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package multiplex
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import (
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"errors"
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"fmt"
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"net"
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"sync"
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"sync/atomic"
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"time"
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log "github.com/sirupsen/logrus"
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)
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const (
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acceptBacklog = 1024
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)
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var ErrBrokenSession = errors.New("broken session")
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var errRepeatSessionClosing = errors.New("trying to close a closed session")
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// Obfuscator is responsible for the obfuscation and deobfuscation of frames
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type Obfuscator struct {
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// Used in Stream.Write. Add multiplexing headers, encrypt and add TLS header
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Obfs Obfser
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// Remove TLS header, decrypt and unmarshall frames
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Deobfs Deobfser
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SessionKey []byte
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}
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type switchboardStrategy int
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type SessionConfig struct {
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*Obfuscator
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Valve
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// This is supposed to read one TLS message.
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UnitRead func(net.Conn, []byte) (int, error)
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Unordered bool
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}
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type Session struct {
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id uint32
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*SessionConfig
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// atomic
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nextStreamID uint32
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streamsM sync.Mutex
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streams map[uint32]*Stream
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// Switchboard manages all connections to remote
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sb *switchboard
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addrs atomic.Value
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// For accepting new streams
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acceptCh chan *Stream
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closed uint32
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terminalMsg atomic.Value
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}
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func MakeSession(id uint32, config *SessionConfig) *Session {
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sesh := &Session{
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id: id,
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SessionConfig: config,
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nextStreamID: 1,
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streams: make(map[uint32]*Stream),
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acceptCh: make(chan *Stream, acceptBacklog),
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}
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sesh.addrs.Store([]net.Addr{nil, nil})
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if config.Valve == nil {
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config.Valve = UNLIMITED_VALVE
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}
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sbConfig := &switchboardConfig{
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Valve: config.Valve,
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}
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if config.Unordered {
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log.Debug("Connection is unordered")
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sbConfig.strategy = UNIFORM_SPREAD
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} else {
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sbConfig.strategy = FIXED_CONN_MAPPING
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}
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sesh.sb = makeSwitchboard(sesh, sbConfig)
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go sesh.timeoutAfter(30 * time.Second)
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return sesh
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}
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func (sesh *Session) AddConnection(conn net.Conn) {
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sesh.sb.addConn(conn)
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addrs := []net.Addr{conn.LocalAddr(), conn.RemoteAddr()}
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sesh.addrs.Store(addrs)
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}
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func (sesh *Session) OpenStream() (*Stream, error) {
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if sesh.IsClosed() {
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return nil, ErrBrokenSession
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}
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id := atomic.AddUint32(&sesh.nextStreamID, 1) - 1
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// Because atomic.AddUint32 returns the value after incrementation
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connId, err := sesh.sb.assignRandomConn()
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if err != nil {
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return nil, err
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}
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stream := makeStream(sesh, id, connId)
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sesh.streamsM.Lock()
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sesh.streams[id] = stream
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sesh.streamsM.Unlock()
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log.Tracef("stream %v of session %v opened", id, sesh.id)
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return stream, nil
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}
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func (sesh *Session) Accept() (net.Conn, error) {
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if sesh.IsClosed() {
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return nil, ErrBrokenSession
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}
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stream := <-sesh.acceptCh
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if stream == nil {
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return nil, ErrBrokenSession
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}
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sesh.streamsM.Lock()
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sesh.streams[stream.id] = stream
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sesh.streamsM.Unlock()
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log.Tracef("stream %v of session %v accepted", stream.id, sesh.id)
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return stream, nil
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}
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func (sesh *Session) delStream(id uint32) {
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sesh.streamsM.Lock()
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delete(sesh.streams, id)
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if len(sesh.streams) == 0 {
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log.Tracef("session %v has no active stream left", sesh.id)
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go sesh.timeoutAfter(30 * time.Second)
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}
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sesh.streamsM.Unlock()
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}
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func (sesh *Session) recvDataFromRemote(data []byte) error {
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frame, err := sesh.Deobfs(data)
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if err != nil {
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return fmt.Errorf("Failed to decrypt a frame for session %v: %v", sesh.id, err)
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}
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sesh.streamsM.Lock()
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defer sesh.streamsM.Unlock()
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stream, existing := sesh.streams[frame.StreamID]
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if existing {
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stream.writeFrame(frame)
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return nil
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} else {
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if frame.Closing == 1 {
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// If the stream has been closed and the current frame is a closing frame, we do noop
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return nil
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} else {
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// it may be tempting to use the connId from which the frame was received. However it doesn't make
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// any difference because we only care to send the data from the same stream through the same
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// TCP connection. The remote may use a different connection to send the same stream than the one the client
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// use to send.
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connId, _ := sesh.sb.assignRandomConn()
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// we ignore the error here. If the switchboard is broken, it will be reflected upon stream.Write
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stream = makeStream(sesh, frame.StreamID, connId)
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sesh.acceptCh <- stream
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stream.writeFrame(frame)
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return nil
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}
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}
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}
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func (sesh *Session) SetTerminalMsg(msg string) {
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sesh.terminalMsg.Store(msg)
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}
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func (sesh *Session) TerminalMsg() string {
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msg := sesh.terminalMsg.Load()
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if msg != nil {
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return msg.(string)
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} else {
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return ""
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}
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}
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func (sesh *Session) Close() error {
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log.Debugf("attempting to close session %v", sesh.id)
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if atomic.SwapUint32(&sesh.closed, 1) == 1 {
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log.Debugf("session %v has already been closed", sesh.id)
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return errRepeatSessionClosing
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}
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sesh.streamsM.Lock()
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sesh.acceptCh <- nil
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for id, stream := range sesh.streams {
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// If we call stream.Close() here, streamsM will result in a deadlock
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// because stream.Close calls sesh.delStream, which locks the mutex.
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// so we need to implement a method of stream that closes the stream without calling
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// sesh.delStream
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go stream.closeNoDelMap()
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delete(sesh.streams, id)
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}
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sesh.streamsM.Unlock()
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sesh.sb.closeAll()
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log.Debugf("session %v closed gracefully", sesh.id)
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return nil
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}
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func (sesh *Session) IsClosed() bool {
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return atomic.LoadUint32(&sesh.closed) == 1
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}
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func (sesh *Session) timeoutAfter(to time.Duration) {
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time.Sleep(to)
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sesh.streamsM.Lock()
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if len(sesh.streams) == 0 && !sesh.IsClosed() {
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sesh.streamsM.Unlock()
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sesh.SetTerminalMsg("timeout")
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sesh.Close()
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} else {
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sesh.streamsM.Unlock()
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}
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}
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func (sesh *Session) Addr() net.Addr { return sesh.addrs.Load().([]net.Addr)[0] }
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