#!/bin/sh
#
# dns-update -- update DNS A and AAAA records automatically
#
# Depends: perl, dnsutils
#
# Copyright 2004 by Nathaniel W. Turner <nate@houseofnate.net>
#
# 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 2, or (at your option) any later
# version.

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
NAME=update-dns


function usage {
    cat <<EOT
USAGE: $NAME [OPTION].. <INTERFACE> {up|down}

This program gets the primary IPv4 and IPv6 address for the specified network
interface <INTERFACE> and updates the appropriate nameserver.

OPTIONS:
    --hostname <fqdn>, -n <fqdn>
        register <fqdn> as the name of this host; if not specified, the output
        of \`hostname -f\` will be used
    --server <host>, -s <host>
        send nsupdate commands to server <host> instead of the host registered
        as namserver for this hostname
    --key <keyfile>, -k <keyfile>
        use <keyfile> as the shared secret for TSIG request signing
    --verbose, -v
        explain what is being done
    --help, -h
        display this usage information

EXAMPLES:
    $NAME eth0 up
    $NAME -n aardvarque.example.com -s 10.136.0.1 eth1 down
    $NAME -k Kmysecret.+157+38323.private eth0 up
EOT
}


eval set -- `getopt -o 'n:s:t:k:vh' \
                    -l 'hostname:,server:,ttl:,key:,verbose,help' \
                    -n "$NAME" -- "$@"`

hostname=`hostname -f`
nameserver=
ttl=600
key=
verbose=
help=
while true; do
    case "$1" in
        -n|--hostname) hostname="$2"; shift 2;;
        -s|--server) nameserver="$2"; shift 2;;
        -t|--ttl) ttl="$2"; shift 2;;
        -k|--key) key="$2"; shift 2;;
        -v|--verbose) verbose=1; shift;;
        -h|--help) help=1; shift;;
        --) shift; break;;
        *) echo "Error: $1"; exit 1
    esac
done
interface="$1"; shift;
command="$1"; shift;

if test "$help"; then
    usage
    exit 0
fi
if test -z "$interface"; then
    usage 1>&2
    exit 1
fi

nsupdate_cmd="nsupdate"
if test -n "$key"; then
    nsupdate_cmd="$nsupdate_cmd -k $key"
fi
case "$command" in
    up)
	myv4ip=`ip -4 addr show dev $interface primary 2>/dev/null \
                 | perl -ne 'print $1 if /^\ *inet (\d+(?:\.\d+){3})/'`
	myv6ip=`ip -6 addr show dev $interface primary 2>/dev/null \
                 | grep 'scope global' \
                 | perl -ne 'print $1 if /^\ *inet6 ([[:xdigit:]:]+)/'`
        if test "$verbose"; then
  	    echo "Updating DNS record(s) for $hostname"
            test "$nameserver" && echo "Using nameserver $nameserver"
            test "$myv4ip" && echo "Setting A record to $myv4ip"
            test "$myv6ip" && echo "Setting AAAA record to $myv6ip"
            test "$key" && echo "Using TSIG key $key"
        fi 
	( 
          test "$nameserver" && echo server $nameserver
	  echo update delete $hostname A
          test -n "$myv4ip" && echo update add $hostname $ttl A $myv4ip
	  echo update delete $hostname AAAA
          test -n "$myv6ip" && echo update add $hostname $ttl AAAA $myv6ip
	  echo send
        ) | $nsupdate_cmd
        rv=$?
        if test "$verbose" && test "$rv" = 0; then
            echo "DNS updated."
        fi
	;;

    down)
        if test "$verbose"; then
            echo "Removing DNS record(s) for $hostname"
            test "$nameserver" && echo "Using nameserver $nameserver"
            test "$key" && echo "Using TSIG key $key"
        fi 
	(
          test "$nameserver" && echo server $nameserver
	  echo update delete $hostname A
	  echo update delete $hostname AAAA
	  echo send
        ) | $nsupdate_cmd
        rv=$?
        if test "$verbose" && test "$rv" = 0; then
            echo "DNS updated."
        fi
	;;

    *)
        echo "Invalid command $command" 1>&2
        usage 1>&2
	exit 1
	;;
esac