[chore] http2: fix integer overflow in unconsumed_bytes_

[vishalmore90]

Commit Message: http2: fix integer overflow in unconsumed_bytes_

Change the type of unconsumed_bytes_ from uint32_t to uint64_t in ConnectionImpl::StreamImpl to prevent flow control state corruption due to integer overflow on read-disabled streams.

Additional Description:
When a stream is read-disabled, Envoy accumulates the number of unconsumed bytes received on the stream. When the stream is later read-enabled, Envoy reports the accumulated unconsumed bytes back to the HTTP/2 codec to restore the peer's flow control window. Because unconsumed_bytes_ was declared as a uint32_t, it could overflow if the peer sent more than 4 GB of data before the stream was read-enabled, leading to connection/stream flow control corruption (stalls or data floods). Changing the type to uint64_t prevents this overflow.

Risk Level: Low (Simple type conversion, fully backward-compatible)

Testing: Added a unit test UnconsumedBytesOverflowPrevention in codec_impl_test.cc that simulates the addition of bytes beyond UINT32_MAX and verifies it doesn't wrap around.

Docs Changes: N/A
Release Notes: N/A

[repokitteh-read-only]

Hi @vishalmore90, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #45974 was opened by vishalmore90.

see: more, trace.