diff --git a/app/proxyman/mux/writer.go b/app/proxyman/mux/writer.go
index 07c7f081..116af25a 100644
--- a/app/proxyman/mux/writer.go
+++ b/app/proxyman/mux/writer.go
@@ -63,7 +63,7 @@ func (w *Writer) writeMetaOnly() error {
 
 func (w *Writer) writeData(mb buf.MultiBuffer) error {
 	meta := w.getNextFrameMeta()
-	meta.Option.Add(OptionData)
+	meta.Option.Set(OptionData)
 
 	frame := buf.New()
 	if err := frame.AppendSupplier(meta.AsSupplier()); err != nil {
diff --git a/common/bitmask/byte.go b/common/bitmask/byte.go
index 724fd9d9..8dcc5c0c 100644
--- a/common/bitmask/byte.go
+++ b/common/bitmask/byte.go
@@ -8,7 +8,7 @@ func (b Byte) Has(bb Byte) bool {
 	return (b & bb) != 0
 }
 
-func (b *Byte) Add(bb Byte) {
+func (b *Byte) Set(bb Byte) {
 	*b |= bb
 }
 
diff --git a/common/bitmask/byte_test.go b/common/bitmask/byte_test.go
new file mode 100644
index 00000000..6e7e2e8b
--- /dev/null
+++ b/common/bitmask/byte_test.go
@@ -0,0 +1,27 @@
+package bitmask_test
+
+import (
+	"testing"
+
+	. "v2ray.com/core/common/bitmask"
+	"v2ray.com/core/testing/assert"
+)
+
+func TestBitmaskByte(t *testing.T) {
+	assert := assert.On(t)
+
+	b := Byte(0)
+	b.Set(Byte(1))
+	assert.Bool(b.Has(1)).IsTrue()
+
+	b.Set(Byte(2))
+	assert.Bool(b.Has(2)).IsTrue()
+	assert.Bool(b.Has(1)).IsTrue()
+
+	b.Clear(Byte(1))
+	assert.Bool(b.Has(2)).IsTrue()
+	assert.Bool(b.Has(1)).IsFalse()
+
+	b.Toggle(Byte(2))
+	assert.Bool(b.Has(2)).IsFalse()
+}
diff --git a/common/protocol/headers.go b/common/protocol/headers.go
index dd541b68..fb64ce71 100644
--- a/common/protocol/headers.go
+++ b/common/protocol/headers.go
@@ -3,6 +3,7 @@ package protocol
 import (
 	"runtime"
 
+	"v2ray.com/core/common/bitmask"
 	"v2ray.com/core/common/net"
 	"v2ray.com/core/common/uuid"
 )
@@ -24,31 +25,16 @@ func (c RequestCommand) TransferType() TransferType {
 	return TransferTypePacket
 }
 
-// RequestOption is the options of a request.
-type RequestOption byte
-
 const (
 	// RequestOptionChunkStream indicates request payload is chunked. Each chunk consists of length, authentication and payload.
-	RequestOptionChunkStream = RequestOption(0x01)
+	RequestOptionChunkStream bitmask.Byte = 0x01
 
 	// RequestOptionConnectionReuse indicates client side expects to reuse the connection.
-	RequestOptionConnectionReuse = RequestOption(0x02)
+	RequestOptionConnectionReuse bitmask.Byte = 0x02
 
-	RequestOptionChunkMasking = RequestOption(0x04)
+	RequestOptionChunkMasking bitmask.Byte = 0x04
 )
 
-func (o RequestOption) Has(option RequestOption) bool {
-	return (o & option) == option
-}
-
-func (o *RequestOption) Set(option RequestOption) {
-	*o = (*o | option)
-}
-
-func (o *RequestOption) Clear(option RequestOption) {
-	*o = (*o & (^option))
-}
-
 type Security byte
 
 func (s Security) Is(t SecurityType) bool {
@@ -65,7 +51,7 @@ func NormSecurity(s Security) Security {
 type RequestHeader struct {
 	Version  byte
 	Command  RequestCommand
-	Option   RequestOption
+	Option   bitmask.Byte
 	Security Security
 	Port     net.Port
 	Address  net.Address
@@ -79,28 +65,14 @@ func (h *RequestHeader) Destination() net.Destination {
 	return net.TCPDestination(h.Address, h.Port)
 }
 
-type ResponseOption byte
-
 const (
-	ResponseOptionConnectionReuse = ResponseOption(0x01)
+	ResponseOptionConnectionReuse bitmask.Byte = 0x01
 )
 
