True and \
                       cn.is_use_notify() == True:

                        # IF bit NTDSSITELINK_OPT_USE_NOTIFY is clear in
                        # ri.Options
                        #    Perform an originating update to clear bits
                        #    NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT and
                        #    NTDSCONN_OPT_USE_NOTIFY in cn!options
                        if (link_opt & dsdb.NTDSSITELINK_OPT_USE_NOTIFY) == 0:
                            cn.options &= \
                                ~(dsdb.NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT | \
                                  dsdb.NTDSCONN_OPT_USE_NOTIFY)
                            cn.set_modified(True)

                    # ELSE
                    else:

                        # IF bit NTDSSITELINK_OPT_USE_NOTIFY is set in
                        # ri.Options
                        #     Perform an originating update to set bits
                        #     NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT and
                        #     NTDSCONN_OPT_USE_NOTIFY in cn!options
                        if (link_opt & dsdb.NTDSSITELINK_OPT_USE_NOTIFY) != 0:
                            cn.options |= \
                                (dsdb.NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT | \
                                 dsdb.NTDSCONN_OPT_USE_NOTIFY)
                            cn.set_modified(True)


                    # IF bit NTDSCONN_OPT_TWOWAY_SYNC is set in cn!options
                    if cn.is_twoway_sync() == True:

                        # IF bit NTDSSITELINK_OPT_TWOWAY_SYNC is clear in
                        # ri.Options
                        #     Perform an originating update to clear bit
                        #     NTDSCONN_OPT_TWOWAY_SYNC in cn!options
                        if (link_opt & dsdb.NTDSSITELINK_OPT_TWOWAY_SYNC) == 0:
                            cn.options &= ~dsdb.NTDSCONN_OPT_TWOWAY_SYNC
                            cn.set_modified(True)

                    # ELSE
                    else:

                        # IF bit NTDSSITELINK_OPT_TWOWAY_SYNC is set in
                        # ri.Options
                        #     Perform an originating update to set bit
                        #     NTDSCONN_OPT_TWOWAY_SYNC in cn!options
                        if (link_opt & dsdb.NTDSSITELINK_OPT_TWOWAY_SYNC) != 0:
                            cn.options |= dsdb.NTDSCONN_OPT_TWOWAY_SYNC
                            cn.set_modified(True)


                    # IF bit NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION is set
                    # in cn!options
                    if cn.is_intersite_compression_disabled() == True:

                        # IF bit NTDSSITELINK_OPT_DISABLE_COMPRESSION is clear
                        # in ri.Options
                        #     Perform an originating update to clear bit
                        #     NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION in
                        #     cn!options
                        if (link_opt & \
                            dsdb.NTDSSITELINK_OPT_DISABLE_COMPRESSION) == 0:
                            cn.options &= \
                                ~dsdb.NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION
                            cn.set_modified(True)

                    # ELSE
                    else:
                        # IF bit NTDSSITELINK_OPT_DISABLE_COMPRESSION is set in
                        # ri.Options
                        #     Perform an originating update to set bit
                        #     NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION in
                        #     cn!options
                        if (link_opt & \
                            dsdb.NTDSSITELINK_OPT_DISABLE_COMPRESSION) != 0:
                            cn.options |= \
                                dsdb.NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION
                            cn.set_modified(True)

                    # Display any modified connection
                    if opts.readonly:
                        if cn.to_be_modified == True:
                            logger.info("TO BE MODIFIED:\n%s" % cn)

                        ldsa.commit_connections(self.samdb, ro=True)
                    else:
                        ldsa.commit_connections(self.samdb)
        # ENDFOR

        valid_connections = 0

        # FOR each nTDSConnection object cn such that cn!parent is
        # a DC in lbhsAll and cn!fromServer references a DC in rbhsAll
        for ldsa in lbhs_all:
            for cn in ldsa.connect_table.values():

                rdsa = None
                for rdsa in rbhs_all:
                    if cn.from_dnstr == rdsa.dsa_dnstr:
                        break

                if rdsa is None:
                    continue

                # IF (bit NTDSCONN_OPT_IS_GENERATED is clear in cn!options or
                # cn!transportType references t) and
                # NTDSCONN_OPT_RODC_TOPOLOGY is clear in cn!options
                if ((not cn.is_generated() or
                     cn.transport_dnstr == transport.dnstr) and
                     not cn.is_rodc_topology()):

                    # LET rguid be the objectGUID of the nTDSDSA object
                    # referenced by cn!fromServer
                    # LET lguid be (cn!parent)!objectGUID

                    # IF BridgeheadDCFailed(rguid, detectFailedDCs) = FALSE and
                    # BridgeheadDCFailed(lguid, detectFailedDCs) = FALSE
                    #     Increment cValidConnections by 1
                    if (not self.is_bridgehead_failed(rdsa, detect_failed) and
                        not self.is_bridgehead_failed(ldsa, detect_failed)):
                        valid_connections += 1

                    # IF keepConnections does not contain cn!objectGUID
                    #     APPEND cn!objectGUID to keepConnections
                    if not self.keep_connection(cn):
                        self.keep_connection_list.append(cn)

