Setup a VM for testing fake networkmanager environment

[shazow]

Something along the lines of

{
  description = "Wi-Fi Frontend Development MicroVM";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    microvm = {
      url = "github:astro/microvm.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, microvm }:
    let
      system = "x86_64-linux";
    in {
      nixosConfigurations.wifi-vm = nixpkgs.lib.nixosSystem {
        inherit system;
        modules = [
          microvm.nixosModules.microvm
          ({ pkgs, lib, ... }: {
            networking.hostName = "wifi-dev";

            # MicroVM specific configuration
            microvm = {
              hypervisor = "qemu";
              interfaces = [ {
                type = "user";
                id = "qemu";
                mac = "02:00:00:00:00:01";
              } ];
            };

            # Log in as root automatically on the console
            users.users.root.password = "";
            services.getty.autologinUser = "root";

            # Automatically load the fake Wi-Fi kernel module with 2 radios
            boot.kernelModules = [ "mac80211_hwsim" ];
            boot.extraModprobeConfig = ''
              options mac80211_hwsim radios=2
            '';

            # Enable the real NetworkManager
            networking.networkmanager = {
              enable = true;
              # Tell NetworkManager to ignore the QEMU wired interface,
              # as well as the wlan0 interface (and its sub-interfaces) 
              # that we are using to broadcast the fake networks.
              unmanaged = [ "eth0" "wlan0" "wlan0_*" ];
            };

            # Declarative HostAPD configuration
            services.hostapd = {
              enable = true;
              radios.wlan0 = {
                band = "2g";
                channel = 6;
                # Define multiple BSS (Basic Service Sets) on the single radio
                networks = {
                  wlan0 = {
                    ssid = "Airport_Free_WiFi";
                  };
                  wlan0_0 = {
                    ssid = "Home_Network";
                    authentication = {
                      mode = "wpa2-sha1";
                      wpaPassword = "supersecret";
                    };
                  };
                  wlan0_1 = {
                    ssid = "Test_IoT_Device";
                  };
                  wlan0_2 = {
                    ssid = "Secret_Corp_Net";
                    settings = {
                      ignore_broadcast_ssid = "1"; # Hidden network
                    };
                  };
                };
              };
            };

            # Ensure hostapd doesn't try to start before the kernel module 
            # has finished creating the wlan0 virtual device.
            systemd.services."hostapd-wlan0" = {
              after = [ "sys-subsystem-net-devices-wlan0.device" ];
              bindsTo = [ "sys-subsystem-net-devices-wlan0.device" ];
            };
          })
        ];
      };
    };
}

Would be helpful for adding some more robust integration tests for the different linux backends.