Bug 1700405 - Make it possible to skip the NS check when a host is added into blocked list, r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D117284

modules/libpref/init/StaticPrefList.yaml

@@ -9548,6 +9548,13 @@
   value: ""
   mirror: never
 
+# Whether to skip the NS check for the blocked host.
+# Note this is used for test only.
+- name: network.trr.skip-check-for-blocked-host
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 # Allow the network changed event to get sent when a network topology or setup
 # change is noticed while running.
 - name: network.notify.changed

netwerk/dns/TRRService.cpp

@@ -1007,7 +1007,10 @@ void TRRService::AddToBlocklist(const nsACString& aHost,
     bl->InsertOrUpdate(hashkey, NowInSeconds());
   }
 
-  if (aParentsToo) {
+  // See bug 1700405. Some test expects 15 trr consecutive failures, but the NS
+  // check against the base domain is successful. So, we skip this NS check when
+  // the pref said so in order to pass the test reliably.
+  if (aParentsToo && !StaticPrefs::network_trr_skip_check_for_blocked_host()) {
     // when given a full host name, verify its domain as well
     int32_t dot = aHost.FindChar('.');
     if (dot != kNotFound) {

netwerk/test/unit/test_trr_confirmation.js

@@ -28,9 +28,15 @@ const CONFIRM_FAILED = 3;
 const CONFIRM_TRYING_FAILED = 4;
 const CONFIRM_DISABLED = 5;
 
-trr_test_setup();
+function setup() {
+  trr_test_setup();
+  Services.prefs.setBoolPref("network.trr.skip-check-for-blocked-host", true);
+}
+
+setup();
 registerCleanupFunction(async () => {
   trr_clear_prefs();
+  Services.prefs.clearUserPref("network.trr.skip-check-for-blocked-host");
 });
 
 let trrServer = null;
@@ -70,7 +76,9 @@ function trigger15Failures() {
   dns.clearCache(true);
 
   let dnsRequests = [];
-  for (let i = 0; i < 15; i++) {
+  // There are actually two TRR requests sent for A and AAAA records, so doing
+  // DNS query 10 times should be enough to trigger confirmation process.
+  for (let i = 0; i < 10; i++) {
     dnsRequests.push(
       new TRRDNSListener(`failing-domain${i}.faily.com`, {
         expectedAnswer: "127.0.0.1",