-func (o *ResponseOption) Set(option ResponseOption) {
-	*o = (*o | option)
-}
-
-func (o ResponseOption) Has(option ResponseOption) bool {
-	return (o & option) == option
-}
-
-func (o *ResponseOption) Clear(option ResponseOption) {
-	*o = (*o & (^option))
-}
-
 type ResponseCommand interface{}
 
 type ResponseHeader struct {
-	Option  ResponseOption
+	Option  bitmask.Byte
 	Command ResponseCommand
 }
 
diff --git a/common/protocol/headers_test.go b/common/protocol/headers_test.go
deleted file mode 100644
index 5ecbdd8a..00000000
--- a/common/protocol/headers_test.go
+++ /dev/null
@@ -1,34 +0,0 @@
-package protocol_test
-
-import (
-	"testing"
-
-	. "v2ray.com/core/common/protocol"
-	"v2ray.com/core/testing/assert"
-)
-
-func TestRequestOptionSet(t *testing.T) {
-	assert := assert.On(t)
-
-	var option RequestOption
-	assert.Bool(option.Has(RequestOptionChunkStream)).IsFalse()
-
-	option.Set(RequestOptionChunkStream)
-	assert.Bool(option.Has(RequestOptionChunkStream)).IsTrue()
-
-	option.Set(RequestOptionChunkMasking)
-	assert.Bool(option.Has(RequestOptionChunkMasking)).IsTrue()
-	assert.Bool(option.Has(RequestOptionChunkStream)).IsTrue()
-}
-
-func TestRequestOptionClear(t *testing.T) {
-	assert := assert.On(t)
-
-	var option RequestOption
-	option.Set(RequestOptionChunkStream)
-	option.Set(RequestOptionChunkMasking)
-
-	option.Clear(RequestOptionChunkStream)
-	assert.Bool(option.Has(RequestOptionChunkStream)).IsFalse()
-	assert.Bool(option.Has(RequestOptionChunkMasking)).IsTrue()
-}
diff --git a/proxy/shadowsocks/protocol.go b/proxy/shadowsocks/protocol.go
index a9cd686c..25a360fa 100644
--- a/proxy/shadowsocks/protocol.go
+++ b/proxy/shadowsocks/protocol.go
@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"io"
 
+	"v2ray.com/core/common/bitmask"
 	"v2ray.com/core/common/buf"
 	"v2ray.com/core/common/crypto"
 	"v2ray.com/core/common/net"
@@ -13,8 +14,8 @@ import (
 )
 
 const (
-	Version                  = 1
-	RequestOptionOneTimeAuth = protocol.RequestOption(101)
+	Version                               = 1
+	RequestOptionOneTimeAuth bitmask.Byte = 0x01
 
 	AddrTypeIPv4   = 1
 	AddrTypeIPv6   = 4
diff --git a/proxy/vmess/encoding/client.go b/proxy/vmess/encoding/client.go
index 0ff3c2bb..d3eab9eb 100644
--- a/proxy/vmess/encoding/client.go
+++ b/proxy/vmess/encoding/client.go
@@ -12,6 +12,7 @@ import (
 
 	"v2ray.com/core/app/log"
 	"v2ray.com/core/common"
+	"v2ray.com/core/common/bitmask"
 	"v2ray.com/core/common/buf"
 	"v2ray.com/core/common/crypto"
 	"v2ray.com/core/common/dice"
@@ -203,7 +204,7 @@ func (c *ClientSession) DecodeResponseHeader(reader io.Reader) (*protocol.Respon
 	}
 
 	header := &protocol.ResponseHeader{
-		Option: protocol.ResponseOption(buffer[1]),
+		Option: bitmask.Byte(buffer[1]),
 	}
 
 	if buffer[2] != 0 {
diff --git a/proxy/vmess/encoding/server.go b/proxy/vmess/encoding/server.go
index 257462c5..eefa9aaa 100644
--- a/proxy/vmess/encoding/server.go
+++ b/proxy/vmess/encoding/server.go
@@ -12,6 +12,7 @@ import (
 
 	"golang.org/x/crypto/chacha20poly1305"
 	"v2ray.com/core/common"
+	"v2ray.com/core/common/bitmask"
 	"v2ray.com/core/common/buf"
 	"v2ray.com/core/common/crypto"
 	"v2ray.com/core/common/net"
@@ -164,8 +165,8 @@ func (s *ServerSession) DecodeRequestHeader(reader io.Reader) (*protocol.Request
 	}
 	s.sessionHistory.add(sid)
 
-	s.responseHeader = buffer[33]                       // 1 byte
-	request.Option = protocol.RequestOption(buffer[34]) // 1 byte
+	s.responseHeader = buffer[33]             // 1 byte
+	request.Option = bitmask.Byte(buffer[34]) // 1 byte
 	padingLen := int(buffer[35] >> 4)
 	request.Security = protocol.NormSecurity(protocol.Security(buffer[35] & 0x0F))
 	// 1 bytes reserved