        # ENDFOR

        # IF cValidConnections = 0
        if valid_connections == 0:

            # LET opt be NTDSCONN_OPT_IS_GENERATED
            opt = dsdb.NTDSCONN_OPT_IS_GENERATED

            # IF bit NTDSSITELINK_OPT_USE_NOTIFY is set in ri.Options
            #     SET bits NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT and
            #     NTDSCONN_OPT_USE_NOTIFY in opt
            if (link_opt & dsdb.NTDSSITELINK_OPT_USE_NOTIFY) != 0:
                opt |= (dsdb.NTDSCONN_OPT_OVERRIDE_NOTIFY_DEFAULT |
                        dsdb.NTDSCONN_USE_NOTIFY)

            # IF bit NTDSSITELINK_OPT_TWOWAY_SYNC is set in ri.Options
            #     SET bit NTDSCONN_OPT_TWOWAY_SYNC opt
            if (link_opt & dsdb.NTDSSITELINK_OPT_TWOWAY_SYNC) != 0:
                opt |= dsdb.NTDSCONN_OPT_TWOWAY_SYNC

            # IF bit NTDSSITELINK_OPT_DISABLE_COMPRESSION is set in
            # ri.Options
            #     SET bit NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION in opt
            if (link_opt &
                dsdb.NTDSSITELINK_OPT_DISABLE_COMPRESSION) != 0:
                opt |= dsdb.NTDSCONN_OPT_DISABLE_INTERSITE_COMPRESSION

            # Perform an originating update to create a new nTDSConnection
            # object cn that is a child of lbh, cn!enabledConnection = TRUE,
            # cn!options = opt, cn!transportType is a reference to t,
            # cn!fromServer is a reference to rbh, and cn!schedule = sch
            cn = lbh.new_connection(opt, 0, transport, lbh.dsa_dnstr, link_sched)

            # Display any added connection
            if opts.readonly:
                if cn.to_be_added == True:
                    logger.info("TO BE ADDED:\n%s" % cn)

                    lbh.commit_connections(self.samdb, ro=True)
            else:
                lbh.commit_connections(self.samdb)

            # APPEND cn!objectGUID to keepConnections
            if not self.keep_connection(cn):
                self.keep_connection_list.append(cn)

    def create_connections(self, graph, part, detect_failed):
        """Construct an NC replica graph for the NC identified by
        the given crossRef, then create any additional nTDSConnection
        objects required.

        :param graph: site graph.
        :param part: crossRef object for NC.
        :param detect_failed:  True to detect failed DCs and route
            replication traffic around them, False to assume no DC
            has failed.

        Modifies self.keep_connection_list by adding any connections
        deemed to be "in use".

        ::returns: (all_connected, found_failed_dc)
        (all_connected) True if the resulting NC replica graph
            connects all sites that need to be connected.
        (found_failed_dc) True if one or more failed DCs were
            detected.
        """
        all_connected = True
        found_failed = False

        logger.debug("create_connections(): enter\n\tpartdn=%s\n\tdetect_failed=%s" %
                     (part.nc_dnstr, detect_failed))

        # XXX - This is a highly abbreviated function from the MS-TECH
        #       ref.  It creates connections between bridgeheads to all
        #       sites that have appropriate replicas.  Thus we are not
        #       creating a minimum cost spanning tree but instead
        #       producing a fully connected tree.  This should produce
        #       a full (albeit not optimal cost) replication topology.
        my_vertex = Vertex(self.my_site, part)
        my_vertex.color_vertex()

        # No NC replicas for this NC in the site of the local DC,
        # so no nTDSConnection objects need be created
        if my_vertex.is_white():
            return all_connected, found_failed

        # LET partialReplicaOkay be TRUE if and only if
        # localSiteVertex.Color = COLOR.BLACK
        if my_vertex.is_black():
            partial_ok = True
        else:
            partial_ok = False

        # Utilize the IP transport only for now
        transport = None
        for transport in self.transport_table.values():
            if transport.name == "IP":
               break

        if transport is None:
            raise Exception("Unable to find inter-site transport for IP")

        for rsite in self.site_table.values():

            # We don't make connections to our own site as that
            # is intrasite topology generator's job
            if rsite is self.my_site:
                continue

            # Determine bridgehead server in remote site
            rbh = self.get_bridgehead(rsite, part, transport,
                                      partial_ok, detect_failed)

            # RODC acts as an BH for itself
            # IF AmIRODC() then
            #     LET lbh be the nTDSDSA object of the local DC
            # ELSE
            #     LET lbh be the result of GetBridgeheadDC(localSiteVertex.ID,
            #     cr, t, partialReplicaOkay, detectFailedDCs)
            if self.my_dsa.is_ro():
               lsite = self.my_site
               lbh = self.my_dsa
            else:
               lsite = self.my_site
               lbh = self.get_bridgehead(lsite, part, transport,
                                           partial_ok, detect_failed)

            # Find the siteLink object that enumerates the connection
            # between the two sites if it is present
            sitelink = self.get_sitelink(lsite.site_dnstr, rsite.site_dnstr)
            if sitelink is None:
                link_opt = 0x0
                link_sched = None
            else:
                link_opt = sitelink.options
                link_sched = sitelink.schedule

            self.create_connection(part, rbh, rsite, transport,
                                   lbh, lsite, link_opt, link_sched,
                                   partial_ok, detect_failed)

        return all_connected, found_failed

    def create_intersite_connections(self):
        """Computes an NC replica graph for each NC replica that "should be
        present" on the local DC or "is present" on any DC in the same site
        as the local DC. For each edge directed to an NC replica on such a
        DC from an NC replica on a DC in another site, the KCC creates an
        nTDSConnection object to imply that edge if one does not already
        exist.

