diff options
Diffstat (limited to 'hotline/tracker.go')
| -rw-r--r-- | hotline/tracker.go | 114 |
1 files changed, 69 insertions, 45 deletions
diff --git a/hotline/tracker.go b/hotline/tracker.go index edd973d..bfba69d 100644 --- a/hotline/tracker.go +++ b/hotline/tracker.go @@ -91,11 +91,22 @@ type TrackerHeader struct { Version [2]byte // Old protocol (1) or new (2) } +// ServerInfoHeader represents a batch header in the tracker response. +// The tracker protocol splits large server lists into batches, with each batch +// preceded by its own ServerInfoHeader. The first header indicates the total +// number of servers across all batches, and each header (including the first) +// indicates how many servers are in the current batch. +// +// Example flow for 106 servers split into batches: +// 1. First ServerInfoHeader: SrvCount=106, BatchSize=97 +// 2. Read 97 ServerRecords +// 3. Second ServerInfoHeader: SrvCount=106, BatchSize=9 +// 4. Read 9 ServerRecords (total: 106) type ServerInfoHeader struct { MsgType [2]byte // Always has value of 1 MsgDataSize [2]byte // Remaining size of request - SrvCount [2]byte // Number of servers in the server list - SrvCountDup [2]byte // Same as previous field ¯\_(ツ)_/¯ + SrvCount [2]byte // Total number of servers across all batches + BatchSize [2]byte // Number of servers in the current batch } // ServerRecord is a tracker listing for a single server @@ -128,79 +139,92 @@ func GetListing(conn io.ReadWriteCloser) ([]ServerRecord, error) { return nil, err } + // Use a buffered reader so we can read both headers and server records from the same buffer + reader := bufio.NewReader(conn) + var info ServerInfoHeader - if err := binary.Read(conn, binary.BigEndian, &info); err != nil { + if err := binary.Read(reader, binary.BigEndian, &info); err != nil { return nil, err } totalSrv := int(binary.BigEndian.Uint16(info.SrvCount[:])) + batchSize := int(binary.BigEndian.Uint16(info.BatchSize[:])) - scanner := bufio.NewScanner(conn) - scanner.Split(serverScanner) + servers := make([]ServerRecord, 0, totalSrv) + serversInCurrentBatch := 0 - var servers []ServerRecord - for { - scanner.Scan() + for len(servers) < totalSrv { + // Check if we've read all servers in the current batch + if serversInCurrentBatch == batchSize { + // Read the next ServerInfoHeader for the next batch from the buffered reader + if err := binary.Read(reader, binary.BigEndian, &info); err != nil { + return nil, fmt.Errorf("failed to read next ServerInfoHeader after %d servers: %w", len(servers), err) + } - // Make a new []byte slice and copy the scanner bytes to it. This is critical as the - // scanner re-uses the buffer for subsequent scans. - buf := make([]byte, len(scanner.Bytes())) - copy(buf, scanner.Bytes()) + batchSize = int(binary.BigEndian.Uint16(info.BatchSize[:])) + serversInCurrentBatch = 0 + } - var srv ServerRecord - _, err = srv.Write(buf) + // Read a server record using our helper function + srv, err := readServerRecord(reader) if err != nil { - return nil, err + return nil, fmt.Errorf("failed to read server record %d: %w", len(servers)+1, err) } servers = append(servers, srv) - if len(servers) == totalSrv { - break - } + serversInCurrentBatch++ } return servers, nil } -// serverScanner implements bufio.SplitFunc for parsing the tracker list into ServerRecords tokens -// Example payload: -// 00000000 18 05 30 63 15 7c 00 02 00 00 10 54 68 65 20 4d |..0c.|.....The M| -// 00000010 6f 62 69 75 73 20 53 74 72 69 70 40 48 6f 6d 65 |obius Strip@Home| -// 00000020 20 6f 66 20 74 68 65 20 4d 6f 62 69 75 73 20 48 | of the Mobius H| -// 00000030 6f 74 6c 69 6e 65 20 73 65 72 76 65 72 20 61 6e |otline server an| -// 00000040 64 20 63 6c 69 65 6e 74 20 7c 20 54 52 54 50 48 |d client | TRTPH| -// 00000050 4f 54 4c 2e 63 6f 6d 3a 35 35 30 30 2d 4f 3a b2 |OTL.com:5500-O:.| -// 00000060 15 7c 00 00 00 00 08 53 65 6e 65 63 74 75 73 20 |.|.....Senectus | -func serverScanner(data []byte, _ bool) (advance int, token []byte, err error) { - // The name length field is the 11th byte of the server record. If we don't have that many bytes, - // return nil token so the Scanner reads more data and continues scanning. - if len(data) < 10 { - return 0, nil, nil +// readServerRecord reads a single ServerRecord from the reader +func readServerRecord(reader *bufio.Reader) (ServerRecord, error) { + var srv ServerRecord + + // Read fixed header: IP (4) + Port (2) + NumUsers (2) + Unused (2) = 10 bytes + header := make([]byte, 10) + if _, err := io.ReadFull(reader, header); err != nil { + return srv, fmt.Errorf("failed to read server header: %w", err) } - // A server entry has two variable length fields: the name and description. - // To get the token length, we first need the name length from the 10th byte - nameLen := int(data[10]) + copy(srv.IPAddr[:], header[0:4]) + copy(srv.Port[:], header[4:6]) + copy(srv.NumUsers[:], header[6:8]) + copy(srv.Unused[:], header[8:10]) - // The description length field is at the 12th + nameLen byte of the server record. - // If we don't have that many bytes, return nil token so the Scanner reads more data and continues scanning. - if len(data) < 11+nameLen { - return 0, nil, nil + // Read name size + nameSizeByte, err := reader.ReadByte() + if err != nil { + return srv, fmt.Errorf("failed to read name size: %w", err) } + srv.NameSize = nameSizeByte - // Next we need the description length from the 11+nameLen byte: - descLen := int(data[11+nameLen]) + // Read name + srv.Name = make([]byte, srv.NameSize) + if _, err := io.ReadFull(reader, srv.Name); err != nil { + return srv, fmt.Errorf("failed to read name: %w", err) + } + + // Read description size + descSizeByte, err := reader.ReadByte() + if err != nil { + return srv, fmt.Errorf("failed to read description size: %w", err) + } + srv.DescriptionSize = descSizeByte - if len(data) < 12+nameLen+descLen { - return 0, nil, nil + // Read description + srv.Description = make([]byte, srv.DescriptionSize) + if _, err := io.ReadFull(reader, srv.Description); err != nil { + return srv, fmt.Errorf("failed to read description: %w", err) } - return 12 + nameLen + descLen, data[0 : 12+nameLen+descLen], nil + return srv, nil } // Write implements io.Writer for ServerRecord func (s *ServerRecord) Write(b []byte) (n int, err error) { - if len(b) < 13 { + if len(b) < 12 { return 0, errors.New("too few bytes") } copy(s.IPAddr[:], b[0:4]) |