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
+ Password string // Tracker password, if required by tracker
+
+ 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),
+ []byte{uint8(len(tr.Password))},
+ []byte(tr.Password),
)
+
+ 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
+}
+
+// Dialer interface to abstract the dialing operation
+type Dialer interface {
+ Dial(network, address string) (net.Conn, error)
}
-func register(tracker string, tr TrackerRegistration) error {
- conn, err := net.Dial("udp", tracker)
+// RealDialer is the real implementation of the Dialer interface
+type RealDialer struct{}
+
+func (d *RealDialer) Dial(network, address string) (net.Conn, error) {
+ return net.Dial(network, address)
+}
+
+func register(dialer Dialer, tracker string, tr io.Reader) error {
+ conn, err := dialer.Dial("udp", tracker)
if err != nil {
- return err
+ return fmt.Errorf("failed to dial tracker: %v", 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.
// Client Interface with Tracker
// After establishing a connection with tracker, the following information is sent:
// Magic number 4 ‘HTRK’
// Version 2 1 or 2 Old protocol (1) or new (2)
-// Reply received from the tracker starts with a header:
+// TrackerHeader is sent in reply Reply received from the tracker starts with a header:
type TrackerHeader struct {
Protocol [4]byte // "HTRK" 0x4854524B
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
type ServerInfoHeader struct {
- MsgType [2]byte // always has value of 1
+ 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)_/¯
}
+// ServerRecord is a tracker listing for a single server
type ServerRecord struct {
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
+ 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
- }
+func GetListing(conn io.ReadWriteCloser) ([]ServerRecord, error) {
defer func() { _ = conn.Close() }()
- _, err = conn.Write(
+ _, err := conn.Write(
[]byte{
0x48, 0x54, 0x52, 0x4B, // HTRK
0x00, 0x01, // Version
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]
+ 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:]
+ // 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())
- if len(servers) == totalSrv {
- return servers, nil
+ var srv ServerRecord
+ _, err = srv.Write(buf)
+ if err != nil {
+ return nil, err
}
- if len(srvBuf) == 0 {
- return servers, errors.New("tracker sent too few bytes for server count")
+ servers = append(servers, srv)
+ if len(servers) == totalSrv {
+ break
}
}
+
+ 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) {
+// Write implements io.Writer for ServerRecord
+func (s *ServerRecord) Write(b []byte) (n int, err error) {
+ if len(b) < 13 {
+ return 0, errors.New("too few bytes")
+ }
copy(s.IPAddr[:], b[0:4])
copy(s.Port[:], b[4:6])
copy(s.NumUsers[:], b[6:8])
+ s.NameSize = b[10]
nameLen := int(b[10])
s.Name = b[11 : 11+nameLen]
return 12 + nameLen + int(s.DescriptionSize), nil
}
-//
-//func (s *ServerRecord) UnmarshalBinary(b []byte) (err error) {
-// r := bytes.NewReader(b[:10])
-// if err := binary.Read(r, binary.BigEndian, s); err != nil {
-// return err
-// }
-//
-// copy(s.IPAddr[:], b[0:4])
-// s.Port = b[4:6]
-// s.NumUsers = b[6:8]
-// s.NameSize = b[10]
-// 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)]
-//
-// return 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[:]),
git.r.bdr.sh / rbdr / mobius / blobdiff