[Bug] engine.Stop method stucks

[coder-free]

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• [X] Is this something you can debug and fix? Send a pull request! Bug fixes and documentation fixes are welcome.
• [X] I have searched on the issue tracker for a related issue.

Version

6cfc25309e35d2c9873864a8b04fffa884a8b4e9

What OS are you seeing the problem on?

macOS

Description

你好，我使用类似于这样的方式启动 tun2socks，在取消阻塞后 engine.Stop() 被调用的时候卡住了

Start() {
    var key = new(engine.Key)
    log := "info"
    if len(logLevel) > 0 {
        log = logLevel
    }
    key.Proxy = proxy
    key.LogLevel = log
    key.MTU = mtu
    key.TCPReceiveBufferSize = "131072"
    key.TCPSendBufferSize = "131072"

    engine.Insert(key)
    engine.Start()
    defer engine.Stop()
        //阻塞

}

Stop() {
       //取消阻塞
}

具体来说卡在了 gvisor stack 的 wait 方法上：

func stop() (err error) {
    log.Errorf("stop 1.")
    _engineMu.Lock()
    log.Errorf("stop 2.")
    if _defaultDevice != nil {
        log.Errorf("stop 3.")
        err = _defaultDevice.Close()
        log.Errorf("stop 4: %v", err)
    }
    if _defaultStack != nil {
        log.Errorf("stop 5.")
        _defaultStack.Close()
        log.Errorf("stop 6.")
        _defaultStack.Wait()
        log.Errorf("stop 7.")
    }
    _engineMu.Unlock()
    log.Errorf("stop 8.")
    return err
}

stop 6 被打印出来，但是 stop 7 一直未出现。

另外，key里面没有device，我是自己创建了一个 io.ReadWriter 来模拟 device 提供数据的读写接口。 像下面这样创建 device：

func open(mtu uint32, rw io.ReadWriter) (device.Device, error) {
    f := &FD{mtu: mtu}
    ep, err := iobased.New(rw, mtu, 0)
    if err != nil {
        return nil, fmt.Errorf("create endpoint: %w", err)
    }
    f.LinkEndpoint = ep

    return f, nil
}

CLI or Config

No response

Logs

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How to Reproduce

No response

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