Difference between revisions of "Configure DHCP to update DNS records with BIND9"

From SambaWiki
m
m (/* update main script, move DHCID check)
Line 75: Line 75:
   
 
#!/bin/bash
 
#!/bin/bash
  +
# shellcheck disable=SC2001
 
 
 
# /usr/local/bin/dhcp-dyndns.sh
 
# /usr/local/bin/dhcp-dyndns.sh
Line 81: Line 82:
 
# it can also add the 'macAddress' to the Computers object.
 
# it can also add the 'macAddress' to the Computers object.
 
#
 
#
# Version: 0.9.0
+
# Version: 0.9.1
 
#
 
#
 
# Copyright (C) Rowland Penny 2020
 
# Copyright (C) Rowland Penny 2020
Line 109: Line 110:
 
usage() {
 
usage() {
 
echo "USAGE:"
 
echo "USAGE:"
echo " $(basename $0) add ip-address dhcid|mac-address hostname"
+
echo " $(basename "$0") add ip-address dhcid|mac-address hostname"
echo " $(basename $0) delete ip-address dhcid|mac-address"
+
echo " $(basename "$0") delete ip-address dhcid|mac-address"
 
}
 
}
 
 
Line 116: Line 117:
 
# get current time as a number
 
# get current time as a number
 
test=$(date +%d'-'%m'-'%y' '%H':'%M':'%S)
 
test=$(date +%d'-'%m'-'%y' '%H':'%M':'%S)
# Note: there have been problems with this
 
# check that 'date' returns something like
 
 
 
 
# Check for valid kerberos ticket
 
# Check for valid kerberos ticket
 
#logger "${test} [dyndns] : Running check for valid kerberos ticket"
 
#logger "${test} [dyndns] : Running check for valid kerberos ticket"
 
klist -c "${KRB5CCNAME}" -s
 
klist -c "${KRB5CCNAME}" -s
  +
retval="$?"
if [ "$?" != "0" ]; then
+
if [ "$retval" != "0" ]; then
 
logger "${test} [dyndns] : Getting new ticket, old one has expired"
 
logger "${test} [dyndns] : Getting new ticket, old one has expired"
 
kinit -F -k -t /etc/dhcpduser.keytab "${SETPRINCIPAL}"
 
kinit -F -k -t /etc/dhcpduser.keytab "${SETPRINCIPAL}"
if [ "$?" != "0" ]; then
+
retval="$?"
 
if [ "$retval" != "0" ]; then
 
logger "${test} [dyndns] : dhcpd kinit for dynamic DNS failed"
 
logger "${test} [dyndns] : dhcpd kinit for dynamic DNS failed"
exit 1;
+
exit 1
 
fi
 
fi
 
fi
 
fi
Line 135: Line 136:
 
local RevZone="$1"
 
local RevZone="$1"
 
local IP="$2"
 
local IP="$2"
local rzoneip=$(echo "$RevZone" | sed 's/\.in-addr.arpa//')
+
local rzoneip
local rzonenum=$(echo "$rzoneip" | sed 's/\./ /g')
+
rzoneip=$(echo "$RevZone" | sed 's/\.in-addr.arpa//')
local words=($rzonenum)
+
local rzonenum
  +
rzonenum=$(echo "$rzoneip" | sed 's/\./ /g')
  +
local words="($rzonenum)"
 
local numwords="${#words[@]}"
 
local numwords="${#words[@]}"
 
case "$numwords" in
 
case "$numwords" in
Line 161: Line 164:
 
echo "$ZoneIP"
 
echo "$ZoneIP"
 
echo "$RZIP"
 
echo "$RZIP"
echo "$IP2add"
+
echo "$IP2add"
 
 
 
}
 
}
Line 173: Line 176:
 
# DNS domain
 
# DNS domain
 
domain=$(hostname -d)
 
domain=$(hostname -d)
if [ -z ${domain} ]; then
+
if [ -z "${domain}" ]; then
 
logger "Cannot obtain domain name, is DNS set up correctly?"
 
logger "Cannot obtain domain name, is DNS set up correctly?"
 
logger "Cannot continue... Exiting."
 
