Update mattermost library (#2152)

* Update mattermost library

* Fix linting

vendor/github.com/hashicorp/yamux/session.go

@@ -0,0 +1,732 @@
+package yamux
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"math"
+	"net"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// Session is used to wrap a reliable ordered connection and to
+// multiplex it into multiple streams.
+type Session struct {
+	// remoteGoAway indicates the remote side does
+	// not want futher connections. Must be first for alignment.
+	remoteGoAway int32
+
+	// localGoAway indicates that we should stop
+	// accepting futher connections. Must be first for alignment.
+	localGoAway int32
+
+	// nextStreamID is the next stream we should
+	// send. This depends if we are a client/server.
+	nextStreamID uint32
+
+	// config holds our configuration
+	config *Config
+
+	// logger is used for our logs
+	logger *log.Logger
+
+	// conn is the underlying connection
+	conn io.ReadWriteCloser
+
+	// bufRead is a buffered reader
+	bufRead *bufio.Reader
+
+	// pings is used to track inflight pings
+	pings    map[uint32]chan struct{}
+	pingID   uint32
+	pingLock sync.Mutex
+
+	// streams maps a stream id to a stream, and inflight has an entry
+	// for any outgoing stream that has not yet been established. Both are
+	// protected by streamLock.
+	streams    map[uint32]*Stream
+	inflight   map[uint32]struct{}
+	streamLock sync.Mutex
+
+	// synCh acts like a semaphore. It is sized to the AcceptBacklog which
+	// is assumed to be symmetric between the client and server. This allows
+	// the client to avoid exceeding the backlog and instead blocks the open.
+	synCh chan struct{}
+
+	// acceptCh is used to pass ready streams to the client
+	acceptCh chan *Stream
+
+	// sendCh is used to mark a stream as ready to send,
+	// or to send a header out directly.
+	sendCh chan *sendReady
+
+	// recvDoneCh is closed when recv() exits to avoid a race
+	// between stream registration and stream shutdown
+	recvDoneCh chan struct{}
+	sendDoneCh chan struct{}
+
+	// shutdown is used to safely close a session
+	shutdown        bool
+	shutdownErr     error
+	shutdownCh      chan struct{}
+	shutdownLock    sync.Mutex
+	shutdownErrLock sync.Mutex
+}
+
+// sendReady is used to either mark a stream as ready
+// or to directly send a header
+type sendReady struct {
+	Hdr  []byte
+	mu   sync.Mutex // Protects Body from unsafe reads.
+	Body []byte
+	Err  chan error
+}
+
+// newSession is used to construct a new session
+func newSession(config *Config, conn io.ReadWriteCloser, client bool) *Session {
+	logger := config.Logger
+	if logger == nil {
+		logger = log.New(config.LogOutput, "", log.LstdFlags)
+	}
+
+	s := &Session{
+		config:     config,
+		logger:     logger,
+		conn:       conn,
+		bufRead:    bufio.NewReader(conn),
+		pings:      make(map[uint32]chan struct{}),
+		streams:    make(map[uint32]*Stream),
+		inflight:   make(map[uint32]struct{}),
+		synCh:      make(chan struct{}, config.AcceptBacklog),
+		acceptCh:   make(chan *Stream, config.AcceptBacklog),
+		sendCh:     make(chan *sendReady, 64),
+		recvDoneCh: make(chan struct{}),
+		sendDoneCh: make(chan struct{}),
+		shutdownCh: make(chan struct{}),
+	}
+	if client {
+		s.nextStreamID = 1
+	} else {
+		s.nextStreamID = 2
+	}
+	go s.recv()
+	go s.send()
+	if config.EnableKeepAlive {
+		go s.keepalive()
+	}
+	return s
+}
+
+// IsClosed does a safe check to see if we have shutdown
+func (s *Session) IsClosed() bool {
+	select {
+	case <-s.shutdownCh:
+		return true
+	default:
+		return false
+	}
+}
+
+// CloseChan returns a read-only channel which is closed as
+// soon as the session is closed.
