Fragment finalmask: Add lengths and delays (#6334)

Usage: https://github.com/XTLS/Xray-core/pull/6334#issue-4685556394

Behavior: https://github.com/XTLS/Xray-core/pull/6334#issuecomment-4751547750

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

infra/conf/transport_internet.go

@@ -1409,10 +1409,12 @@ func (c *HeaderCustomTCP) Build() (proto.Message, error) {
 }
 
 type FragmentMask struct {
-	Packets  string     `json:"packets"`
+	Packets  string       `json:"packets"`
-	Length   Int32Range `json:"length"`
+	Length   Int32Range   `json:"length"`
-	Delay    Int32Range `json:"delay"`
+	Delay    Int32Range   `json:"delay"`
-	MaxSplit Int32Range `json:"maxSplit"`
+	Lengths  []Int32Range `json:"lengths"`
+	Delays   []Int32Range `json:"delays"`
+	MaxSplit Int32Range   `json:"maxSplit"`
 }
 
 func (c *FragmentMask) Build() (proto.Message, error) {
@@ -1437,14 +1439,29 @@ func (c *FragmentMask) Build() (proto.Message, error) {
 		}
 	}
 
-	config.LengthMin = int64(c.Length.From)
+	if len(c.Lengths) > 0 {
-	config.LengthMax = int64(c.Length.To)
+		for _, r := range c.Lengths {
-	if config.LengthMin == 0 {
+			config.LengthsMin = append(config.LengthsMin, int64(r.From))
-		return nil, errors.New("LengthMin can't be 0")
+			config.LengthsMax = append(config.LengthsMax, int64(r.To))
+		}
+	} else {
+		config.LengthsMin = append(config.LengthsMin, int64(c.Length.From))
+		config.LengthsMax = append(config.LengthsMax, int64(c.Length.To))
 	}
 
-	config.DelayMin = int64(c.Delay.From)
+	if config.LengthsMin[len(config.LengthsMin)-1] == 0 {
-	config.DelayMax = int64(c.Delay.To)
+		return nil, errors.New("last lengths entry min can't be 0")
+	}
+
+	if len(c.Delays) > 0 {
+		for _, r := range c.Delays {
+			config.DelaysMin = append(config.DelaysMin, int64(r.From))
+			config.DelaysMax = append(config.DelaysMax, int64(r.To))
+		}
+	} else {
+		config.DelaysMin = append(config.DelaysMin, int64(c.Delay.From))
+		config.DelaysMax = append(config.DelaysMax, int64(c.Delay.To))
+	}
 
 	config.MaxSplitMin = int64(c.MaxSplit.From)
 	config.MaxSplitMax = int64(c.MaxSplit.To)

transport/internet/finalmask/fragment/config.pb.go

@@ -25,12 +25,12 @@ type Config struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	PacketsFrom   int64                  `protobuf:"varint,1,opt,name=packets_from,json=packetsFrom,proto3" json:"packets_from,omitempty"`
 	PacketsTo     int64                  `protobuf:"varint,2,opt,name=packets_to,json=packetsTo,proto3" json:"packets_to,omitempty"`
-	LengthMin     int64                  `protobuf:"varint,3,opt,name=length_min,json=lengthMin,proto3" json:"length_min,omitempty"`
-	LengthMax     int64                  `protobuf:"varint,4,opt,name=length_max,json=lengthMax,proto3" json:"length_max,omitempty"`
-	DelayMin      int64                  `protobuf:"varint,5,opt,name=delay_min,json=delayMin,proto3" json:"delay_min,omitempty"`
-	DelayMax      int64                  `protobuf:"varint,6,opt,name=delay_max,json=delayMax,proto3" json:"delay_max,omitempty"`
 	MaxSplitMin   int64                  `protobuf:"varint,7,opt,name=max_split_min,json=maxSplitMin,proto3" json:"max_split_min,omitempty"`
 	MaxSplitMax   int64                  `protobuf:"varint,8,opt,name=max_split_max,json=maxSplitMax,proto3" json:"max_split_max,omitempty"`
+	LengthsMin    []int64                `protobuf:"varint,9,rep,packed,name=lengths_min,json=lengthsMin,proto3" json:"lengths_min,omitempty"`
+	LengthsMax    []int64                `protobuf:"varint,10,rep,packed,name=lengths_max,json=lengthsMax,proto3" json:"lengths_max,omitempty"`
+	DelaysMin     []int64                `protobuf:"varint,11,rep,packed,name=delays_min,json=delaysMin,proto3" json:"delays_min,omitempty"`
+	DelaysMax     []int64                `protobuf:"varint,12,rep,packed,name=delays_max,json=delaysMax,proto3" json:"delays_max,omitempty"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
@@ -79,34 +79,6 @@ func (x *Config) GetPacketsTo() int64 {
 	return 0
 }
 
