#!/bin/bash

# vim:tw=80:tabstop=2:shiftwidth=2

# Copyright (c) 2012-present, Phil Dibowitz <phil@ipom.com>
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#  * Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
#  * Redistributions in
#    binary form must reproduce the above copyright notice, this list of
#    conditions and the following disclaimer in the documentation and/or other
#    materials provided with the distribution.
#  * Neither the name of the author nor the names of its contributors may be
#    used to endorse or promote products derived from this software without
#    specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

#
# You can find the latest version of this at:
#   http://www.phildev.net/linux/dhclient-ipv6
#
# Will, given a 'dhclient -6 -P ...' on $EXT_IFACE and assign the prefix
# given to the $INT_IFACE, and twiddle radvd.
#
# For radvd, it takes /etc/radvd.conf.tmpl, replaces "__PREFIX__" with your
# prefix, and - if it's different from /etc/radvd.conf - replaces the config
# file and restarts the daemon.
#

# Make sure these are correct.
CONF='/etc/ipv6_prefix_dhclient.conf'
INT_IFACE='eth0'
EXT_IFACE='eth1'

[ -r $CONF ] && . $CONF

ipv6_prefix_setup() {
  current_ip=$(/sbin/ip -6 addr show dev $INT_IFACE scope global |\
               /usr/bin/awk '/inet6/ {print $2}')
  current_prefix=$(echo $current_ip | /bin/sed -e 's@::1/64@::/64@')
  if [ "$current_prefix" == "$new_ip6_prefix" ] ; then
    return
  fi

  # Setup the new IP
  new_ip=$(echo $new_ip6_prefix | /bin/sed -e 's@::/64@::1/64@g')
  if [ ! -z "$current_ip" ] ; then
    ip -6 addr del $current_ip dev $INT_IFACE
  fi
  ip -6 addr add $new_ip dev $INT_IFACE

  # Ensure we'll get router advertisements
  sysctl -w "net.ipv6.conf.$EXT_IFACE.accept_ra=2"
  # Needed for kernels before 2.6.37, don't worry,
  # forwarding will still work as long as you have it set
  # on your other interface.
  sysctl -w "net.ipv6.conf.$EXT_IFACE.forwarding=0"

  # Update radvd
  tmpfile=/tmp/radvd.conf.$$
  sed -e "s@__PREFIX__@$new_ip6_prefix@g" /etc/radvd.conf.tmpl > $tmpfile
  diff $tmpfile /etc/radvd.conf >/dev/null
  if [ $? == 1 ]; then
    mv $tmpfile /etc/radvd.conf
    /etc/init.d/radvd restart
  else
    rm $tmpfile
  fi
}

if [ "$interface" != "$EXT_IFACE" ] ; then
  return
fi

case "$reason" in
  BOUND6|REBIND6)
    # We will get called twice here - once for the temp address
    # and once for the prefix. We only care about the prefix.
    if [ ! -z "$new_ip6_prefix" ] ; then
      ipv6_prefix_setup
    fi
    ;;
esac