+func (s *Session) CloseChan() <-chan struct{} {
+	return s.shutdownCh
+}
+
+// NumStreams returns the number of currently open streams
+func (s *Session) NumStreams() int {
+	s.streamLock.Lock()
+	num := len(s.streams)
+	s.streamLock.Unlock()
+	return num
+}
+
+// Open is used to create a new stream as a net.Conn
+func (s *Session) Open() (net.Conn, error) {
+	conn, err := s.OpenStream()
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// OpenStream is used to create a new stream
+func (s *Session) OpenStream() (*Stream, error) {
+	if s.IsClosed() {
+		return nil, ErrSessionShutdown
+	}
+	if atomic.LoadInt32(&s.remoteGoAway) == 1 {
+		return nil, ErrRemoteGoAway
+	}
+
+	// Block if we have too many inflight SYNs
+	select {
+	case s.synCh <- struct{}{}:
+	case <-s.shutdownCh:
+		return nil, ErrSessionShutdown
+	}
+
+GET_ID:
+	// Get an ID, and check for stream exhaustion
+	id := atomic.LoadUint32(&s.nextStreamID)
+	if id >= math.MaxUint32-1 {
+		return nil, ErrStreamsExhausted
+	}
+	if !atomic.CompareAndSwapUint32(&s.nextStreamID, id, id+2) {
+		goto GET_ID
+	}
+
+	// Register the stream
+	stream := newStream(s, id, streamInit)
+	s.streamLock.Lock()
+	s.streams[id] = stream
+	s.inflight[id] = struct{}{}
+	s.streamLock.Unlock()
+
+	if s.config.StreamOpenTimeout > 0 {
+		go s.setOpenTimeout(stream)
+	}
+
+	// Send the window update to create
+	if err := stream.sendWindowUpdate(); err != nil {
+		select {
+		case <-s.synCh:
+		default:
+			s.logger.Printf("[ERR] yamux: aborted stream open without inflight syn semaphore")
+		}
+		return nil, err
+	}
+	return stream, nil
+}
+
+// setOpenTimeout implements a timeout for streams that are opened but not established.
+// If the StreamOpenTimeout is exceeded we assume the peer is unable to ACK,
+// and close the session.
+// The number of running timers is bounded by the capacity of the synCh.
+func (s *Session) setOpenTimeout(stream *Stream) {
+	timer := time.NewTimer(s.config.StreamOpenTimeout)
+	defer timer.Stop()
+
+	select {
+	case <-stream.establishCh:
+		return
+	case <-s.shutdownCh:
+		return
+	case <-timer.C:
+		// Timeout reached while waiting for ACK.
+		// Close the session to force connection re-establishment.
+		s.logger.Printf("[ERR] yamux: aborted stream open (destination=%s): %v", s.RemoteAddr().String(), ErrTimeout.err)
+		s.Close()
+	}
+}
+
+// Accept is used to block until the next available stream
+// is ready to be accepted.
+func (s *Session) Accept() (net.Conn, error) {
+	conn, err := s.AcceptStream()
+	if err != nil {
+		return nil, err
+	}
+	return conn, err
+}
+
+// AcceptStream is used to block until the next available stream
+// is ready to be accepted.
+func (s *Session) AcceptStream() (*Stream, error) {
+	select {
+	case stream := <-s.acceptCh:
+		if err := stream.sendWindowUpdate(); err != nil {
+			return nil, err
+		}
+		return stream, nil
+	case <-s.shutdownCh:
+		return nil, s.shutdownErr
+	}
+}
+
+// Close is used to close the session and all streams.
+// Attempts to send a GoAway before closing the connection.
