feat: add support socks5 proxy

cmd/cmd.go

@@ -13,11 +13,12 @@ import (
 )
 
 var (
-	command   string
-	proxyPort uint16
-	proxyPid  uint64
-	pids      []string
-	ipStr     string
+	command         string
+	proxyPort       uint16
+	proxyPid        uint64
+	pids            []string
+	ipStr           string
+	socks5ProxyAddr string
 )
 
 var rootCmd = &cobra.Command{
@@ -45,7 +46,7 @@ var rootCmd = &cobra.Command{
 		Options.Ip4 = ip
 
 		if proxyPid == 0 {
-			StartProxy(proxyPort)
+			StartProxy()
 		}
 		for _, pid := range pids {
 			pidInt, err := strconv.ParseUint(pid, 10, 64)
@@ -92,4 +93,5 @@ func init() {
 	rootCmd.PersistentFlags().Uint64Var(&proxyPid, "p-pid", 0, "The process ID of the proxy. If not provided, the program will automatically start a forwarding proxy.")
 	rootCmd.PersistentFlags().StringSliceVar(&pids, "pids", []string{}, "The pid to be proxied, seperate by ','")
 	rootCmd.PersistentFlags().StringVar(&ipStr, "ip", "", "The ip to be proxied,only support ipv4")
+	rootCmd.PersistentFlags().StringVar(&socks5ProxyAddr, "socks5", "", "The socks5 proxyAddr.")
 }

cmd/tcpProxy.go

@@ -9,9 +9,11 @@ import (
 	"syscall"
 	"time"
 	"unsafe"
+
+	"golang.org/x/net/proxy"
 )
 
-func StartProxy(proxyPort uint16) {
+func StartProxy() {
 	// log.Printf("Proxy server with PID %d listening on %s", options.ProxyPid, proxyAddr)
 	proxyAddr := fmt.Sprintf("127.0.0.1:%d", proxyPort)
 	// Start the proxy server on the localhost
@@ -49,13 +51,33 @@ func getsockopt(s int, level int, optname int, optval unsafe.Pointer, optlen *ui
 func handleConnection(conn net.Conn) {
 	defer conn.Close()
 
+	targetConn, err := getTargetConnection(conn)
+	if err != nil {
+		log.Printf("Connection error: %v", err)
+		return
+	}
+
+	go func() {
+		_, err = io.Copy(targetConn, conn)
+		if err != nil {
+			log.Printf("Failed copying data to target: %v", err)
+		}
+	}()
+	_, err = io.Copy(conn, targetConn)
+	if err != nil {
+		log.Printf("Failed copying data from target: %v", err)
+	}
+}
+
+func getTargetConnection(conn net.Conn) (net.Conn, error) {
+
 	// Using RawConn is necessary to perform low-level operations on the underlying socket file descriptor in Go.
 	// This allows us to use getsockopt to retrieve the original destination address set by the SO_ORIGINAL_DST option,
 	// which isn't directly accessible through Go's higher-level networking API.
 	rawConn, err := conn.(*net.TCPConn).SyscallConn()
 	if err != nil {
 		log.Printf("Failed to get raw connection: %v", err)
-		return
+		return nil, err
 	}
 
 	var originalDst SockAddrIn
@@ -74,27 +96,22 @@ func handleConnection(conn net.Conn) {
 
 	fmt.Printf("Original destination: %s:%d\n", targetAddr, targetPort)
 
-	// Check that the original destination address is reachable from the proxy
-	targetConn, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%d", targetAddr, targetPort), 5*time.Second)
-	if err != nil {
-		log.Printf("Failed to connect to original destination: %v", err)
-		return
+	if socks5ProxyAddr == "" {
+		targetConn, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%d", targetAddr, targetPort), 5*time.Second)
+		if err != nil {
+			return nil, fmt.Errorf("failed to connect to destination: %w", err)
+		}
+		return targetConn, nil
 	}
-	defer targetConn.Close()
 
-	fmt.Printf("Proxying connection from %s to %s\n", conn.RemoteAddr(), targetConn.RemoteAddr())
+	dialer, err := proxy.SOCKS5("tcp", socks5ProxyAddr, nil, proxy.Direct)
+	if err != nil {
+		return nil, fmt.Errorf("cannot create SOCKS5 dialer: %w", err)
+	}
 
-	// The following code creates two data transfer channels:
-	// - From the client to the target server (handled by a separate goroutine).
-	// - From the target server to the client (handled by the main goroutine).
-	go func() {
-		_, err = io.Copy(targetConn, conn)
-		if err != nil {
-			log.Printf("Failed copying data to target: %v", err)
-		}
-	}()
-	_, err = io.Copy(conn, targetConn)
+	targetConn, err := dialer.Dial("tcp", fmt.Sprintf("%s:%d", targetAddr, targetPort))
 	if err != nil {
-		log.Printf("Failed copying data from target: %v", err)
+		return nil, fmt.Errorf("failed to connect via SOCKS5: %w", err)
 	}
+	return targetConn, nil
 }

go.mod

@@ -5,10 +5,11 @@ go 1.24.4
 require (
 	github.com/cilium/ebpf v0.19.0
 	github.com/spf13/cobra v1.9.1
+	golang.org/x/net v0.38.0
+	golang.org/x/sys v0.31.0
 )
 
 require (
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.6 // indirect
-	golang.org/x/sys v0.31.0 // indirect
 )