nixos/modules/tailscale/exit-node.nix

_:

{
  imports = [ ./enable-service.nix ];

  services.tailscale = {
    # Enables the sysctl forwarding settings exit nodes/subnet routers need;
    # without this, --advertise-exit-node has no effect.
    useRoutingFeatures = "server";

    # Lets peers reach this node directly over the tailscale UDP port
    # instead of relaying through DERP.
    openFirewall = true;

    # extraSetFlags (tailscale set, via the always-on tailscaled-set
    # service), not extraUpFlags -- extraUpFlags is only ever applied by
    # tailscaled-autoconnect, which itself only runs when
    # services.tailscale.authKeyFile is set (nothing in this repo sets one,
    # so tailscale up is a manual, one-time operator step on every host that
    # uses this service). extraSetFlags has no such gate, so
    # --advertise-exit-node self-reapplies on every boot once the operator
    # has authenticated the node once.
    extraSetFlags = [
      "--advertise-exit-node"
    ];
  };
}