#!/usr/bin/ksh
# rmx
# Jukka.Inkeri At_sign awot.fi
# 29.11.2003 ,ver 2
# lookup reverse host MX or reverse domain or hostname
# use dig 

nameserver=""

#-------------------------------------------------------------------------
usage()
#-------------------------------------------------------------------------
{
	echo "usage: $PRG [-d] [@nameserver] ip  mx | net | host| contact" >&2
	exit 1
}

#-------------------------------------------------------------------------
resolvedom()
#-------------------------------------------------------------------------
{

revnet=$(dig $nameserver $revhost ptr | \
  sed -n "/^;; AUTHORITY SECTION:/,/;; ADDITIONAL SECTION:/p" | \
  grep "^[0-9].*IN.*NS" | tr "\t" " " | cut -d" " -f1 | sort -u -k 1,1)

if [ "$func" = "net" ];then
	echo "$revnet"
	exit 0
fi

dig $nameserver $revnet mx | \
  sed -n "/^;; ANSWER SECTION:/,/;; AUTHORITY SECTION:/p" | \
  grep "IN.*MX" | tr "\t" " "|tr -s " " | cut -d" " -f6 

}

#----------------------------------------------------------------------------
resolvehost()
#-------------------------------------------------------------------------
{
func="$1"
field="$2"
typeset -l func

dig $nameserver $revhost $func | \
  grep -i "^[^;].*IN.*$func" | tr "\t" " " |  tr -s " " | cut -d" " -f$field 
}


#----------------------------------------------------------------------------
# MAIN
#----------------------------------------------------------------------------

[ $# -lt 2 ] && usage

debug=0
if [ "$1" = "-d" ] ; then
	shift
	debug=1
fi

case "$1" in
	   \@*) nameserver="$1"
		shift
		;;
esac

ip="$1"
func="$2"
case "$func" in
	contact|mx|net|host|soa|txt) ;;
	*) usage ;;
esac

revhost=$(echo "$ip" | \
sed "s/\([0-9][0-9]*\)\.\([0-9][0-9]*\)\.\([0-9][0-9]*\)\.\([0-9][0-9]*\)/\4.\3.\2.\1.in-addr.arpa/")

[ "$debug" = "1" ] && echo "Reverse lookup $revhost"

case "$func" in
        net) resolvedom ;;
        host) resolvehost ptr "5";;
        mx) resolvehost mx "5,6";;
        contact) resolvehost soa "6";;
        [a-z]*) resolvehost $func "5,6";;
esac