dhcpd_to_unbound -- add dhcpd entries as local_data to unbound

dhcpd_to_unbound

#!/bin/sh

#
# Copyright (c) 2017, 2019 Aaron Poffenberger <[email protected]>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#

#
# Add dhcpd(8) entries as local_data to unbound(8).
#
# v1.0.0
#
# Add host assignments from:
# /etc/dhcpd.conf
# /var/db/dhcpd.leases
#
# Clears existing entries for DOMAIN_NAME.
#
# Adds one entry per `host` declaration in `/etc/dhcpd.conf`
#
# Adds one unique entry per `hardware ethernet` (MAC address)
# in `/var/db/dhcpd.leases` (with hostname)
#
# Adds reverse lookup records.
#
# This script should be run regularly from cron(8). E.g.
# */3	*	*	*	*	dhcpd_to_unbound
# @reboot				dhcpd_to_unbound
#
# BUGS:
#	Probably doesn't work with IPv6.
#
#	Does not validate unbound(8) or dhcpd(8) are running.
#
#	Only works with the first `option domain-name` found
#	in /etc/dhcpd.conf, meaning it assumes all clients
#	found in `/var/db/dhcpd.leases` belong to first the
#	`option domain-name` found.


__progname="${0##*/}"

CONF='/etc/dhcpd.conf'
LEASES='/var/db/dhcpd.leases'
TMP_FILE='/tmp/dhcpd_to_unbound'
CUR_DATA='/tmp/dhcpd_to_unbound_cur_data'
UC_FLAGS='-q'


[ -f "$TMP_FILE" ] && exit


err() { log "$__progname: $*"; }
log() { printf "%s\\n" "$*" > /dev/stderr; }


[ ! -f "$CONF" ] && err "No $CONF file" && exit 1
[ ! -f "$LEASES" ] && err "No $LEASES file" && exit 1


cleanup() {
	trap "" EXIT
	rm -f "$TMP_FILE" "$CUR_DATA"
}
trap cleanup EXIT INT QUIT
touch "$TMP_FILE"


while getopts :c:hl:sv opt ; do
	case $opt in
		c)
			CONF="$OPTARG"
			;;
		h)
			CMD="usage"
			;;
		l)
			LEASES="$OPTARG"
			;;
		s)
			CMD=show
			;;
		v)
			unset UC_FLAGS
			;;
		:)
			echo "$__progname: option requires an argument" \
				"-- $OPTARG"
			CMD=abort
			;;
		\?)
			echo "$__progname: invalid option -- $OPTARG"
			CMD=abort
			;;
	esac
done
shift $(( OPTIND - 1 ))


DOMAIN_NAME=$(grep 'domain-name ' "$CONF" | \
	head -n1 | cut -d ' ' -f 3 | tr -d ';"')


case ${CMD:-run} in
	abort)
		exit;
		;;
	usage)
		log "usage: $__progname [-c file] [-h] [-l file] [-s] [-v]"
		log "  -c    path to conf to use instead of ${CONF}."
		log "  -h    this message."
		log "  -l    path to leases file to use instead of ${LEASES}."
		log "  -s    show unbound entries for the specified domain."
		log "  -v    verbose."
		exit
		;;
	show)
		unbound-control list_local_data | grep "$DOMAIN_NAME"
		exit
		;;
esac


# /etc/dhcpd.conf
grep -E 'host|fixed-address|{|}' "$CONF" \
	| grep -v subnet \
	| tr -d '\t' \
	| sed 's#host ##g' \
	| tr -d '\n' \
	| tr '{' ';' \
	| tr '}' '\n' \
	| tr -s ' ' \
	| tr -d '";' \
	| sort -k3 \
	| awk 'NF == 3 { print $3, $1 }' \
	> "$TMP_FILE"


# /var/db/dhcpd.leases
grep -E 'lease|starts|ends|hardware ethernet|abandoned|client-hostname|}' \
	"$LEASES" \
	| tr -d '\t' \
	| sed 's#starts [0-9]##g ; s#ends [0-9]##g ; s# UTC##g ; s#lease ##g ; s#{#;#g' \
	| tr -d '\n' \
	| tr '}' '\n' \
	| sed 's# *; *#;#g' \
	| awk -v cur_ts="$(date +%s)" '
	BEGIN { FS=";" }
	$0 !~ /abandon/ {
		end_ts = strptime($3)
		if ( length(end_ts) == 0 || cur_ts > end_ts ) { exit }

		split($4, hardwares, " ")
		mac = hardwares[3]
		if ( split($5, clients, " ") == 2) {
			hostname = clients[2]
			gsub("\"", "", hostname)
		} else {
			# use the MAC address as the hostname if none found
			hostname = mac
			gsub(":", "_", hostname)
		}

		print $1, hostname
	}


	# a static implementation .. only knows one format
	function strptime(str,		 elems, times, dt) {
		split(str, elems, " ")
		gsub("\/", "", elems[1])
		split(elems[2], times, ":")
		cmd = sprintf("date -uj \"+%s\" %s%s%s.%s\n",
			"%s", elems[1], times[1], times[2], times[3])
		cmd | getline dt
		return dt
	}

'	| sort -k5 -k4r \
	| uniq -f1 \
	>> "$TMP_FILE"


[ -z "$UC_FLAGS" ] && log "Add host entries for $DOMAIN_NAME to" \
	"unbound"


# remove all addresses for $DOMAIN_NAME
unbound-control $UC_FLAGS list_local_data | grep "$DOMAIN_NAME" \
	| cut -f 1 \
	| sed 's#.$##g' \
	> "$CUR_DATA"
unbound-control $UC_FLAGS local_datas_remove < "$CUR_DATA"


# load new data
awk -v domain_name="$DOMAIN_NAME" '
	{
		rev_ip = reverse_ip($1)
		printf("%s.%s IN A %s\n", $2, domain_name, $1)
		printf("%s.in-addr.arpa. IN PTR %s.%s\n",
			rev_ip, $2,domain_name)
	}

	function reverse_ip(ip,		 elems) {
		split(ip, elems, ".")
		rev_ip = sprintf("%s.%s.%s.%s",
			elems[4], elems[3], elems[2], elems[1])
		return rev_ip
	}
'	"$TMP_FILE" \
	| unbound-control $UC_FLAGS local_datas

Note that dhcpd_to_unbound is meant for low-traffic environments. It probably won't scale well in high-traffic environments due to the need to delete all existing records and reload them every time cron(8) invokes it.

I'm looking at doing something more dynamic based on log entries. Nothing to report at this time.

Thank you for inspiration!
https://github.com/mizhka/jdhcp2dns

Nice! Thanks for the comment.

…

--Aaron

On 2020-12-09 18:31 +0000, Michael Zhilin ***@***.***> wrote: Thank you for inspiration! https://github.com/mizhka/jdhcp2dns -- You are receiving this because you authored the thread. Reply to this email directly or view it on GitHub: https://gist.github.com/1c1b994a7b51dab34d1413ca7eab0628#gistcomment-3555961