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Fixes #113

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

vendor/google.golang.org/grpc/transport/http2_server.go

@@ -0,0 +1,694 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package transport
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"math"
+	"net"
+	"strconv"
+	"sync"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/metadata"
+)
+
+// ErrIllegalHeaderWrite indicates that setting header is illegal because of
+// the stream's state.
+var ErrIllegalHeaderWrite = errors.New("transport: the stream is done or WriteHeader was already called")
+
+// http2Server implements the ServerTransport interface with HTTP2.
+type http2Server struct {
+	conn        net.Conn
+	maxStreamID uint32               // max stream ID ever seen
+	authInfo    credentials.AuthInfo // auth info about the connection
+	// writableChan synchronizes write access to the transport.
+	// A writer acquires the write lock by sending a value on writableChan
+	// and releases it by receiving from writableChan.
+	writableChan chan int
+	// shutdownChan is closed when Close is called.
+	// Blocking operations should select on shutdownChan to avoid
+	// blocking forever after Close.
+	shutdownChan chan struct{}
+	framer       *framer
+	hBuf         *bytes.Buffer  // the buffer for HPACK encoding
+	hEnc         *hpack.Encoder // HPACK encoder
+
+	// The max number of concurrent streams.
+	maxStreams uint32
+	// controlBuf delivers all the control related tasks (e.g., window
+	// updates, reset streams, and various settings) to the controller.
+	controlBuf *recvBuffer
+	fc         *inFlow
+	// sendQuotaPool provides flow control to outbound message.
+	sendQuotaPool *quotaPool
+
+	mu            sync.Mutex // guard the following
+	state         transportState
+	activeStreams map[uint32]*Stream
+	// the per-stream outbound flow control window size set by the peer.
+	streamSendQuota uint32
+}
+
+// newHTTP2Server constructs a ServerTransport based on HTTP2. ConnectionError is
+// returned if something goes wrong.
+func newHTTP2Server(conn net.Conn, maxStreams uint32, authInfo credentials.AuthInfo) (_ ServerTransport, err error) {
+	framer := newFramer(conn)
+	// Send initial settings as connection preface to client.
+	var settings []http2.Setting
+	// TODO(zhaoq): Have a better way to signal "no limit" because 0 is
+	// permitted in the HTTP2 spec.
+	if maxStreams == 0 {
+		maxStreams = math.MaxUint32
+	} else {
+		settings = append(settings, http2.Setting{http2.SettingMaxConcurrentStreams, maxStreams})
+	}
+	if initialWindowSize != defaultWindowSize {
+		settings = append(settings, http2.Setting{http2.SettingInitialWindowSize, uint32(initialWindowSize)})
+	}
+	if err := framer.writeSettings(true, settings...); err != nil {
+		return nil, ConnectionErrorf("transport: %v", err)
+	}
+	// Adjust the connection flow control window if needed.
+	if delta := uint32(initialConnWindowSize - defaultWindowSize); delta > 0 {
+		if err := framer.writeWindowUpdate(true, 0, delta); err != nil {
+			return nil, ConnectionErrorf("transport: %v", err)
+		}
+	}
+	var buf bytes.Buffer
+	t := &http2Server{
+		conn:            conn,
+		authInfo:        authInfo,
+		framer:          framer,
+		hBuf:            &buf,
+		hEnc:            hpack.NewEncoder(&buf),
+		maxStreams:      maxStreams,
+		controlBuf:      newRecvBuffer(),
+		fc:              &inFlow{limit: initialConnWindowSize},
+		sendQuotaPool:   newQuotaPool(defaultWindowSize),
+		state:           reachable,
+		writableChan:    make(chan int, 1),
+		shutdownChan:    make(chan struct{}),
+		activeStreams:   make(map[uint32]*Stream),
+		streamSendQuota: defaultWindowSize,
+	}
+	go t.controller()
+	t.writableChan <- 0
+	return t, nil
+}
+
+// operateHeader takes action on the decoded headers. It returns the current
+// stream if there are remaining headers on the wire (in the following
+// Continuation frame).
+func (t *http2Server) operateHeaders(hDec *hpackDecoder, s *Stream, frame headerFrame, endStream bool, handle func(*Stream)) (pendingStream *Stream) {
+	defer func() {
+		if pendingStream == nil {
+			hDec.state = decodeState{}
+		}
+	}()
+	endHeaders, err := hDec.decodeServerHTTP2Headers(frame)
+	if s == nil {
+		// s has been closed.
