#!/bin/sh

# This script can be installed in /etc/dhclient-enter-hooks to set the client's
# hostname based either on the hostname that the DHCP server supplied or the
# hostname in whatever ptr record exists for the assigned IP address.

if [ x$new_host_name = x ]; then
  ptrname=`echo $new_ip_address \
	   |sed -e \
  's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\)/\4.\3.\2.\1.in-addr.arpa/'`
  (echo "set type=ptr"; echo "$ptrname") |nslookup >/tmp/nslookup.$$
  set `sed -n -e "s/$ptrname[ 	]*\(canonical \)*name *= *\(.*\)/\2 \1/p" \
							< /tmp/nslookup.$$` _
  if [ x$1 = x_ ]; then
    new_host_name=""
  else
    if [ $# -gt 1 ] && [ x$2 = xcanonical ]; then
      new_host_name=`sed -n -e "s/$1[ 	]*name *= *\(.*\)/\1/p" \
							</tmp/nslookup.$$`
    else
      new_host_name=$1
    fi
  fi
  rm /tmp/nslookup.$$
fi
if [ x$new_host_name != x ]; then
  hostname $new_host_name
fi