Port Mirroring

[stokito]

I need a proxy to imitate a port mirroring (SPAN) that will be used for a logging.
There is some NGINX module http://nginx.org/en/docs/http/ngx_http_mirror_module.html but it mirrors only requests. For my case I need responses from the remote too.
Here I patched your proxy and hope this may be useful to add as a fature

[stokito]

Just an example of response listener using FastHttp library:

var ReadBufferSize = 30000
var readerPool sync.Pool

func startResponseLoggerServer() {
	l, err := net.Listen("tcp", "localhost:9092")
	if err != nil {
		fmt.Fprintf("Error listening: %s\n", err.Error())
	}

	for {
		in, err := l.Accept()
		if err != nil {
			continue
		}
		fmt.Fprintf("Incoming connection from %s\n", in.RemoteAddr())
		//handleClient(in)

		resp := fasthttp.AcquireResponse()
		br := acquireReader(in)
		err = resp.ReadLimitBody(br, ReadBufferSize)
		if err != nil {
			fmt.Fprintf("Failed to read body: %s\n", err)
		}
		releaseReader(br)
		fmt.Fprintf("Bid resp: %s\n", resp.Body())
		fasthttp.ReleaseResponse(resp)
	}
}

func handleClient(conn net.Conn) {
	var buf [512]byte
	for {
		n, err := conn.Read(buf[0:])
		if err != nil {
			return
		}
		fmt.Println(string(buf[0:n]))
	}
}

func acquireReader(conn net.Conn) *bufio.Reader {
	v := readerPool.Get()
	if v == nil {
		return bufio.NewReaderSize(conn, ReadBufferSize)
	}
	br := v.(*bufio.Reader)
	br.Reset(conn)
	return br
}

func releaseReader(br *bufio.Reader) {
	readerPool.Put(br)
}