+		return nil
+	}
+	if err != nil {
+		grpclog.Printf("transport: http2Server.operateHeader found %v", err)
+		if se, ok := err.(StreamError); ok {
+			t.controlBuf.put(&resetStream{s.id, statusCodeConvTab[se.Code]})
+		}
+		return nil
+	}
+	if endStream {
+		// s is just created by the caller. No lock needed.
+		s.state = streamReadDone
+	}
+	if !endHeaders {
+		return s
+	}
+	if hDec.state.timeoutSet {
+		s.ctx, s.cancel = context.WithTimeout(context.TODO(), hDec.state.timeout)
+	} else {
+		s.ctx, s.cancel = context.WithCancel(context.TODO())
+	}
+	// Attach Auth info if there is any.
+	if t.authInfo != nil {
+		s.ctx = credentials.NewContext(s.ctx, t.authInfo)
+	}
+	// Cache the current stream to the context so that the server application
+	// can find out. Required when the server wants to send some metadata
+	// back to the client (unary call only).
+	s.ctx = newContextWithStream(s.ctx, s)
+	// Attach the received metadata to the context.
+	if len(hDec.state.mdata) > 0 {
+		s.ctx = metadata.NewContext(s.ctx, hDec.state.mdata)
+	}
+
+	s.dec = &recvBufferReader{
+		ctx:  s.ctx,
+		recv: s.buf,
+	}
+	s.method = hDec.state.method
+	t.mu.Lock()
+	if t.state != reachable {
+		t.mu.Unlock()
+		return nil
+	}
+	if uint32(len(t.activeStreams)) >= t.maxStreams {
+		t.mu.Unlock()
+		t.controlBuf.put(&resetStream{s.id, http2.ErrCodeRefusedStream})
+		return nil
+	}
+	s.sendQuotaPool = newQuotaPool(int(t.streamSendQuota))
+	t.activeStreams[s.id] = s
+	t.mu.Unlock()
+	s.windowHandler = func(n int) {
+		t.updateWindow(s, uint32(n))
+	}
+	handle(s)
+	return nil
+}
+
+// HandleStreams receives incoming streams using the given handler. This is
+// typically run in a separate goroutine.
+func (t *http2Server) HandleStreams(handle func(*Stream)) {
+	// Check the validity of client preface.
+	preface := make([]byte, len(clientPreface))
+	if _, err := io.ReadFull(t.conn, preface); err != nil {
+		grpclog.Printf("transport: http2Server.HandleStreams failed to receive the preface from client: %v", err)
+		t.Close()
+		return
+	}
+	if !bytes.Equal(preface, clientPreface) {
+		grpclog.Printf("transport: http2Server.HandleStreams received bogus greeting from client: %q", preface)
+		t.Close()
+		return
+	}
+
+	frame, err := t.framer.readFrame()
+	if err != nil {
+		grpclog.Printf("transport: http2Server.HandleStreams failed to read frame: %v", err)
+		t.Close()
+		return
+	}
+	sf, ok := frame.(*http2.SettingsFrame)
+	if !ok {
+		grpclog.Printf("transport: http2Server.HandleStreams saw invalid preface type %T from client", frame)
+		t.Close()
+		return
+	}
+	t.handleSettings(sf)
+
+	hDec := newHPACKDecoder()
+	var curStream *Stream
+	for {
+		frame, err := t.framer.readFrame()
+		if err != nil {
+			t.Close()
+			return
+		}
+		switch frame := frame.(type) {
+		case *http2.HeadersFrame:
+			id := frame.Header().StreamID
+			if id%2 != 1 || id <= t.maxStreamID {
+				// illegal gRPC stream id.
