anchor.diff:      "pre-down" = "pre-down.d/";
     };
   
  +  macAddressOpt = mkOption {
  +    type = types.either types.str (types.enum ["permanent" "preserve" "random" "stable"]);
  +    default = "preserve";
  +    example = "00:11:22:33:44:55";
  +    description = ''
  +      "XX:XX:XX:XX:XX:XX": MAC address of the interface.
  +      <literal>permanent</literal>: use the permanent MAC address of the device.
  +      <literal>preserve</literal>: don’t change the MAC address of the device upon activation.
  +      <literal>random</literal>: generate a randomized value upon each connect.
  +      <literal>stable</literal>: generate a stable, hashed MAC address.
  +    '';
  +  };
  +
   in {
   
     ###### interface
  
positive.code: 
      systemd.services."network-manager" = {
        wantedBy = [ "network.target" ];
  
        preStart = ''
          mkdir -m 700 -p /etc/NetworkManager/system-connections
  
negative.code: 
      [connection]
      ipv6.ip6-privacy=2
      ethernet.cloned-mac-address=${cfg.ethernet.macAddress}
      wifi.cloned-mac-address=${cfg.wifi.macAddress}
    '';
  
    /*
  