logger "Cannot continue... Exiting."
Line 179: Line 182:
 
fi
 
fi
 
# Samba realm
 
# Samba realm
REALM=$(echo ${domain^^})
+
REALM="${domain^^}"
 
 
 
# krbcc ticket cache
 
# krbcc ticket cache
Line 216: Line 219:
 
name="${4%%.*}"
 
name="${4%%.*}"
 
 
# Exit if no ip address or mac-address
+
# Exit if no ip address
if [ -z "${ip}" ] || [ -z "${DHCID}" ]; then
+
if [ -z "${ip}" ]; then
 
usage
 
usage
 
exit 1
 
exit 1
 
fi
 
fi
 
 
 
 
# Exit if no computer name supplied, unless the action is 'delete'
 
# Exit if no computer name supplied, unless the action is 'delete'
Line 228: Line 232:
 
else
 
else
 
usage
 
usage
exit 1;
+
exit 1
 
fi
 
fi
 
fi
 
fi
Line 243: Line 247:
 
# if you do not want computers without a hostname in AD
 
# if you do not want computers without a hostname in AD
 
# uncomment the following block of code.
 
# uncomment the following block of code.
<nowiki>if [[ $name == dhcp* ]]; then</nowiki>
+
<nowiki>#if [[ $name == dhcp* \]]; then</nowiki>
logger "not updating DNS record in AD, invalid name"
+
# logger "not updating DNS record in AD, invalid name"
exit 0
+
# exit 0
fi
+
#fi
 
 
 
## update ##
 
## update ##
Line 257: Line 261:
 
# check for dots
 
# check for dots
 
<nowiki>if [[ $A_REC == *.* ]]; then</nowiki>
 
<nowiki>if [[ $A_REC == *.* ]]; then</nowiki>
samba-tool dns delete ${Server} ${domain} "${name}" A ${ip} -k yes
+
samba-tool dns delete "${Server}" "${domain}" "${name}" A "${ip}" -k yes
 
result1="$?"
 
result1="$?"
 
else
 
else
 
result1=0
 
result1=0
 
fi
 
fi
samba-tool dns add ${Server} ${domain} "${name}" A ${ip} -k yes
+
samba-tool dns add "${Server}" "${domain}" "${name}" A "${ip}" -k yes
 
result2="$?"
 
result2="$?"
 
 
 
# get existing reverse zones (if any)
 
# get existing reverse zones (if any)
ReverseZones=$(samba-tool dns zonelist ${Server} --reverse | grep 'pszZoneName' | awk '{print $NF}')
+
ReverseZones=$(samba-tool dns zonelist "${Server}" --reverse | grep 'pszZoneName' | awk '{print $NF}')
 
if [ -z "$ReverseZones" ]; then
 
if [ -z "$ReverseZones" ]; then
 
echo "No reverse zone found, not updating"
 
echo "No reverse zone found, not updating"
Line 276: Line 280:
 
rev_zone_info "$revzone" "${ip}"
 
rev_zone_info "$revzone" "${ip}"
 
if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
 
if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
host -t PTR ${ip} > /dev/null 2>&1
+
host -t PTR "${ip}" > /dev/null 2>&1
if [ "$?" -eq 0 ]; then
+
retval="$?"
samba-tool dns delete ${Server} ${revzone} ${IP2add} PTR "${name}".${domain} -k yes
+
if [ "$retval" -eq 0 ]; then
  +
samba-tool dns delete "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
 
result3="$?"
 
result3="$?"
 
else
 
else
 
result3='0'
 
result3='0'
 
fi
 
fi
samba-tool dns add ${Server} ${revzone} ${IP2add} PTR "${name}".${domain} -k yes
+
samba-tool dns add "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
 
result4="$?"
 
result4="$?"
 
break
 
break
Line 295: Line 300:
 
_KERBEROS
 
_KERBEROS
 
 
samba-tool dns delete ${Server} ${domain} "${name}" A ${ip} -k yes
+
samba-tool dns delete "${Server}" "${domain}" "${name}" A "${ip}" -k yes
 
result1="$?"
 
result1="$?"
 
