early-hints-preconnect.html

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<!DOCTYPE html>

<meta charset=utf-8>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<body>

<script>

const RESOURCES_PATH = '/connection-allowlist/tentative/resources';

const params = new URLSearchParams(window.location.search);

const allow = params.get("allow");

const key = params.get("key");

const alt_host = params.get("alt_host");

const https_port = params.get("https_port");

const expected = allow === "true" ? "allowed" : "blocked";

promise_test(async (t) => {

  const base_url = `https://${key}.${alt_host}:${https_port}`;

  const resource_url = `${base_url}${RESOURCES_PATH}/empty.js?${key}`;

  // We fetch a cross-origin resource (`empty.js`) to evaluate whether the

  // preconnect was allowed or blocked by the connection allowlist.

//

  // This is done by using Resource Timing API:

  // - `empty.js.headers` returns `Timing-Allow-Origin: *` to allow this page to

  //   read detailed network timing values (like connectStart and connectEnd).

  // - If the Early Hint preconnect was allowed: The connection handshake (DNS,

  //   TCP, TLS) has been completed already by the preconnect. The subsequent

  //   `fetch()` will reuse this existing socket. Which means

  //   `connectStart == connectEnd`.

  // - If the Early Hint preconnect was blocked: The `fetch()` must establish a

  //   new socket, performing the full handshake. This takes time, resulting

  //   in `connectStart < connectEnd`.

  const response = await fetch(resource_url);

  assert_true(response.ok, `Fetch should succeed. Status: ${response.status}`);

  await response.text();

  const resource_entries = performance.getEntriesByName(resource_url);

  assert_equals(resource_entries.length, 1);

  const connect_start = resource_entries[0].connectStart;

  const connect_end = resource_entries[0].connectEnd;

  if (expected === "allowed") {

    assert_equals(connect_start, connect_end,

        "Connection allowlist should allow the Early Hints preconnect.");

  } else if (expected === "blocked") {

    assert_true(connect_start < connect_end,

        "Connection allowlist should block the Early Hints preconnect.");

}, `Early Hints preconnect connection allowlist test: ${expected}`);

</script>

</body>