tailscale/cmd/tailscale/cli/web.html

<!doctype html>
<html><title>Tailscale Client</title><body>
<h1>Tailscale</h1>
<div style="float:right;">{{.SynologyUser}}</div>
<table>
<tr><th>Status:</th><td>{{.Status}}</td></tr>
<tr><th>Device Name:</th><td>{{.DeviceName}}</td></tr>
<tr><th>Tailscale IP:</th><td>{{.IP}}</td></tr>
</table>

<p><input id="login" type="button" value="Log in…"></p>

<script>
login.onclick = function() {
	const urlParams = new URLSearchParams(window.location.search);
	const token = urlParams.get("SynoToken");

	var params = new URLSearchParams("up=true");
	if (token) {
		params.set("SynoToken", token)
	}

	var req = new XMLHttpRequest();
	const url = [location.protocol, '//', location.host, location.pathname, "?", params.toString()].join('');
	req.overrideMimeType("application/json");
	req.open("POST", url, true);
	req.onload = function() {
		var jsonResponse = JSON.parse(req.responseText);
		const err = jsonResponse["error"];
		if (err) {
			document.body.innerText = err;
			return
		}
		var url = jsonResponse["url"];
		console.log("jsonResponse: ", jsonResponse);
		if (url) {
			document.location.href = url;
		} else {
			//location.reload();
		}
	};
	req.send(null);
}
</script>

</body>
</html>