        Modifies self.keep_connection_list - A list of nTDSConnection
        objects for edges that are directed
        to the local DC's site in one or more NC replica graphs.

        returns: True if spanning trees were created for all NC replica
            graphs, otherwise False.
        """
        all_connected = True
        self.keep_connection_list = []

        # LET crossRefList be the set containing each object o of class
        # crossRef such that o is a child of the CN=Partitions child of the
        # config NC

        # FOR each crossRef object cr in crossRefList
        #    IF cr!enabled has a value and is false, or if FLAG_CR_NTDS_NC
        #        is clear in cr!systemFlags, skip cr.
        #    LET g be the GRAPH return of SetupGraph()

        for part in self.part_table.values():

            if not part.is_enabled():
                continue

            if part.is_foreign():
                continue

            graph = self.setup_graph()

            # Create nTDSConnection objects, routing replication traffic
            # around "failed" DCs.
            found_failed = False

            connected, found_failed = self.create_connections(graph, part, True)

            if not connected:
                all_connected = False

                if found_failed:
                    # One or more failed DCs preclude use of the ideal NC
                    # replica graph. Add connections for the ideal graph.
                    self.create_connections(graph, part, False)

        return all_connected

    def intersite(self):
        """The head method for generating the inter-site KCC replica
        connection graph and attendant nTDSConnection objects
        in the samdb.

        Produces self.keep_connection_list[] of NTDS Connections
        that should be kept during subsequent pruning process.

        ::return (True or False):  (True) if the produced NC replica
            graph connects all sites that need to be connected
        """

        # Retrieve my DSA
        mydsa = self.my_dsa
        mysite = self.my_site
        all_connected = True

        logger.debug("intersite(): enter")

        # Determine who is the ISTG
        if opts.readonly:
            mysite.select_istg(self.samdb, mydsa, ro=True)
        else:
            mysite.select_istg(self.samdb, mydsa, ro=False)

        # Test whether local site has topology disabled
        if mysite.is_intersite_topology_disabled():
            logger.debug("intersite(): exit disabled all_connected=%d" %
                         all_connected)
            return all_connected

        if not mydsa.is_istg():
            logger.debug("intersite(): exit not istg all_connected=%d" %
                         all_connected)
            return all_connected

        self.merge_failed_links()

        # For each NC with an NC replica that "should be present" on the
        # local DC or "is present" on any DC in the same site as the
        # local DC, the KCC constructs a site graph--a precursor to an NC
        # replica graph. The site connectivity for a site graph is defined
        # by objects of class interSiteTransport, siteLink, and
        # siteLinkBridge in the config NC.

        all_connected = self.create_intersite_connections()

        logger.debug("intersite(): exit all_connected=%d" % all_connected)
        return all_connected

    def update_rodc_connection(self):
        """Runs when the local DC is an RODC and updates the RODC NTFRS
        connection object.
        """
        # Given an nTDSConnection object cn1, such that cn1.options contains
        # NTDSCONN_OPT_RODC_TOPOLOGY, and another nTDSConnection object cn2,
        # does not contain NTDSCONN_OPT_RODC_TOPOLOGY, modify cn1 to ensure
        # that the following is true:
        #
        #     cn1.fromServer = cn2.fromServer
        #     cn1.schedule = cn2.schedule
        #
        # If no such cn2 can be found, cn1 is not modified.
        # If no such cn1 can be found, nothing is modified by this task.

        # XXX - not implemented yet

    def intrasite_max_node_edges(self, node_count):
        """Returns the maximum number of edges directed to a node in
        the intrasite replica graph.

        The KCC does not create more
        than 50 edges directed to a single DC. To optimize replication,
        we compute that each node should have n+2 total edges directed
        to it such that (n) is the smallest non-negative integer
        satisfying (node_count <= 2*(n*n) + 6*n + 7)

        :param node_count: total number of nodes in the replica graph
        """
        n = 0
        while True:
            if node_count <= (2 * (n * n) + (6 * n) + 7):
                break
            n = n + 1
        n = n + 2
        if n < 50:
            return n
        return 50

    def construct_intrasite_graph(self, site_local, dc_local,
                                  nc_x, gc_only, detect_stale):

        # We're using the MS notation names here to allow
        # correlation back to the published algorithm.
        #
        # nc_x     - naming context (x) that we are testing if it
        #            "should be present" on the local DC
        # f_of_x   - replica (f) found on a DC (s) for NC (x)
        # dc_s     - DC where f_of_x replica was found
        # dc_local - local DC that potentially needs a replica
        #            (f_of_x)
        # r_list   - replica list R
        # p_of_x   - replica (p) is partial and found on a DC (s)
        #            for NC (x)
        # l_of_x   - replica (l) is the local replica for NC (x)
        #            that should appear on the local DC
        # r_len = is length of replica list |R|
        #
        # If the DSA doesn't need a replica for this
        # partition (NC x) then continue
        needed, ro, partial = nc_x.should_be_present(dc_local)

        logger.debug("construct_intrasite_graph(): enter" +
                     "\n\tgc_only=%d" % gc_only +
                     "\n\tdetect_stale=%d" % detect_stale +
                     "\n\tneeded=%s" % needed +
                     "\n\tro=%s" % ro +
                     "\n\tpartial=%s" % partial +
                     "\n%s" % nc_x)

        if not needed:
            return

        # Create a NCReplica that matches what the local replica
        # should say.  We'll use this below in our r_list
        l_of_x = NCReplica(dc_local.dsa_dnstr, dc_local.dsa_guid,
                           nc_x.nc_dnstr)

        l_of_x.identify_by_basedn(self.samdb)

        l_of_x.rep_partial = partial
        l_of_x.rep_ro = ro

        # Add this replica that "should be present" to the
        # needed replica table for this DSA
        dc_local.add_needed_replica(l_of_x)