# get existing reverse zones (if any)
 
# get existing reverse zones (if any)
ReverseZones=$(samba-tool dns zonelist ${Server} --reverse | grep 'pszZoneName' | awk '{print $NF}')
+
ReverseZones=$(samba-tool dns zonelist "${Server}" --reverse | grep 'pszZoneName' | awk '{print $NF}')
 
if [ -z "$ReverseZones" ]; then
 
if [ -z "$ReverseZones" ]; then
 
logger "No reverse zone found, not updating"
 
logger "No reverse zone found, not updating"
Line 307: Line 312:
 
rev_zone_info "$revzone" "${ip}"
 
rev_zone_info "$revzone" "${ip}"
 
if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
 
if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
host -t PTR ${ip} > /dev/null 2>&1
+
host -t PTR "${ip}" > /dev/null 2>&1
if [ "$?" -eq 0 ]; then
+
retval="$?"
samba-tool dns delete ${Server} ${revzone} ${IP2add} PTR "${name}".${domain} -k yes
+
if [ "$retval" -eq 0 ]; then
  +
samba-tool dns delete "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
 
result2="$?"
 
result2="$?"
 
else
 
else
Line 337: Line 343:
 
logger "DHCP-DNS Update succeeded"
 
logger "DHCP-DNS Update succeeded"
 
fi
 
fi
  +
 
 
if [ "$Add_macAddress" != 'no' ]; then
 
if [ "$Add_macAddress" != 'no' ]; then
 
if [ -n "$DHCID" ]; then
Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(objectclass=ieee802Device)(cn=$name))" | grep -v '#' | grep -v 'ref:')
+
Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(objectclass=ieee802Device)(cn=$name))" | grep -v '#' | grep -v 'ref:')
if [ -z "$Computer_Object" ]; then
 
# Computer object not found with the 'ieee802Device' objectclass, does the computer actually exist, it should.
 
Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(cn=$name))" | grep -v '#' | grep -v 'ref:')
 
 
if [ -z "$Computer_Object" ]; then
 
if [ -z "$Computer_Object" ]; then
logger "Computer '$name' not found. Exiting."
+
# Computer object not found with the 'ieee802Device' objectclass, does the computer actually exist, it should.
 
Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(cn=$name))" | grep -v '#' | grep -v 'ref:')
exit 68
 
 
if [ -z "$Computer_Object" ]; then
else
 
DN=$(echo "$Computer_Object" | grep 'dn:')
+
logger "Computer '$name' not found. Exiting."
objldif="$DN
+
exit 68
  +
else
  +
DN=$(echo "$Computer_Object" | grep 'dn:')
 
objldif="$DN
 
changetype: modify
 
changetype: modify
 
add: objectclass
 
add: objectclass
 
objectclass: ieee802Device"
 
objectclass: ieee802Device"
 
 
 
attrldif="$DN
 
changetype: modify
 
add: macAddress
 
macAddress: $DHCID"
 
 
# add the ldif
 
echo "$objldif" | ldbmodify -k yes -H ldap://"$Server"
 
ret="$?"
 
if [ "$ret" -ne 0 ]; then
 
logger "Error modifying Computer objectclass $name in AD."
 
exit "${ret}"
 
fi
 
sleep 2
 
echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
 
ret="$?"
  +
if [ "$ret" -ne 0 ]; then
 
logger "Error modifying Computer attribute $name in AD."
  +
exit "${ret}"
  +
fi
 
unset objldif
  +
unset attrldif
 
logger "Successfully modified Computer $name in AD"
 
fi
 
else
  +
DN=$(echo "$Computer_Object" | grep 'dn:')
 
attrldif="$DN
 
attrldif="$DN
 
changetype: modify
 
changetype: modify
add: macAddress
+
replace: macAddress
 
macAddress: $DHCID"
 
macAddress: $DHCID"
 
 
# add the ldif
 
echo "$objldif" | ldbmodify -k yes -H ldap://"$Server"
 
ret="$?"
 
if [ "$ret" -ne 0 ]; then
 
logger "Error modifying Computer objectclass $name in AD."
 
