syncthing/vendor/github.com/xtaci/smux/session.go
2017-04-05 14:34:41 +00:00

335 lines
7.2 KiB
Go

package smux
import (
"encoding/binary"
"io"
"sync"
"sync/atomic"
"time"
"github.com/pkg/errors"
)
const (
defaultAcceptBacklog = 1024
)
const (
errBrokenPipe = "broken pipe"
errInvalidProtocol = "invalid protocol version"
)
type writeRequest struct {
frame Frame
result chan writeResult
}
type writeResult struct {
n int
err error
}
// Session defines a multiplexed connection for streams
type Session struct {
conn io.ReadWriteCloser
config *Config
nextStreamID uint32 // next stream identifier
bucket int32 // token bucket
bucketNotify chan struct{} // used for waiting for tokens
streams map[uint32]*Stream // all streams in this session
streamLock sync.Mutex // locks streams
die chan struct{} // flag session has died
dieLock sync.Mutex
chAccepts chan *Stream
dataReady int32 // flag data has arrived
deadline atomic.Value
writes chan writeRequest
}
func newSession(config *Config, conn io.ReadWriteCloser, client bool) *Session {
s := new(Session)
s.die = make(chan struct{})
s.conn = conn
s.config = config
s.streams = make(map[uint32]*Stream)
s.chAccepts = make(chan *Stream, defaultAcceptBacklog)
s.bucket = int32(config.MaxReceiveBuffer)
s.bucketNotify = make(chan struct{}, 1)
s.writes = make(chan writeRequest)
if client {
s.nextStreamID = 1
} else {
s.nextStreamID = 2
}
go s.recvLoop()
go s.sendLoop()
go s.keepalive()
return s
}
// OpenStream is used to create a new stream
func (s *Session) OpenStream() (*Stream, error) {
if s.IsClosed() {
return nil, errors.New(errBrokenPipe)
}
sid := atomic.AddUint32(&s.nextStreamID, 2)
stream := newStream(sid, s.config.MaxFrameSize, s)
if _, err := s.writeFrame(newFrame(cmdSYN, sid)); err != nil {
return nil, errors.Wrap(err, "writeFrame")
}
s.streamLock.Lock()
s.streams[sid] = stream
s.streamLock.Unlock()
return stream, nil
}
// AcceptStream is used to block until the next available stream
// is ready to be accepted.
func (s *Session) AcceptStream() (*Stream, error) {
var deadline <-chan time.Time
if d, ok := s.deadline.Load().(time.Time); ok && !d.IsZero() {
timer := time.NewTimer(d.Sub(time.Now()))
defer timer.Stop()
deadline = timer.C
}
select {
case stream := <-s.chAccepts:
return stream, nil
case <-deadline:
return nil, errTimeout
case <-s.die:
return nil, errors.New(errBrokenPipe)
}
}
// Close is used to close the session and all streams.
func (s *Session) Close() (err error) {
s.dieLock.Lock()
select {
case <-s.die:
s.dieLock.Unlock()
return errors.New(errBrokenPipe)
default:
close(s.die)
s.dieLock.Unlock()
s.streamLock.Lock()
for k := range s.streams {
s.streams[k].sessionClose()
}
s.streamLock.Unlock()
s.notifyBucket()
return s.conn.Close()
}
}
// notifyBucket notifies recvLoop that bucket is available
func (s *Session) notifyBucket() {
select {
case s.bucketNotify <- struct{}{}:
default:
}
}
// IsClosed does a safe check to see if we have shutdown
func (s *Session) IsClosed() bool {
select {
case <-s.die:
return true
default:
return false
}
}
// NumStreams returns the number of currently open streams
func (s *Session) NumStreams() int {
if s.IsClosed() {
return 0
}
s.streamLock.Lock()
defer s.streamLock.Unlock()
return len(s.streams)
}
// SetDeadline sets a deadline used by Accept* calls.
