X-Git-Url: https://git.r.bdr.sh/rbdr/mobius/blobdiff_plain/d80b37ca4c5801d5dbb5c4313a3d1d5fbdf2d593..a55350daaf83498b7a237c027ad0dd2377f06fee:/hotline/tracker.go diff --git a/hotline/tracker.go b/hotline/tracker.go index 69d9fd4..b927986 100644 --- a/hotline/tracker.go +++ b/hotline/tracker.go @@ -1,57 +1,68 @@ package hotline import ( - "bytes" + "bufio" "encoding/binary" - "errors" "fmt" - "github.com/jhalter/mobius/concat" + "io" "net" + "slices" "strconv" "time" ) +// TrackerRegistration represents the payload a Hotline server sends to a Tracker to register type TrackerRegistration struct { - Port []byte // Server listening port number - UserCount int // Number of users connected to this particular server - PassID []byte // Random number generated by the server - Name string // Server name - Description string // Description of the server + Port [2]byte // Server's listening TCP port number + UserCount int // Number of users connected to this particular server + PassID [4]byte // Random number generated by the server + Name string // Server Name + Description string // Description of the server + + readOffset int // Internal offset to track read progress } -func (tr *TrackerRegistration) Payload() []byte { +// Read implements io.Reader to write tracker registration payload bytes to slice +func (tr *TrackerRegistration) Read(p []byte) (int, error) { userCount := make([]byte, 2) binary.BigEndian.PutUint16(userCount, uint16(tr.UserCount)) - return concat.Slices( - []byte{0x00, 0x01}, - tr.Port, + buf := slices.Concat( + []byte{0x00, 0x01}, // Magic number, always 1 + tr.Port[:], userCount, - []byte{0x00, 0x00}, - tr.PassID, + []byte{0x00, 0x00}, // Magic number, always 0 + tr.PassID[:], []byte{uint8(len(tr.Name))}, []byte(tr.Name), []byte{uint8(len(tr.Description))}, []byte(tr.Description), ) + + if tr.readOffset >= len(buf) { + return 0, io.EOF // All bytes have been read + } + + n := copy(p, buf[tr.readOffset:]) + tr.readOffset += n + + return n, nil } -func register(tracker string, tr TrackerRegistration) error { +func register(tracker string, tr *TrackerRegistration) error { conn, err := net.Dial("udp", tracker) if err != nil { - return err + return fmt.Errorf("failed to dial tracker: %w", err) } + defer conn.Close() - if _, err := conn.Write(tr.Payload()); err != nil { - return err + if _, err := io.Copy(conn, tr); err != nil { + return fmt.Errorf("failed to write to connection: %w", err) } return nil } -type ServerListing struct { -} - const trackerTimeout = 5 * time.Second // All string values use 8-bit ASCII character set encoding. @@ -67,10 +78,10 @@ type TrackerHeader struct { Version [2]byte // Old protocol (1) or new (2) } -//Message type 2 1 Sending list of servers -//Message data size 2 Remaining size of this request -//Number of servers 2 Number of servers in the server list -//Number of servers 2 Same as previous field +// Message type 2 1 Sending list of servers +// Message data size 2 Remaining size of this request +// Number of servers 2 Number of servers in the server list +// Number of servers 2 Same as previous field type ServerInfoHeader struct { MsgType [2]byte // always has value of 1 MsgDataSize [2]byte // Remaining size of request @@ -79,18 +90,21 @@ type ServerInfoHeader struct { } type ServerRecord struct { - IPAddr []byte - Port []byte - NumUsers []byte // Number of users connected to this particular server - Unused []byte - NameSize byte // Length of name string - Name []byte // Server’s name + IPAddr [4]byte + Port [2]byte + NumUsers [2]byte // Number of users connected to this particular server + Unused [2]byte + NameSize byte // Length of Name string + Name []byte // Server Name DescriptionSize byte Description []byte } func GetListing(addr string) ([]ServerRecord, error) { conn, err := net.DialTimeout("tcp", addr, trackerTimeout) + if err != nil { + return []ServerRecord{}, err + } defer func() { _ = conn.Close() }() _, err = conn.Write( @@ -103,71 +117,83 @@ func GetListing(addr string) ([]ServerRecord, error) { return nil, err } - totalRead := 0 - - buf := make([]byte, 4096) - var readLen int - if readLen, err = conn.Read(buf); err != nil { - return nil, err - } - totalRead += readLen // 1514 - var th TrackerHeader - if err := binary.Read(bytes.NewReader(buf[:6]), binary.BigEndian, &th); err != nil { + if err := binary.Read(conn, binary.BigEndian, &th); err != nil { return nil, err } var info ServerInfoHeader - if err := binary.Read(bytes.NewReader(buf[6:14]), binary.BigEndian, &info); err != nil { + if err := binary.Read(conn, binary.BigEndian, &info); err != nil { return nil, err } - payloadSize := int(binary.BigEndian.Uint16(info.MsgDataSize[:])) - - buf = buf[:readLen] - if totalRead < payloadSize { - for { - tmpBuf := make([]byte, 4096) - if readLen, err = conn.Read(tmpBuf); err != nil { - return nil, err - } - buf = append(buf, tmpBuf[:readLen]...) - totalRead += readLen - if totalRead >= payloadSize { - break - } - } - } totalSrv := int(binary.BigEndian.Uint16(info.SrvCount[:])) - srvBuf := buf[14:totalRead] - totalRead += readLen + scanner := bufio.NewScanner(conn) + scanner.Split(serverScanner) var servers []ServerRecord - for { - var srv ServerRecord - n, _ := srv.Read(srvBuf) - servers = append(servers, srv) + scanner.Scan() - srvBuf = srvBuf[n:] + var srv ServerRecord + _, err = srv.Write(scanner.Bytes()) + if err != nil { + return nil, err + } + servers = append(servers, srv) if len(servers) == totalSrv { - return servers, nil + break } + } - if len(srvBuf) == 0 { - return servers, errors.New("tracker sent too few bytes for server count") - } + 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 } + + // 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]) + + // 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 + } + + // Next we need the description length from the 11+nameLen byte: + descLen := int(data[11+nameLen]) + + if len(data) < 12+nameLen+descLen { + return 0, nil, nil + } + + return 12 + nameLen + descLen, data[0 : 12+nameLen+descLen], nil } -func (s *ServerRecord) Read(b []byte) (n int, err error) { - s.IPAddr = b[0:4] - s.Port = b[4:6] - s.NumUsers = b[6:8] - s.NameSize = b[10] +// Write implements io.Writer for ServerRecord +func (s *ServerRecord) Write(b []byte) (n int, err error) { + copy(s.IPAddr[:], b[0:4]) + copy(s.Port[:], b[4:6]) + copy(s.NumUsers[:], b[6:8]) nameLen := int(b[10]) + s.Name = b[11 : 11+nameLen] s.DescriptionSize = b[11+nameLen] s.Description = b[12+nameLen : 12+nameLen+int(s.DescriptionSize)] @@ -175,14 +201,9 @@ func (s *ServerRecord) Read(b []byte) (n int, err error) { return 12 + nameLen + int(s.DescriptionSize), nil } -func (s *ServerRecord) PortInt() int { - data := binary.BigEndian.Uint16(s.Port) - return int(data) -} - func (s *ServerRecord) Addr() string { return fmt.Sprintf("%s:%s", - net.IP(s.IPAddr), - strconv.Itoa(int(binary.BigEndian.Uint16(s.Port))), + net.IP(s.IPAddr[:]), + strconv.Itoa(int(binary.BigEndian.Uint16(s.Port[:]))), ) }