-func (x *Config) GetLengthMin() int64 {
-	if x != nil {
-		return x.LengthMin
-	}
-	return 0
-}
-
-func (x *Config) GetLengthMax() int64 {
-	if x != nil {
-		return x.LengthMax
-	}
-	return 0
-}
-
-func (x *Config) GetDelayMin() int64 {
-	if x != nil {
-		return x.DelayMin
-	}
-	return 0
-}
-
-func (x *Config) GetDelayMax() int64 {
-	if x != nil {
-		return x.DelayMax
-	}
-	return 0
-}
-
 func (x *Config) GetMaxSplitMin() int64 {
 	if x != nil {
 		return x.MaxSplitMin
@@ -121,23 +93,54 @@ func (x *Config) GetMaxSplitMax() int64 {
 	return 0
 }
 
+func (x *Config) GetLengthsMin() []int64 {
+	if x != nil {
+		return x.LengthsMin
+	}
+	return nil
+}
+
+func (x *Config) GetLengthsMax() []int64 {
+	if x != nil {
+		return x.LengthsMax
+	}
+	return nil
+}
+
+func (x *Config) GetDelaysMin() []int64 {
+	if x != nil {
+		return x.DelaysMin
+	}
+	return nil
+}
+
+func (x *Config) GetDelaysMax() []int64 {
+	if x != nil {
+		return x.DelaysMax
+	}
+	return nil
+}
+
 var File_transport_internet_finalmask_fragment_config_proto protoreflect.FileDescriptor
 
 const file_transport_internet_finalmask_fragment_config_proto_rawDesc = "" +
 	"\n" +
-	"2transport/internet/finalmask/fragment/config.proto\x12*xray.transport.internet.finalmask.fragment\"\x8a\x02\n" +
+	"2transport/internet/finalmask/fragment/config.proto\x12*xray.transport.internet.finalmask.fragment\"\x92\x02\n" +
 	"\x06Config\x12!\n" +
 	"\fpackets_from\x18\x01 \x01(\x03R\vpacketsFrom\x12\x1d\n" +
 	"\n" +
-	"packets_to\x18\x02 \x01(\x03R\tpacketsTo\x12\x1d\n" +
+	"packets_to\x18\x02 \x01(\x03R\tpacketsTo\x12\"\n" +
-	"\n" +
-	"length_min\x18\x03 \x01(\x03R\tlengthMin\x12\x1d\n" +
-	"\n" +
-	"length_max\x18\x04 \x01(\x03R\tlengthMax\x12\x1b\n" +
-	"\tdelay_min\x18\x05 \x01(\x03R\bdelayMin\x12\x1b\n" +
-	"\tdelay_max\x18\x06 \x01(\x03R\bdelayMax\x12\"\n" +
 	"\rmax_split_min\x18\a \x01(\x03R\vmaxSplitMin\x12\"\n" +
-	"\rmax_split_max\x18\b \x01(\x03R\vmaxSplitMaxB\xa0\x01\n" +
+	"\rmax_split_max\x18\b \x01(\x03R\vmaxSplitMax\x12\x1f\n" +
+	"\vlengths_min\x18\t \x03(\x03R\n" +
+	"lengthsMin\x12\x1f\n" +
+	"\vlengths_max\x18\n" +
+	" \x03(\x03R\n" +
+	"lengthsMax\x12\x1d\n" +
+	"\n" +
+	"delays_min\x18\v \x03(\x03R\tdelaysMin\x12\x1d\n" +
+	"\n" +
+	"delays_max\x18\f \x03(\x03R\tdelaysMaxB\xa0\x01\n" +
 	".com.xray.transport.internet.finalmask.fragmentP\x01Z?github.com/xtls/xray-core/transport/internet/finalmask/fragment\xaa\x02*Xray.Transport.Internet.Finalmask.Fragmentb\x06proto3"
 
 var (

transport/internet/finalmask/fragment/config.proto

@@ -9,10 +9,10 @@ option java_multiple_files = true;
 message Config {
   int64 packets_from = 1;
   int64 packets_to = 2;
-  int64 length_min = 3;
-  int64 length_max = 4;
-  int64 delay_min = 5;
-  int64 delay_max = 6;
   int64 max_split_min = 7;
   int64 max_split_max = 8;
+  repeated int64 lengths_min = 9;
+  repeated int64 lengths_max = 10;
+  repeated int64 delays_min = 11;
+  repeated int64 delays_max = 12;
 }

