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path: root/sys/boot/pxe.nix
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{
  config,
  lib,
  ...
}:
with lib; let
  cfg = config.local.boot.pxe;
in {
  options.local.boot.pxe = {
    enable = mkEnableOption "PXE netboot";

    setupMode = mkOption {
      type = types.bool;
      default = false;
    };

    initrdInterface = mkOption {
      type = types.str;
    };

    linkLocal6 = mkOption {
      type = types.str;
    };

    networkDriver = mkOption {
      type = types.str;
    };

    mac = mkOption {
      type = types.str;
    };

    panicTimeout = mkOption {
      type = types.nullOr types.ints.u16;
      default = 30;
    };
  };

  # Based on nixpkgs/nixos/modules/installer/netboot/netboot.nix
  config = mkIf cfg.enable {
    boot = {
      initrd = {
        kernelModules = [cfg.networkDriver];

        network = {
          enable = true;
          flushBeforeStage2 = true;
          ssh = {
            enable = true;
            ignoreEmptyHostKeys = true;
          };
        };

        preFailCommands = mkIf (!cfg.setupMode) ''
          echo "init stage1 failed in unattended mode, rebooting"
          reboot -f
        '';

        postResumeCommands = ''
          store_img_dir="/nix/.ro-store-img"
          store_img="$store_img_dir/nix-store.squashfs"

          mkdir -p "$store_img_dir"
          mount -t tmpfs -o mode=0700,nr_inodes=2,huge=within_size,nodev,nosuid tmpfs "$store_img_dir"

          ip link set up ${cfg.initrdInterface}
          ip addr add ${cfg.linkLocal6}/64 dev ${cfg.initrdInterface}

          recv_init_timeout=120
          echo -n "Waiting up to ''${recv_init_timeout}s for $store_img"

          t="$recv_init_timeout"
          while true; do
              echo -n . | nc -u -w1 -s ${cfg.linkLocal6}%${cfg.initrdInterface} fe80::b007:b007%${cfg.initrdInterface} 1792 >/dev/null 2>&1 &

              if [ -e "$store_img.tmp" ]; then
                  kill -x nc
                  break
              elif [ "$t" -le 0 ]; then
                  echo "timed out"
                  fail
              fi

              # sleep builtin de ash retorna cuando nc termina (lo cual puede pasar muchas veces debido a IPv6 DAD)
              /bin/sleep 1
              echo -n .
              t=$((t - 1))
          done

          recv_poll=60
          recv_timeout=1800

          t=0
          last_mtime=""
          poll_time="$recv_poll"
          while true; do
              if [ -e "$store_img" ]; then
                  break
              elif [ "$t" -ge "$recv_timeout" ]; then
                  echo "Store image upload timed out"
                  fail
              fi

              sleep 1
              t=$((t + 1))
              poll_time=$((poll_time - 1))

              if [ "$poll_time" -le 0 ]; then
                  current_size=$(stat -c '%s' "$store_img.tmp" || echo -)
                  current_mtime=$(stat -c '%y' "$store_img.tmp" || echo final)
                  echo "Store upload: $current_mtime: $current_size bytes"

                  if [ "$current_mtime" = "$last_mtime" ]; then
                      echo "Store image upload stalled, image not modified in ''${recv_poll}s"
                      fail
                  fi

                  last_mtime="$current_mtime"
                  poll_time="$recv_poll"
              fi
          done

          sleep 1
          kill -x sshd

          chmod 0500 "$store_img_dir"
          chmod 0400 "$store_img"
          chattr +i "$store_img"
          mount -o remount,ro "$store_img_dir"

          store_size=$(stat -c '%s' "$store_img")
          echo "Store image upload complete, final size is $store_size bytes"

          ln -sf "$store_img" /dev/nix-store
        '';

        postMountCommands = ''
          mkdir -p "/mnt-root$store_img_dir"
          mount --move "$store_img_dir" "/mnt-root$store_img_dir"
        '';
      };

      kernelParams =
        optional (cfg.panicTimeout != null) "panic=${toString cfg.panicTimeout}"
        ++ optional cfg.setupMode "boot.shell_on_fail";
    };

    fileSystems = {
      "/" = {
        fsType = "tmpfs";
        neededForBoot = true;

        options = ["mode=0755"];
      };

      "/nix/store" = {
        fsType = "overlay";
        neededForBoot = true;

        overlay = {
          lowerdir = ["/nix/.ro-store"];
          upperdir = "/nix/.rw-store/store";
          workdir = "/nix/.rw-store/work";
        };
      };

      "/nix/.ro-store" = {
        fsType = "squashfs";
        neededForBoot = true;

        device = "/dev/nix-store";
        options = ["loop" "threads=multi"];
      };

      "/nix/.rw-store" = {
        fsType = "tmpfs";
        neededForBoot = true;

        options = ["mode=0755"];
      };
    };

    local = {
      boot.loader = "out-of-band";
    };
  };
}