format_ip6_from_mac(){
  local template=$1
  IFS=':'; set $2; unset IFS
  printf "$template" 0x${3} 0x${4} 0x${5} 0x${6}
}

add_ip6(){
  local interface=$1
  local ip=$2
  local prefixlen=$3
  if has ip; then
    _add_ip_linux "$ip" "$prefixlen" "$interface"
  elif has ifconfig; then
    ifconfig "$interface" inet6 del "$ip" prefixlen "$prefixlen" || true
    ifconfig "$interface" inet6 add "$ip" prefixlen "$prefixlen"
  else
    die "no suitable program found to configure the network interface, need iproute2 or ifconfig"
  fi
}

add_ip4() {
  local interface=$1
  local ip=$2
  local netmask=$3
  if has ip; then
    local cidr="$(mask2cidr $netmask)"
    _add_ip_linux "$ip" "$cidr" "$interface"
  elif has ifconfig; then
    ifconfig "$interface" del "$ip" netmask "$netmask" || true
    ifconfig "$interface" add "$ip" netmask "$netmask"
  else
    die "no suitable program found to set ip address, need iproute2 or ifconfig"
  fi
}

_add_ip_linux() {
  ip addr del "$1/$2" dev "$3" || true
  ip addr add "$1/$2" dev "$3"
}