From 70c821348920535845de489a6b759b32df45419f Mon Sep 17 00:00:00 2001
From: sukun <sukunrt@gmail.com>
Date: Sat, 17 Feb 2024 09:10:00 +0530
Subject: [PATCH 1/2] server: fix deadlock when closing concurrently with
 transport

---
 server.go | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/server.go b/server.go
index a87a3647f33..b3c85543662 100644
--- a/server.go
+++ b/server.go
@@ -98,7 +98,7 @@ type baseServer struct {
 		protocol.Version,
 	) quicConn
 
-	closeOnce sync.Once
+	closeMx   sync.Mutex
 	errorChan chan struct{} // is closed when the server is closed
 	closeErr  error
 	running   chan struct{} // closed as soon as run() returns
@@ -338,15 +338,19 @@ func (s *baseServer) Close() error {
 }
 
 func (s *baseServer) close(e error, notifyOnClose bool) {
-	s.closeOnce.Do(func() {
-		s.closeErr = e
-		close(s.errorChan)
+	s.closeMx.Lock()
+	if s.closeErr != nil {
+		s.closeMx.Unlock()
+		return
+	}
+	s.closeErr = e
+	close(s.errorChan)
+	<-s.running
+	s.closeMx.Unlock()
 
-		<-s.running
-		if notifyOnClose {
-			s.onClose()
-		}
-	})
+	if notifyOnClose {
+		s.onClose()
+	}
 }
 
 // Addr returns the server's network address

From 121b82c836008f0b984dc40d0e6903f07c473294 Mon Sep 17 00:00:00 2001
From: sukun <sukunrt@gmail.com>
Date: Sun, 3 Mar 2024 13:56:30 +0530
Subject: [PATCH 2/2] add test for checking no deadlock

---
 transport_test.go | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/transport_test.go b/transport_test.go
index 4e89dcfbb8a..aeeb1153c98 100644
--- a/transport_test.go
+++ b/transport_test.go
@@ -122,6 +122,27 @@ var _ = Describe("Transport", func() {
 		tr.Close()
 	})
 
+	It("closes transport concurrently with listener", func() {
+		// try 10 times to trigger race conditions
+		for i := 0; i < 10; i++ {
+			packetChan := make(chan packetToRead)
+			tr := &Transport{Conn: newMockPacketConn(packetChan)}
+			ln, err := tr.Listen(&tls.Config{}, nil)
+			Expect(err).ToNot(HaveOccurred())
+			ch := make(chan bool)
+			// Close transport and listener concurrently.
+			go func() {
+				ch <- true
+				Expect(ln.Close()).To(Succeed())
+				ch <- true
+			}()
+			<-ch
+			close(packetChan)
+			Expect(tr.Close()).To(Succeed())
+			<-ch
+		}
+	})
+
 	It("drops unparseable QUIC packets", func() {
 		addr := &net.UDPAddr{IP: net.IPv4(9, 8, 7, 6), Port: 1234}
 		packetChan := make(chan packetToRead)