Run DNS check against current domain

README.md

@@ -54,9 +54,9 @@ the request is also explicitly disabled. This test is run every 30 seconds.
 
 ### DNS Test
 
-Test DNS is working by making a HTTP GET request to a [random-number]dns-check.pinging.net.
-Caching is explicitly disabled and the random number part of the subdomain prevents common caching
-of the DNS lookup. This test is run every 30 seconds.
+Test DNS is working by making a HTTP GET request to a `[random-number]dns-check.<this site's
+domain>`. Caching is explicitly disabled and the random number part of the subdomain prevents
+common caching of the DNS lookup. This test is run every 30 seconds.
 
 ### Browser Check
 

frontend/about.html

@@ -79,9 +79,9 @@ <h2 id="dns">DNS Test</h2>
     understands (e.g. 192.168.100.100).
   </p>
   <p>
-    Test DNS is working by making a HTTP GET request to a [random-number]dns-check.pinging.net.
-    Caching is explicitly disabled and the random number part of the subdomain prevents common
-    caching of the DNS lookup. This test is run once when the page is loaded.
+    Test DNS is working by making a HTTP GET request to a [random-number]dns-check.&lt;this site's
+    domain&gt;. Caching is explicitly disabled and the random number part of the subdomain prevents
+    common caching of the DNS lookup. This test is run once when the page is loaded.
   </p>
 
   <h2 id="browser">Browser Check</h2>

frontend/index.ts

@@ -397,7 +397,11 @@ async function testHttpOrDns(testName: string) {
     });
   } else {
     pong = fetch(
-      "https://" + randomNumber + "dns-check.pinging.net/api/dns-check",
+      "https://" +
+        randomNumber +
+        "dns-check." +
+        window.location.hostname +
+        "/api/dns-check",
       {
         method: "GET",
         cache: "no-store",