diff --git a/cmd/tun2socks/main_proxy.go b/cmd/tun2socks/main_proxy.go
new file mode 100644
index 0000000..9050c24
--- /dev/null
+++ b/cmd/tun2socks/main_proxy.go
@@ -0,0 +1,3 @@
+// +build proxy
+
+package main
diff --git a/proxy/proxy.go b/proxy/proxy.go
new file mode 100644
index 0000000..62755dc
--- /dev/null
+++ b/proxy/proxy.go
@@ -0,0 +1,54 @@
+package proxy
+
+import (
+	"io"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/xjasonlyu/tun2socks/common/pool"
+)
+
+func TCPRelay(localConn, remoteConn net.Conn) {
+	var once sync.Once
+	closeOnce := func() {
+		once.Do(func() {
+			localConn.Close()
+			remoteConn.Close()
+		})
+	}
+
+	// Close
+	defer closeOnce()
+
+	// WaitGroup
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	// Up Link
+	go func() {
+		buf := pool.BufPool.Get().([]byte)
+		defer pool.BufPool.Put(buf[:cap(buf)])
+		if _, err := io.CopyBuffer(remoteConn, localConn, buf); err != nil {
+			closeOnce()
+		} else {
+			localConn.SetDeadline(time.Now())
+			remoteConn.SetDeadline(time.Now())
+			TCPCloseRead(remoteConn)
+		}
+		wg.Done()
+	}()
+
+	// Down Link
+	buf := pool.BufPool.Get().([]byte)
+	if _, err := io.CopyBuffer(localConn, remoteConn, buf); err != nil {
+		closeOnce()
+	} else {
+		localConn.SetDeadline(time.Now())
+		remoteConn.SetDeadline(time.Now())
+		TCPCloseRead(localConn)
+	}
+	pool.BufPool.Put(buf[:cap(buf)])
+
+	wg.Wait() // Wait for Up Link done
+}
diff --git a/proxy/utils.go b/proxy/utils.go
new file mode 100644
index 0000000..3c7e261
--- /dev/null
+++ b/proxy/utils.go
@@ -0,0 +1,31 @@
+package proxy
+
+import (
+	"net"
+	"time"
+)
+
+type duplexConn interface {
+	net.Conn
+	CloseRead() error
+	CloseWrite() error
+}
+
+func TCPCloseRead(conn net.Conn) {
+	if c, ok := conn.(duplexConn); ok {
+		c.CloseRead()
+	}
+}
+
+func TCPCloseWrite(conn net.Conn) {
+	if c, ok := conn.(duplexConn); ok {
+		c.CloseWrite()
+	}
+}
+
+func TCPKeepAlive(conn net.Conn) {
+	if tcp, ok := conn.(*net.TCPConn); ok {
+		tcp.SetKeepAlive(true)
+		tcp.SetKeepAlivePeriod(30 * time.Second)
+	}
+}