// A zero time value disables the deadline.
func (s *Session) SetDeadline(t time.Time) error {
s.deadline.Store(t)
return nil
}
// notify the session that a stream has closed
func (s *Session) streamClosed(sid uint32) {
s.streamLock.Lock()
if n := s.streams[sid].recycleTokens(); n > 0 { // return remaining tokens to the bucket
if atomic.AddInt32(&s.bucket, int32(n)) > 0 {
s.notifyBucket()
}
}
delete(s.streams, sid)
s.streamLock.Unlock()
}
// returnTokens is called by stream to return token after read
func (s *Session) returnTokens(n int) {
if atomic.AddInt32(&s.bucket, int32(n)) > 0 {
s.notifyBucket()
}
}
// session read a frame from underlying connection
// it's data is pointed to the input buffer
func (s *Session) readFrame(buffer []byte) (f Frame, err error) {
if _, err := io.ReadFull(s.conn, buffer[:headerSize]); err != nil {
return f, errors.Wrap(err, "readFrame")
}
dec := rawHeader(buffer)
if dec.Version() != version {
return f, errors.New(errInvalidProtocol)
}
f.ver = dec.Version()
f.cmd = dec.Cmd()
f.sid = dec.StreamID()
if length := dec.Length(); length > 0 {
if _, err := io.ReadFull(s.conn, buffer[headerSize:headerSize+length]); err != nil {
return f, errors.Wrap(err, "readFrame")
}
f.data = buffer[headerSize : headerSize+length]
}
return f, nil
}
// recvLoop keeps on reading from underlying connection if tokens are available
func (s *Session) recvLoop() {
buffer := make([]byte, (1<<16)+headerSize)
for {
for atomic.LoadInt32(&s.bucket) <= 0 && !s.IsClosed() {
<-s.bucketNotify
}
if f, err := s.readFrame(buffer); err == nil {
atomic.StoreInt32(&s.dataReady, 1)
switch f.cmd {
case cmdNOP:
case cmdSYN:
s.streamLock.Lock()
if _, ok := s.streams[f.sid]; !ok {
stream := newStream(f.sid, s.config.MaxFrameSize, s)
s.streams[f.sid] = stream
select {
case s.chAccepts <- stream:
case <-s.die:
}
}
s.streamLock.Unlock()
case cmdFIN:
s.streamLock.Lock()
if stream, ok := s.streams[f.sid]; ok {
stream.markRST()
stream.notifyReadEvent()
}
s.streamLock.Unlock()
case cmdPSH:
s.streamLock.Lock()
if stream, ok := s.streams[f.sid]; ok {
atomic.AddInt32(&s.bucket, -int32(len(f.data)))
stream.pushBytes(f.data)
stream.notifyReadEvent()
}
s.streamLock.Unlock()
default:
s.Close()
return
}
} else {
s.Close()
return
}
}
}
func (s *Session) keepalive() {
tickerPing := time.NewTicker(s.config.KeepAliveInterval)
tickerTimeout := time.NewTicker(s.config.KeepAliveTimeout)
defer tickerPing.Stop()
defer tickerTimeout.Stop()
for {
select {
case <-tickerPing.C:
s.writeFrame(newFrame(cmdNOP, 0))
s.notifyBucket() // force a signal to the recvLoop
case <-tickerTimeout.C:
if !atomic.CompareAndSwapInt32(&s.dataReady, 1, 0) {
s.Close()
return
}
case <-s.die:
return
}
}
}
func (s *Session) sendLoop() {
buf := make([]byte, (1<<16)+headerSize)
for {
select {
case <-s.die:
return
case request, ok := <-s.writes:
if !ok {
continue
}
buf[0] = request.frame.ver
buf[1] = request.frame.cmd
binary.LittleEndian.PutUint16(buf[2:], uint16(len(request.frame.data)))
binary.LittleEndian.PutUint32(buf[4:], request.frame.sid)
copy(buf[headerSize:], request.frame.data)
n, err := s.conn.Write(buf[:headerSize+len(request.frame.data)])
n -= headerSize
if n < 0 {
n = 0
}
result := writeResult{
n: n,
err: err,
}
request.result <- result
close(request.result)
}
}
}
// writeFrame writes the frame to the underlying connection
// and returns the number of bytes written if successful
func (s *Session) writeFrame(f Frame) (n int, err error) {
req := writeRequest{
frame: f,
result: make(chan writeResult, 1),
}
select {
case <-s.die:
return 0, errors.New(errBrokenPipe)
case s.writes <- req:
}
result := <-req.result
return result.n, result.err
}