exit "${ret}"
 
fi
 
sleep 2
 
 
echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
 
echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
 
ret="$?"
 
ret="$?"
Line 372: Line 396:
 
exit "${ret}"
 
exit "${ret}"
 
fi
 
fi
unset objldif
 
 
unset attrldif
 
unset attrldif
 
logger "Successfully modified Computer $name in AD"
 
logger "Successfully modified Computer $name in AD"
 
fi
 
fi
 
else
 
else
DN=$(echo "$Computer_Object" | grep 'dn:')
+
# $DHCID not set
  +
logger "Error: DHCID not supplied, required to store in AD."
attrldif="$DN
 
  +
usage
changetype: modify
 
 
exit 1
replace: macAddress
 
macAddress: $DHCID"
 
 
echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
 
ret="$?"
 
if [ "$ret" -ne 0 ]; then
 
logger "Error modifying Computer attribute $name in AD."
 
exit "${ret}"
 
fi
 
unset attrldif
 
logger "Successfully modified Computer $name in AD"
 
 
fi
 
fi
 
fi
 
fi
  +
 
exit 0
 
exit 0
   

Revision as of 15:35, 29 January 2021

Introduction

This HowTo describes how to configure isc DHCP to update a Samba DC BIND DNS backend. See Setting_up_a_BIND_DNS_Server for how to set up Bind.

It has not been tested with the Samba AD internal DNS server and it probably will not work with the Samba AD internal DNS.

This HowTo is based on a Debian OS install, the paths given may be different if you use another OS.

The script has now been modified to use samba-tool instead of nsupdate, it also can optionally add the macAddress attribute to a computers AD object, this attribute will contain the computers MAC address.


Preconditions

  • The computer has been provisioned as an AD DC and the samba, smbd and winbindd daemons are running.
  • Bind9_dlz is installed and working on the Samba AD DC, tested with various 9.x versions.
  • You have created the reverse zone.
  • You are logged into the DC as 'root'
  • You are doing this on the same DC as Bind9 is installed on


Names and Addresses used in this howto

  • Realm : SAMDOM.EXAMPLE.COM
  • Subnet : 192.168.0.0
  • Netmask : 255.255.255.0
  • Subnet-mask : 255.255.255.0
  • Broadcast-address : 192.168.0.255
  • Gateway : 192.168.0.1
  • Domain-name : samdom.example.com
  • Domain-name-servers : 192.168.0.6, 192.168.0.5
  • Netbios-name-servers : 192.168.0.5, 192.168.0.6
  • Ntp-servers : 192.168.0.5, 192.168.0.6;
  • Pool range : 192.168.0.50 192.168.0.229


Install isc DHCP

First install the DHCP server

# apt-get install isc-dhcp-server


Create a user to carry out the updates

You need a user that the script will run as, set a random password because you will never logon as the user.

# samba-tool user create dhcpduser --description="Unprivileged user for TSIG-GSSAPI DNS updates via ISC DHCP server" --random-password

Now set the users password to never expire and add the user to the DnsAdmins group.

# samba-tool user setexpiry dhcpduser --noexpiry
# samba-tool group addmembers DnsAdmins dhcpduser

Now export the required keytab.

# samba-tool domain exportkeytab --principal=dhcpduser@SAMDOM.EXAMPLE.COM /etc/dhcpduser.keytab
# chown root:root  /etc/dhcpduser.keytab
# chmod 400  /etc/dhcpduser.keytab


Create the script for the updates

Copy this script to /usr/local/bin/dhcp-dyndns.sh

#!/bin/bash
# shellcheck disable=SC2001

# /usr/local/bin/dhcp-dyndns.sh

# This script is for secure DDNS updates on Samba,
# it can also add the 'macAddress' to the Computers object.
#
# Version: 0.9.1
#
# Copyright (C) Rowland Penny 2020
#
# 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/>.

