From 344feb9ea58b3e7cf1259f8dbd922b2941a13d3a Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sat, 16 Oct 2021 17:45:43 +0200
Subject: [PATCH 1/2] don't unlock the receive stream mutex for copying from
 STREAM frames

---
 receive_stream.go | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/receive_stream.go b/receive_stream.go
index cca3f709..f9a1e066 100644
--- a/receive_stream.go
+++ b/receive_stream.go
@@ -166,13 +166,10 @@ func (s *receiveStream) readImpl(p []byte) (bool /*stream completed */, int, err
 			return false, bytesRead, fmt.Errorf("BUG: readPosInFrame (%d) > frame.DataLen (%d) in stream.Read", s.readPosInFrame, len(s.currentFrame))
 		}
 
-		s.mutex.Unlock()
-
 		m := copy(p[bytesRead:], s.currentFrame[s.readPosInFrame:])
 		s.readPosInFrame += m
 		bytesRead += m
 
-		s.mutex.Lock()
 		// when a RESET_STREAM was received, the was already informed about the final byteOffset for this stream
 		if !s.resetRemotely {
 			s.flowController.AddBytesRead(protocol.ByteCount(m))

From 2c8b939d4c2df4d95165ba49ca8edab3480d6e4f Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sat, 16 Oct 2021 19:00:26 +0200
Subject: [PATCH 2/2] add an integration tests that cancels streams frequently

---
 integrationtests/self/cancelation_test.go | 88 +++++++++++++++++++++++
 1 file changed, 88 insertions(+)

diff --git a/integrationtests/self/cancelation_test.go b/integrationtests/self/cancelation_test.go
index 97697c84..651bb06e 100644
--- a/integrationtests/self/cancelation_test.go
+++ b/integrationtests/self/cancelation_test.go
@@ -631,4 +631,92 @@ var _ = Describe("Stream Cancelations", func() {
 			Expect(server.Close()).To(Succeed())
 		})
 	})
+
+	It("doesn't run into any errors when streams are canceled all the time", func() {
+		const maxIncomingStreams = 1000
+		server, err := quic.ListenAddr(
+			"localhost:0",
+			getTLSConfig(),
+			getQuicConfig(&quic.Config{MaxIncomingStreams: maxIncomingStreams, MaxIdleTimeout: 10 * time.Second}),
+		)
+		Expect(err).ToNot(HaveOccurred())
+
+		var wg sync.WaitGroup
+		wg.Add(2 * 4 * maxIncomingStreams)
+		handleStream := func(str quic.Stream) {
+			str.SetDeadline(time.Now().Add(time.Second))
+			go func() {
+				defer wg.Done()
+				if rand.Int31()%2 == 0 {
+					defer GinkgoRecover()
+					io.ReadAll(str)
+				}
+			}()
+			go func() {
+				defer wg.Done()
+				if rand.Int31()%2 == 0 {
+					str.Write([]byte("foobar"))
+					if rand.Int31()%2 == 0 {
+						str.Close()
+					}
+				}
+			}()
+			go func() {
+				defer wg.Done()
+				// Make sure we at least send out *something* for the last stream,
+				// otherwise the peer might never receive this anything for this stream.
+				if rand.Int31()%2 == 0 || str.StreamID() == 4*(maxIncomingStreams-1) {
+					str.CancelWrite(1234)
+				}
+			}()
+			go func() {
+				defer wg.Done()
+				if rand.Int31()%2 == 0 {
+					str.CancelRead(1234)
+				}
+			}()
+		}
+
+		serverRunning := make(chan struct{})
+		go func() {
+			defer GinkgoRecover()
+			defer close(serverRunning)
+			conn, err := server.Accept(context.Background())
+			Expect(err).ToNot(HaveOccurred())
+			for {
+				str, err := conn.AcceptStream(context.Background())
+				if err != nil {
+					// Make sure the session is closed regularly.
+					Expect(err).To(BeAssignableToTypeOf(&quic.ApplicationError{}))
+					return
+				}
+				handleStream(str)
+			}
+		}()
+
+		sess, err := quic.DialAddr(
+			fmt.Sprintf("localhost:%d", server.Addr().(*net.UDPAddr).Port),
+			getTLSClientConfig(),
+			getQuicConfig(&quic.Config{}),
+		)
+		Expect(err).ToNot(HaveOccurred())
+
+		for i := 0; i < maxIncomingStreams; i++ {
+			str, err := sess.OpenStreamSync(context.Background())
+			Expect(err).ToNot(HaveOccurred())
+			handleStream(str)
+		}
+
+		// We don't expect to accept any stream here.
+		// We're just making sure the session stays open and there's no error.
+		ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
+		defer cancel()
+		_, err = sess.AcceptStream(ctx)
+		Expect(err).To(MatchError(context.DeadlineExceeded))
+
+		wg.Wait()
+
+		Expect(sess.CloseWithError(0, "")).To(Succeed())
+		Eventually(serverRunning).Should(BeClosed())
+	})
 })