nixos/mchprs: init module

Co-authored-by: Ryan Lahfa <[e-mail]>

nixos/doc/manual/release-notes/rl-2311.section.md

···
 
 ## New Services {#sec-release-23.11-new-services}
 
-- Create the first release note entry in this section!
+- [MCHPRS](https://github.com/MCHPR/MCHPRS), a multithreaded Minecraft server built for redstone. Available as [services.mchprs](#opt-services.mchprs.enable).
 
 - [acme-dns](https://github.com/joohoi/acme-dns), a limited DNS server to handle ACME DNS challenges easily and securely. Available as [services.acme-dns](#opt-services.acme-dns.enable).
 

nixos/modules/module-list.nix

···
   ./services/games/deliantra-server.nix
   ./services/games/factorio.nix
   ./services/games/freeciv.nix
+  ./services/games/mchprs.nix
   ./services/games/minecraft-server.nix
   ./services/games/minetest-server.nix
   ./services/games/openarena.nix

nixos/modules/services/games/mchprs.nix

···
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.mchprs;
+  settingsFormat = pkgs.formats.toml { };
+
+  whitelistFile = pkgs.writeText "whitelist.json"
+    (builtins.toJSON
+      (mapAttrsToList (n: v: { name = n; uuid = v; }) cfg.whitelist.list));
+
+  configToml =
+    (removeAttrs cfg.settings [ "address" "port" ]) //
+    {
+      bind_address = cfg.settings.address + ":" + toString cfg.settings.port;
+      whitelist = cfg.whitelist.enable;
+    };
+
+  configTomlFile = settingsFormat.generate "Config.toml" configToml;
+in
+{
+  options = {
+    services.mchprs = {
+      enable = mkEnableOption "MCHPRS";
+
+      declarativeSettings = mkOption {
+        type = types.bool;
+        default = false;
+        description = mdDoc ''
+          Whether to use a declarative configuration for MCHPRS.
+        '';
+      };
+
+      declarativeWhitelist = mkOption {
+        type = types.bool;
+        default = false;
+        description = mdDoc ''
+          Whether to use a declarative whitelist.
+          The options {option}`services.mchprs.whitelist.list`
+          will be applied if and only if set to `true`.
+        '';
+      };
+
+      dataDir = mkOption {
+        type = types.path;
+        default = "/var/lib/mchprs";
+        description = mdDoc ''
+          Directory to store MCHPRS database and other state/data files.
+        '';
+      };
+
+      openFirewall = mkOption {
+        type = types.bool;
+        default = false;
+        description = mdDoc ''
+          Whether to open ports in the firewall for the server.
+          Only has effect when
+          {option}`services.mchprs.declarativeSettings` is `true`.
+        '';
+      };
+
+      maxRuntime = mkOption {
+        type = types.str;
+        default = "infinity";
+        example = "7d";
+        description = mdDoc ''
+          Automatically restart the server after
+          {option}`services.mchprs.maxRuntime`.
+          The time span format is described here:
+          https://www.freedesktop.org/software/systemd/man/systemd.time.html#Parsing%20Time%20Spans.
+          If `null`, then the server is not restarted automatically.
+        '';
+      };
+
+      package = mkOption {
+        type = types.package;
+        default = pkgs.mchprs;
+        defaultText = literalExpression "pkgs.mchprs";
+        description = mdDoc "Version of MCHPRS to run.";
+      };
+
+      settings = mkOption {
+        type = types.submodule {
+          freeformType = settingsFormat.type;
+
+          options = {
+            port = mkOption {
+              type = types.port;
+              default = 25565;
+              description = mdDoc ''
+                Port for the server.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            address = mkOption {
+              type = types.str;
+              default = "0.0.0.0";
+              description = mdDoc ''
+                Address for the server.
+                Please use enclosing square brackets when using ipv6.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            motd = mkOption {
+              type = types.str;
+              default = "Minecraft High Performance Redstone Server";
+              description = mdDoc ''
+                Message of the day.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            chat_format = mkOption {
+              type = types.str;
+              default = "<{username}> {message}";
+              description = mdDoc ''
+                How to format chat message interpolating `username`
+                and `message` with curly braces.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            max_players = mkOption {
+              type = types.ints.positive;
+              default = 99999;
+              description = mdDoc ''
+                Maximum number of simultaneous players.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            view_distance = mkOption {
+              type = types.ints.positive;
+              default = 8;
+              description = mdDoc ''
+                Maximal distance (in chunks) between players and loaded chunks.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            bungeecord = mkOption {
+              type = types.bool;
+              default = false;
+              description = mdDoc ''
+                Enable compatibility with
+                [BungeeCord](https://github.com/SpigotMC/BungeeCord).
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            schemati = mkOption {