##########################################################################
#                                                                        #
#    You can optionally add the 'macAddress' to the Computers object.    #
#    Add 'dhcpduser' to the 'Domain Admins' group if used                #
#    Change the next line to 'yes' to make this happen                   #
Add_macAddress='no'
#                                                                        #
##########################################################################

usage() {
echo "USAGE:"
echo "  $(basename "$0") add ip-address dhcid|mac-address hostname"
echo "  $(basename "$0") delete ip-address dhcid|mac-address"
}

_KERBEROS () {
# get current time as a number
test=$(date +%d'-'%m'-'%y' '%H':'%M':'%S)

# Check for valid kerberos ticket
#logger "${test} [dyndns] : Running check for valid kerberos ticket"
klist -c "${KRB5CCNAME}" -s
retval="$?"
if [ "$retval" != "0" ]; then
    logger "${test} [dyndns] : Getting new ticket, old one has expired"
    kinit -F -k -t /etc/dhcpduser.keytab "${SETPRINCIPAL}"
    retval="$?"
    if [ "$retval" != "0" ]; then
        logger "${test} [dyndns] : dhcpd kinit for dynamic DNS failed"
        exit 1
    fi
fi
}

rev_zone_info () {
    local RevZone="$1"
    local IP="$2"
    local rzoneip
    rzoneip=$(echo "$RevZone" | sed 's/\.in-addr.arpa//')
    local rzonenum
    rzonenum=$(echo "$rzoneip" | sed 's/\./ /g')
    local words="($rzonenum)"
    local numwords="${#words[@]}"
    case "$numwords" in
        1) # single ip rev zone '192'
           ZoneIP=$(echo "${IP}" | awk -F '.' '{print $1}')
           RZIP=$(echo "${rzoneip}" | awk -F '.' '{print $3}')
           IP2add=$(echo "${IP}" | awk -F '.' '{print $4"."$3"."$2}')
           ;;
        2) # double ip rev zone '168.192'
           ZoneIP=$(echo "${IP}" | awk -F '.' '{print $1"."$2}')
           RZIP=$(echo "${rzoneip}" | awk -F '.' '{print $2"."$1}')
           IP2add=$(echo "${IP}" | awk -F '.' '{print $4"."$3}')
           ;;
        3) # triple ip rev zone '0.168.192'
           ZoneIP=$(echo "${IP}" | awk -F '.' '{print $1"."$2"."$3}')
           RZIP=$(echo "${rzoneip}" | awk -F '.' '{print $3"."$2"."$1}')
           IP2add=$(echo "${IP}" | awk -F '.' '{print $4}')
           ;;
        *) # should never happen
           exit 1
           ;;
    esac
    echo "$ZoneIP"
    echo "$RZIP"
    echo "$IP2add" 

}

BINDIR=$(samba -b | grep 'BINDIR' | grep -v 'SBINDIR' | awk '{print $NF}')
WBINFO="$BINDIR/wbinfo"

# DHCP Server hostname
Server=$(hostname -s)

# DNS domain
domain=$(hostname -d)
if [ -z "${domain}" ]; then
    logger "Cannot obtain domain name, is DNS set up correctly?"
    logger "Cannot continue... Exiting."
    exit 1
fi
# Samba realm
REALM="${domain^^}"

# krbcc ticket cache
export KRB5CCNAME="/tmp/dhcp-dyndns.cc"

# Kerberos principal
SETPRINCIPAL="dhcpduser@${REALM}"
# Kerberos keytab : /etc/dhcpduser.keytab
# krbcc ticket cache : /tmp/dhcp-dyndns.cc
TESTUSER="$($WBINFO -u | grep 'dhcpduser')"
if [ -z "${TESTUSER}" ]; then
    logger "No AD dhcp user exists, need to create it first.. exiting."
    logger "you can do this by typing the following commands"
    logger "kinit Administrator@${REALM}"
    logger "samba-tool user create dhcpduser --random-password --description='Unprivileged user for DNS updates via ISC DHCP server'"
    logger "samba-tool user setexpiry dhcpduser --noexpiry"
    logger "samba-tool group addmembers DnsAdmins dhcpduser"
    exit 1
fi