transport/internet/finalmask/fragment/conn.go

@@ -43,6 +43,29 @@ func (c *fragmentConn) Splice() bool {
 	return true
 }
 
+// lengthForSegment returns the length range (min, max) for the given segment index (0-based).
+// Clamps to the last entry when the index exceeds the list length.
+func (c *fragmentConn) lengthForSegment(segIdx int) (int64, int64) {
+	if segIdx >= len(c.config.LengthsMin) {
+		segIdx = len(c.config.LengthsMin) - 1
+	}
+	return c.config.LengthsMin[segIdx], c.config.LengthsMax[segIdx]
+}
+
+// delayForSegment returns the delay range (min, max) for the given segment index (0-based).
+// Clamps to the last entry when the index exceeds the list length.
+func (c *fragmentConn) delayForSegment(segIdx int) (int64, int64) {
+	if segIdx >= len(c.config.DelaysMin) {
+		segIdx = len(c.config.DelaysMin) - 1
+	}
+	return c.config.DelaysMin[segIdx], c.config.DelaysMax[segIdx]
+}
+
+// mergeTlsHelloSegments returns true only when delays has exactly one zero entry.
+func (c *fragmentConn) mergeTlsHelloSegments() bool {
+	return len(c.config.DelaysMax) == 1 && c.config.DelaysMax[0] == 0
+}
+
 func (c *fragmentConn) Write(p []byte) (n int, err error) {
 	c.count++
 
@@ -57,12 +80,13 @@ func (c *fragmentConn) Write(p []byte) (n int, err error) {
 		data := p[5:recordLen]
 		buff := make([]byte, 2048)
 		var hello []byte
+		mergeHello := c.mergeTlsHelloSegments()
 		maxSplit := crypto.RandBetween(c.config.MaxSplitMin, c.config.MaxSplitMax)
 		var splitNum int64
 		for from := 0; ; {
-			to := from + int(crypto.RandBetween(c.config.LengthMin, c.config.LengthMax))
+			lengthMin, lengthMax := c.lengthForSegment(int(splitNum))
-			splitNum++
+			to := from + int(crypto.RandBetween(lengthMin, lengthMax))
-			if to > len(data) || (maxSplit > 0 && splitNum >= maxSplit) {
+			if to > len(data) || (maxSplit > 0 && splitNum+1 >= maxSplit) {
 				to = len(data)
 			}
 			l := to - from
@@ -74,15 +98,19 @@ func (c *fragmentConn) Write(p []byte) (n int, err error) {
 			from = to
 			buff[3] = byte(l >> 8)
 			buff[4] = byte(l)
-			if c.config.DelayMax == 0 {
+			if mergeHello {
 				hello = append(hello, buff[:5+l]...)
 			} else {
+				delayMin, delayMax := c.delayForSegment(int(splitNum))
 				_, err := c.Conn.Write(buff[:5+l])
-				time.Sleep(time.Duration(crypto.RandBetween(c.config.DelayMin, c.config.DelayMax)) * time.Millisecond)
+				if delayMax > 0 {
+					time.Sleep(time.Duration(crypto.RandBetween(delayMin, delayMax)) * time.Millisecond)
+				}
 				if err != nil {
 					return 0, err
 				}
 			}
+			splitNum++
 			if from == len(data) {
 				if len(hello) > 0 {
 					_, err := c.Conn.Write(hello)
@@ -107,9 +135,9 @@ func (c *fragmentConn) Write(p []byte) (n int, err error) {
 	maxSplit := crypto.RandBetween(c.config.MaxSplitMin, c.config.MaxSplitMax)
 	var splitNum int64
 	for from := 0; ; {
-		to := from + int(crypto.RandBetween(c.config.LengthMin, c.config.LengthMax))
+		lengthMin, lengthMax := c.lengthForSegment(int(splitNum))
-		splitNum++
+		to := from + int(crypto.RandBetween(lengthMin, lengthMax))
-		if to > len(p) || (maxSplit > 0 && splitNum >= maxSplit) {
+		if to > len(p) || (maxSplit > 0 && splitNum+1 >= maxSplit) {
 			to = len(p)
 		}
 		n, err := c.Conn.Write(p[from:to])
@@ -117,7 +145,11 @@ func (c *fragmentConn) Write(p []byte) (n int, err error) {
 		if err != nil {
 			return from, err
 		}
-		time.Sleep(time.Duration(crypto.RandBetween(c.config.DelayMin, c.config.DelayMax)) * time.Millisecond)
+		delayMin, delayMax := c.delayForSegment(int(splitNum))
+		if delayMax > 0 {
+			time.Sleep(time.Duration(crypto.RandBetween(delayMin, delayMax)) * time.Millisecond)
+		}
+		splitNum++
 		if from >= len(p) {
 			return from, nil
 		}