fix: stream flow control insufficient size before ack (#746)

* fix: stream flow control insufficient size before ack

* test: client sending data before initial settings ack

Author: dswij

src/proto/connection.rs

@@ -106,10 +106,6 @@ where
     pub fn new(codec: Codec<T, Prioritized<B>>, config: Config) -> Connection<T, P, B> {
         fn streams_config(config: &Config) -> streams::Config {
             streams::Config {
-                local_init_window_sz: config
-                    .settings
-                    .initial_window_size()
-                    .unwrap_or(DEFAULT_INITIAL_WINDOW_SIZE),
                 initial_max_send_streams: config.initial_max_send_streams,
                 local_max_buffer_size: config.max_send_buffer_size,
                 local_next_stream_id: config.next_stream_id,

src/proto/streams/mod.rs

@@ -33,9 +33,6 @@ use std::time::Duration;
 
 #[derive(Debug)]
 pub struct Config {
-    /// Initial window size of locally initiated streams
-    pub local_init_window_sz: WindowSize,
-
     /// Initial maximum number of locally initiated streams.
     /// After receiving a Settings frame from the remote peer,
     /// the connection will overwrite this value with the

src/proto/streams/recv.rs

@@ -93,7 +93,7 @@ impl Recv {
         flow.assign_capacity(DEFAULT_INITIAL_WINDOW_SIZE).unwrap();
 
         Recv {
-            init_window_sz: config.local_init_window_sz,
+            init_window_sz: DEFAULT_INITIAL_WINDOW_SIZE,
             flow,
             in_flight_data: 0 as WindowSize,
             next_stream_id: Ok(next_stream_id.into()),

tests/h2-tests/tests/server.rs

@@ -1453,3 +1453,48 @@ async fn client_drop_connection_without_close_notify() {
 
     join(client, h2).await;
 }
+
+#[tokio::test]
+async fn init_window_size_smaller_than_default_should_use_default_before_ack() {
+    h2_support::trace_init!();
+
+    let (io, mut client) = mock::new();
+    let client = async move {
+        // Client can send in some data before ACK;
+        // Server needs to make sure the Recv stream has default window size
+        // as per https://datatracker.ietf.org/doc/html/rfc9113#name-initial-flow-control-window
+        client.write_preface().await;
+        client
+            .send(frame::Settings::default().into())
+            .await
+            .unwrap();
+        client.next().await.expect("unexpected EOF").unwrap();
+        client
+            .send_frame(frames::headers(1).request("GET", "https://example.com/"))
+            .await;
+        client.send_frame(frames::data(1, &b"hello"[..])).await;
+        client.send(frame::Settings::ack().into()).await.unwrap();
+        client.next().await;
+        client
+            .recv_frame(frames::headers(1).response(200).eos())
+            .await;
+    };
+
+    let mut builder = server::Builder::new();
+    builder.max_concurrent_streams(1);
+    builder.initial_window_size(1);
+    let h2 = async move {
+        let mut srv = builder.handshake::<_, Bytes>(io).await.expect("handshake");
+        let (req, mut stream) = srv.next().await.unwrap().unwrap();
+
+        assert_eq!(req.method(), &http::Method::GET);
+
+        let rsp = http::Response::builder().status(200).body(()).unwrap();
+        stream.send_response(rsp, true).unwrap();
+
+        // Drive the state forward
+        let _ = poll_fn(|cx| srv.poll_closed(cx)).await.unwrap();
+    };
+
+    join(client, h2).await;
+}