#!/bin/bash
# sets the IPv6 routes correctly
# from the 6to4 tunnel

# the 6to4 tunnel interface
SITDEV="sit0"
# LAN interface
LANDEV="eth0"
# our private subnet suffix (without the first 48 bits)
PRIV="1111::/64"

# 6to4 addresses start with 2002: and give us a complete /48 subnet
# For LANDEV we use a /64 PRIV subnet out of this one.

# Our current tunnel 6to4 IP (2002:xxxx:yyyy::1/16)
# where xxxx:yyyy is our IPv4 IP
IP6=$(ip addr show dev ${SITDEV} scope global to 2002::/8 | awk '$1=="inet6" { print $2; }')
if [ -z "${IP6}" ]; then
        # no IP
        exit;
fi
# the /48 subnet (2002:xxxx:yyyy:)
NET48="${IP6:0:15}"
# our route prefix (2002:xxxx:yyyy:PRIV)
PREFIX="${NET48}${PRIV}"

# Current route (2002:xxxx:yyyy:SUBNET::/64)
CUR_ROUTE=$(ip -6 route list dev ${LANDEV} | awk '$1~/^2002:/ { print $1; }' )
if [ "${CUR_ROUTE:0:15}" = "${NET48}" ]; then
        # the route is uptodate
        exit;
elif [ ! -z "${CUR_ROUTE}" ]; then
        # route is outdated
        ip -6 route del "${CUR_ROUTE}"
fi
ip -6 route add "${PREFIX}" dev "${LANDEV}"