TUN-5285: Fallback to HTTP2 immediately if connection times out with no network activity

Author: sudarshan-reddy

connection/quic.go

@@ -49,12 +49,12 @@ func NewQUICConnection(
 ) (*QUICConnection, error) {
 	session, err := quic.DialAddr(edgeAddr.String(), tlsConfig, quicConfig)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to dial to edge")
+		return nil, fmt.Errorf("failed to dial to edge: %w", err)
 	}
 
 	registrationStream, err := session.OpenStream()
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to open a registration stream")
+		return nil, fmt.Errorf("failed to open a registration stream: %w", err)
 	}
 
 	err = controlStreamHandler.ServeControlStream(ctx, registrationStream, connOptions, false)
@@ -82,7 +82,7 @@ func (q *QUICConnection) Serve(ctx context.Context) error {
 			if errors.Is(err, context.Canceled) {
 				return nil
 			}
-			return errors.Wrap(err, "failed to accept QUIC stream")
+			return fmt.Errorf("failed to accept QUIC stream: %w", err)
 		}
 		go func() {
 			defer stream.Close()

origin/tunnel.go

@@ -190,7 +190,13 @@ func ServeTunnelLoop(
 		case <-gracefulShutdownC:
 			return nil
 		case <-protocolFallback.BackoffTimer():
-			if !selectNextProtocol(&connLog, protocolFallback, config.ProtocolSelector) {
+			var idleTimeoutError *quic.IdleTimeoutError
+			if !selectNextProtocol(
+				&connLog,
+				protocolFallback,
+				config.ProtocolSelector,
+				errors.As(err, &idleTimeoutError),
+			) {
 				return err
 			}
 		}
@@ -222,8 +228,9 @@ func selectNextProtocol(
 	connLog *zerolog.Logger,
 	protocolBackoff *protocolFallback,
 	selector connection.ProtocolSelector,
+	isNetworkActivityTimeout bool,
 ) bool {
-	if protocolBackoff.ReachedMaxRetries() {
+	if protocolBackoff.ReachedMaxRetries() || isNetworkActivityTimeout {
 		fallback, hasFallback := selector.Fallback()
 		if !hasFallback {
 			return false

origin/tunnel_test.go

@@ -62,15 +62,15 @@ func TestWaitForBackoffFallback(t *testing.T) {
 	// Retry #0 and #1. At retry #2, we switch protocol, so the fallback loop has one more retry than this
 	for i := 0; i < int(maxRetries-1); i++ {
 		protocolFallback.BackoffTimer() // simulate retry
-		ok := selectNextProtocol(&log, protocolFallback, protocolSelector)
+		ok := selectNextProtocol(&log, protocolFallback, protocolSelector, false)
 		assert.True(t, ok)
 		assert.Equal(t, initProtocol, protocolFallback.protocol)
 	}
 
 	// Retry fallback protocol
 	for i := 0; i < int(maxRetries); i++ {
 		protocolFallback.BackoffTimer() // simulate retry
-		ok := selectNextProtocol(&log, protocolFallback, protocolSelector)
+		ok := selectNextProtocol(&log, protocolFallback, protocolSelector, false)
 		assert.True(t, ok)
 		fallback, ok := protocolSelector.Fallback()
 		assert.True(t, ok)
@@ -82,12 +82,19 @@ func TestWaitForBackoffFallback(t *testing.T) {
 
 	// No protocol to fallback, return error
 	protocolFallback.BackoffTimer() // simulate retry
-	ok := selectNextProtocol(&log, protocolFallback, protocolSelector)
+	ok := selectNextProtocol(&log, protocolFallback, protocolSelector, false)
 	assert.False(t, ok)
 
 	protocolFallback.reset()
 	protocolFallback.BackoffTimer() // simulate retry
-	ok = selectNextProtocol(&log, protocolFallback, protocolSelector)
+	ok = selectNextProtocol(&log, protocolFallback, protocolSelector, false)
 	assert.True(t, ok)
 	assert.Equal(t, initProtocol, protocolFallback.protocol)
+
+	protocolFallback.reset()
+	protocolFallback.BackoffTimer() // simulate retry
+	ok = selectNextProtocol(&log, protocolFallback, protocolSelector, true)
+	// Check that we get a true after the first try itself when this flag is true. This allows us to immediately
+	// switch protocols.
+	assert.True(t, ok)
 }