+func (s *Session) Close() error {
+	s.shutdownLock.Lock()
+	defer s.shutdownLock.Unlock()
+
+	if s.shutdown {
+		return nil
+	}
+	s.shutdown = true
+
+	s.shutdownErrLock.Lock()
+	if s.shutdownErr == nil {
+		s.shutdownErr = ErrSessionShutdown
+	}
+	s.shutdownErrLock.Unlock()
+
+	close(s.shutdownCh)
+
+	s.conn.Close()
+	<-s.recvDoneCh
+
+	s.streamLock.Lock()
+	defer s.streamLock.Unlock()
+	for _, stream := range s.streams {
+		stream.forceClose()
+	}
+	<-s.sendDoneCh
+	return nil
+}
+
+// exitErr is used to handle an error that is causing the
+// session to terminate.
+func (s *Session) exitErr(err error) {
+	s.shutdownErrLock.Lock()
+	if s.shutdownErr == nil {
+		s.shutdownErr = err
+	}
+	s.shutdownErrLock.Unlock()
+	s.Close()
+}
+
+// GoAway can be used to prevent accepting further
+// connections. It does not close the underlying conn.
+func (s *Session) GoAway() error {
+	return s.waitForSend(s.goAway(goAwayNormal), nil)
+}
+
+// goAway is used to send a goAway message
+func (s *Session) goAway(reason uint32) header {
+	atomic.SwapInt32(&s.localGoAway, 1)
+	hdr := header(make([]byte, headerSize))
+	hdr.encode(typeGoAway, 0, 0, reason)
+	return hdr
+}
+
+// Ping is used to measure the RTT response time
+func (s *Session) Ping() (time.Duration, error) {
+	// Get a channel for the ping
+	ch := make(chan struct{})
+
+	// Get a new ping id, mark as pending
+	s.pingLock.Lock()
+	id := s.pingID
+	s.pingID++
+	s.pings[id] = ch
+	s.pingLock.Unlock()
+
+	// Send the ping request
+	hdr := header(make([]byte, headerSize))
+	hdr.encode(typePing, flagSYN, 0, id)
+	if err := s.waitForSend(hdr, nil); err != nil {
+		return 0, err
+	}
+
+	// Wait for a response
+	start := time.Now()
+	select {
+	case <-ch:
+	case <-time.After(s.config.ConnectionWriteTimeout):
+		s.pingLock.Lock()
+		delete(s.pings, id) // Ignore it if a response comes later.
+		s.pingLock.Unlock()
+		return 0, ErrTimeout
+	case <-s.shutdownCh:
+		return 0, ErrSessionShutdown
+	}
+
+	// Compute the RTT
+	return time.Now().Sub(start), nil
+}
+
+// keepalive is a long running goroutine that periodically does
+// a ping to keep the connection alive.
+func (s *Session) keepalive() {
+	for {
+		select {
+		case <-time.After(s.config.KeepAliveInterval):
+			_, err := s.Ping()
+			if err != nil {
+				if err != ErrSessionShutdown {
+					s.logger.Printf("[ERR] yamux: keepalive failed: %v", err)
+					s.exitErr(ErrKeepAliveTimeout)
+				}
+				return
+			}
+		case <-s.shutdownCh:
+			return
+		}
+	}
+}
+
+// waitForSendErr waits to send a header, checking for a potential shutdown
+func (s *Session) waitForSend(hdr header, body []byte) error {
+	errCh := make(chan error, 1)
+	return s.waitForSendErr(hdr, body, errCh)
+}
+
+// waitForSendErr waits to send a header with optional data, checking for a
+// potential shutdown. Since there's the expectation that sends can happen
+// in a timely manner, we enforce the connection write timeout here.
