#!/bin/bash

if [[ $# -ne 1 ]]; then
  echo "USAGE: $0 <domain>"
  exit 0
else
  domain="$1"
fi

if [[ ! -e /etc/libvirt/qemu/${domain}.xml ]]; then
  echo "Error: ${domain} configuration not found on this system"
  exit 1
fi

macAddress=$(sudo grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}' /etc/libvirt/qemu/${domain}.xml)
# courtesy of https://stackoverflow.com/a/48378567
printf "%02x%s" $(( 16#${macAddress:0:2} ^ 2#00000010 )) "${macAddress:2}" \
 | sed -E -e 's/([0-9a-zA-Z]{2})*/0x\0|/g' \
 | tr -d ':\n' \
 | xargs -d '|' \
 printf "fe80::%02x%02x:%02xff:fe%02x:%02x%02x\n"