# Check for Kerberos keytab
if [ ! -f /etc/dhcpduser.keytab ]; then
    echo "Required keytab /etc/dhcpduser.keytab not found, it needs to be created."
    echo "Use the following commands as root"
    echo "samba-tool domain exportkeytab --principal=${SETPRINCIPAL} /etc/dhcpduser.keytab"
    echo "chown XXXX:XXXX /etc/dhcpduser.keytab"
    echo "Replace 'XXXX:XXXX' with the user & group that dhcpd runs as on your distro"
    echo "chmod 400 /etc/dhcpduser.keytab"
    exit 1
fi

# Variables supplied by dhcpd.conf
action="$1"
ip="$2"
DHCID="$3"
name="${4%%.*}"

# Exit if no ip address
if [ -z "${ip}" ]; then  
    usage
    exit 1
fi


# Exit if no computer name supplied, unless the action is 'delete'
if [ -z "${name}" ]; then
    if [ "${action}" = "delete" ]; then
        name=$(host -t PTR "${ip}" | awk '{print $NF}' | awk -F '.' '{print $1}')
    else
        usage
        exit 1
    fi
fi

# exit if name contains a space
case ${name} in
  *\ * ) logger "Invalid hostname '${name}' ...Exiting"
         exit
         ;;
  #  * ) : ;;
esac

# exit if $name starts with 'dhcp'
# if you do not want computers without a hostname in AD
# uncomment the following block of code.
#if [[ $name == dhcp* \]]; then
#    logger "not updating DNS record in AD, invalid name"
#    exit 0
#fi

## update ##
case "${action}" in
    add)
        _KERBEROS

        # does host have an existing 'A' record ?
        A_REC=$(host -t A "${name}" | awk '{print $NF}')
        # check for dots
        if [[ $A_REC == *.* ]]; then
            samba-tool dns delete "${Server}" "${domain}" "${name}" A "${ip}" -k yes
            result1="$?"
        else
            result1=0
        fi
        samba-tool dns add "${Server}" "${domain}" "${name}" A "${ip}" -k yes
        result2="$?"

        # get existing reverse zones (if any)
        ReverseZones=$(samba-tool dns zonelist "${Server}" --reverse | grep 'pszZoneName' | awk '{print $NF}')
        if [ -z "$ReverseZones" ]; then
            echo "No reverse zone found, not updating"
            result3='0'
            result4='0'
        else
            for revzone in $ReverseZones
            do
              rev_zone_info "$revzone" "${ip}"
              if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
                  host -t PTR "${ip}" > /dev/null 2>&1
                  retval="$?"
                  if [ "$retval" -eq 0 ]; then
                      samba-tool dns delete "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
                      result3="$?"
                  else
                      result3='0'
                  fi
                  samba-tool dns add "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
                  result4="$?"
                  break
              else
                  continue
              fi
            done
        fi
        ;;
 delete)
        _KERBEROS

        samba-tool dns delete "${Server}" "${domain}" "${name}" A "${ip}" -k yes
        result1="$?"
        # get existing reverse zones (if any)
        ReverseZones=$(samba-tool dns zonelist "${Server}" --reverse | grep 'pszZoneName' | awk '{print $NF}')
        if [ -z "$ReverseZones" ]; then
            logger "No reverse zone found, not updating"
            result2='0'
        else
            for revzone in $ReverseZones
            do
              rev_zone_info "$revzone" "${ip}"
              if [[ ${ip} = $ZoneIP* ]] && [ "$ZoneIP" = "$RZIP" ]; then
                  host -t PTR "${ip}" > /dev/null 2>&1
                  retval="$?"
                  if [ "$retval" -eq 0 ]; then
                      samba-tool dns delete "${Server}" "${revzone}" "${IP2add}" PTR "${name}.${domain}" -k yes
                      result2="$?"
                  else
                      result2='0'
                  fi
                  break
              else
                  continue
              fi
            done
        fi
        result3='0'
        result4='0'
        ;;
      *)
        logger "Invalid action specified"
        exit 103
        ;;
esac

result="${result1}:${result2}:${result3}:${result4}"

if [ "${result}" != "0:0:0:0" ]; then
    logger "DHCP-DNS Update failed: ${result}"
    exit 1
else
    logger "DHCP-DNS Update succeeded"
fi
 
