config/modules/services/headscale/default.nix

{
  config,
  lib,
  pkgs,
  ...
}: {
  options.mj.services.headscale = with lib.types; {
    enable = lib.mkEnableOption "Enable headscale";
    clientOidcPath = lib.mkOption {type = str;};
    subnetCIDR = lib.mkOption {type = str;};
  };

  config = lib.mkIf config.mj.services.headscale.enable {
    environment.systemPackages = [pkgs.headscale];

    networking.firewall.allowedTCPPorts = [3478];
    networking.firewall.allowedUDPPorts = [3478];

    services = {
      headscale = {
        enable = true;
        settings = {
          server_url = "https://vpn.jakstys.lt";
          ip_prefixes = [config.mj.services.headscale.subnetCIDR];
          log.level = "warn";
          dns_config = {
            nameservers = ["1.1.1.1" "8.8.4.4"];
            magic_dns = false;
            base_domain = "jakst";
          };
          oidc = {
            issuer = "https://git.jakstys.lt/";
            client_id = "e25c15ea-41ca-4bf0-9ebf-2be9f2d1ccea";
            # TODO 23.11 from https://github.com/NixOS/nixpkgs/pull/249101/files
            #client_secret_path = "\${CREDENTIALS_DIRECTORY}/oidc-client-secret";
            client_secret_path = "/run/credentials/headscale.service/oidc-client-secret";
          };
        };
      };

      caddy = {
        virtualHosts."vpn.jakstys.lt".extraConfig = ''
          reverse_proxy 127.0.0.1:8080
        '';
      };
    };

    systemd.services.headscale = {
      unitConfig.StartLimitIntervalSec = "5m";

      # Allow restarts for up to a minute. A start
      # itself may take a while, thus the window of restart
      # is higher.
      unitConfig.StartLimitBurst = 50;
      serviceConfig.RestartSec = 1;
      serviceConfig.LoadCredential = [
        "oidc-client-secret:${config.mj.services.headscale.clientOidcPath}"
      ];
    };
  };
}