Fix: avoid extra copy on windows

core/device/tun/io_unix.go

@@ -0,0 +1,29 @@
+// +build darwin freebsd linux,!amd64,!arm64 openbsd
+
+package tun
+
+import (
+	"github.com/xjasonlyu/tun2socks/common/pool"
+)
+
+const offset = 4 /* 4 bytes TUN_PI */
+
+func (t *TUN) Read(packet []byte) (n int, err error) {
+	buf := pool.Get(offset + len(packet))
+	defer pool.Put(buf)
+
+	if n, err = t.nt.Read(buf, offset); err != nil {
+		return
+	}
+
+	copy(packet, buf[offset:offset+n])
+	return
+}
+
+func (t *TUN) Write(packet []byte) (int, error) {
+	buf := pool.Get(offset + len(packet))
+	defer pool.Put(buf)
+
+	copy(buf[offset:], packet)
+	return t.nt.Write(buf[:offset+len(packet)], offset)
+}