Bug 1689550 - Add a pref to disable 0RTT only for HTTP3 r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D106560

modules/libpref/init/StaticPrefList.yaml

@@ -8916,6 +8916,11 @@
   value: false
   mirror: always
 
+- name: network.http.http3.enable_0rtt
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+
 # When a h3 transaction is inserted in the pending queue, the time (ms) we wait
 # to create a TCP backup connection.
 - name: network.http.http3.backup_timer_delay

netwerk/protocol/http/Http3Session.cpp

@@ -186,7 +186,8 @@ nsresult Http3Session::Init(const nsHttpConnectionInfo* aConnInfo,
   nsAutoCString peerId;
   mSocketControl->GetPeerId(peerId);
   nsTArray<uint8_t> token;
-  if (NS_SUCCEEDED(SSLTokensCache::Get(peerId, token))) {
+  if (StaticPrefs::network_http_http3_enable_0rtt() &&
+      NS_SUCCEEDED(SSLTokensCache::Get(peerId, token))) {
     LOG(("Found a resumption token in the cache."));
     mHttp3Connection->SetResumptionToken(token);
     if (mHttp3Connection->IsZeroRtt()) {
@@ -487,7 +488,8 @@ nsresult Http3Session::ProcessEvents() {
         break;
       case Http3Event::Tag::ResumptionToken: {
         LOG(("Http3Session::ProcessEvents - ResumptionToken"));
-        if (!data.IsEmpty()) {
+        if (StaticPrefs::network_http_http3_enable_0rtt() &&
+            !data.IsEmpty()) {
           LOG(("Got a resumption token"));
           nsAutoCString peerId;
           mSocketControl->GetPeerId(peerId);