        # Empty replica sequence list
        r_list = []

        # We'll loop thru all the DSAs looking for
        # writeable NC replicas that match the naming
        # context dn for (nc_x)
        #
        for dc_s_dn, dc_s in self.my_site.dsa_table.items():

            # If this partition (nc_x) doesn't appear as a
            # replica (f_of_x) on (dc_s) then continue
            if not nc_x.nc_dnstr in dc_s.current_rep_table.keys():
                continue

            # Pull out the NCReplica (f) of (x) with the dn
            # that matches NC (x) we are examining.
            f_of_x = dc_s.current_rep_table[nc_x.nc_dnstr]

            # Replica (f) of NC (x) must be writable
            if f_of_x.is_ro():
                continue

            # Replica (f) of NC (x) must satisfy the
            # "is present" criteria for DC (s) that
            # it was found on
            if not f_of_x.is_present():
                continue

            # DC (s) must be a writable DSA other than
            # my local DC.  In other words we'd only replicate
            # from other writable DC
            if dc_s.is_ro() or dc_s is dc_local:
                continue

            # Certain replica graphs are produced only
            # for global catalogs, so test against
            # method input parameter
            if gc_only and not dc_s.is_gc():
                continue

            # DC (s) must be in the same site as the local DC
            # as this is the intra-site algorithm. This is
            # handled by virtue of placing DSAs in per
            # site objects (see enclosing for() loop)

            # If NC (x) is intended to be read-only full replica
            # for a domain NC on the target DC then the source
            # DC should have functional level at minimum WIN2008
            #
            # Effectively we're saying that in order to replicate
            # to a targeted RODC (which was introduced in Windows 2008)
            # then we have to replicate from a DC that is also minimally
            # at that level.
            #
            # You can also see this requirement in the MS special
            # considerations for RODC which state that to deploy
            # an RODC, at least one writable domain controller in
            # the domain must be running Windows Server 2008
            if ro and not partial and nc_x.nc_type == NCType.domain:
                if not dc_s.is_minimum_behavior(DS_BEHAVIOR_WIN2008):
                    continue

            # If we haven't been told to turn off stale connection
            # detection and this dsa has a stale connection then
            # continue
            if detect_stale and self.is_stale_link_connection(dc_s) == True:
               continue

            # Replica meets criteria.  Add it to table indexed
            # by the GUID of the DC that it appears on
            r_list.append(f_of_x)

        # If a partial (not full) replica of NC (x) "should be present"
        # on the local DC, append to R each partial replica (p of x)
        # such that p "is present" on a DC satisfying the same
        # criteria defined above for full replica DCs.
        if partial == True:

            # Now we loop thru all the DSAs looking for
            # partial NC replicas that match the naming
            # context dn for (NC x)
            for dc_s_dn, dc_s in self.my_site.dsa_table.items():

                # If this partition NC (x) doesn't appear as a
                # replica (p) of NC (x) on the dsa DC (s) then
                # continue
                if not nc_x.nc_dnstr in dc_s.current_rep_table.keys():
                    continue

                # Pull out the NCReplica with the dn that
                # matches NC (x) we are examining.
                p_of_x = dsa.current_rep_table[nc_x.nc_dnstr]

                # Replica (p) of NC (x) must be partial
                if not p_of_x.is_partial():
                    continue

                # Replica (p) of NC (x) must satisfy the
                # "is present" criteria for DC (s) that
                # it was found on
                if not p_of_x.is_present():
                    continue

                # DC (s) must be a writable DSA other than
                # my DSA.  In other words we'd only replicate
                # from other writable DSA
                if dc_s.is_ro() or dc_s is dc_local:
                    continue

                # Certain replica graphs are produced only
                # for global catalogs, so test against
                # method input parameter
                if gc_only and not dc_s.is_gc():
                    continue

                # DC (s) must be in the same site as the local DC
                # as this is the intra-site algorithm. This is
                # handled by virtue of placing DSAs in per
                # site objects (see enclosing for() loop)

                # This criteria is moot (a no-op) for this case
                # because we are scanning for (partial = True).  The
                # MS algorithm statement says partial replica scans
                # should adhere to the "same" criteria as full replica
                # scans so the criteria doesn't change here...its just
                # rendered pointless.
                #
                # The case that is occurring would be a partial domain
                # replica is needed on a local DC global catalog.  There
                # is no minimum windows behavior for those since GCs
                # have always been present.
                if ro and not partial and nc_x.nc_type == NCType.domain:
                    if not dc_s.is_minimum_behavior(DS_BEHAVIOR_WIN2008):
                        continue

