239 lines
8.7 KiB
Nix
239 lines
8.7 KiB
Nix
{ config, lib, pkgs, ... }:
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let
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inherit (lib) mkIf mkOption;
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inherit (lib.types) nullOr path bool listOf str;
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keysPath = "/var/lib/yggdrasil/keys.json";
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cfg = config.services.yggdrasil;
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settingsProvided = cfg.settings != { };
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configFileProvided = cfg.configFile != null;
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format = pkgs.formats.json { };
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in
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{
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imports = [
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(lib.mkRenamedOptionModule
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[ "services" "yggdrasil" "config" ]
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[ "services" "yggdrasil" "settings" ])
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];
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options = {
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services.yggdrasil = {
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enable = lib.mkEnableOption "the yggdrasil system service";
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settings = mkOption {
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type = format.type;
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default = { };
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example = {
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Peers = [
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"tcp://aa.bb.cc.dd:eeeee"
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"tcp://[aaaa:bbbb:cccc:dddd::eeee]:fffff"
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];
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Listen = [
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"tcp://0.0.0.0:xxxxx"
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];
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};
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description = ''
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Configuration for yggdrasil, as a Nix attribute set.
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Warning: this is stored in the WORLD-READABLE Nix store!
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Therefore, it is not appropriate for private keys. If you
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wish to specify the keys, use {option}`configFile`.
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If the {option}`persistentKeys` is enabled then the
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keys that are generated during activation will override
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those in {option}`settings` or
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{option}`configFile`.
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If no keys are specified then ephemeral keys are generated
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and the Yggdrasil interface will have a random IPv6 address
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each time the service is started. This is the default.
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If both {option}`configFile` and {option}`settings`
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are supplied, they will be combined, with values from
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{option}`configFile` taking precedence.
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You can use the command `nix-shell -p yggdrasil --run "yggdrasil -genconf"`
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to generate default configuration values with documentation.
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'';
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};
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configFile = mkOption {
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type = nullOr path;
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default = null;
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example = "/run/keys/yggdrasil.conf";
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description = ''
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A file which contains JSON or HJSON configuration for yggdrasil. See
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the {option}`settings` option for more information.
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Note: This file must not be larger than 1 MB because it is passed to
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the yggdrasil process via systemd‘s LoadCredential mechanism. For
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details, see <https://systemd.io/CREDENTIALS/> and `man 5
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systemd.exec`.
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'';
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};
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group = mkOption {
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type = nullOr str;
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default = null;
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example = "wheel";
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description = "Group to grant access to the Yggdrasil control socket. If `null`, only root can access the socket.";
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};
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openMulticastPort = mkOption {
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type = bool;
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default = false;
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description = ''
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Whether to open the UDP port used for multicast peer discovery. The
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NixOS firewall blocks link-local communication, so in order to make
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incoming local peering work you will also need to configure
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`MulticastInterfaces` in your Yggdrasil configuration
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({option}`settings` or {option}`configFile`). You will then have to
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add the ports that you configure there to your firewall configuration
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({option}`networking.firewall.allowedTCPPorts` or
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{option}`networking.firewall.interfaces.<name>.allowedTCPPorts`).
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'';
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};
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denyDhcpcdInterfaces = mkOption {
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type = listOf str;
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default = [ ];
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example = [ "tap*" ];
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description = ''
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Disable the DHCP client for any interface whose name matches
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any of the shell glob patterns in this list. Use this
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option to prevent the DHCP client from broadcasting requests
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on the yggdrasil network. It is only necessary to do so
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when yggdrasil is running in TAP mode, because TUN
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interfaces do not support broadcasting.
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'';
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};
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package = lib.mkPackageOption pkgs "yggdrasil" { };
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persistentKeys = lib.mkEnableOption ''
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persistent keys. If enabled then keys will be generated once and Yggdrasil
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will retain the same IPv6 address when the service is
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restarted. Keys are stored at ${keysPath}
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'';
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extraArgs = mkOption {
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type = listOf str;
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default = [ ];
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example = [ "-loglevel" "info" ];
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description = "Extra command line arguments.";
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};
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};
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};
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config = mkIf cfg.enable (
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let
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binYggdrasil = "${cfg.package}/bin/yggdrasil";
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binHjson = "${pkgs.hjson-go}/bin/hjson-cli";
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in
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{
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assertions = [{
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assertion = config.networking.enableIPv6;
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message = "networking.enableIPv6 must be true for yggdrasil to work";
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}];
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# This needs to be a separate service. The yggdrasil service fails if
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# this is put into its preStart.
