sail: Add tailscale

system/hosts/sail.nix

@@ -9,6 +9,7 @@ in
     ../nixos/ssh.nix
 
     ../nixos/git.nix
+    ../nixos/tailscale.nix
 
     ../nixos/arion.nix
     ../../container/webserver

system/nixos/tailscale.nix

@@ -0,0 +1,31 @@
+{ pkgs, secret, ... }:
+
+{
+  environment.systemPackages = [ pkgs.tailscale ];
+
+  services.tailscale.enable = true;
+
+  systemd.services.tailscale-autoconnect = {
+    description = "Automatic connection to Tailscale";
+
+    after = [ "network-pre.target" "tailscale.service" ];
+    wants = [ "network-pre.target" "tailscale.service" ];
+    wantedBy = [ "multi-user.target" ];
+
+    serviceConfig.Type = "oneshot";
+
+    script = ''
+      # wait for tailscaled to settle
+      sleep 2
+
+      # check if we are already authenticated to tailscale
+      status="$(${pkgs.tailscale}/bin/tailscale status -json | ${pkgs.jq}/bin/jq -r .BackendState)"
+      if [ $status = "Running" ]; then # if so, then do nothing
+        exit 0
+      fi
+
+      # otherwise authenticate with tailscale
+      ${pkgs.tailscale}/bin/tailscale up -authkey ${secret.tailscale.key}
+    '';
+  };
+}