forked from jpillora/cloud-torrent
/
udp.go
276 lines (248 loc) · 5.36 KB
/
udp.go
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package tracker
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math/rand"
"net"
"net/url"
"time"
"github.com/anacrolix/missinggo"
"github.com/anacrolix/missinggo/pproffd"
"github.com/anacrolix/torrent/util"
)
type Action int32
const (
ActionConnect Action = iota
ActionAnnounce
ActionScrape
ActionError
connectRequestConnectionId = 0x41727101980
// BEP 41
optionTypeEndOfOptions = 0
optionTypeNOP = 1
optionTypeURLData = 2
)
type ConnectionRequest struct {
ConnectionId int64
Action int32
TransctionId int32
}
type ConnectionResponse struct {
ConnectionId int64
}
type ResponseHeader struct {
Action Action
TransactionId int32
}
type RequestHeader struct {
ConnectionId int64
Action Action
TransactionId int32
} // 16 bytes
type AnnounceResponseHeader struct {
Interval int32
Leechers int32
Seeders int32
}
func init() {
registerClientScheme("udp", newUDPClient)
}
func newUDPClient(url *url.URL) client {
return &udpClient{
url: *url,
}
}
func newTransactionId() int32 {
return int32(rand.Uint32())
}
func timeout(contiguousTimeouts int) (d time.Duration) {
if contiguousTimeouts > 8 {
contiguousTimeouts = 8
}
d = 15 * time.Second
for ; contiguousTimeouts > 0; contiguousTimeouts-- {
d *= 2
}
return
}
type udpClient struct {
contiguousTimeouts int
connectionIdReceived time.Time
connectionId int64
socket net.Conn
url url.URL
}
func (me *udpClient) Close() error {
if me.socket != nil {
return me.socket.Close()
}
return nil
}
func (c *udpClient) URL() string {
return c.url.String()
}
func (c *udpClient) String() string {
return c.URL()
}
func (c *udpClient) Announce(req *AnnounceRequest) (res AnnounceResponse, err error) {
if !c.connected() {
err = ErrNotConnected
return
}
reqURI := c.url.RequestURI()
// Clearly this limits the request URI to 255 bytes. BEP 41 supports
// longer but I'm not fussed.
options := append([]byte{optionTypeURLData, byte(len(reqURI))}, []byte(reqURI)...)
b, err := c.request(ActionAnnounce, req, options)
if err != nil {
return
}
var h AnnounceResponseHeader
err = readBody(b, &h)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
err = fmt.Errorf("error parsing announce response: %s", err)
return
}
res.Interval = h.Interval
res.Leechers = h.Leechers
res.Seeders = h.Seeders
cps, err := util.UnmarshalIPv4CompactPeers(b.Bytes())
if err != nil {
return
}
for _, cp := range cps {
res.Peers = append(res.Peers, Peer{
IP: cp.IP[:],
Port: int(cp.Port),
})
}
return
}
// body is the binary serializable request body. trailer is optional data
// following it, such as for BEP 41.
func (c *udpClient) write(h *RequestHeader, body interface{}, trailer []byte) (err error) {
var buf bytes.Buffer
err = binary.Write(&buf, binary.BigEndian, h)
if err != nil {
panic(err)
}
if body != nil {
err = binary.Write(&buf, binary.BigEndian, body)
if err != nil {
panic(err)
}
}
_, err = buf.Write(trailer)
if err != nil {
return
}
n, err := c.socket.Write(buf.Bytes())
if err != nil {
return
}
if n != buf.Len() {
panic("write should send all or error")
}
return
}
func read(r io.Reader, data interface{}) error {
return binary.Read(r, binary.BigEndian, data)
}
func write(w io.Writer, data interface{}) error {
return binary.Write(w, binary.BigEndian, data)
}
// args is the binary serializable request body. trailer is optional data
// following it, such as for BEP 41.
func (c *udpClient) request(action Action, args interface{}, options []byte) (responseBody *bytes.Buffer, err error) {
tid := newTransactionId()
err = c.write(&RequestHeader{
ConnectionId: c.connectionId,
Action: action,
TransactionId: tid,
}, args, options)
if err != nil {
return
}
c.socket.SetReadDeadline(time.Now().Add(timeout(c.contiguousTimeouts)))
b := make([]byte, 0x800) // 2KiB
for {
var n int
n, err = c.socket.Read(b)
if opE, ok := err.(*net.OpError); ok {
if opE.Timeout() {
c.contiguousTimeouts++
return
}
}
if err != nil {
return
}
buf := bytes.NewBuffer(b[:n])
var h ResponseHeader
err = binary.Read(buf, binary.BigEndian, &h)
switch err {
case io.ErrUnexpectedEOF:
continue
case nil:
default:
return
}
if h.TransactionId != tid {
continue
}
c.contiguousTimeouts = 0
if h.Action == ActionError {
err = errors.New(buf.String())
}
responseBody = buf
return
}
}
func readBody(r io.Reader, data ...interface{}) (err error) {
for _, datum := range data {
err = binary.Read(r, binary.BigEndian, datum)
if err != nil {
break
}
}
return
}
func (c *udpClient) connected() bool {
return !c.connectionIdReceived.IsZero() && time.Now().Before(c.connectionIdReceived.Add(time.Minute))
}
func (c *udpClient) Connect() (err error) {
if c.connected() {
return nil
}
c.connectionId = connectRequestConnectionId
if c.socket == nil {
hmp := missinggo.SplitHostMaybePort(c.url.Host)
if hmp.NoPort {
hmp.NoPort = false
hmp.Port = 80
}
c.socket, err = net.Dial("udp", hmp.String())
if err != nil {
return
}
c.socket = pproffd.WrapNetConn(c.socket)
}
b, err := c.request(ActionConnect, nil, nil)
if err != nil {
return
}
var res ConnectionResponse
err = readBody(b, &res)
if err != nil {
return
}
c.connectionId = res.ConnectionId
c.connectionIdReceived = time.Now()
return
}