Refactoring, cleanup, test backfilling

[rbdr/mobius] / hotline / tracker.go

diff --git a/hotline/tracker.go b/hotline/tracker.go
index e0cbe569eaa3d31eaff9e9e796d00c3b936aa175..d0ccff4658a3a19bf32f7f14a8dcfe1362f95dde 100644 (file)
--- a/hotline/tracker.go
+++ b/hotline/tracker.go
@@ -1,59 +1,80 @@
 package hotline
 
 import (
 package hotline
 
 import (

-       "bytes"
+       "bufio"

        "encoding/binary"
        "errors"
        "fmt"
        "encoding/binary"
        "errors"
        "fmt"

-       "github.com/jhalter/mobius/concat"
+       "io"

        "net"
        "net"

+       "slices"

        "strconv"
        "strconv"

-       "time"

 )
 
 )
 

+// TrackerRegistration represents the payload a Hotline server sends to a Tracker to register

 type TrackerRegistration struct {
 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))
 
        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,
                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.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 {
-       conn, err := net.Dial("udp", tracker)
+// Dialer interface to abstract the dialing operation
+type Dialer interface {
+       Dial(network, address string) (net.Conn, error)
+}
+
+// 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 {
        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
 }
 
        }
 
        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:
 // 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:


@@ -61,42 +82,35 @@ const trackerTimeout = 5 * time.Second
 // Magic number        4       ‘HTRK’
 // Version     2       1 or 2  Old protocol (1) or new (2)
 
 // 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)
 }
 
 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 {
 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)_/¯
 }
 
        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 {
 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
 }
 
        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() }()
 
        defer func() { _ = conn.Close() }()
 

-       _, err = conn.Write(
+       _, err := conn.Write(

                []byte{
                        0x48, 0x54, 0x52, 0x4B, // HTRK
                        0x00, 0x01, // Version
                []byte{
                        0x48, 0x54, 0x52, 0x4B, // HTRK
                        0x00, 0x01, // Version


@@ -106,70 +120,87 @@ func GetListing(addr string) ([]ServerRecord, error) {
                return nil, err
        }
 
                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
        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
                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
        }
 
                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[:]))
 
        totalSrv := int(binary.BigEndian.Uint16(info.SrvCount[:]))
 

-       srvBuf := buf[14:totalRead]
+       scanner := bufio.NewScanner(conn)
+       scanner.Split(serverScanner)

 
        var servers []ServerRecord
 
        var servers []ServerRecord

-

        for {
        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 {
                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]
+// 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.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)]
        s.Name = b[11 : 11+nameLen]
        s.DescriptionSize = b[11+nameLen]
        s.Description = b[12+nameLen : 12+nameLen+int(s.DescriptionSize)]


@@ -177,14 +208,9 @@ func (s *ServerRecord) Read(b []byte) (n int, err error) {
        return 12 + nameLen + int(s.DescriptionSize), nil
 }
 
        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",
 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[:]))),

        )
 }
        )
 }