WebTransportImpl fix StreamReadHandle::dataAvailable

Summary:
grr, undo-ing a mistake in the previous diff (D83162391)
the window was a session-level recv window, and it should be WebTransportImpl's job to ensure we don't invoke TransportProvider::sendWTMaxData() if only eof is read on the stream

Reviewed By: afrind

Differential Revision: D83355330

fbshipit-source-id: 8df6ff2518f04d5738d789011a0c131108bfb098

Author: hanidamlaj

proxygen/lib/http/session/test/HTTPTransactionWebTransportTest.cpp

@@ -206,12 +206,8 @@ TEST_F(HTTPTransactionWebTransportTest, ReadStream) {
   EXPECT_CALL(transport_, readWebTransportData(_, _)).WillOnce(Invoke([] {
     return std::make_pair(makeBuf(32768), false);
   }));
-  // hmm, should WebTransportImpl ensure this isn't invoked if we've rx'd eof or
-  // is it the transport's responsiblity to not send WTMaxData capsule in this
-  // case – leaning towards the latter
   EXPECT_CALL(transport_, sendWTMaxData(kDefaultWTReceiveWindow + 10 + 65536))
-      .Times(2)
-      .WillRepeatedly(Return(folly::unit));
+      .WillOnce(Return(folly::unit));
   implHandle->readAvailable(0);
   EXPECT_CALL(transport_, resumeWebTransportIngress(0));
   fut = readHandle->readStreamData()
@@ -449,8 +445,7 @@ TEST_F(HTTPTransactionWebTransportTest, BidiStreamEdgeCases) {
   EXPECT_CALL(transport_,
               stopReadingWebTransportIngress(0, folly::Optional<uint32_t>()));
 
-  EXPECT_CALL(transport_, sendWTMaxData(kDefaultWTReceiveWindow))
-      .WillOnce(Return(folly::unit));
+  EXPECT_CALL(transport_, sendWTMaxData(kDefaultWTReceiveWindow)).Times(0);
   auto fut = streamHandle.readHandle->readStreamData()
                  .via(&eventBase_)
                  .thenTry([](auto streamData) {

proxygen/lib/http/webtransport/WebTransportImpl.cpp

@@ -363,8 +363,7 @@ WebTransportImpl::StreamReadHandle::readStreamData() {
     VLOG(4) << __func__ << " returning data len=" << buf_.chainLength();
     auto bufLen = buf_.chainLength();
     StreamData streamData({.data = buf_.move(), .fin = eof_});
-    impl_.bytesRead_ += bufLen;
-    impl_.maybeGrantFlowControl();
+    impl_.maybeGrantFlowControl(bufLen);
 
     if (eof_) {
       // unregister the read callback, but don't send STOP_SENDING
@@ -415,8 +414,7 @@ WebTransport::FCState WebTransportImpl::StreamReadHandle::dataAvailable(
   }
 
   if (readPromise_.valid()) {
-    impl_.bytesRead_ += len;
-    impl_.maybeGrantFlowControl();
+    impl_.maybeGrantFlowControl(len);
     readPromise_.setValue(StreamData({.data = std::move(data), .fin = eof}));
     readPromise_ = emptyReadPromise();
     if (eof) {
@@ -474,8 +472,9 @@ void WebTransportImpl::StreamReadHandle::deliverReadError(
   }
 }
 
-void WebTransportImpl::maybeGrantFlowControl() {
-  if (shouldGrantFlowControl()) {
+void WebTransportImpl::maybeGrantFlowControl(uint64_t bytesRead) {
+  bytesRead_ += bytesRead;
+  if (bytesRead && shouldGrantFlowControl()) {
     auto newMaxData = bytesRead_ + kDefaultWTReceiveWindow;
     recvFlowController_.grant(newMaxData);
     tp_.sendWTMaxData(newMaxData);

proxygen/lib/http/webtransport/WebTransportImpl.h

@@ -370,7 +370,7 @@ class WebTransportImpl : public WebTransport {
 
   void onWebTransportStopSending(HTTPCodec::StreamID id, uint32_t errorCode);
 
-  void maybeGrantFlowControl();
+  void maybeGrantFlowControl(uint64_t bytesRead);
   [[nodiscard]] bool shouldGrantFlowControl() const;
 
   void setFlowControlLimits(