                # If we haven't been told to turn off stale connection
                # detection and this dsa has a stale connection then
                # continue
                if detect_stale and self.is_stale_link_connection(dc_s) == True:
                    continue

                # Replica meets criteria.  Add it to table indexed
                # by the GUID of the DSA that it appears on
                r_list.append(p_of_x)

        # Append to R the NC replica that "should be present"
        # on the local DC
        r_list.append(l_of_x)

        r_list.sort(sort_replica_by_dsa_guid)

        r_len = len(r_list)

        max_node_edges = self.intrasite_max_node_edges(r_len)

        # Add a node for each r_list element to the replica graph
        graph_list = []
        for rep in r_list:
            node = GraphNode(rep.rep_dsa_dnstr, max_node_edges)
            graph_list.append(node)

        # For each r(i) from (0 <= i < |R|-1)
        i = 0
        while i < (r_len-1):
            # Add an edge from r(i) to r(i+1) if r(i) is a full
            # replica or r(i+1) is a partial replica
            if not r_list[i].is_partial() or r_list[i+1].is_partial():
                graph_list[i+1].add_edge_from(r_list[i].rep_dsa_dnstr)

            # Add an edge from r(i+1) to r(i) if r(i+1) is a full
            # replica or ri is a partial replica.
            if not r_list[i+1].is_partial() or r_list[i].is_partial():
                graph_list[i].add_edge_from(r_list[i+1].rep_dsa_dnstr)
            i = i + 1

        # Add an edge from r|R|-1 to r0 if r|R|-1 is a full replica
        # or r0 is a partial replica.
        if not r_list[r_len-1].is_partial() or r_list[0].is_partial():
            graph_list[0].add_edge_from(r_list[r_len-1].rep_dsa_dnstr)

        # Add an edge from r0 to r|R|-1 if r0 is a full replica or
        # r|R|-1 is a partial replica.
        if not r_list[0].is_partial() or r_list[r_len-1].is_partial():
            graph_list[r_len-1].add_edge_from(r_list[0].rep_dsa_dnstr)

        # For each existing nTDSConnection object implying an edge
        # from rj of R to ri such that j != i, an edge from rj to ri
        # is not already in the graph, and the total edges directed
        # to ri is less than n+2, the KCC adds that edge to the graph.
        i = 0
        while i < r_len:
            dsa = self.my_site.dsa_table[graph_list[i].dsa_dnstr]
            graph_list[i].add_edges_from_connections(dsa)
            i = i + 1

        i = 0
        while i < r_len:
            tnode = graph_list[i]

            # To optimize replication latency in sites with many NC replicas, the
            # KCC adds new edges directed to ri to bring the total edges to n+2,
            # where the NC replica rk of R from which the edge is directed
            # is chosen at random such that k != i and an edge from rk to ri
            # is not already in the graph.
            #
            # Note that the KCC tech ref does not give a number for the definition
            # of "sites with many NC replicas".   At a bare minimum to satisfy
            # n+2 edges directed at a node we have to have at least three replicas
            # in |R| (i.e. if n is zero then at least replicas from two other graph
            # nodes may direct edges to us).
            if r_len >= 3:
                # pick a random index
                findex = rindex = random.randint(0, r_len-1)

                # while this node doesn't have sufficient edges
                while tnode.has_sufficient_edges() == False:
                    # If this edge can be successfully added (i.e. not
                    # the same node and edge doesn't already exist) then
                    # select a new random index for the next round
                    if tnode.add_edge_from(graph_list[rindex].dsa_dnstr) == True:
                        findex = rindex = random.randint(0, r_len-1)
                    else:
                        # Otherwise continue looking against each node
                        # after the random selection
                        rindex = rindex + 1
                        if rindex >= r_len:
                            rindex = 0

                        if rindex == findex:
                            logger.error("Unable to satisfy max edge criteria!")
                            break

            # Print the graph node in debug mode
            logger.debug("%s" % tnode)

            # For each edge directed to the local DC, ensure a nTDSConnection
            # points to us that satisfies the KCC criteria
            if graph_list[i].dsa_dnstr == dc_local.dsa_dnstr:
                graph_list[i].add_connections_from_edges(dc_local)

            i = i + 1

    def intrasite(self):
        """The head method for generating the intra-site KCC replica
        connection graph and attendant nTDSConnection objects
        in the samdb
        """
        # Retrieve my DSA
        mydsa = self.my_dsa

        logger.debug("intrasite(): enter")

        # Test whether local site has topology disabled
        mysite = self.site_table[self.my_site_dnstr]
        if mysite.is_intrasite_topology_disabled():
            return

        detect_stale = (mysite.is_detect_stale_disabled() == False)

        # Loop thru all the partitions.
        for partdn, part in self.part_table.items():
            self.construct_intrasite_graph(mysite, mydsa, part, False,
                                           detect_stale)

        # If the DC is a GC server, the KCC constructs an additional NC
        # replica graph (and creates nTDSConnection objects) for the
        # config NC as above, except that only NC replicas that "are present"
        # on GC servers are added to R.
        for partdn, part in self.part_table.items():
            if part.is_config():
                self.construct_intrasite_graph(mysite, mydsa, part, True,
                                               detect_stale)

