nix/hosts/common/configs/system/networking/options.nix

{ lib, ... }:
{
  options.networking =
    with lib;
    with types;
    {
      publicIPv4 = mkOption {
        type = nullOr str;
        description = "The public IPv4 address of this device.";
      };

      publicIPv6 = mkOption {
        type = nullOr str;
        description = "The public IPv6 address of this device.";
      };
    };
}