+func (s *Session) waitForSendErr(hdr header, body []byte, errCh chan error) error {
+	t := timerPool.Get()
+	timer := t.(*time.Timer)
+	timer.Reset(s.config.ConnectionWriteTimeout)
+	defer func() {
+		timer.Stop()
+		select {
+		case <-timer.C:
+		default:
+		}
+		timerPool.Put(t)
+	}()
+
+	ready := &sendReady{Hdr: hdr, Body: body, Err: errCh}
+	select {
+	case s.sendCh <- ready:
+	case <-s.shutdownCh:
+		return ErrSessionShutdown
+	case <-timer.C:
+		return ErrConnectionWriteTimeout
+	}
+
+	bodyCopy := func() {
+		if body == nil {
+			return // A nil body is ignored.
+		}
+
+		// In the event of session shutdown or connection write timeout,
+		// we need to prevent `send` from reading the body buffer after
+		// returning from this function since the caller may re-use the
+		// underlying array.
+		ready.mu.Lock()
+		defer ready.mu.Unlock()
+
+		if ready.Body == nil {
+			return // Body was already copied in `send`.
+		}
+		newBody := make([]byte, len(body))
+		copy(newBody, body)
+		ready.Body = newBody
+	}
+
+	select {
+	case err := <-errCh:
+		return err
+	case <-s.shutdownCh:
+		bodyCopy()
+		return ErrSessionShutdown
+	case <-timer.C:
+		bodyCopy()
+		return ErrConnectionWriteTimeout
+	}
+}
+
+// sendNoWait does a send without waiting. Since there's the expectation that
+// the send happens right here, we enforce the connection write timeout if we
+// can't queue the header to be sent.
+func (s *Session) sendNoWait(hdr header) error {
+	t := timerPool.Get()
+	timer := t.(*time.Timer)
+	timer.Reset(s.config.ConnectionWriteTimeout)
+	defer func() {
+		timer.Stop()
+		select {
+		case <-timer.C:
+		default:
+		}
+		timerPool.Put(t)
+	}()
+
+	select {
+	case s.sendCh <- &sendReady{Hdr: hdr}:
+		return nil
+	case <-s.shutdownCh:
+		return ErrSessionShutdown
+	case <-timer.C:
+		return ErrConnectionWriteTimeout
+	}
+}
+
+// send is a long running goroutine that sends data
+func (s *Session) send() {
+	if err := s.sendLoop(); err != nil {
+		s.exitErr(err)
+	}
+}
+
+func (s *Session) sendLoop() error {
+	defer close(s.sendDoneCh)
+	var bodyBuf bytes.Buffer
+	for {
+		bodyBuf.Reset()
+
+		select {
+		case ready := <-s.sendCh:
+			// Send a header if ready
+			if ready.Hdr != nil {
+				_, err := s.conn.Write(ready.Hdr)
+				if err != nil {
+					s.logger.Printf("[ERR] yamux: Failed to write header: %v", err)
+					asyncSendErr(ready.Err, err)
+					return err
+				}
+			}
+
+			ready.mu.Lock()
+			if ready.Body != nil {
+				// Copy the body into the buffer to avoid
+				// holding a mutex lock during the write.
