anchor.diff:        # (Xen) and virbr* and vnet* (libvirt).
         denyinterfaces ${toString ignoredInterfaces} lo peth* vif* tap* tun* virbr* vnet* vboxnet*
   
  -      ${config.networking.dhcpcd.extraConfig}
  +      # Use the list of allowed interfaces if specified
  +      ${optionalString (cfg.allowInterfaces != [ ]) "allowinterfaces ${toString cfg.allowInterfaces}"}
  +
  +      ${cfg.extraConfig}
       '';
   
     # Hook for emitting ip-up/ip-down events.
  
positive.code:          any of the shell glob patterns in this list. The purpose of
           this option is to blacklist virtual interfaces such as those
           created by Xen, libvirt, LXC, etc.
        '';
      };
  
  
negative.code: let
  
    dhcpcd = if !config.boot.isContainer then pkgs.dhcpcd else pkgs.dhcpcd.override { udev = null; };
  
    cfg = config.networking.dhcpcd;
  
    # Don't start dhcpcd on explicitly configured interfaces or on
    # interfaces that are part of a bridge.
  