[chore] http2: fix integer overflow in unconsumed_bytes_

source/common/http/http2/codec_impl.h

@@ -426,7 +426,7 @@ class ConnectionImpl : public virtual Connection,
     const StreamInfo::BytesMeterSharedPtr& bytesMeter() override { return bytes_meter_; }
     ConnectionImpl& parent_;
     int32_t stream_id_{-1};
-    uint32_t unconsumed_bytes_{0};
+    uint64_t unconsumed_bytes_{0};
     uint32_t read_disable_count_{0};
     StreamInfo::BytesMeterSharedPtr bytes_meter_{std::make_shared<StreamInfo::BytesMeter>()};
 

test/common/http/http2/codec_impl_test.cc

@@ -2595,6 +2595,28 @@ TEST_P(Http2CodecImplFlowControlTest, RstStreamOnPendingFlushTimeoutFlood) {
   EXPECT_EQ(1, server_stats_store_.counter("http2.outbound_flood").value());
 }
 
+// Verify that unconsumed_bytes_ is 64-bit and does not overflow.
+TEST_P(Http2CodecImplFlowControlTest, UnconsumedBytesOverflowPrevention) {
+  initialize();
+
+  TestRequestHeaderMapImpl request_headers;
+  HttpTestUtility::addDefaultHeaders(request_headers);
+  EXPECT_TRUE(request_encoder_->encodeHeaders(request_headers, false).ok());
+  driveToCompletion();
+
+  auto* stream = server_->getStream(1);
+  ASSERT_NE(stream, nullptr);
+
+  // Directly set unconsumed_bytes_ to a value close to UINT32_MAX.
+  stream->unconsumed_bytes_ = static_cast<uint64_t>(UINT32_MAX) - 100;
+
+  // Add more bytes to simulate receiving data while read-disabled.
+  stream->unconsumed_bytes_ += 200;
+
+  // Verify that it has successfully held a value larger than UINT32_MAX without overflow/wrap-around.
+  EXPECT_EQ(stream->unconsumed_bytes_, static_cast<uint64_t>(UINT32_MAX) + 100);
+}
+
 TEST_P(Http2CodecImplTest, WatermarkUnderEndStream) {
   initialize();
   MockStreamCallbacks callbacks;