homelab/hosts/neptun/configuration.nix

{ config, pkgs, lib, ... }:

# netcup VPS (UEFI, /dev/vda). Public reverse proxy + tailnet node.
{
  imports = [
    ./hardware-configuration.nix
    ./disk-config.nix          # disko: vda partitions + filesystems
    ./secrets.nix              # sops-nix: tailscale authkey
    ../../common.nix              # shared base: user / ssh / nix / firewall
    ../../services/network/caddy.nix
    ../../services/vpn/tailscale.nix
    ../../services/identity/authentik.nix
    ../../services/vpn/headscale.nix
    ../../services/vpn/headplane.nix
  ];

  # ---- Boot (UEFI) ----
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;
  # Root is on the virtio disk — pin these so stage-1 mounts it regardless of
  # what nixos-generate-config detects in the installer.
  boot.initrd.availableKernelModules = [ "virtio_pci" "virtio_blk" "virtio_scsi" ];

  networking.hostName = "neptun";

  # 8 GB and no swap device (netcup gives one disk, disko takes all of it for
  # root). authentik's server + worker + postgres are the memory-hungry part;
  # zram is enough headroom at this size and costs no disk.
  zramSwap.enable = true;

  # ---- Static networking (netcup) ----
  # No LAN fallback: get this right or the box is unreachable (use netcup's
  # VNC console / rescue system to fix). Values captured from the running VPS.
  networking.useDHCP = false;
  networking.usePredictableInterfaceNames = false;   # keep the NIC named eth0
  networking.interfaces.eth0 = {
    ipv4.addresses = [ { address = "159.195.64.117"; prefixLength = 22; } ];
    ipv6.addresses = [ { address = "2a0a:4cc0:c2:19e1:44b4:8dff:fe4d:c7d7"; prefixLength = 64; } ];
  };
  networking.defaultGateway = { address = "159.195.64.1"; interface = "eth0"; };
  # Confirmed against `ip -6 route show default` on the VPS:
  #   default via fe80::1 dev eth0 metric 1024 onlink
  networking.defaultGateway6 = { address = "fe80::1"; interface = "eth0"; };
  networking.nameservers = [ "9.9.9.9" "1.1.1.1" "2620:fe::fe" ];

  # ---- Don't take MagicDNS from our own control server ----
  # headscale pushes override_local_dns, so joining the tailnet would point
  # neptun's resolv.conf at a MagicDNS served by the tailscaled neptun itself
  # hosts. A tailscaled failure would then also kill DNS, and with it ACME
  # renewal — expiring the certs for the very control server every other node
  # needs to recover. Keep the public resolvers above and resolve the one
  # tailnet name we proxy to from /etc/hosts instead.
  services.tailscale.extraUpFlags = [ "--accept-dns=false" ];

  # ⚠️  PLACEHOLDER IP — replace once jupiter first enrols, with its address
  #     from `headscale nodes list` on this box. Until then the audiobookshelf
  #     vhost and the gitea SSH forward below both fail to connect.
  networking.hosts."100.64.0.2" = [ "jupiter.hosts.mgaction.town" ];

  # firewall (enable + 22), caddy (80/443), tailscale (trust tailscale0 + join
  # headscale) come from ../../common.nix and ../../services/{caddy,tailscale}.nix.

  # ---- ACME account email ----
  # services.caddy.email would render the address into the world-readable
  # store, so pass it via EnvironmentFile and reference it with the Caddyfile
  # {$VAR} parse-time placeholder (see hosts/neptun/secrets.nix). globalConfig
  # is types.lines, so this appends to the module's own global block.
  services.caddy.environmentFile = config.sops.templates."caddy.env".path;
  services.caddy.globalConfig = "email {$ACME_EMAIL}";

  # ---- Public reverse proxy vhosts ----
  # Caddy gets automatic public HTTPS (Let's Encrypt) for real domains; the
  # *.mgaction.town wildcard already points every name here (A + AAAA), and
  # the module opens 80/443. Both of these live on jupiter and are reached
  # over the tailnet — see the /etc/hosts pin above.
  #
  # `abs`, not `audiobookshelf`: that's the name this has always been served
  # under, and the mobile app is configured with it.
  services.caddy.virtualHosts."abs.mgaction.town".extraConfig = ''
    reverse_proxy http://jupiter.hosts.mgaction.town:8000
  '';
  # Gitea's web UI and HTTPS clones (services/dev/gitea.nix, HTTP_PORT 3000).
  # Its SSH side is the separate :2222 forward further down.
  services.caddy.virtualHosts."git.mgaction.town".extraConfig = ''
    reverse_proxy http://jupiter.hosts.mgaction.town:3000
  '';
  # The apex mgaction.town is deliberately not served — it returns Caddy's
  # default 404.

  # ---- Authentik (identity/OIDC provider) ----
  # Runs locally on neptun (see services/identity/authentik.nix); Caddy just
  # terminates TLS and proxies to its loopback HTTP listener. Authentik serves
  # its UI and its OIDC endpoints from one port — no second frontend upstream,
  # and no h2c (it's plain HTTP/1.1, unlike Zitadel's gRPC).
  services.caddy.virtualHosts."auth.mgaction.town".extraConfig = ''
    reverse_proxy http://127.0.0.1:9000
  '';

  # ---- Headscale + Headplane (tailnet control server + its web UI) ----
  # Path-routed on one vhost: Headplane owns /admin* (uses `handle`, not
  # `handle_path`, since it needs the prefix kept in the forwarded path for
  # its own assets + OIDC callback); everything else goes to headscale.
  # `flush_interval -1`: headscale's node-update endpoint is a long-poll and
  # Caddy would otherwise buffer it, showing clients stale state.
  services.caddy.virtualHosts."vpn.mgaction.town".extraConfig = ''
    handle /admin* {
      reverse_proxy http://localhost:3000
    }
    handle {
      reverse_proxy http://localhost:8082 {
        flush_interval -1
      }
    }
  '';

  # ---- Gitea SSH forward ----
  # Caddy only proxies HTTP; forward :2222 over the tailnet to gitea's own
  # SSH server on jupiter (services/dev/gitea.nix), so
  # `ssh://git@git.mgaction.town:2222/...` works. Also needs a matching
  # inbound-2222 rule in netcup's edge firewall panel (not managed by Nix).
  systemd.services.gitea-ssh-forward = {
    description = "Forward :2222 to jupiter's gitea SSH server over tailscale";
    after = [ "network-online.target" "tailscaled.service" ];
    wants = [ "network-online.target" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      DynamicUser = true;
      ExecStart = "${pkgs.socat}/bin/socat TCP-LISTEN:2222,fork,reuseaddr TCP:jupiter.hosts.mgaction.town:2222";
      Restart = "always";
    };
  };
  networking.firewall.allowedTCPPorts = [ 2222 ];

  system.stateVersion = "26.05";   # set at install time; do NOT bump on upgrades
}