Fix Envoy Mobile bug where writing prevents the read loop from running,

by scheduling repeated onSendWindowAvailable calls in the next
dispatcher iteration.

Adds the regression test Charles cooked up in envoyproxy#2212

Fixes envoyproxy#2213

Signed-off-by: Ryan Hamilton <rch@google.com>

library/common/event/provisional_dispatcher.cc

@@ -44,6 +44,13 @@ envoy_status_t ProvisionalDispatcher::post(Event::PostCb callback) {
   return ENVOY_SUCCESS;
 }
 
+Event::SchedulableCallbackPtr ProvisionalDispatcher::createSchedulableCallback(std::function<void()> cb) {
+  RELEASE_ASSERT(
+      isThreadSafe(),
+      "ProvisionalDispatcher::createSchedulableCallback must be called from a threadsafe context");
+ return event_dispatcher_->createSchedulableCallback(cb);
+}
+
 bool ProvisionalDispatcher::isThreadSafe() const {
   // Doesn't require locking because if a thread has a stale view of drained_, then by definition
   // this wasn't a threadsafe call.

library/common/event/provisional_dispatcher.h

@@ -41,6 +41,15 @@ class ProvisionalDispatcher : public ScopeTracker {
    */
   virtual envoy_status_t post(Event::PostCb callback);
 
+  /**
+   * Allocates a schedulable callback. @see SchedulableCallback for docs on how to use the wrapped
+   * callback.
+   * @param cb supplies the callback to invoke when the SchedulableCallback is triggered on the
+   * event loop.
+   * Must be called from context where ProvisionalDispatcher::isThreadSafe() is true.
+   */
+  virtual Event::SchedulableCallbackPtr createSchedulableCallback(std::function<void()> cb);
+
   /**
    * @return false before the Event::Dispatcher is running, otherwise the result of the
    * underlying call to Event::Dispatcher::isThreadSafe().

library/common/http/client.cc

@@ -471,9 +471,10 @@ void Client::sendData(envoy_stream_t stream, envoy_data data, bool end_stream) {
     if (direct_stream->explicit_flow_control_ && !end_stream) {
       if (direct_stream->read_disable_count_ == 0) {
         // If there is still buffer space after the write, notify the sender
-        // that send window is available.
+        // that send window is available, on the next dispatcher iteration.
         direct_stream->wants_write_notification_ = false;
-        direct_stream->callbacks_->onSendWindowAvailable();
+        scheduled_callback_ = dispatcher_.createSchedulableCallback([direct_stream] {direct_stream->callbacks_->onSendWindowAvailable();});
+        scheduled_callback_->scheduleCallbackNextIteration();
       } else {
         // Otherwise, make sure the stack will send a notification when the
         // buffers are drained.

library/common/http/client.h

@@ -321,6 +321,7 @@ class Client : public Logger::Loggable<Logger::Id::http> {
 
   ApiListener& api_listener_;
   Event::ProvisionalDispatcher& dispatcher_;
+  Event::SchedulableCallbackPtr scheduled_callback_;
   HttpClientStats stats_;
   // The set of open streams, which can safely have request data sent on them
   // or response data received.

test/java/org/chromium/net/testing/BUILD

@@ -90,3 +90,22 @@ envoy_mobile_android_test(
         "//library/kotlin/io/envoyproxy/envoymobile:envoy_lib",
     ],
 )
+
+envoy_mobile_android_test(
+    name = "temporary_test",
+    srcs = [
+        "AndroidEnvoyExplicitH2FlowTest.java",
+    ],
+    exec_properties = {
+        # TODO(lfpino): Remove this once the sandboxNetwork=off works for ipv4 localhost addresses.
+        "sandboxNetwork": "standard",
+    },
+    native_deps = [
+        "//library/common/jni:libndk_envoy_jni.so",
+        "//library/common/jni:libndk_envoy_jni.jnilib",
+    ],
+    deps = [
+        ":testing",
+        "//library/kotlin/io/envoyproxy/envoymobile:envoy_lib",
+    ],
+)