#!/bin/sh

# $1 what to watch
# $2 what should be

while true; do
    IF=`ip addr show $1`
    if [ -z "$IF" ]; then
        echo "No $1"
    else
        sleep 10
        echo "Rename $1 to $2"
        ip link set $1 down
        ip link set $1 name $2
        ip link set $2 up
        if [ -z "$3" ]; then
            echo "No need to replace default"
        else
            ip route add default via $3 dev $2
        fi
    fi
    sleep 2
done