if [ "$Add_macAddress" != 'no' ]; then
    if [ -n "$DHCID" ]; then
        Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(objectclass=ieee802Device)(cn=$name))" | grep -v '#' | grep -v 'ref:')
        if [ -z "$Computer_Object" ]; then
            # Computer object not found with the 'ieee802Device' objectclass, does the computer actually exist, it should.
            Computer_Object=$(ldbsearch -k yes -H ldap://"$Server" "(&(objectclass=computer)(cn=$name))" | grep -v '#' | grep -v 'ref:')
            if [ -z "$Computer_Object" ]; then
                logger "Computer '$name' not found. Exiting."
                exit 68
            else
                DN=$(echo "$Computer_Object" | grep 'dn:')
                objldif="$DN
changetype: modify
add: objectclass
objectclass: ieee802Device"

                attrldif="$DN
 changetype: modify
add: macAddress
macAddress: $DHCID"

                # add the ldif
                echo "$objldif" | ldbmodify -k yes -H ldap://"$Server"
                ret="$?"
                if [ "$ret" -ne 0 ]; then
                    logger "Error modifying Computer objectclass $name in AD."
                    exit "${ret}"
                fi
                sleep 2
                echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
                ret="$?"
                if [ "$ret" -ne 0 ]; then
                    logger "Error modifying Computer attribute $name in AD."
                    exit "${ret}"
                fi
                unset objldif
                unset attrldif
                logger "Successfully modified Computer $name in AD"
            fi
        else
            DN=$(echo "$Computer_Object" | grep 'dn:')
            attrldif="$DN
changetype: modify
replace: macAddress
macAddress: $DHCID"

            echo "$attrldif" | ldbmodify -k yes -H ldap://"$Server"
            ret="$?"
            if [ "$ret" -ne 0 ]; then
                logger "Error modifying Computer attribute $name in AD."
                exit "${ret}"
            fi
            unset attrldif
            logger "Successfully modified Computer $name in AD"
        fi
    else
        # $DHCID not set
        logger "Error: DHCID not supplied, required to store in AD."
        usage
        exit 1
    fi
fi

exit 0

If you wish to store the computers MAC address in AD, find this line:

Add_macAddress='no'

It is near the top of the script. Change 'no' to 'yes'


Set the permissions on the script.

# chmod 755 /usr/local/bin/dhcp-dyndns.sh



Modify the dhcp conf file

First backup the original conf file.

# cp /etc/dhcp/dhcpd.conf /etc/dhcp/dhcpd.conf.orig

Now edit /etc/dhcp/dhcpd.conf and make it look similar to the this.

authoritative;
ddns-update-style none;

subnet 192.168.0.0 netmask 255.255.255.0 {
  option subnet-mask 255.255.255.0;
  option broadcast-address 192.168.0.255;
  option time-offset 0;
  option routers 192.168.0.1;
  option domain-name "samdom.example.com";
  option domain-name-servers 192.168.0.6, 192.168.0.5;
  option ntp-servers 192.168.0.5, 192.168.0.6;
  pool {
    max-lease-time 1800; # 30 minutes
    range 192.168.0.50 192.168.0.229;
  }
}

on commit {
set noname = concat("dhcp-", binary-to-ascii(10, 8, "-", leased-address));
set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
set ClientDHCID = concat (
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,1,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,2,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,3,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,4,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,5,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,6,1))),2)
);
set ClientName = pick-first-value(option host-name, config-option-host-name, client-name, noname);
log(concat("Commit: IP: ", ClientIP, " DHCID: ", ClientDHCID, " Name: ", ClientName));
execute("/usr/local/bin/dhcp-dyndns.sh", "add", ClientIP, ClientDHCID, ClientName);
}

on release {
set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
set ClientDHCID = concat (
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,1,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,2,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,3,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,4,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,5,1))),2), ":",
suffix (concat ("0", binary-to-ascii (16, 8, "", substring(hardware,6,1))),2)
);
log(concat("Release: IP: ", ClientIP));
execute("/usr/local/bin/dhcp-dyndns.sh", "delete", ClientIP, ClientDHCID);
}

on expiry {
set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
# cannot get a ClientMac here, apparently this only works when actually receiving a packet
log(concat("Expired: IP: ", ClientIP));
# cannot get a ClientName here, for some reason that always fails
# however the dhcp update script will obtain the short hostname.
execute("/usr/local/bin/dhcp-dyndns.sh", "delete", ClientIP, "", "0");
}


Start the dhcp server and see what happens.



