Merge pull request 'Fix tailscale exit-node module: enable routing, compose on enable-service' (#11) from worktree-tailscale-exit-node into main

Reviewed-on: #11

modules/tailscale/exit-node.nix

@@ -1,8 +1,16 @@
 _:
 
 {
+  imports = [ ./enable-service.nix ];
+
   services.tailscale = {
-    enable = true;
+    # 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