golang 转到TCP代理模式

Posted 2021-05-24

package proxy

import (
	"io"
	"log"
	"net"
)

func Proxy(srvConn, cliConn *net.TCPConn) {
	// channels to wait on the close event for each connection
	serverClosed := make(chan struct{}, 1)
	clientClosed := make(chan struct{}, 1)

	go broker(srvConn, cliConn, clientClosed)
	go broker(cliConn, srvConn, serverClosed)

	// wait for one half of the proxy to exit, then trigger a shutdown of the
	// other half by calling CloseRead(). This will break the read loop in the
	// broker and allow us to fully close the connection cleanly without a
	// "use of closed network connection" error.
	var waitFor chan struct{}
	select {
	case <-clientClosed:
		// the client closed first and any more packets from the server aren't
		// useful, so we can optionally SetLinger(0) here to recycle the port
		// faster.
		srvConn.SetLinger(0)
		srvConn.CloseRead()
		waitFor = serverClosed
	case <-serverClosed:
		cliConn.CloseRead()
		waitFor = clientClosed
	}

	// Wait for the other connection to close.
	// This "waitFor" pattern isn't required, but gives us a way to track the
	// connection and ensure all copies terminate correctly; we can trigger
	// stats on entry and deferred exit of this function.
	<-waitFor
}

// This does the actual data transfer.
// The broker only closes the Read side.
func broker(dst, src net.Conn, srcClosed chan struct{}) {
	// We can handle errors in a finer-grained manner by inlining io.Copy (it's
	// simple, and we drop the ReaderFrom or WriterTo checks for
	// net.Conn->net.Conn transfers, which aren't needed). This would also let
	// us adjust buffersize.
	_, err := io.Copy(dst, src)

	if err != nil {
		log.Printf("Copy error: %s", err)
	}
	if err := src.Close(); err != nil {
		log.Printf("Close error: %s", err)
	}
	srcClosed <- struct{}{}
}

golang 转到TCP代理/端口转发示例（https://zupzup.org/go-port-forwarding/）

package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"os/signal"
)

var (
	target string
	port   int
)

func init() {
	flag.StringVar(&target, "target", "", "the target (<host>:<port>)")
	flag.IntVar(&port, "port", 7757, "the tunnelthing port")
}

func main() {
	flag.Parse()

	signals := make(chan os.Signal, 1)
	stop := make(chan bool)
	signal.Notify(signals, os.Interrupt)
	go func() {
		for _ = range signals {
			fmt.Println("\nReceived an interrupt, stopping...")
			stop <- true
		}
	}()

	incoming, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
	if err != nil {
		log.Fatalf("could not start server on %d: %v", port, err)
	}
	fmt.Printf("server running on %d\n", port)

	client, err := incoming.Accept()
	if err != nil {
		log.Fatal("could not accept client connection", err)
	}
	defer client.Close()
	fmt.Printf("client '%v' connected!\n", client.RemoteAddr())

	target, err := net.Dial("tcp", target)
	if err != nil {
		log.Fatal("could not connect to target", err)
	}
	defer target.Close()
	fmt.Printf("connection to server %v established!\n", target.RemoteAddr())

	go func() { io.Copy(target, client) }()
	go func() { io.Copy(client, target) }()

	<-stop
}