#!/bin/sh -e

dev="wlan0"

prefix="$(ip link show "$dev" | awk '/link\/ether/ {print substr($2, 0, 8)}')"
suffix="$(hexdump -n3 -e'3/1 "%02x:""\n"' /dev/urandom | cut -d: -f1-3)"
address="$prefix:$suffix"

ip link set "$dev" down
ip link set "$dev" address "$address"
ip link set "$dev" up