+				grpclog.Println("transport: http2Server.HandleStreams received an illegal stream id: ", id)
+				t.Close()
+				break
+			}
+			t.maxStreamID = id
+			buf := newRecvBuffer()
+			fc := &inFlow{
+				limit: initialWindowSize,
+				conn:  t.fc,
+			}
+			curStream = &Stream{
+				id:  frame.Header().StreamID,
+				st:  t,
+				buf: buf,
+				fc:  fc,
+			}
+			endStream := frame.Header().Flags.Has(http2.FlagHeadersEndStream)
+			curStream = t.operateHeaders(hDec, curStream, frame, endStream, handle)
+		case *http2.ContinuationFrame:
+			curStream = t.operateHeaders(hDec, curStream, frame, frame.HeadersEnded(), handle)
+		case *http2.DataFrame:
+			t.handleData(frame)
+		case *http2.RSTStreamFrame:
+			t.handleRSTStream(frame)
+		case *http2.SettingsFrame:
+			t.handleSettings(frame)
+		case *http2.PingFrame:
+			t.handlePing(frame)
+		case *http2.WindowUpdateFrame:
+			t.handleWindowUpdate(frame)
+		case *http2.GoAwayFrame:
+			break
+		default:
+			grpclog.Printf("transport: http2Server.HandleStreams found unhandled frame type %v.", frame)
+		}
+	}
+}
+
+func (t *http2Server) getStream(f http2.Frame) (*Stream, bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.activeStreams == nil {
+		// The transport is closing.
+		return nil, false
+	}
+	s, ok := t.activeStreams[f.Header().StreamID]
+	if !ok {
+		// The stream is already done.
+		return nil, false
+	}
+	return s, true
+}
+
+// updateWindow adjusts the inbound quota for the stream and the transport.
+// Window updates will deliver to the controller for sending when
+// the cumulative quota exceeds the corresponding threshold.
+func (t *http2Server) updateWindow(s *Stream, n uint32) {
+	swu, cwu := s.fc.onRead(n)
+	if swu > 0 {
+		t.controlBuf.put(&windowUpdate{s.id, swu})
+	}
+	if cwu > 0 {
+		t.controlBuf.put(&windowUpdate{0, cwu})
+	}
+}
+
+func (t *http2Server) handleData(f *http2.DataFrame) {
+	// Select the right stream to dispatch.
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	size := len(f.Data())
+	if size > 0 {
+		if err := s.fc.onData(uint32(size)); err != nil {
+			if _, ok := err.(ConnectionError); ok {
+				grpclog.Printf("transport: http2Server %v", err)
+				t.Close()
+				return
+			}
+			t.closeStream(s)
+			t.controlBuf.put(&resetStream{s.id, http2.ErrCodeFlowControl})
+			return
+		}
+		// TODO(bradfitz, zhaoq): A copy is required here because there is no
+		// guarantee f.Data() is consumed before the arrival of next frame.
+		// Can this copy be eliminated?
+		data := make([]byte, size)
+		copy(data, f.Data())
+		s.write(recvMsg{data: data})
+	}
+	if f.Header().Flags.Has(http2.FlagDataEndStream) {
+		// Received the end of stream from the client.
+		s.mu.Lock()
+		if s.state != streamDone {
+			if s.state == streamWriteDone {
+				s.state = streamDone
+			} else {
+				s.state = streamReadDone
+			}
+		}
+		s.mu.Unlock()
+		s.write(recvMsg{err: io.EOF})
+	}
+}
+
+func (t *http2Server) handleRSTStream(f *http2.RSTStreamFrame) {
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	t.closeStream(s)
+}
+
+func (t *http2Server) handleSettings(f *http2.SettingsFrame) {
+	if f.IsAck() {
+		return
+	}
+	var ss []http2.Setting
+	f.ForeachSetting(func(s http2.Setting) error {
+		ss = append(ss, s)
+		return nil
+	})
+	// The settings will be applied once the ack is sent.
+	t.controlBuf.put(&settings{ack: true, ss: ss})
+}
+
+func (t *http2Server) handlePing(f *http2.PingFrame) {
+	pingAck := &ping{ack: true}
+	copy(pingAck.data[:], f.Data[:])
+	t.controlBuf.put(pingAck)
+}
+
+func (t *http2Server) handleWindowUpdate(f *http2.WindowUpdateFrame) {
+	id := f.Header().StreamID
+	incr := f.Increment
+	if id == 0 {
+		t.sendQuotaPool.add(int(incr))
+		return
+	}
+	if s, ok := t.getStream(f); ok {
+		s.sendQuotaPool.add(int(incr))
+	}
+}
+
+func (t *http2Server) writeHeaders(s *Stream, b *bytes.Buffer, endStream bool) error {
+	first := true
+	endHeaders := false
+	var err error
+	// Sends the headers in a single batch.
