vnet: fix route cleanup and reconnect backoff (#5492)

pkg/plugin/visitor/virtual_net.go

@@ -48,6 +48,11 @@ type VirtualNetPlugin struct {
 	cancel context.CancelFunc
 }
 
+const (
+	virtualNetReconnectBaseDelay = 60 * time.Second
+	virtualNetReconnectMaxDelay  = 300 * time.Second
+)
+
 func NewVirtualNetPlugin(pluginCtx PluginContext, options v1.VisitorPluginOptions) (Plugin, error) {
 	opts := options.(*v1.VirtualNetVisitorPluginOptions)
 
@@ -152,8 +157,7 @@ func (p *VirtualNetPlugin) run() {
 					p.pluginCtx.Name, p.consecutiveErrors, closeErr)
 
 				// Exponential backoff: 60s, 120s, 240s, 300s (capped)
-				baseDelay := 60 * time.Second
-				reconnectDelay = min(baseDelay*time.Duration(1<<uint(p.consecutiveErrors-1)), 300*time.Second)
+				reconnectDelay = virtualNetReconnectDelay(p.consecutiveErrors)
 			} else {
 				// Reset consecutive errors on successful connection
 				if p.consecutiveErrors > 0 {
@@ -182,6 +186,18 @@ func (p *VirtualNetPlugin) run() {
 	}
 }
 
+// virtualNetReconnectDelay returns a bounded reconnect delay without allowing
+// the exponential shift to overflow for large consecutive error counts.
+func virtualNetReconnectDelay(consecutiveErrors int) time.Duration {
+	if consecutiveErrors <= 1 {
+		return virtualNetReconnectBaseDelay
+	}
+	if consecutiveErrors >= 4 {
+		return virtualNetReconnectMaxDelay
+	}
+	return virtualNetReconnectBaseDelay * time.Duration(1<<uint(consecutiveErrors-1))
+}
+
 // cleanupControllerConn closes the current controllerConn (if it exists) under lock.
 func (p *VirtualNetPlugin) cleanupControllerConn(xl *xlog.Logger) {
 	p.mu.Lock()
@@ -202,9 +218,12 @@ func (p *VirtualNetPlugin) Close() error {
 	// Signal the run loop goroutine to stop.
 	p.cancel()
 
-	// Unregister the route from the controller.
-	if p.pluginCtx.VnetController != nil {
-		p.pluginCtx.VnetController.UnregisterClientRoute(p.pluginCtx.Name)
+	// Unregister the route only if it is still owned by this plugin instance.
+	p.mu.Lock()
+	controllerConn := p.controllerConn
+	p.mu.Unlock()
+	if p.pluginCtx.VnetController != nil && controllerConn != nil &&
+		p.pluginCtx.VnetController.UnregisterClientRoute(p.pluginCtx.Name, controllerConn) {
 		xl.Infof("unregistered client route for visitor [%s]", p.pluginCtx.Name)
 	}
 

pkg/plugin/visitor/virtual_net_test.go

@@ -0,0 +1,47 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !frps
+
+package visitor
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestVirtualNetReconnectDelay verifies the documented exponential backoff and
+// ensures large error counts remain capped instead of overflowing to zero.
+func TestVirtualNetReconnectDelay(t *testing.T) {
+	tests := []struct {
+		name              string
+		consecutiveErrors int
+		want              time.Duration
+	}{
+		{name: "first error", consecutiveErrors: 1, want: 60 * time.Second},
+		{name: "second error", consecutiveErrors: 2, want: 120 * time.Second},
+		{name: "third error", consecutiveErrors: 3, want: 240 * time.Second},
+		{name: "fourth error", consecutiveErrors: 4, want: 300 * time.Second},
+		{name: "shift width boundary", consecutiveErrors: 64, want: 300 * time.Second},
+		{name: "observed retry storm", consecutiveErrors: 329769, want: 300 * time.Second},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equal(t, tt.want, virtualNetReconnectDelay(tt.consecutiveErrors))
+		})
+	}
+}