package bittorrent import ( "encoding/binary" "errors" "math" "time" "github.com/v2fly/v2ray-core/v4/common" "github.com/v2fly/v2ray-core/v4/common/buf" ) type SniffHeader struct{} func (h *SniffHeader) Protocol() string { return "bittorrent" } func (h *SniffHeader) Domain() string { return "" } var errNotBittorrent = errors.New("not bittorrent header") func SniffBittorrent(b []byte) (*SniffHeader, error) { if len(b) < 20 { return nil, common.ErrNoClue } if b[0] == 19 && string(b[1:20]) == "BitTorrent protocol" { return &SniffHeader{}, nil } return nil, errNotBittorrent } func SniffUTP(b []byte) (*SniffHeader, error) { if len(b) < 20 { return nil, common.ErrNoClue } buffer := buf.FromBytes(b) var typeAndVersion uint8 if binary.Read(buffer, binary.BigEndian, &typeAndVersion) != nil { return nil, common.ErrNoClue } else if b[0]>>4&0xF > 4 || b[0]&0xF != 1 { return nil, errNotBittorrent } var extension uint8 if binary.Read(buffer, binary.BigEndian, &extension) != nil { return nil, common.ErrNoClue } else if extension != 0 && extension != 1 { return nil, errNotBittorrent } for extension != 0 { if extension != 1 { return nil, errNotBittorrent } if binary.Read(buffer, binary.BigEndian, &extension) != nil { return nil, common.ErrNoClue } var length uint8 if err := binary.Read(buffer, binary.BigEndian, &length); err != nil { return nil, common.ErrNoClue } if common.Error2(buffer.ReadBytes(int32(length))) != nil { return nil, common.ErrNoClue } } if common.Error2(buffer.ReadBytes(2)) != nil { return nil, common.ErrNoClue } var timestamp uint32 if err := binary.Read(buffer, binary.BigEndian, ×tamp); err != nil { return nil, common.ErrNoClue } if math.Abs(float64(time.Now().UnixMicro()-int64(timestamp))) > float64(24*time.Hour) { return nil, errNotBittorrent } return &SniffHeader{}, nil }