Bug 1809843 - Add a pref to force using HTTPS RR, r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D166643

modules/libpref/init/StaticPrefList.yaml

@@ -12360,6 +12360,13 @@
   value: false
   mirror: always
 
+# Whether to use HTTPS RR and ignore NS_HTTP_DISALLOW_HTTPS_RR
+# This pref is only set when running tests
+- name: network.dns.force_use_https_rr
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 - name: network.cache.frecency_array_check_enabled
   type: RelaxedAtomicBool
   value: @IS_EARLY_BETA_OR_EARLIER@

netwerk/protocol/http/nsHttpTransaction.cpp

@@ -357,13 +357,15 @@ nsresult nsHttpTransaction::Init(
     mPushedStream = trans->TakePushedStreamById(aPushedStreamId);
   }
 
-  if (gHttpHandler->UseHTTPSRRAsAltSvcEnabled() &&
-      !(mCaps & NS_HTTP_DISALLOW_HTTPS_RR)) {
+  bool forceUseHTTPSRR = StaticPrefs::network_dns_force_use_https_rr();
+  if ((gHttpHandler->UseHTTPSRRAsAltSvcEnabled() &&
+       !(mCaps & NS_HTTP_DISALLOW_HTTPS_RR)) ||
+      forceUseHTTPSRR) {
     nsCOMPtr<nsIEventTarget> target;
     Unused << gHttpHandler->GetSocketThreadTarget(getter_AddRefs(target));
     if (target) {
       if (StaticPrefs::network_dns_force_waiting_https_rr() ||
-          StaticPrefs::network_dns_echconfig_enabled()) {
+          StaticPrefs::network_dns_echconfig_enabled() || forceUseHTTPSRR) {
         mCaps |= NS_HTTP_FORCE_WAIT_HTTP_RR;
       }