nixos/vwifi: init module

This module does not currently have its own test suite: it is intended
to be used in test suites for other modules that use wifi.

nixos/modules/module-list.nix

@@ -1352,6 +1352,7 @@
   ./services/networking/veilid.nix
   ./services/networking/vdirsyncer.nix
   ./services/networking/vsftpd.nix
+  ./services/networking/vwifi.nix
   ./services/networking/wasabibackend.nix
   ./services/networking/websockify.nix
   ./services/networking/wg-access-server.nix

nixos/modules/services/networking/vwifi.nix

@@ -0,0 +1,200 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib.modules) mkIf mkMerge;
+  inherit (lib.options) mkOption mkPackageOption mkEnableOption;
+  inherit (lib.lists) optional optionals;
+  inherit (lib.strings)
+    hasSuffix
+    escapeShellArgs
+    ;
+  inherit (lib) types;
+  cfg = config.services.vwifi;
+in
+{
+  options = {
+    services.vwifi =
+      let
+        mkOptionalPort =
+          name:
+          mkOption {
+            description = ''
+              The ${name} port. Set to null if we should leave it unset.
+            '';
+            type = with types; nullOr port;
+            default = null;
+          };
+      in
+      {
+        package = mkPackageOption pkgs "vwifi" { };
+        module = {
+          enable = mkEnableOption "mac80211_hwsim module";
+          numRadios = mkOption {
+            description = "The number of virtual radio interfaces to create.";
+            type = types.int;
+            default = 1;
+          };
+          macPrefix = mkOption {
+            description = ''
+              The prefix for MAC addresses to use, without the trailing ':'.
+              If one radio is created, you can specify the whole MAC address here.
+              The default is defined in vwifi/src/config.h.
+            '';
+            type = types.strMatching "^(([0-9A-Fa-f]{2}:){0,5}[0-9A-Fa-f]{2})$";
+            default = "74:F8:F6";
+          };
+        };
+        client = {
+          enable = mkEnableOption "vwifi client";
+          spy = mkEnableOption "spy mode, useful for wireless monitors";
+          serverAddress = mkOption {
+            description = ''
+              The address of the server. If set to null, will try to use the vsock protocol.
+              Note that this assumes that the server is spawned on the host and passed through to
+              QEMU, with something like:
+
+              -device vhost-vsock-pci,id=vwifi0,guest-cid=42
+            '';
+            type = with types; nullOr str;
+            default = null;
+          };
+          serverPort = mkOptionalPort "server port";
+          extraArgs = mkOption {
+            description = ''
+              Extra arguments to pass to vwifi-client. You can use this if you want to bring
+              the radios up using vwifi-client instead of at boot.
+            '';
+            type = with types; listOf str;
+            default = [ ];
+            example = [
+              "--number"
+              "3"
+            ];
+          };
+        };
+        server = {
+          enable = mkEnableOption "vwifi server";
+          vsock.enable = mkEnableOption "vsock kernel module";
+          ports = {
+            vhost = mkOptionalPort "vhost";
+            tcp = mkOptionalPort "TCP server";
+            spy = mkOptionalPort "spy interface";
+            control = mkOptionalPort "control interface";
+          };
+          openFirewall = mkEnableOption "opening the firewall for the TCP and spy ports";
+          extraArgs = mkOption {
+            description = ''
+              Extra arguments to pass to vwifi-server. You can use this for things including
+              changing the ports or inducing packet loss.
+            '';
+            type = with types; listOf str;
+            default = [ ];
+            example = [ "--lost-packets" ];
+          };
+        };
+      };
+  };
+
+  config = mkMerge [
+    (mkIf cfg.module.enable {
+      boot.kernelModules = [
+        "mac80211_hwsim"
+      ];
+      boot.extraModprobeConfig = ''
+        # We'll add more radios using vwifi-add-interfaces in the systemd unit.
+        options mac80211_hwsim radios=0
+      '';
+      systemd.services.vwifi-add-interfaces = mkIf (cfg.module.numRadios > 0) {
+        description = "vwifi interface bringup";
+        wantedBy = [ "network-pre.target" ];
+        serviceConfig = {
+          Type = "oneshot";
+          ExecStart =
+            let
+              args = [
+                (toString cfg.module.numRadios)
+                cfg.module.macPrefix
+              ];
+            in
+            "${cfg.package}/bin/vwifi-add-interfaces ${escapeShellArgs args}";
+        };
+      };
+      assertions = [
+        {
+          assertion = !(hasSuffix ":" cfg.module.macPrefix);
+          message = ''
+            services.vwifi.module.macPrefix should not have a trailing ":".
+          '';
+        }
+      ];
+    })
+    (mkIf cfg.client.enable {
+      systemd.services.vwifi-client =
+        let
+          clientArgs =
+            optional cfg.client.spy "--spy"
+            ++ optional (cfg.client.serverAddress != null) cfg.client.serverAddress
+            ++ optionals (cfg.client.serverPort != null) [
+              "--port"
+              cfg.client.serverPort
+            ]
+            ++ cfg.client.extraArgs;
+        in
+        rec {
+          description = "vwifi client";
+          wantedBy = [ "multi-user.target" ];
+          after = [ "network.target" ];
+          requires = after;
+          serviceConfig = {
+            ExecStart = "${cfg.package}/bin/vwifi-client ${escapeShellArgs clientArgs}";
+          };
+        };
+    })
+    (mkIf cfg.server.enable {
+      boot.kernelModules = mkIf cfg.server.vsock.enable [
+        "vhost_vsock"
+      ];
+      networking.firewall.allowedTCPPorts = mkIf cfg.server.openFirewall (
+        optional (cfg.server.ports.tcp != null) cfg.server.ports.tcp
+        ++ optional (cfg.server.ports.spy != null) cfg.server.ports.spy
+      );
+      systemd.services.vwifi-server =
+        let
+          serverArgs =
+            optionals (cfg.server.ports.vhost != null) [
+              "--port-vhost"
+              (toString cfg.server.ports.vhost)
+            ]
+            ++ optionals (cfg.server.ports.tcp != null) [
+              "--port-tcp"
+              (toString cfg.server.ports.tcp)
+            ]
+            ++ optionals (cfg.server.ports.spy != null) [
+              "--port-spy"
+              (toString cfg.server.ports.spy)
+            ]
+            ++ optionals (cfg.server.ports.control != null) [
+              "--port-ctrl"
+              (toString cfg.server.ports.control)
+            ]
+            ++ cfg.server.extraArgs;
+        in
+        rec {
+          description = "vwifi server";
+          wantedBy = [ "multi-user.target" ];
+          after = [ "network.target" ];
+          requires = after;
+          serviceConfig = {
+            ExecStart = "${cfg.package}/bin/vwifi-server ${escapeShellArgs serverArgs}";
+          };
+        };
+    })
+  ];
+
+  meta.maintainers = with lib.maintainers; [ numinit ];
+}