#! /bin/sh -e

action=$1; shift

read n < ip.txt

if grep -q ipv4 /proc/cmdline; then
    # IPv4
    IP="10.0.0.$n/16"
else
    # IPv6
    l=$(busybox dc 16 o $n p)
    IP="fd84:b410:3441::$l/64"
fi



[ "$action" ] && ip addr $action $IP dev eth0

if [ "$action" = "add" ]; then
    fail=fail
    for i in $(seq 5); do
        if ip addr | grep -v tentative | grep -Fq $IP; then
            fail=
            break
        fi
        sleep 1
    done
    [ "$fail" ] && return 1
fi

[ "$action" = del ] || echo $IP