+	for !endHeaders {
+		size := t.hBuf.Len()
+		if size > http2MaxFrameLen {
+			size = http2MaxFrameLen
+		} else {
+			endHeaders = true
+		}
+		if first {
+			p := http2.HeadersFrameParam{
+				StreamID:      s.id,
+				BlockFragment: b.Next(size),
+				EndStream:     endStream,
+				EndHeaders:    endHeaders,
+			}
+			err = t.framer.writeHeaders(endHeaders, p)
+			first = false
+		} else {
+			err = t.framer.writeContinuation(endHeaders, s.id, endHeaders, b.Next(size))
+		}
+		if err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+	}
+	return nil
+}
+
+// WriteHeader sends the header metedata md back to the client.
+func (t *http2Server) WriteHeader(s *Stream, md metadata.MD) error {
+	s.mu.Lock()
+	if s.headerOk || s.state == streamDone {
+		s.mu.Unlock()
+		return ErrIllegalHeaderWrite
+	}
+	s.headerOk = true
+	s.mu.Unlock()
+	if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+		return err
+	}
+	t.hBuf.Reset()
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+	for k, v := range md {
+		for _, entry := range v {
+			t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: entry})
+		}
+	}
+	if err := t.writeHeaders(s, t.hBuf, false); err != nil {
+		return err
+	}
+	t.writableChan <- 0
+	return nil
+}
+
+// WriteStatus sends stream status to the client and terminates the stream.
+// There is no further I/O operations being able to perform on this stream.
+// TODO(zhaoq): Now it indicates the end of entire stream. Revisit if early
+// OK is adopted.
+func (t *http2Server) WriteStatus(s *Stream, statusCode codes.Code, statusDesc string) error {
+	var headersSent bool
+	s.mu.Lock()
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return nil
+	}
+	if s.headerOk {
+		headersSent = true
+	}
+	s.mu.Unlock()
+	if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+		return err
+	}
+	t.hBuf.Reset()
+	if !headersSent {
+		t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+		t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+	}
+	t.hEnc.WriteField(
+		hpack.HeaderField{
+			Name:  "grpc-status",
+			Value: strconv.Itoa(int(statusCode)),
+		})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-message", Value: statusDesc})
+	// Attach the trailer metadata.
+	for k, v := range s.trailer {
+		for _, entry := range v {
+			t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: entry})
+		}
+	}
+	if err := t.writeHeaders(s, t.hBuf, true); err != nil {
+		t.Close()
+		return err
+	}
+	t.closeStream(s)
+	t.writableChan <- 0
+	return nil
+}
+
+// Write converts the data into HTTP2 data frame and sends it out. Non-nil error
+// is returns if it fails (e.g., framing error, transport error).
+func (t *http2Server) Write(s *Stream, data []byte, opts *Options) error {
+	// TODO(zhaoq): Support multi-writers for a single stream.
+	var writeHeaderFrame bool
+	s.mu.Lock()
+	if !s.headerOk {
+		writeHeaderFrame = true
+		s.headerOk = true
+	}
+	s.mu.Unlock()
+	if writeHeaderFrame {
+		if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+			return err
+		}
+		t.hBuf.Reset()
+		t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+		t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+		p := http2.HeadersFrameParam{
+			StreamID:      s.id,
+			BlockFragment: t.hBuf.Bytes(),
+			EndHeaders:    true,
+		}
+		if err := t.framer.writeHeaders(false, p); err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+		t.writableChan <- 0
+	}
+	r := bytes.NewBuffer(data)
+	for {
+		if r.Len() == 0 {
+			return nil
+		}
+		size := http2MaxFrameLen
+		s.sendQuotaPool.add(0)
+		// Wait until the stream has some quota to send the data.
+		sq, err := wait(s.ctx, t.shutdownChan, s.sendQuotaPool.acquire())
+		if err != nil {
+			return err
+		}
+		t.sendQuotaPool.add(0)
+		// Wait until the transport has some quota to send the data.
+		tq, err := wait(s.ctx, t.shutdownChan, t.sendQuotaPool.acquire())
+		if err != nil {
+			if _, ok := err.(StreamError); ok {
+				t.sendQuotaPool.cancel()
+			}
+			return err
+		}
+		if sq < size {
+			size = sq
+		}
+		if tq < size {
+			size = tq
+		}
+		p := r.Next(size)
+		ps := len(p)
+		if ps < sq {
+			// Overbooked stream quota. Return it back.