+				_, err := bodyBuf.Write(ready.Body)
+				if err != nil {
+					ready.Body = nil
+					ready.mu.Unlock()
+					s.logger.Printf("[ERR] yamux: Failed to copy body into buffer: %v", err)
+					asyncSendErr(ready.Err, err)
+					return err
+				}
+				ready.Body = nil
+			}
+			ready.mu.Unlock()
+
+			if bodyBuf.Len() > 0 {
+				// Send data from a body if given
+				_, err := s.conn.Write(bodyBuf.Bytes())
+				if err != nil {
+					s.logger.Printf("[ERR] yamux: Failed to write body: %v", err)
+					asyncSendErr(ready.Err, err)
+					return err
+				}
+			}
+
+			// No error, successful send
+			asyncSendErr(ready.Err, nil)
+		case <-s.shutdownCh:
+			return nil
+		}
+	}
+}
+
+// recv is a long running goroutine that accepts new data
+func (s *Session) recv() {
+	if err := s.recvLoop(); err != nil {
+		s.exitErr(err)
+	}
+}
+
+// Ensure that the index of the handler (typeData/typeWindowUpdate/etc) matches the message type
+var (
+	handlers = []func(*Session, header) error{
+		typeData:         (*Session).handleStreamMessage,
+		typeWindowUpdate: (*Session).handleStreamMessage,
+		typePing:         (*Session).handlePing,
+		typeGoAway:       (*Session).handleGoAway,
+	}
+)
+
+// recvLoop continues to receive data until a fatal error is encountered
+func (s *Session) recvLoop() error {
+	defer close(s.recvDoneCh)
+	hdr := header(make([]byte, headerSize))
+	for {
+		// Read the header
+		if _, err := io.ReadFull(s.bufRead, hdr); err != nil {
+			if err != io.EOF && !strings.Contains(err.Error(), "closed") && !strings.Contains(err.Error(), "reset by peer") {
+				s.logger.Printf("[ERR] yamux: Failed to read header: %v", err)
+			}
+			return err
+		}
+
+		// Verify the version
+		if hdr.Version() != protoVersion {
+			s.logger.Printf("[ERR] yamux: Invalid protocol version: %d", hdr.Version())
+			return ErrInvalidVersion
+		}
+
+		mt := hdr.MsgType()
+		if mt < typeData || mt > typeGoAway {
+			return ErrInvalidMsgType
+		}
+
+		if err := handlers[mt](s, hdr); err != nil {
+			return err
+		}
+	}
+}
+
+// handleStreamMessage handles either a data or window update frame
+func (s *Session) handleStreamMessage(hdr header) error {
+	// Check for a new stream creation
+	id := hdr.StreamID()
+	flags := hdr.Flags()
+	if flags&flagSYN == flagSYN {
+		if err := s.incomingStream(id); err != nil {
+			return err
+		}
+	}
+
+	// Get the stream
+	s.streamLock.Lock()
+	stream := s.streams[id]
+	s.streamLock.Unlock()
+
+	// If we do not have a stream, likely we sent a RST
+	if stream == nil {
+		// Drain any data on the wire
+		if hdr.MsgType() == typeData && hdr.Length() > 0 {
+			s.logger.Printf("[WARN] yamux: Discarding data for stream: %d", id)
+			if _, err := io.CopyN(ioutil.Discard, s.bufRead, int64(hdr.Length())); err != nil {
+				s.logger.Printf("[ERR] yamux: Failed to discard data: %v", err)
+				return nil
+			}
+		} else {
+			s.logger.Printf("[WARN] yamux: frame for missing stream: %v", hdr)
+		}
+		return nil
+	}
+
+	// Check if this is a window update
+	if hdr.MsgType() == typeWindowUpdate {
+		if err := stream.incrSendWindow(hdr, flags); err != nil {
+			if sendErr := s.sendNoWait(s.goAway(goAwayProtoErr)); sendErr != nil {
+				s.logger.Printf("[WARN] yamux: failed to send go away: %v", sendErr)
+			}
+			return err
+		}
+		return nil
+	}
+
+	// Read the new data
+	if err := stream.readData(hdr, flags, s.bufRead); err != nil {
+		if sendErr := s.sendNoWait(s.goAway(goAwayProtoErr)); sendErr != nil {
+			s.logger.Printf("[WARN] yamux: failed to send go away: %v", sendErr)
+		}
+		return err
+	}
+	return nil
+}
+
+// handlePing is invokde for a typePing frame
+func (s *Session) handlePing(hdr header) error {
+	flags := hdr.Flags()
+	pingID := hdr.Length()
+
+	// Check if this is a query, respond back in a separate context so we
+	// don't interfere with the receiving thread blocking for the write.