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systemd.services.yggdrasil-persistent-keys = lib.mkIf cfg.persistentKeys {
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wantedBy = [ "multi-user.target" ];
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before = [ "yggdrasil.service" ];
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serviceConfig.Type = "oneshot";
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serviceConfig.RemainAfterExit = true;
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script = ''
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if [ ! -e ${keysPath} ]
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then
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mkdir --mode=700 -p ${builtins.dirOf keysPath}
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${binYggdrasil} -genconf -json \
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| ${pkgs.jq}/bin/jq \
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'to_entries|map(select(.key|endswith("Key")))|from_entries' \
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> ${keysPath}
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fi
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'';
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};
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systemd.services.yggdrasil = {
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description = "Yggdrasil Network Service";
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after = [ "network-pre.target" ];
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wants = [ "network.target" ];
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before = [ "network.target" ];
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wantedBy = [ "multi-user.target" ];
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# This script first prepares the config file, then it starts Yggdrasil.
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# The preparation could also be done in ExecStartPre/preStart but only
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# systemd versions >= v252 support reading credentials in ExecStartPre. As
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# of February 2023, systemd v252 is not yet in the stable branch of NixOS.
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#
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# This could be changed in the future once systemd version v252 has
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# reached NixOS but it does not have to be. Config file preparation is
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# fast enough, it does not need elevated privileges, and `set -euo
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# pipefail` should make sure that the service is not started if the
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# preparation fails. Therefore, it is not necessary to move the
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# preparation to ExecStartPre.
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script = ''
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set -euo pipefail
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# prepare config file
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${(if settingsProvided || configFileProvided || cfg.persistentKeys then
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"echo "
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+ (lib.optionalString settingsProvided
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"'${builtins.toJSON cfg.settings}'")
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+ (lib.optionalString configFileProvided
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"$(${binHjson} -c \"$CREDENTIALS_DIRECTORY/yggdrasil.conf\")")
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+ (lib.optionalString cfg.persistentKeys "$(cat ${keysPath})")
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+ " | ${pkgs.jq}/bin/jq -s add | ${binYggdrasil} -normaliseconf -useconf"
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else
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"${binYggdrasil} -genconf") + " > /run/yggdrasil/yggdrasil.conf"}
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# start yggdrasil
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${binYggdrasil} -useconffile /run/yggdrasil/yggdrasil.conf ${lib.strings.escapeShellArgs cfg.extraArgs}
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'';
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serviceConfig = {
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ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
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Restart = "always";
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DynamicUser = true;
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StateDirectory = "yggdrasil";
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RuntimeDirectory = "yggdrasil";
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RuntimeDirectoryMode = "0750";
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BindReadOnlyPaths = lib.optional cfg.persistentKeys keysPath;
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LoadCredential =
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mkIf configFileProvided "yggdrasil.conf:${cfg.configFile}";
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AmbientCapabilities = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE";
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CapabilityBoundingSet = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE";
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MemoryDenyWriteExecute = true;
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ProtectControlGroups = true;
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ProtectHome = "tmpfs";
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ProtectKernelModules = true;
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ProtectKernelTunables = true;
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RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6 AF_NETLINK";
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RestrictNamespaces = true;
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RestrictRealtime = true;
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SystemCallArchitectures = "native";
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SystemCallFilter = [ "@system-service" "~@privileged @keyring" ];
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} // (if (cfg.group != null) then {
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Group = cfg.group;
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} else { });
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};
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networking.dhcpcd.denyInterfaces = cfg.denyDhcpcdInterfaces;
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networking.firewall.allowedUDPPorts = mkIf cfg.openMulticastPort [ 9001 ];
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# Make yggdrasilctl available on the command line.
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environment.systemPackages = [ cfg.package ];
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}
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);
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meta = {
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doc = ./yggdrasil.md;
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maintainers = with lib.maintainers; [ gazally ehmry nagy ];
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};
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}
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