+			s.sendQuotaPool.add(sq - ps)
+		}
+		if ps < tq {
+			// Overbooked transport quota. Return it back.
+			t.sendQuotaPool.add(tq - ps)
+		}
+		t.framer.adjustNumWriters(1)
+		// Got some quota. Try to acquire writing privilege on the
+		// transport.
+		if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+			if t.framer.adjustNumWriters(-1) == 0 {
+				// This writer is the last one in this batch and has the
+				// responsibility to flush the buffered frames. It queues
+				// a flush request to controlBuf instead of flushing directly
+				// in order to avoid the race with other writing or flushing.
+				t.controlBuf.put(&flushIO{})
+			}
+			return err
+		}
+		var forceFlush bool
+		if r.Len() == 0 && t.framer.adjustNumWriters(0) == 1 && !opts.Last {
+			forceFlush = true
+		}
+		if err := t.framer.writeData(forceFlush, s.id, false, p); err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+		if t.framer.adjustNumWriters(-1) == 0 {
+			t.framer.flushWrite()
+		}
+		t.writableChan <- 0
+	}
+
+}
+
+func (t *http2Server) applySettings(ss []http2.Setting) {
+	for _, s := range ss {
+		if s.ID == http2.SettingInitialWindowSize {
+			t.mu.Lock()
+			defer t.mu.Unlock()
+			for _, stream := range t.activeStreams {
+				stream.sendQuotaPool.reset(int(s.Val - t.streamSendQuota))
+			}
+			t.streamSendQuota = s.Val
+		}
+
+	}
+}
+
+// controller running in a separate goroutine takes charge of sending control
+// frames (e.g., window update, reset stream, setting, etc.) to the server.
+func (t *http2Server) controller() {
+	for {
+		select {
+		case i := <-t.controlBuf.get():
+			t.controlBuf.load()
+			select {
+			case <-t.writableChan:
+				switch i := i.(type) {
+				case *windowUpdate:
+					t.framer.writeWindowUpdate(true, i.streamID, i.increment)
+				case *settings:
+					if i.ack {
+						t.framer.writeSettingsAck(true)
+						t.applySettings(i.ss)
+					} else {
+						t.framer.writeSettings(true, i.ss...)
+					}
+				case *resetStream:
+					t.framer.writeRSTStream(true, i.streamID, i.code)
+				case *flushIO:
+					t.framer.flushWrite()
+				case *ping:
+					t.framer.writePing(true, i.ack, i.data)
+				default:
+					grpclog.Printf("transport: http2Server.controller got unexpected item type %v\n", i)
+				}
+				t.writableChan <- 0
+				continue
+			case <-t.shutdownChan:
+				return
+			}
+		case <-t.shutdownChan:
+			return
+		}
+	}
+}
+
+// Close starts shutting down the http2Server transport.
+// TODO(zhaoq): Now the destruction is not blocked on any pending streams. This
+// could cause some resource issue. Revisit this later.
+func (t *http2Server) Close() (err error) {
+	t.mu.Lock()
+	if t.state == closing {
+		t.mu.Unlock()
+		return errors.New("transport: Close() was already called")
+	}
+	t.state = closing
+	streams := t.activeStreams
+	t.activeStreams = nil
+	t.mu.Unlock()
+	close(t.shutdownChan)
+	err = t.conn.Close()
+	// Cancel all active streams.
+	for _, s := range streams {
+		s.cancel()
+	}
+	return
+}
+
+// closeStream clears the footprint of a stream when the stream is not needed
+// any more.
+func (t *http2Server) closeStream(s *Stream) {
+	t.mu.Lock()
+	delete(t.activeStreams, s.id)
+	t.mu.Unlock()
+	if q := s.fc.restoreConn(); q > 0 {
+		t.controlBuf.put(&windowUpdate{0, q})
+	}
+	s.mu.Lock()
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return
+	}
+	s.state = streamDone
+	s.mu.Unlock()
+	// In case stream sending and receiving are invoked in separate
+	// goroutines (e.g., bi-directional streaming), cancel needs to be
+	// called to interrupt the potential blocking on other goroutines.
+	s.cancel()
+}
+
+func (t *http2Server) RemoteAddr() net.Addr {
+	return t.conn.RemoteAddr()
+}