quic: fix infinite loop if STOP_SENDING received on a buffering stream

src/quic/application.cc

@@ -410,6 +410,12 @@ class DefaultApplication final : public Session::Application {
 
   void ResumeStream(stream_id id) override { ScheduleStream(id); }
 
+  void StreamWriteShut(stream_id id) override {
+    if (auto stream = session().FindStream(id)) [[likely]] {
+      stream->Unschedule();
+    }
+  }
+
   void BlockStream(stream_id id) override {
     if (auto stream = session().FindStream(id)) [[likely]] {
       // Remove the stream from the send queue. It will be re-scheduled

test/parallel/test-quic-stream-stop-sending-buffered.mjs

@@ -0,0 +1,49 @@
+// Flags: --experimental-quic --no-warnings
+
+// A peer STOP_SENDING must unschedule buffered outbound data.
+
+import { hasQuic, mustCall, skip } from '../common/index.mjs';
+import assert from 'node:assert';
+
+if (!hasQuic) {
+  skip('QUIC is not enabled');
+}
+
+const { connect, listen } = await import('../common/quic.mjs');
+
+const serverStreamReady = Promise.withResolvers();
+const clientBuffered = Promise.withResolvers();
+const serverReset = Promise.withResolvers();
+
+const serverEndpoint = await listen(mustCall((serverSession) => {
+  serverSession.onstream = mustCall(async (stream) => {
+    serverStreamReady.resolve();
+    await clientBuffered.promise;
+
+    const closed = assert.rejects(stream.closed, {
+      code: 'ERR_QUIC_APPLICATION_ERROR',
+    });
+    stream.stopSending(1n);
+    stream.writer.endSync();
+    await closed;
+    serverSession.close();
+    serverReset.resolve();
+  });
+}));
+
+const clientSession = await connect(serverEndpoint.address);
+await clientSession.opened;
+
+const stream = await clientSession.createBidirectionalStream();
+const clientClosed = stream.closed.catch(() => {});
+const writer = stream.writer;
+writer.writeSync(new Uint8Array([1]));
+await serverStreamReady.promise;
+
+writer.writeSync(new Uint8Array(64 * 1024));
+clientBuffered.resolve();
+
+await serverReset.promise;
+
+await Promise.all([clientClosed, clientSession.closed]);
+await serverEndpoint.close();