Add bittorrent protocol sniffer support

common/sniff/bittorrent.go

@@ -0,0 +1,86 @@
+package sniff
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"io"
+	"io/ioutil"
+	"math"
+	"os"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+)
+
+func BittorrentTCPMessage(ctx context.Context, reader io.Reader) (*adapter.InboundContext, error) {
+	packet, err := ioutil.ReadAll(reader)
+	if err != nil {
+		return nil, os.ErrInvalid
+	}
+	if len(packet) < 20 {
+		return nil, os.ErrInvalid
+	}
+	if packet[0] != 19 || string(packet[1:20]) != "BitTorrent protocol" {
+		return nil, os.ErrInvalid
+	}
+	return &adapter.InboundContext{Protocol: C.ProtocolBittorrent}, nil
+}
+
+func BittorrentUDPMessage(ctx context.Context, packet []byte) (*adapter.InboundContext, error) {
+	pLen := len(packet)
+	if pLen < 20 {
+		return nil, os.ErrInvalid
+	}
+
+	buffer := bytes.NewReader(packet)
+
+	var typeAndVersion uint8
+
+	if binary.Read(buffer, binary.BigEndian, &typeAndVersion) != nil {
+		return nil, os.ErrInvalid
+	} else if packet[0]>>4&0xF > 4 || packet[0]&0xF != 1 {
+		return nil, os.ErrInvalid
+	}
+
+	var extension uint8
+
+	if binary.Read(buffer, binary.BigEndian, &extension) != nil {
+		return nil, os.ErrInvalid
+	} else if extension != 0 && extension != 1 {
+		return nil, os.ErrInvalid
+	}
+
+	for extension != 0 {
+		if extension != 1 {
+			return nil, os.ErrInvalid
+		}
+		if binary.Read(buffer, binary.BigEndian, &extension) != nil {
+			return nil, os.ErrInvalid
+		}
+
+		var length uint8
+
+		if err := binary.Read(buffer, binary.BigEndian, &length); err != nil {
+			return nil, os.ErrInvalid
+		}
+		if int32(pLen) >= int32(length) {
+			return nil, os.ErrInvalid
+		}
+	}
+
+	if int32(pLen) >= int32(2) {
+		return nil, os.ErrInvalid
+	}
+
+	var timestamp uint32
+
+	if err := binary.Read(buffer, binary.BigEndian, &timestamp); err != nil {
+		return nil, os.ErrInvalid
+	}
+	if math.Abs(float64(time.Now().UnixMicro()-int64(timestamp))) > float64(24*time.Hour) {
+		return nil, os.ErrInvalid
+	}
+	return &adapter.InboundContext{Protocol: C.ProtocolBittorrent}, nil
+}

constant/protocol.go

@@ -6,4 +6,5 @@ const (
 	ProtocolQUIC       = "quic"
 	ProtocolDNS        = "dns"
 	ProtocolSTUN       = "stun"
+	ProtocolBittorrent = "bittorrent"
 )

docs/configuration/route/sniff.md

@@ -3,9 +3,10 @@ If enabled in the inbound, the protocol and domain name (if present) of by the c
 #### Supported Protocols
 
 | Network |  Protocol  | Domain Name |
-|:-------:|:--------:|:-----------:|
+|:-------:|:----------:|:-----------:|
 |   TCP   |    HTTP    |    Host     |
 |   TCP   |    TLS     | Server Name |
 |   UDP   |    QUIC    | Server Name |
 |   UDP   |    STUN    |      /      |
 | TCP/UDP |    DNS     |      /      |
+| TCP/UDP | Bittorrent |      /      |

docs/configuration/route/sniff.zh.md

@@ -3,9 +3,10 @@
 #### 支持的协议
 
 |   网络   |    协议    |     域名     |
-|:-------:|:----:|:-----------:|
+|:-------:|:----------:|:-----------:|
 |   TCP   |    HTTP    |    Host     |
 |   TCP   |    TLS     | Server Name |
 |   UDP   |    QUIC    | Server Name |
 |   UDP   |    STUN    |      /      |
 | TCP/UDP |    DNS     |      /      |
+| TCP/UDP | Bittorrent |      /      |

route/router.go

@@ -26,9 +26,9 @@ import (
 	"github.com/sagernet/sing-box/option"
 	"github.com/sagernet/sing-box/outbound"
 	"github.com/sagernet/sing-box/transport/fakeip"
-	"github.com/sagernet/sing-dns"
-	"github.com/sagernet/sing-tun"
-	"github.com/sagernet/sing-vmess"
+	dns "github.com/sagernet/sing-dns"
+	tun "github.com/sagernet/sing-tun"
+	vmess "github.com/sagernet/sing-vmess"
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
 	"github.com/sagernet/sing/common/bufio"
@@ -652,7 +652,7 @@ func (r *Router) RouteConnection(ctx context.Context, conn net.Conn, metadata ad
 	if metadata.InboundOptions.SniffEnabled {
 		buffer := buf.NewPacket()
 		buffer.FullReset()
-		sniffMetadata, err := sniff.PeekStream(ctx, conn, buffer, time.Duration(metadata.InboundOptions.SniffTimeout), sniff.StreamDomainNameQuery, sniff.TLSClientHello, sniff.HTTPHost)
+		sniffMetadata, err := sniff.PeekStream(ctx, conn, buffer, time.Duration(metadata.InboundOptions.SniffTimeout), sniff.StreamDomainNameQuery, sniff.TLSClientHello, sniff.HTTPHost, sniff.BittorrentTCPMessage)
 		if sniffMetadata != nil {
 			metadata.Protocol = sniffMetadata.Protocol
 			metadata.Domain = sniffMetadata.Domain
@@ -771,7 +771,7 @@ func (r *Router) RoutePacketConnection(ctx context.Context, conn N.PacketConn, m
 			metadata.Destination = destination
 		}
 		if metadata.InboundOptions.SniffEnabled {
-			sniffMetadata, _ := sniff.PeekPacket(ctx, buffer.Bytes(), sniff.DomainNameQuery, sniff.QUICClientHello, sniff.STUNMessage)
+			sniffMetadata, _ := sniff.PeekPacket(ctx, buffer.Bytes(), sniff.DomainNameQuery, sniff.QUICClientHello, sniff.STUNMessage, sniff.BittorrentUDPMessage)
 			if sniffMetadata != nil {
 				metadata.Protocol = sniffMetadata.Protocol
 				metadata.Domain = sniffMetadata.Domain