# set up an ipv6 tunnel
emulate -L zsh

case $1 in
start)
    if ifconfig sit1 2>/dev/null | grep -q 'inet6 addr: 2002:.*:1::1' ; then
        print 'ipv6 tunnel already set up, nothing to be done.'
        print 'execute: "ifconfig sit1 down ; ifconfig sit0 down" to remove ipv6-tunnel.' ; return 1
    else
        [[ -n "$PUBLIC_IP" ]] || \
            local PUBLIC_IP=$(ifconfig $(route -n | awk '/^0\.0\.0\.0/{print $8; exit}') | \
            awk '/inet addr:/ {print $2}' | tr -d 'addr:')

        [[ -n "$PUBLIC_IP" ]] || {
            print 'No $PUBLIC_IP set and could not determine default one.'
            return 1
        }
        local IPV6ADDR=$(printf "2002:%02x%02x:%02x%02x:1::1" $(print ${PUBLIC_IP//./ }))
        print -n "Setting up ipv6 tunnel $IPV6ADDR via ${PUBLIC_IP}: "
        ifconfig sit0 tunnel ::192.88.99.1 up
        ifconfig sit1 add "$IPV6ADDR" && print done || print failed
    fi
    ;;
status)
    if ifconfig sit1 2>/dev/null | grep -q 'inet6 addr: 2002:.*:1::1' ; then
        print 'ipv6 tunnel available' ; return 0
    else
        print 'ipv6 tunnel not available' ; return 1
    fi
    ;;
stop)
    if ifconfig sit1 2>/dev/null | grep -q 'inet6 addr: 2002:.*:1::1' ; then
        print -n 'Stopping ipv6 tunnel (sit0 + sit1): '
        ifconfig sit1 down ; ifconfig sit0 down && print done || print failed
    else
        print 'No ipv6 tunnel found, nothing to be done.' ; return 1
    fi
    ;;
*)
    print "Usage: ipv6-tunnel [start|stop|status]">&2 ; return 1
    ;;
esac