+	if flags&flagSYN == flagSYN {
+		go func() {
+			hdr := header(make([]byte, headerSize))
+			hdr.encode(typePing, flagACK, 0, pingID)
+			if err := s.sendNoWait(hdr); err != nil {
+				s.logger.Printf("[WARN] yamux: failed to send ping reply: %v", err)
+			}
+		}()
+		return nil
+	}
+
+	// Handle a response
+	s.pingLock.Lock()
+	ch := s.pings[pingID]
+	if ch != nil {
+		delete(s.pings, pingID)
+		close(ch)
+	}
+	s.pingLock.Unlock()
+	return nil
+}
+
+// handleGoAway is invokde for a typeGoAway frame
+func (s *Session) handleGoAway(hdr header) error {
+	code := hdr.Length()
+	switch code {
+	case goAwayNormal:
+		atomic.SwapInt32(&s.remoteGoAway, 1)
+	case goAwayProtoErr:
+		s.logger.Printf("[ERR] yamux: received protocol error go away")
+		return fmt.Errorf("yamux protocol error")
+	case goAwayInternalErr:
+		s.logger.Printf("[ERR] yamux: received internal error go away")
+		return fmt.Errorf("remote yamux internal error")
+	default:
+		s.logger.Printf("[ERR] yamux: received unexpected go away")
+		return fmt.Errorf("unexpected go away received")
+	}
+	return nil
+}
+
+// incomingStream is used to create a new incoming stream
+func (s *Session) incomingStream(id uint32) error {
+	// Reject immediately if we are doing a go away
+	if atomic.LoadInt32(&s.localGoAway) == 1 {
+		hdr := header(make([]byte, headerSize))
+		hdr.encode(typeWindowUpdate, flagRST, id, 0)
+		return s.sendNoWait(hdr)
+	}
+
+	// Allocate a new stream
+	stream := newStream(s, id, streamSYNReceived)
+
+	s.streamLock.Lock()
+	defer s.streamLock.Unlock()
+
+	// Check if stream already exists
+	if _, ok := s.streams[id]; ok {
+		s.logger.Printf("[ERR] yamux: duplicate stream declared")
+		if sendErr := s.sendNoWait(s.goAway(goAwayProtoErr)); sendErr != nil {
+			s.logger.Printf("[WARN] yamux: failed to send go away: %v", sendErr)
+		}
+		return ErrDuplicateStream
+	}
+
+	// Register the stream
+	s.streams[id] = stream
+
+	// Check if we've exceeded the backlog
+	select {
+	case s.acceptCh <- stream:
+		return nil
+	default:
+		// Backlog exceeded! RST the stream
+		s.logger.Printf("[WARN] yamux: backlog exceeded, forcing connection reset")
+		delete(s.streams, id)
+		hdr := header(make([]byte, headerSize))
+		hdr.encode(typeWindowUpdate, flagRST, id, 0)
+		return s.sendNoWait(hdr)
+	}
+}
+
+// closeStream is used to close a stream once both sides have
+// issued a close. If there was an in-flight SYN and the stream
+// was not yet established, then this will give the credit back.
+func (s *Session) closeStream(id uint32) {
+	s.streamLock.Lock()
+	if _, ok := s.inflight[id]; ok {
+		select {
+		case <-s.synCh:
+		default:
+			s.logger.Printf("[ERR] yamux: SYN tracking out of sync")
+		}
+	}
+	delete(s.streams, id)
+	s.streamLock.Unlock()
+}
+
+// establishStream is used to mark a stream that was in the
+// SYN Sent state as established.
+func (s *Session) establishStream(id uint32) {
+	s.streamLock.Lock()
+	if _, ok := s.inflight[id]; ok {
+		delete(s.inflight, id)
+	} else {
+		s.logger.Printf("[ERR] yamux: established stream without inflight SYN (no tracking entry)")
+	}
+	select {
+	case <-s.synCh:
+	default:
+		s.logger.Printf("[ERR] yamux: established stream without inflight SYN (didn't have semaphore)")
+	}
+	s.streamLock.Unlock()
+}