dhclient-ipv6

#!/bin/bash

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

# 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:
#   https://github.com/jaymzh/v6-gw-scripts
#
# 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 "__IFACE__" with your internal interface, and - if it's different
# from /etc/radvd.conf - replaces the config file and restarts the daemon.
#

# Change INT_IFACE or EXT_IFACE by setting them in the config file
CONF='/etc/ipv6_prefix_dhclient.conf'
EXT_IFACE='eth0'
INT_IFACE='eth1'
OTHER_IFACES=''
RADVD_TEMPLATE='/etc/radvd.conf.tmpl'
DNSMASQ_TEMPLATE='/etc/dnsmasq.conf.tmpl'
RA_DAEMON='radvd'

# shellcheck disable=SC1090
[ -r $CONF ] && . $CONF

STATE_DIR=/var/lib/dhcp/dhclient-ipv6-mapping

set_iaid_mapping() {
  local iaid="$1"
  local iface="$2"

  echo "$iface" > "$STATE_DIR/iaid_$iaid"
}

get_interface() {
  local iaid=$1
  if [ ! -d $STATE_DIR ]; then
    mkdir -p $STATE_DIR
    set_iaid_mapping "$iaid" "$INT_IFACE"
    echo $INT_IFACE
    return
  fi

  ls $STATE_DIR/iaid_* >/dev/null 2>/dev/null
  if [ $? -eq 2 ]; then
    echo $INT_IFACE
    set_iaid_mapping "$iaid" "$INT_IFACE"
  fi


  # if we've mapped this iaid to an interface, just cat it out
  if [ -e "$STATE_DIR/iaid_$iaid" ]; then
    iface=$(cat "$STATE_DIR/iaid_$iaid")
    # we're not changing the mapping, but we call update anyway mostly
    # as a `touch` for the code below that checks the time
    echo "$iface"
    set_iaid_mapping "$iaid" "$iface"
    return
  fi

  # we haven't - so let's see if we have an interfaces not-yet-mapped
  known=""
  for file in "$STATE_DIR"/iaid_*; do
    known="$known $(cat "$file")"
  done
  for iface in $INT_IFACE $OTHER_IFACES; do
    for kface in $known; do
      if [ "$kface" = "$iface" ]; then
        continue 2
      fi
    done
    # This interface is not yet mapped, return it
    echo $iface
    set_iaid_mapping "$iaid" "$iface"
    return
  done

  # OK, all of our interfaces are mapped, but none of them is this one, so we'll
  # just return the least-recently touched file. This is a bit odd, because
  # we'll end up populating them in the reverse order, but we won't just end up
  # re-doing one we just did
  # shellcheck disable=SC2012
  last=$(ls -t $STATE_DIR/iaid_* | tail -n 1)
  iface=$(cat "$last")
  rm -f "$last"
  echo "$iface"
  set_iaid_mapping "$iaid" "$iface"
}

get_prefix() {
  local iface="$1"
  current_ip=$(
    /sbin/ip -6 addr show dev "$iface" scope global |\
    /usr/bin/awk '/inet6/ {print $2}'
  )
  # We'll always configure with a /64 even if we got something bigger
  echo "$current_ip" | /bin/sed -E 's@::1/64@::/64@'
}

update_dnsmasq() {
  local iface="$1"
  local prefix="$2"

  tmpfile="/tmp/dnsmasq.conf.$$"
  rm -f "$tmpfile"

  interfaces=''
  prefixes=''
  for tface in $INT_IFACE $OTHER_IFACES; do
    interfaces="${interfaces}interface=${tface}\n"

    int_prefix="$(get_prefix $tface)"
    int_dhcp_range="$(echo "$int_prefix" | cut -d '/' -f 1)"

    prefixes="${prefixes}dhcp-range=${int_dhcp_range}, ra-stateless, ra-names\n"
  done

  sed -e "s@__INTERFACES__@$interfaces@g" \
      -e "s@__PREFIXES__@$prefixes@g" $DNSMASQ_TEMPLATE \
      >> $tmpfile

  if ! diff $tmpfile /etc/dnsmasq.conf > /dev/null 2>&1; then
    # Update config and restart radvd
    mv $tmpfile /etc/dnsmasq.conf
    systemctl restart dnsmasq
  else
    rm $tmpfile
    # ensure it's running anyway
    systemctl start dnsmasq
  fi
}

update_radvd() {
  local iface="$1"
  local prefix="$2"

