github.com/la5nta/wl2k-go@v0.11.8/transport/ax25/agwpe/agwpe.go (about)

     1  package agwpe
     2  
     3  import (
     4  	"bytes"
     5  	"context"
     6  	"encoding/binary"
     7  	"errors"
     8  	"fmt"
     9  	"log"
    10  	"net"
    11  	"os"
    12  	"strconv"
    13  	"time"
    14  )
    15  
    16  var (
    17  	ErrTNCClosed  = errors.New("TNC closed")
    18  	ErrPortClosed = errors.New("port closed")
    19  )
    20  
    21  type TNC struct {
    22  	conn  net.Conn
    23  	demux *demux
    24  }
    25  
    26  func newTNC(conn net.Conn) *TNC {
    27  	t := &TNC{
    28  		conn:  conn,
    29  		demux: newDemux(),
    30  	}
    31  	go t.run()
    32  	return t
    33  }
    34  
    35  func (t *TNC) run() {
    36  	defer debugf("TNC run() exited")
    37  	defer t.Close()
    38  	for {
    39  		var f frame
    40  		if err := t.read(&f); err != nil {
    41  			debugf("read failed: %v", err)
    42  			return
    43  		}
    44  		if !t.demux.Enqueue(f) {
    45  			return
    46  		}
    47  	}
    48  }
    49  
    50  func OpenTCP(addr string) (*TNC, error) {
    51  	conn, err := net.Dial("tcp", addr)
    52  	if err != nil {
    53  		return nil, err
    54  	}
    55  	return newTNC(conn), nil
    56  }
    57  
    58  func (t *TNC) Ping() error { _, err := t.Version(); return err }
    59  
    60  func (t *TNC) Version() (string, error) {
    61  	resp := t.demux.NextFrame(kindVersionNumber)
    62  	t.write(versionNumberFrame())
    63  	select {
    64  	case <-time.After(3 * time.Second):
    65  		return "", fmt.Errorf("response timeout")
    66  	case f, ok := <-resp:
    67  		if !ok {
    68  			return "", ErrTNCClosed
    69  		}
    70  		if len(f.Data) != 8 {
    71  			return "", fmt.Errorf("'%c' frame with invalid data length", f.DataKind)
    72  		}
    73  		var v struct{ Major, _, Minor, _ uint16 }
    74  		binary.Read(bytes.NewReader(f.Data), binary.LittleEndian, &v)
    75  		return fmt.Sprintf("%d.%d", v.Major, v.Minor), nil
    76  	}
    77  }
    78  
    79  func (t *TNC) Close() error {
    80  	t.demux.Close()
    81  	return t.conn.Close()
    82  }
    83  
    84  func (t *TNC) RegisterPort(port int, mycall string) (*Port, error) {
    85  	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    86  	defer cancel()
    87  	p := newPort(t, uint8(port), mycall)
    88  	if err := p.register(ctx); err != nil {
    89  		t.Close()
    90  		return nil, err
    91  	}
    92  	return p, nil
    93  }
    94  
    95  func (t *TNC) write(f frame) error {
    96  	_, err := f.WriteTo(t.conn)
    97  	if err == nil && f.DataKind != kindOutstandingFramesForConn {
    98  		debugf("-> %v", f)
    99  	}
   100  	return err
   101  }
   102  
   103  func (t *TNC) read(f *frame) error {
   104  	_, err := f.ReadFrom(t.conn)
   105  	if err == nil && f.DataKind != kindOutstandingFramesForConn {
   106  		debugf("<- %v", *f)
   107  	}
   108  	return err
   109  }
   110  
   111  func debugf(s string, v ...interface{}) {
   112  	if t, _ := strconv.ParseBool(os.Getenv("AGWPE_DEBUG")); !t {
   113  		return
   114  	}
   115  	log.Printf(s, v...)
   116  }