+              type = types.bool;
+              default = false;
+              description = mdDoc ''
+                Mimic the verification and directory layout used by the
+                Open Redstone Engineers
+                [Schemati plugin](https://github.com/OpenRedstoneEngineers/Schemati).
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            block_in_hitbox = mkOption {
+              type = types.bool;
+              default = true;
+              description = mdDoc ''
+                Allow placing blocks inside of players
+                (hitbox logic is simplified).
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+
+            auto_redpiler = mkOption {
+              type = types.bool;
+              default = true;
+              description = mdDoc ''
+                Use redpiler automatically.
+                Only has effect when
+                {option}`services.mchprs.declarativeSettings` is `true`.
+              '';
+            };
+          };
+        };
+        default = { };
+
+        description = mdDoc ''
+          Configuration for MCHPRS via `Config.toml`.
+          See https://github.com/MCHPR/MCHPRS/blob/master/README.md for documentation.
+        '';
+      };
+
+      whitelist = {
+        enable = mkOption {
+          type = types.bool;
+          default = false;
+          description = mdDoc ''
+            Whether or not the whitelist (in `whitelist.json`) shoud be enabled.
+            Only has effect when {option}`services.mchprs.declarativeSettings` is `true`.
+          '';
+        };
+
+        list = mkOption {
+          type =
+            let
+              minecraftUUID = types.strMatching
+                "[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}" // {
+                description = "Minecraft UUID";
+              };
+            in
+            types.attrsOf minecraftUUID;
+          default = { };
+          example = literalExpression ''
+            {
+              username1 = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";
+              username2 = "yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy";
+            };
+          '';
+          description = mdDoc ''
+            Whitelisted players, only has an effect when
+            {option}`services.mchprs.declarativeWhitelist` is
+            `true` and the whitelist is enabled
+            via {option}`services.mchprs.whitelist.enable`.
+            This is a mapping from Minecraft usernames to UUIDs.
+            You can use <https://mcuuid.net/> to get a
+            Minecraft UUID for a username.
+          '';
+        };
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    users.users.mchprs = {
+      description = "MCHPRS service user";
+      home = cfg.dataDir;
+      createHome = true;
+      isSystemUser = true;
+      group = "mchprs";
+    };
+    users.groups.mchprs = { };
+
+    systemd.services.mchprs = {
+      description = "MCHPRS Service";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      serviceConfig = {
+        ExecStart = "${lib.getExe cfg.package}";
+        Restart = "always";
+        RuntimeMaxSec = cfg.maxRuntime;
+        User = "mchprs";
+        WorkingDirectory = cfg.dataDir;
+
+        StandardOutput = "journal";
+        StandardError = "journal";
+
+        # Hardening
+        CapabilityBoundingSet = [ "" ];
+        DeviceAllow = [ "" ];
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        PrivateDevices = true;
+        PrivateTmp = true;
+        PrivateUsers = true;
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "invisible";
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        UMask = "0077";
+      };
+
+      preStart =
+        (if cfg.declarativeSettings then ''
+          if [ -e .declarativeSettings ]; then
+
+            # Settings were declarative before, no need to back up anything
+            cp -f ${configTomlFile} Config.toml
+
+          else
+
+            # Declarative settings for the first time, backup stateful files
+            cp -b --suffix=.stateful ${configTomlFile} Config.toml
+
+            echo "Autogenerated file that implies that this server configuration is managed declaratively by NixOS" \
+              > .declarativeSettings
+
+          fi
+        '' else ''
+          if [ -e .declarativeSettings ]; then
+            rm .declarativeSettings
+          fi
+        '') + (if cfg.declarativeWhitelist then ''
+          if [ -e .declarativeWhitelist ]; then
+
+            # Whitelist was declarative before, no need to back up anything
+            ln -sf ${whitelistFile} whitelist.json
+
+          else
+
+            # Declarative whitelist for the first time, backup stateful files
+            ln -sb --suffix=.stateful ${whitelistFile} whitelist.json
+
+            echo "Autogenerated file that implies that this server's whitelist is managed declaratively by NixOS" \
+              > .declarativeWhitelist
+
+          fi
+        '' else ''
+          if [ -e .declarativeWhitelist ]; then
+            rm .declarativeWhitelist
+          fi
+        '');
+    };
+
+    networking.firewall = mkIf (cfg.declarativeSettings && cfg.openFirewall) {
+      allowedUDPPorts = [ cfg.settings.port ];
+      allowedTCPPorts = [ cfg.settings.port ];
+    };
+  };
+
+  meta.maintainers = with maintainers; [ gdd ];
+}