  # the shell we get from dhclient doesn't have [[ ]]
  if ! echo "$prefix" | grep -q '/64$'; then
    # if we got something bigger than a /64, we must just use the
    # first /64 as autoconfig only works in /64s
    net=$(echo "$prefix" | cut -f1 -d/)
    prefix="$net/64"
  fi
  tmpfile="/tmp/radvd.conf.$$"
  rm -f "$tmpfile"
  for tface in $INT_IFACE $OTHER_IFACES; do
    if [ "$iface" = "$tface" ]; then
      sed -e "s@__PREFIX__@$prefix@g" \
          -e "s@__IFACE__@$iface@g" $RADVD_TEMPLATE \
          >> $tmpfile
    else
      tprefix=$(get_prefix $tface)
      if [ -z "$tprefix" ]; then
        continue
      fi
      sed -e "s@__PREFIX__@$tprefix@g" \
          -e "s@__IFACE__@$tface@g" $RADVD_TEMPLATE \
          >> $tmpfile
    fi
  done
  if ! diff $tmpfile /etc/radvd.conf >/dev/null 2>/dev/null; then
    # Update config and restart radvd
    mv $tmpfile /etc/radvd.conf
    service radvd restart
  else
    rm $tmpfile
    # ensure it's running anyway
    service radvd start
  fi
}

ipv6_prefix_setup() {
  local iface
  local current_prefix

  # new_iaid comes from DHCP
  # shellcheck disable=SC2154
  iface=$(get_interface "$new_iaid")
  current_prefix=$(get_prefix "$iface")

  # shellcheck disable=SC2154
  if [ -z "$current_prefix" ] || \
     ! [ "$current_prefix" = "$new_ip6_prefix" ] ; then

    # Setup the new IP
    # Note that no matter what size prefix we were given, you have to make
    # it a /64 for autoconfig to work, so we cut it down to /64
    #
    # TODO for the future - if your ISP gives us bigger than a /54, allow
    # the user to cut it up instead of requesting multiple
    new_ip=$(echo "$new_ip6_prefix" | /bin/sed -E 's@::/([0-9]{2})@::1/64@')
    if [ -n "$current_ip" ] ; then
      ip -6 addr del "$current_ip" dev "$iface"
    fi
    ip -6 addr add "$new_ip" dev "$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"
  fi

  if [ "$RA_DAEMON" = "dnsmasq" ]; then
    update_dnsmasq "$iface" "$new_ip6_prefix"
  else
    update_radvd "$iface" "$new_ip6_prefix"
  fi
}

# interface comes from DHCP
# shellcheck disable=SC2154
if [ "$interface" != "$EXT_IFACE" ] ; then
  return
fi

# reason comes from DHCP
# shellcheck disable=SC2154
case "$reason" in
  BOUND6|REBIND6)
    # We will get called twice here - once for the temp address
    # and once for the prefix. We only care about the prefix.
    if [ -n "$new_ip6_prefix" ] ; then
      ipv6_prefix_setup
    fi
    ;;
  RELEASE)
    ext_iface_pid="/var/run/dhclient6.${EXT_IFACE}.pid"
    if [ -e "$ext_iface_pid" ]; then
      echo "Shutting down dhclient6.${EXT_IFACE} via SIGINT"
      kill "$(cat "$ext_iface_pid")"
    fi
    ;;
esac