#!/bin/bash

# This script is written by Peter Poeml <peter@poeml.de> and distributable under
# the terms of the GPL.

me=$(basename $0)
conf=/etc/dnsupdate.conf

usage() {
	cat >&2 <<-EOF
	Usage examples:
	
	$me add host.domain. 86400 A 10.10.100.230
	$me add 230.100.10.10.in-addr.arpa. 86400 IN PTR host.domain.
	$me delete host.domain.
	$me delete 230.100.10.10.in-addr.arpa PTR
	$me add nickname.domain. 86400 CNAME host.domain.
	$me delete nickname.domain.

	add -b as first argument to add/delete both forward/reverse mapping.
	EOF
}

if [ $# -lt 1 ]; then usage; exit 1; fi

if [ $1 = "-b" ]; then 
	do_both=true
	shift
else 
	do_both=false
fi

args=$@

if [ -s $conf ]; then
	key=$(<$conf)
else
	cat >&2 <<-EOF

	Error:
	The configuration file $conf does not exist. It needs to contain the name
	of the key file to use, e.g.:

	--# cat /etc/dnsupdate.conf
	/etc/Kdhcp_updater.+157+14275.private

	EOF
	exit 1
fi

case $args in 
add*) action=add;;
del*) action=del;;
*) echo >&2 invalid action.; echo >&2; usage; exit 1;;
esac

if $do_both; then
	# need to transform: host.domain 86400 A 10.10.100.230
	# into:              230.100.10.10.in-addr.arpa. 86400 IN PTR host.domain.

	# convert into array
	t=($args)

	# sanity check
	if [ $action = "add" ]; then
		case ${t[3]} in 
			A) ;;
			*) echo >&2 something is wrong -- dns_class is not 'A'... args were:; echo $args; exit 1;;
		esac
	fi

	dns_name=${t[1]}
	dns_ttl=${t[2]}

	# if action is "delete", we need to look up the IP address to be removed
	if [ $action = "add" ]; then
		dns_data=${t[4]}
	else
		addr=$(host $dns_name)
		addr=($addr)
		case ${addr[3]} in
			found*) echo >&2 reverse mapping not found, not deleting.; do_both=false;;
			*) dns_data=${addr[3]}
		esac
	fi

	# split address in octets and reverse it
	IFS_SAVE=$IFS; IFS="."; tmp1=($dns_data); IFS=$IFS_SAVE
	for i in 0 1 2 3; do
		octet[$i]=$[ ${tmp1[$i]} ]
		r_dns_data=.${octet[$i]}$r_dns_data
	done
	r_dns_data=${r_dns_data#*.}
	r_dns_data=${r_dns_data}.in-addr.arpa


	# now set up the actual command line
	case $action in 
	add) r_args="add $r_dns_data $dns_ttl IN PTR $dns_name";;
	del) r_args="delete $r_dns_data PTR";;
	esac
fi

echo command line:
echo update $args
$do_both && echo update $r_args
echo ---



echo -e "update $args \n" | nsupdate -k $key
if $do_both; then 
	echo -e "update $r_args \n" | nsupdate -k $key
fi