        # The DC repeats the NC replica graph computation and nTDSConnection
        # creation for each of the NC replica graphs, this time assuming
        # that no DC has failed. It does so by re-executing the steps as
        # if the bit NTDSSETTINGS_OPT_IS_TOPL_DETECT_STALE_DISABLED were
        # set in the options attribute of the site settings object for
        # the local DC's site.  (ie. we set "detec_stale" flag to False)

        # Loop thru all the partitions.
        for partdn, part in self.part_table.items():
            self.construct_intrasite_graph(mysite, mydsa, part, False,
                                           False) # don't detect stale

        # If the DC is a GC server, the KCC constructs an additional NC
        # replica graph (and creates nTDSConnection objects) for the
        # config NC as above, except that only NC replicas that "are present"
        # on GC servers are added to R.
        for partdn, part in self.part_table.items():
            if part.is_config():
                self.construct_intrasite_graph(mysite, mydsa, part, True,
                                               False)  # don't detect stale

        if opts.readonly:
            # Display any to be added or modified repsFrom
            for dnstr, connect in mydsa.connect_table.items():
                if connect.to_be_deleted == True:
                    logger.info("TO BE DELETED:\n%s" % connect)
                if connect.to_be_modified == True:
                    logger.info("TO BE MODIFIED:\n%s" % connect)
                if connect.to_be_added == True:
                    logger.info("TO BE ADDED:\n%s" % connect)

            mydsa.commit_connections(self.samdb, ro=True)
        else:
            # Commit any newly created connections to the samdb
            mydsa.commit_connections(self.samdb)

    def run(self, dburl, lp, creds):
        """Method to perform a complete run of the KCC and
        produce an updated topology for subsequent NC replica
        syncronization between domain controllers
        """
        # We may already have a samdb setup if we are
        # currently importing an ldif for a test run
        if self.samdb is None:
            try:
                self.samdb = SamDB(url=lp.samdb_url(),
                                   session_info=system_session(),
                                   credentials=creds, lp=lp)

            except ldb.LdbError, (num, msg):
                logger.error("Unable to open sam database %s : %s" %
                             (lp.samdb_url(), msg))
                return 1

        try:
            # Setup
            self.load_my_site()
            self.load_my_dsa()

            self.load_all_sites()
            self.load_all_partitions()
            self.load_all_transports()
            self.load_all_sitelinks()

            # These are the published steps (in order) for the
            # MS-TECH description of the KCC algorithm

            # Step 1
            self.refresh_failed_links_connections()

            # Step 2
            self.intrasite()

            # Step 3
            all_connected = self.intersite()

            # Step 4
            self.remove_unneeded_ntdsconn(all_connected)

            # Step 5
            self.translate_ntdsconn()

            # Step 6
            self.remove_unneeded_failed_links_connections()

            # Step 7
            self.update_rodc_connection()

        except Exception, estr:
            logger.error("%s" % estr)
            return 1

        return 0

    def import_ldif(self, dburl, lp, creds, ldif_file):
        """Routine to import all objects and attributes that are relevent
        to the KCC algorithms from a previously exported LDIF file.

        The point of this function is to allow a programmer/debugger to
        import an LDIF file with non-security relevent information that
        was previously extracted from a DC database.  The LDIF file is used
        to create a temporary abbreviated database.  The KCC algorithm can
        then run against this abbreviated database for debug or test
        verification that the topology generated is computationally the
        same between different OSes and algorithms.

        :param dburl: path to the temporary abbreviated db to create
        :param ldif_file: path to the ldif file to import
        """
        if os.path.exists(dburl):
            logger.error("Specify a database (%s) that doesn't already exist." %
                         dburl)
            return 1

        # Use ["modules:"] as we are attempting to build a sam
        # database as opposed to start it here.
        self.samdb = Ldb(url=dburl, session_info=system_session(),
                         lp=lp, options=["modules:"])

        self.samdb.transaction_start()
        try:
            data = read_and_sub_file(ldif_file, None)
            self.samdb.add_ldif(data, None)

        except Exception, estr:
            logger.error("%s" % estr)
            self.samdb.transaction_cancel()
            return 1
        else:
            self.samdb.transaction_commit()

        self.samdb = None

        # We have an abbreviated list of options here because we have built
        # an abbreviated database.  We use the rootdse and extended-dn
        # modules only during this re-open
        self.samdb = SamDB(url=dburl, session_info=system_session(),
                           credentials=creds, lp=lp,
                           options=["modules:rootdse,extended_dn_out_ldb"])
        return 0

    def export_ldif(self, dburl, lp, creds, ldif_file):
        """Routine to extract all objects and attributes that are relevent
        to the KCC algorithms from a DC database.

        The point of this function is to allow a programmer/debugger to
        extract an LDIF file with non-security relevent information from
        a DC database.  The LDIF file can then be used to "import" via
        the import_ldif() function this file into a temporary abbreviated
        database.  The KCC algorithm can then run against this abbreviated
        database for debug or test verification that the topology generated
        is computationally the same between different OSes and algorithms.

