h2: give back connection credit in the callback, as h2v2 does

include/anyhttp/h2/stream.hpp

@@ -195,7 +195,7 @@ class NGHttp2Stream : public std::enable_shared_from_this<NGHttp2Stream>
    ~NGHttp2Stream();
 
    /// This function is called on receiving a data frame `nghttp2_on_data_chunk_recv_callback`.
-   void on_data(nghttp2_session* session, int32_t id_, const uint8_t* data, size_t len);
+   void on_data(const uint8_t* data, size_t len);
 
    /// This function is called on receiving a header or data frame that has the EOF flag set.
    void on_eof(nghttp2_session* session, int32_t id_);

src/h2/session.cpp

@@ -373,15 +373,23 @@ static int on_data_chunk_recv_callback(nghttp2_session* session, uint8_t flags,
    auto handler = static_cast<NGHttp2Session*>(user_data);
    auto stream = handler->find_stream(stream_id);
 
-   if (!stream)
+   //
+   // Connection-level credit is given back right away, with or without a stream: nobody else would,
+   // and the connection would run out of it. The stream-level window is only reopened once the
+   // reader has taken the data, which is what applies back pressure.
+   //
+   nghttp2_session_consume_connection(session, len);
+
+   if (stream)
    {
+      logd("[{}.{}] on_data_chunk_recv_callback: DATA, len={}", handler->log_prefix(), stream_id,
+           len);
+      stream->on_data(data, len);
+   }
+   else
       logw("[{}.{}] on_data_chunk_recv_callback: DATA, but no stream found (id={})",
            handler->log_prefix(), stream_id, stream_id);
-      return 0;
-   }
 
-   logd("[{}.{}] on_data_chunk_recv_callback: DATA, len={}", handler->log_prefix(), stream_id, len);
-   stream->on_data(session, stream_id, data, len);
    handler->start_write(); // might re-open windows
 
    return 0;

src/h2/stream.cpp

@@ -571,16 +571,13 @@ void NGHttp2Stream::call_read_handler(asio::const_buffer view)
 #endif
 }
 
-void NGHttp2Stream::on_data(nghttp2_session* session, int32_t id_, const uint8_t* data, size_t len)
+void NGHttp2Stream::on_data(const uint8_t* data, size_t len)
 {
-   assert(id == id_);
    assert(!eof_received);
    assert(len); // for EOF, on_eof() is called instead
 
    mlogd("read callback: {} bytes...", len);
 
-   nghttp2_session_consume_connection(session, len);
-
    //
    // We try to invoke the read handler directly with the new buffer view. Only if there is no
    // pending read handler that can be invoked immediately, the data will be copied into a buffer.

src/h2v2/session.cpp

@@ -204,23 +204,22 @@ static int on_recv_data(nghttp2_conn* conn, int64_t stream_id, const uint8_t* da
    auto handler = static_cast<NGHttp2Session*>(user_data);
    auto stream = static_cast<NGHttp2Stream*>(stream_user_data);
 
-   if (!stream)
-   {
-      logw("[{}] on_recv_data: DATA, but no stream found", handler->log_prefix(stream_id));
-      nghttp2_conn_extend_max_offset(conn, datalen);
-      return 0;
-   }
-
-   logd("[{}] on_recv_data: DATA, len={}", handler->log_prefix(stream_id), datalen);
-
    //
-   // Connection-level credit is given back right away; the stream-level window is only reopened
-   // once the reader has taken the data, which is what applies back pressure. Version 1 split the
-   // same two steps between nghttp2_session_consume_connection() and consume_stream().
+   // Connection-level credit is given back right away, with or without a stream: nobody else would,
+   // and the connection would run out of it. The stream-level window is only reopened once the
+   // reader has taken the data, which is what applies back pressure. Version 1 split the same two
+   // steps between nghttp2_session_consume_connection() and consume_stream().
    //
    nghttp2_conn_extend_max_offset(conn, datalen);
 
-   stream->on_data(data, datalen);
+   if (stream)
+   {
+      logd("[{}] on_recv_data: DATA, len={}", handler->log_prefix(stream_id), datalen);
+      stream->on_data(data, datalen);
+   }
+   else
+      logw("[{}] on_recv_data: DATA, but no stream found", handler->log_prefix(stream_id));
+
    handler->start_write(); // might re-open windows
 
    return 0;