From 210c3795f92e4c76f24a6fa43d885275accfdb5d Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Fri, 10 Jun 2022 11:53:43 +0100
Subject: [PATCH] LibWeb: Apply content filter to DNS prefetch and pre-connect

Performing DNS prefetch or pre-connect on filtered URLs is wasteful,
as we would block any actual use further down the line.

A bunch of websites perform DNS prefetch and/or pre-connect to trackers
as well, for example:
```
prefetch DNS for 'https://adserver-us.adtech.advertising.com/'
prefetch DNS for 'https://secure.adnxs.com/'
prefetch DNS for 'https://bidder.criteo.com/'
prefetch DNS for 'https://static.criteo.net/'
prefetch DNS for 'https://cdn.krxd.net/'
prefetch DNS for 'https://widgets.outbrain.com/'
prefetch DNS for 'https://images.outbrain.com/'
prefetch DNS for 'https://log.outbrain.com/
prefetch DNS for 'https://amplifypixel.outbrain.com/'
prefetch DNS for 'https://odb.outbrain.com/'
prefetch DNS for 'https://js-sec.indexww.com/'
prefetch DNS for 'https://as-sec.casalemedia.com/'
prefetch DNS for 'https://as.casalemedia.com/'
prefetch DNS for 'https://sofia.trustx.org/'
prefetch DNS for 'https://c.amazon-adsystem.com/'
prefetch DNS for 'https://s.amazon-adsystem.com/'
prefetch DNS for 'https://aax.amazon-adsystem.com/'
prefetch DNS for 'https://t.teads.tv/'
prefetch DNS for 'https://beacon.krxd.net/'
pre-connect to 'https://www.google-analytics.com/'
pre-connect to 'https://www.googletagmanager.com/'
```
---
 Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
index 498286e3bd..b7bc502001 100644
--- a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
+++ b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
@@ -61,11 +61,21 @@ ResourceLoader::ResourceLoader(NonnullRefPtr<ResourceLoaderConnector> connector)
 
 void ResourceLoader::prefetch_dns(AK::URL const& url)
 {
+    if (ContentFilter::the().is_filtered(url)) {
+        dbgln("ResourceLoader: Refusing to prefetch DNS for '{}': \033[31;1mURL was filtered\033[0m", url);
+        return;
+    }
+
     m_connector->prefetch_dns(url);
 }
 
 void ResourceLoader::preconnect(AK::URL const& url)
 {
+    if (ContentFilter::the().is_filtered(url)) {
+        dbgln("ResourceLoader: Refusing to pre-connect to '{}': \033[31;1mURL was filtered\033[0m", url);
+        return;
+    }
+
     m_connector->preconnect(url);
 }