        :param dburl: LDAP database URL to extract info from
        :param ldif_file: output LDIF file name to create
        """
        try:
            self.samdb = SamDB(url=dburl,
                               session_info=system_session(),
                               credentials=creds, lp=lp)
        except ldb.LdbError, (enum, estr):
            logger.error("Unable to open sam database (%s) : %s" %
                         (lp.samdb_url(), estr))
            return 1

        if os.path.exists(ldif_file):
            logger.error("Specify a file (%s) that doesn't already exist." %
                         ldif_file)
            return 1

        try:
            f = open(ldif_file, "w")
        except (enum, estr):
            logger.error("Unable to open (%s) : %s" % (ldif_file, estr))
            return 1

        try:
            # Query Partitions
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "objectSid",
                      "Enabled",
                      "systemFlags",
                      "dnsRoot",
                      "nCName",
                      "msDS-NC-Replica-Locations",
                      "msDS-NC-RO-Replica-Locations" ]

            sstr = "CN=Partitions,%s" % self.samdb.get_config_basedn()
            res = self.samdb.search(base=sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=crossRef)")

            # Write partitions output
            write_search_result(self.samdb, f, res)

            # Query cross reference container
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "fSMORoleOwner",
                      "systemFlags",
                      "msDS-Behavior-Version",
                      "msDS-EnabledFeature" ]

            sstr = "CN=Partitions,%s" % self.samdb.get_config_basedn()
            res = self.samdb.search(base=sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=crossRefContainer)")

            # Write cross reference container output
            write_search_result(self.samdb, f, res)

            # Query Sites
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "systemFlags" ]

            sstr = "CN=Sites,%s" % self.samdb.get_config_basedn()
            sites = self.samdb.search(base=sstr, scope=ldb.SCOPE_SUBTREE,
                                      attrs=attrs,
                                      expression="(objectClass=site)")

            # Write sites output
            write_search_result(self.samdb, f, sites)

            # Query NTDS Site Settings
            for msg in sites:
                sitestr = str(msg.dn)

                attrs = [ "objectClass",
                          "objectGUID",
                          "cn",
                          "whenChanged",
                          "interSiteTopologyGenerator",
                          "interSiteTopologyFailover",
                          "schedule",
                          "options" ]

                sstr = "CN=NTDS Site Settings,%s" % sitestr
                res = self.samdb.search(base=sstr, scope=ldb.SCOPE_BASE,
                                         attrs=attrs)

                # Write Site Settings output
                write_search_result(self.samdb, f, res)

            # Naming context list
            nclist = []

            # Query Directory Service Agents
            for msg in sites:
                sstr = str(msg.dn)

                ncattrs = [ "hasMasterNCs",
                            "msDS-hasMasterNCs",
                            "hasPartialReplicaNCs",
                            "msDS-HasDomainNCs",
                            "msDS-hasFullReplicaNCs",
                            "msDS-HasInstantiatedNCs" ]
                attrs = [ "objectClass",
                            "objectGUID",
                            "cn",
                            "whenChanged",
                            "invocationID",
                            "options",
                            "msDS-isRODC",
                            "msDS-Behavior-Version" ]

                res = self.samdb.search(base=sstr, scope=ldb.SCOPE_SUBTREE,
                                        attrs=attrs + ncattrs,
                                        expression="(objectClass=nTDSDSA)")

                # Spin thru all the DSAs looking for NC replicas
                # and build a list of all possible Naming Contexts
                # for subsequent retrieval below
                for msg in res:
                    for k in msg.keys():
                        if k in ncattrs:
                            for value in msg[k]:
                                # Some of these have binary DNs so
                                # use dsdb_Dn to split out relevent parts
                                dsdn = dsdb_Dn(self.samdb, value)
                                dnstr = str(dsdn.dn)
                                if dnstr not in nclist:
                                    nclist.append(dnstr)

                # Write DSA output
                write_search_result(self.samdb, f, res)

            # Query NTDS Connections
            for msg in sites:
                sstr = str(msg.dn)

                attrs = [ "objectClass",
                          "objectGUID",
                          "cn",
                          "whenChanged",
                          "options",
                          "whenCreated",
                          "enabledConnection",
                          "schedule",
                          "transportType",
                          "fromServer",
                          "systemFlags" ]

                res = self.samdb.search(base=sstr, scope=ldb.SCOPE_SUBTREE,
                                        attrs=attrs,
                                        expression="(objectClass=nTDSConnection)")
                # Write NTDS Connection output
                write_search_result(self.samdb, f, res)


            # Query Intersite transports
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "options",
                      "name",
                      "bridgeheadServerListBL",
                      "transportAddressAttribute" ]

            sstr = "CN=Inter-Site Transports,CN=Sites,%s" % \
                   self.samdb.get_config_basedn()
            res = self.samdb.search(sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=interSiteTransport)")

            # Write inter-site transport output
            write_search_result(self.samdb, f, res)

            # Query siteLink
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "systemFlags",
                      "options",
                      "schedule",
                      "replInterval",
                      "siteList",
                      "cost" ]

            sstr = "CN=Sites,%s" % \
                   self.samdb.get_config_basedn()
            res = self.samdb.search(sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=siteLink)")

            # Write siteLink output
            write_search_result(self.samdb, f, res)

            # Query siteLinkBridge
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "siteLinkList" ]

            sstr = "CN=Sites,%s" % self.samdb.get_config_basedn()
            res = self.samdb.search(sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=siteLinkBridge)")

            # Write siteLinkBridge output
            write_search_result(self.samdb, f, res)

            # Query servers containers
            # Needed for samdb.server_site_name()
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "systemFlags" ]

            sstr = "CN=Sites,%s" % self.samdb.get_config_basedn()
            res = self.samdb.search(sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=serversContainer)")

