Bug 1552438 - Remove TRR mode 1 (MODE_PARALLEL) r=agrover

Differential Revision: https://phabricator.services.mozilla.com/D32996

--HG--
extra : moz-landing-system : lando

netwerk/dns/TRRService.cpp

@@ -125,13 +125,16 @@ void TRRService::GetPrefBranch(nsIPrefBranch** result) {
 nsresult TRRService::ReadPrefs(const char* name) {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
   if (!name || !strcmp(name, TRR_PREF("mode"))) {
-    // 0 - off, 1 - parallel, 2 - TRR first, 3 - TRR only, 4 - shadow,
+    // 0 - off, 1 - reserved, 2 - TRR first, 3 - TRR only, 4 - shadow,
     // 5 - explicit off
     uint32_t tmp;
     if (NS_SUCCEEDED(Preferences::GetUint(TRR_PREF("mode"), &tmp))) {
       if (tmp > MODE_TRROFF) {
         tmp = MODE_TRROFF;
       }
+      if (tmp == MODE_RESERVED1) {
+        tmp = MODE_TRROFF;
+      }
       mMode = tmp;
     }
   }

netwerk/dns/nsHostResolver.cpp

@@ -469,8 +469,7 @@ void AddrHostRecord::ResolveComplete() {
     }
   }
 
-  if (mTRRUsed && mNativeUsed &&
-      ((mResolverMode == MODE_SHADOW) || (mResolverMode == MODE_PARALLEL))) {
+  if (mTRRUsed && mNativeUsed && ((mResolverMode == MODE_SHADOW))) {
     // both were used, accumulate comparative success
     AccumulateCategorical(
         mNativeSuccess && mTRRSuccess
@@ -505,9 +504,6 @@ void AddrHostRecord::ResolveComplete() {
     case MODE_TRROFF:
       AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::nativeOnly);
       break;
-    case MODE_PARALLEL:
-      AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::trrRace);
-      break;
     case MODE_TRRFIRST:
       AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::trrFirst);
       break;
@@ -517,6 +513,9 @@ void AddrHostRecord::ResolveComplete() {
     case MODE_SHADOW:
       AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::trrShadow);
       break;
+    case MODE_RESERVED1:
+      MOZ_DIAGNOSTIC_ASSERT(false, "MODE_RESERVED1 should not be used");
+      break;
   }
 
   if (mTRRUsed && !mTRRSuccess && mNativeSuccess && gTRRService) {
@@ -1414,6 +1413,7 @@ nsresult nsHostResolver::NameLookup(nsHostRecord* rec) {
   }
 
   ResolverMode mode = rec->mResolverMode = Mode();
+  MOZ_ASSERT(mode != MODE_RESERVED1);
 
   if (rec->IsAddrRecord()) {
     RefPtr<AddrHostRecord> addrRec = do_QueryObject(rec);
@@ -1448,7 +1448,7 @@ nsresult nsHostResolver::NameLookup(nsHostRecord* rec) {
     rv = TrrLookup(rec);
   }
 
-  if ((mode == MODE_PARALLEL) || TRR_DISABLED(mode) || (mode == MODE_SHADOW) ||
+  if (TRR_DISABLED(mode) || (mode == MODE_SHADOW) ||
       ((mode == MODE_TRRFIRST) && NS_FAILED(rv)) ||
       (mode == MODE_TRRONLY && skipTRR)) {
     if (!rec->IsAddrRecord()) {

netwerk/dns/nsHostResolver.h

@@ -32,7 +32,7 @@ namespace net {
 class TRR;
 enum ResolverMode {
   MODE_NATIVEONLY,  // 0 - TRR OFF (by default)
-  MODE_PARALLEL,    // 1 - race and use the first response
+  MODE_RESERVED1,   // 1 - Reserved value. Used to be parallel resolve.
   MODE_TRRFIRST,    // 2 - fallback to native on TRR failure
   MODE_TRRONLY,     // 3 - don't even fallback
   MODE_SHADOW,      // 4 - race for stats, but always use native result

netwerk/test/unit/test_trr.js

@@ -343,12 +343,16 @@ add_task(async function test18() {
   Assert.ok(!Components.isSuccessCode(inStatus), `${inStatus} should be an error code`);
 });
 
-// TRR-race and a CNAME loop
+// Test that MODE_RESERVED1 (previously MODE_PARALLEL) is treated as TRR off.
 add_task(async function test19() {
   dns.clearCache(true);
-  Services.prefs.setIntPref("network.trr.mode", 1); // Race them!
+  Services.prefs.setIntPref("network.trr.mode", 1); // MODE_RESERVED1. Interpreted as TRR off.
   Services.prefs.setCharPref("network.trr.uri", `https://foo.example.com:${h2Port}/doh?responseIP=none&cnameloop=true`);
   await new DNSListener("test19.example.com", "127.0.0.1");
+
+  Services.prefs.setIntPref("network.trr.mode", 1); // MODE_RESERVED1. Interpreted as TRR off.
+  Services.prefs.setCharPref("network.trr.uri", `https://foo.example.com:${h2Port}/doh?responseIP=2.2.2.2`);
+  await new DNSListener("bar.example.com", "127.0.0.1");
 });
 
 // TRR-first and a CNAME loop