Don't send stream-level flow control updates for stopped streams

We only queue MAX_STREAM_DATA when stream data is read by the
application, which never happens for stopped streams, but loss of
packets carrying previously sent MAX_STREAM_DATA frames could still
cause fresh ones to be queued unnecessarily. Filtering them out isn't
strictly necessary, but saves some space in the packet.

quinn-proto/src/connection/streams/recv.rs

@@ -107,7 +107,8 @@ impl Recv {
         // smaller than `stream_receive_window` in order to make sure the stream
         // does not get stuck.
         let diff = max_stream_data - self.sent_max_stream_data;
-        let transmit = self.receiving_unknown_size() && diff >= (stream_receive_window / 8);
+        let transmit =
+            self.receiving_unknown_size() && !self.stopped && diff >= (stream_receive_window / 8);
         (max_stream_data, ShouldTransmit(transmit))
     }
 

quinn-proto/src/connection/streams/state.rs

@@ -358,7 +358,7 @@ impl StreamsState {
         self.recv
             .get(&id)
             .and_then(|s| s.as_ref())
-            .map_or(false, |s| s.receiving_unknown_size())
+            .map_or(false, |s| s.receiving_unknown_size() && !s.stopped)
     }
 
     pub(in crate::connection) fn write_control_frames(
@@ -446,7 +446,7 @@ impl StreamsState {
                 Some(x) => x,
                 None => continue,
             };
-            if !rs.receiving_unknown_size() {
+            if !rs.receiving_unknown_size() || rs.stopped {
                 continue;
             }
             retransmits.get_or_create().max_stream_data.insert(id);