            # Write servers container output
            write_search_result(self.samdb, f, res)

            # Query servers
            # Needed because some transport interfaces refer back to
            # attributes found in the server object.   Also needed
            # so extended-dn will be happy with dsServiceName in rootDSE
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "systemFlags",
                      "dNSHostName",
                      "mailAddress" ]

            sstr = "CN=Sites,%s" % self.samdb.get_config_basedn()
            res = self.samdb.search(sstr, scope=ldb.SCOPE_SUBTREE,
                                     attrs=attrs,
                                     expression="(objectClass=server)")

            # Write server output
            write_search_result(self.samdb, f, res)

            # Query Naming Context replicas
            attrs = [ "objectClass",
                      "objectGUID",
                      "cn",
                      "whenChanged",
                      "objectSid",
                      "fSMORoleOwner",
                      "msDS-Behavior-Version",
                      "repsFrom",
                      "repsTo" ]

            for sstr in nclist:
                res = self.samdb.search(sstr, scope=ldb.SCOPE_BASE,
                                        attrs=attrs)

                # Write naming context output
                write_search_result(self.samdb, f, res)

            # Query rootDSE replicas
            attrs=[ "objectClass",
                    "objectGUID",
                    "cn",
                    "whenChanged",
                    "rootDomainNamingContext",
                    "configurationNamingContext",
                    "schemaNamingContext",
                    "defaultNamingContext",
                    "dsServiceName" ]

            sstr = ""
            res = self.samdb.search(sstr, scope=ldb.SCOPE_BASE,
                                     attrs=attrs)

            # Record the rootDSE object as a dn as it
            # would appear in the base ldb file.  We have
            # to save it this way because we are going to
            # be importing as an abbreviated database.
            res[0].dn = ldb.Dn(self.samdb, "@ROOTDSE")

            # Write rootdse output
            write_search_result(self.samdb, f, res)

        except ldb.LdbError, (enum, estr):
            logger.error("Error processing (%s) : %s" % (sstr, estr))
            return 1

        f.close()
        return 0

##################################################
# Global Functions
##################################################
def sort_replica_by_dsa_guid(rep1, rep2):
    return cmp(rep1.rep_dsa_guid, rep2.rep_dsa_guid)

def sort_dsa_by_gc_and_guid(dsa1, dsa2):
    if dsa1.is_gc() == True and dsa2.is_gc() == False:
        return -1
    if dsa1.is_gc() == False and dsa2.is_gc() == True:
        return +1
    return cmp(dsa1.dsa_guid, dsa2.dsa_guid)

def is_smtp_replication_available():
    """Currently always returns false because Samba
    doesn't implement SMTP transfer for NC changes
    between DCs
    """
    return False

def write_search_result(samdb, f, res):
    for msg in res:
        lstr = samdb.write_ldif(msg, ldb.CHANGETYPE_NONE)
        f.write("%s" % lstr)

##################################################
# samba_kcc entry point
##################################################

parser = optparse.OptionParser("samba_kcc [options]")
sambaopts = options.SambaOptions(parser)
credopts = options.CredentialsOptions(parser)

parser.add_option_group(sambaopts)
parser.add_option_group(credopts)
parser.add_option_group(options.VersionOptions(parser))

parser.add_option("--readonly",
                  help="compute topology but do not update database",
                  action="store_true")

parser.add_option("--debug",
                  help="debug output",
                  action="store_true")

parser.add_option("--seed",
                  help="random number seed",
                  type=str, metavar="<number>")

parser.add_option("--importldif",
                  help="import topology ldif file",
                  type=str, metavar="<file>")

parser.add_option("--exportldif",
                  help="export topology ldif file",
                  type=str, metavar="<file>")

parser.add_option("-H", "--URL" ,
                  help="LDB URL for database or target server",
                  type=str, metavar="<URL>", dest="dburl")

parser.add_option("--tmpdb",
                  help="schemaless database file to create for ldif import",
                  type=str, metavar="<file>")

logger = logging.getLogger("samba_kcc")
logger.addHandler(logging.StreamHandler(sys.stdout))

lp = sambaopts.get_loadparm()
creds = credopts.get_credentials(lp, fallback_machine=True)

opts, args = parser.parse_args()

if opts.readonly is None:
    opts.readonly = False

if opts.debug:
    logger.setLevel(logging.DEBUG)
elif opts.readonly:
    logger.setLevel(logging.INFO)
else:
    logger.setLevel(logging.WARNING)

# initialize seed from optional input parameter
if opts.seed:
    random.seed(int(opts.seed))
else:
    random.seed(0xACE5CA11)

if opts.dburl is None:
    opts.dburl = lp.samdb_url()

# Instantiate Knowledge Consistency Checker and perform run
kcc = KCC()

if opts.exportldif:
    rc = kcc.export_ldif(opts.dburl, lp, creds, opts.exportldif)
    sys.exit(rc)

if opts.importldif:
    if opts.tmpdb is None or opts.tmpdb.startswith('ldap'):
        logger.error("Specify a target temp database file with --tmpdb option.")
        sys.exit(1)

    rc = kcc.import_ldif(opts.tmpdb, lp, creds, opts.importldif)
    if rc != 0:
        sys.exit(rc)

rc = kcc.run(opts.dburl, lp, creds)
sys.exit(rc)