Add failover

Add the following to the /etc/dhcp/dhcpd.conf file on the primary:

failover peer "dhcp-failover" {
  primary;
  address dc1.samdom.example.com;
  peer address dc2.samdom.example.com;
  max-response-delay 60;
  max-unacked-updates 10;
  mclt 3600;
  split 255;
  load balance max seconds 3;
}

..and secondary:

failover peer "dhcp-failover" {
  secondary;
  address dc2.samdom.example.com;
  peer address dc1.samdom.example.com;
  max-response-delay 60;
  max-unacked-updates 10;
  load balance max seconds 3;
}


Add references for the subnet/pool which will do failover.

subnet 192.168.0.0 netmask 255.255.255.0 {
  option subnet-mask 255.255.255.0;
  option broadcast-address 192.168.0.255;
  option time-offset 0;
  option routers 192.168.0.1;
  option domain-name "samdom.example.com";
  option domain-name-servers 192.168.0.5, 192.168.0.6;
  option ntp-servers 192.168.0.5, 192.168.0.6;
  pool {
    failover peer "dhcp-failover";
    max-lease-time 1800; # 30 minutes
    range 192.168.0.50 192.168.0.229;
  }
}

Configure OMAPI and define a secret key.

Generate a random OMAPI key on the primary, using the dnssec-keygen utility distributed with BIND.

dnssec‐keygen ‐a HMAC‐MD5 ‐b 512 ‐n USER DHCP_OMAPI

Now extract the actual key:

cat Kdhcp_omapi.+*.private |grep ^Key|cut -d ' ' -f2-

Add the following to dhcpd.conf on both primary and secondary.

omapi-port 7911;
omapi-key omapi_key;

key omapi_key {
     algorithm hmac-md5;
     secret "PUT_YOUR_KEY_HERE";
}

Replace PUT_YOUR_KEY_HERE with the key you extracted from the private key created by the dnssec command

Restart both servers to apply the configuration changes.

You should find lines similar to these, in the system logs on both machines:

Feb 28 17:34:39 dc1 dhcpd: failover peer dhcp-failover: peer moves from recover-done to normal
Feb 28 17:34:39 dc1 dhcpd: failover peer dhcp-failover: Both servers normal

If OMAPI is working properly you can test failover by stopping the primary server.

If you are using a firewall, you will need to open TCP ports 647 and 7911

Once you are sure everything is working as expected, restart both servers to ensure everything is running correctly.

The 'split' value '255' on the 'primary', makes it responsible for the clients. With the value set to '255', the primary will answer all dhcp requests unless it is down (for whatever reason), use '0' to make the secondary responsible.

For more information, read the dhcpd.conf manpage man dhcpd.conf.



Apparmor

To get DHCP updates working with Apparmor, you need to alter /etc/apparmor.d/usr.sbin.dhcpd to match this.

/etc/dhcp/ r,
/etc/dhcp/** r,
/etc/dhcpd{,6}.conf r,
/etc/dhcpd{,6}_ldap.conf r,
/usr/local/bin/dhcp-dyndns.sh ix,
/bin/grep rix,
/usr/sbin/samba rix,
/usr/bin/gawk rix,
/bin/hostname rix,
/usr/bin/wbinfo rix,
/usr/bin/heimtools rix,
/usr/bin/logger rix,
/usr/bin/kinit.heimdal rix,
/bin/date rix,
/dev/tty wr,
/dev/urandom w,
/proc/** r,
/usr/bin/kinit w,
/run/samba/winbindd/pipe wr,


The first 4 lines are the default, you will need to add everything else. With these settings the dhcp-server will start and work.

The above settings have been tested on Ubuntu 18.04 and were supplied by Stefan Kania.


Any questions or problems, ask on the Samba mailing list.