#!/bin/bash

test -f /etc/default/6to4 || exit 1
. /etc/default/6to4

test "$DYNDNS" || exit 1
test "$IFACE6" || IFACE6=6to4
test "$HOSTV6" || HOSTV6=1
test "$TTL"    || TTL=128
test "$ROUTER" || ROUTER=192.88.99.1
test "$METRIC" || METRIC=1

test "$MODE" || MODE=$1
test "$MODE" || exit 1

test "$IFACE" || IFACE=eth0

case "$MODE" in
  start)
    ADDRV4=$(host $DYNDNS | awk '/address /{print $4}')
    test "$ADDRV4" || exit
    PREFIX=$(printf '2002:%02x%02x:%02x%02x:' $(echo $ADDRV4 | tr '.' ' '))

    ADDRV4=$(ip -4 addr show dev $IFACE | awk '/inet/{split($2, a, "/"); print a[1]}')
    test "$ADDRV4" || exit

    ADDRV6=$PREFIX:$HOSTV6

    ip tunnel add $IFACE6 mode sit ttl $TTL remote any local $ADDRV4
    ip link set $IFACE6 up
    ip -6 addr add $ADDRV6/16 dev $IFACE6
    ip -6 route add 2000::/3 via ::$ROUTER dev $IFACE6 metric $METRIC
  ;;
  stop)
    ip -6 route flush dev $IFACE6
    ip link set dev $IFACE6 down
    ip tunnel del $IFACE6
  ;;
  *)
    exit 1
  ;;
esac