Cloak/internal/multiplex/stream.go
2019-09-01 20:23:45 +01:00

189 lines
4.7 KiB
Go

package multiplex
import (
"errors"
"io"
"net"
"time"
log "github.com/sirupsen/logrus"
"math"
prand "math/rand"
"sync"
"sync/atomic"
)
var ErrBrokenStream = errors.New("broken stream")
type Stream struct {
id uint32
session *Session
recvBuf recvBuffer
// atomic
nextSendSeq uint64
writingM sync.RWMutex
// atomic
closed uint32
obfsBuf []byte
// we assign each stream a fixed underlying TCP connection to utilise order guarantee provided by TCP itself
// so that frameSorter should have few to none ooo frames to deal with
// overall the streams in a session should be uniformly distributed across all connections
// This is not used in unordered connection mode
assignedConnId uint32
}
func makeStream(sesh *Session, id uint32, assignedConnId uint32) *Stream {
var recvBuf recvBuffer
if sesh.Unordered {
recvBuf = NewDatagramBuffer()
} else {
recvBuf = NewStreamBuffer()
}
stream := &Stream{
id: id,
session: sesh,
recvBuf: recvBuf,
obfsBuf: make([]byte, 17000), //TODO don't leave this hardcoded
assignedConnId: assignedConnId,
}
return stream
}
func (s *Stream) isClosed() bool { return atomic.LoadUint32(&s.closed) == 1 }
func (s *Stream) writeFrame(frame Frame) error {
return s.recvBuf.Write(frame)
}
// Read implements io.Read
func (s *Stream) Read(buf []byte) (n int, err error) {
//log.Tracef("attempting to read from stream %v", s.id)
if len(buf) == 0 {
if s.isClosed() {
return 0, ErrBrokenStream
} else {
return 0, nil
}
}
n, err = s.recvBuf.Read(buf)
if err == io.EOF {
return n, ErrBrokenStream
}
log.Tracef("%v read from stream %v with err %v", n, s.id, err)
return
}
// Write implements io.Write
func (s *Stream) Write(in []byte) (n int, err error) {
// RWMutex used here isn't really for RW.
// we use it to exploit the fact that RLock doesn't create contention.
// The use of RWMutex is so that the stream will not actively close
// in the middle of the execution of Write. This may cause the closing frame
// to be sent before the data frame and cause loss of packet.
//log.Tracef("attempting to write %v bytes to stream %v",len(in),s.id)
s.writingM.RLock()
defer s.writingM.RUnlock()
if s.isClosed() {
return 0, ErrBrokenStream
}
f := &Frame{
StreamID: s.id,
Seq: atomic.AddUint64(&s.nextSendSeq, 1) - 1,
Closing: 0,
Payload: in,
}
i, err := s.session.Obfs(f, s.obfsBuf)
if err != nil {
return i, err
}
n, err = s.session.sb.send(s.obfsBuf[:i], &s.assignedConnId)
log.Tracef("%v sent to remote through stream %v with err %v", len(in), s.id, err)
if err != nil {
return
}
return len(in), nil
}
// the necessary steps to mark the stream as closed and to release resources
func (s *Stream) _close() {
atomic.StoreUint32(&s.closed, 1)
_ = s.recvBuf.Close() // both datagramBuffer and streamBuffer won't return err on Close()
}
// only close locally. Used when the stream close is notified by the remote
func (s *Stream) passiveClose() {
s._close()
s.session.delStream(s.id)
log.Tracef("stream %v passively closed", s.id)
}
// active close. Close locally and tell the remote that this stream is being closed
func (s *Stream) Close() error {
s.writingM.Lock()
defer s.writingM.Unlock()
if s.isClosed() {
return errors.New("Already Closed")
}
// Notify remote that this stream is closed
prand.Seed(int64(s.id))
padLen := int(math.Floor(prand.Float64()*200 + 300))
pad := make([]byte, padLen)
prand.Read(pad)
f := &Frame{
StreamID: s.id,
Seq: atomic.AddUint64(&s.nextSendSeq, 1) - 1,
Closing: 1,
Payload: pad,
}
i, err := s.session.Obfs(f, s.obfsBuf)
if err != nil {
return err
}
_, err = s.session.sb.send(s.obfsBuf[:i], &s.assignedConnId)
if err != nil {
return err
}
s._close()
s.session.delStream(s.id)
log.Tracef("stream %v actively closed", s.id)
return nil
}
// Same as passiveClose() but no call to session.delStream.
// This is called in session.Close() to avoid mutex deadlock
// We don't notify the remote because session.Close() is always
// called when the session is passively closed
func (s *Stream) closeNoDelMap() {
log.Tracef("stream %v closed by session", s.id)
s._close()
}
// the following functions are purely for implementing net.Conn interface.
// they are not used
var errNotImplemented = errors.New("Not implemented")
func (s *Stream) LocalAddr() net.Addr { return s.session.addrs.Load().([]net.Addr)[0] }
func (s *Stream) RemoteAddr() net.Addr { return s.session.addrs.Load().([]net.Addr)[1] }
// TODO: implement the following
func (s *Stream) SetDeadline(t time.Time) error { return errNotImplemented }
func (s *Stream) SetReadDeadline(t time.Time) error { return errNotImplemented }
func (s *Stream) SetWriteDeadline(t time.Time) error { return errNotImplemented }