rebase: bump google.golang.org/grpc from 1.51.0 to 1.52.0

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.51.0 to 1.52.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.51.0...v1.52.0)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/google.golang.org/grpc/internal/transport/controlbuf.go

@@ -191,7 +191,7 @@ type goAway struct {
 	code      http2.ErrCode
 	debugData []byte
 	headsUp   bool
-	closeConn bool
+	closeConn error // if set, loopyWriter will exit, resulting in conn closure
 }
 
 func (*goAway) isTransportResponseFrame() bool { return false }
@@ -209,6 +209,14 @@ type outFlowControlSizeRequest struct {
 
 func (*outFlowControlSizeRequest) isTransportResponseFrame() bool { return false }
 
+// closeConnection is an instruction to tell the loopy writer to flush the
+// framer and exit, which will cause the transport's connection to be closed
+// (by the client or server).  The transport itself will close after the reader
+// encounters the EOF caused by the connection closure.
+type closeConnection struct{}
+
+func (closeConnection) isTransportResponseFrame() bool { return false }
+
 type outStreamState int
 
 const (
@@ -408,7 +416,7 @@ func (c *controlBuffer) get(block bool) (interface{}, error) {
 		select {
 		case <-c.ch:
 		case <-c.done:
-			return nil, ErrConnClosing
+			return nil, errors.New("transport closed by client")
 		}
 	}
 }
@@ -519,18 +527,6 @@ const minBatchSize = 1000
 // As an optimization, to increase the batch size for each flush, loopy yields the processor, once
 // if the batch size is too low to give stream goroutines a chance to fill it up.
 func (l *loopyWriter) run() (err error) {
-	defer func() {
-		if err == ErrConnClosing {
-			// Don't log ErrConnClosing as error since it happens
-			// 1. When the connection is closed by some other known issue.
-			// 2. User closed the connection.
-			// 3. A graceful close of connection.
-			if logger.V(logLevel) {
-				logger.Infof("transport: loopyWriter.run returning. %v", err)
-			}
-			err = nil
-		}
-	}()
 	for {
 		it, err := l.cbuf.get(true)
 		if err != nil {
@@ -574,7 +570,6 @@ func (l *loopyWriter) run() (err error) {
 			}
 			l.framer.writer.Flush()
 			break hasdata
-
 		}
 	}
 }
@@ -662,11 +657,10 @@ func (l *loopyWriter) headerHandler(h *headerFrame) error {
 func (l *loopyWriter) originateStream(str *outStream) error {
 	hdr := str.itl.dequeue().(*headerFrame)
 	if err := hdr.initStream(str.id); err != nil {
-		if err == ErrConnClosing {
-			return err
+		if err == errStreamDrain { // errStreamDrain need not close transport
+			return nil
 		}
-		// Other errors(errStreamDrain) need not close transport.
-		return nil
+		return err
 	}
 	if err := l.writeHeader(str.id, hdr.endStream, hdr.hf, hdr.onWrite); err != nil {
 		return err
@@ -764,7 +758,7 @@ func (l *loopyWriter) cleanupStreamHandler(c *cleanupStream) error {
 		}
 	}
 	if l.side == clientSide && l.draining && len(l.estdStreams) == 0 {
-		return ErrConnClosing
+		return errors.New("finished processing active streams while in draining mode")
 	}
 	return nil
 }
@@ -799,7 +793,7 @@ func (l *loopyWriter) incomingGoAwayHandler(*incomingGoAway) error {
 	if l.side == clientSide {
 		l.draining = true
 		if len(l.estdStreams) == 0 {
-			return ErrConnClosing
+			return errors.New("received GOAWAY with no active streams")
 		}
 	}
 	return nil
@@ -817,6 +811,14 @@ func (l *loopyWriter) goAwayHandler(g *goAway) error {
 	return nil
 }
 
+func (l *loopyWriter) closeConnectionHandler() error {
+	l.framer.writer.Flush()
+	// Exit loopyWriter entirely by returning an error here.  This will lead to
+	// the transport closing the connection, and, ultimately, transport
+	// closure.
+	return ErrConnClosing
+}
+
 func (l *loopyWriter) handle(i interface{}) error {
 	switch i := i.(type) {
 	case *incomingWindowUpdate:
@@ -845,6 +847,8 @@ func (l *loopyWriter) handle(i interface{}) error {
 		return l.goAwayHandler(i)
 	case *outFlowControlSizeRequest:
 		return l.outFlowControlSizeRequestHandler(i)
+	case closeConnection:
+		return l.closeConnectionHandler()
 	default:
 		return fmt.Errorf("transport: unknown control message type %T", i)
 	}

vendor/google.golang.org/grpc/internal/transport/handler_server.go

@@ -46,24 +46,32 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-// NewServerHandlerTransport returns a ServerTransport handling gRPC
-// from inside an http.Handler. It requires that the http Server
-// supports HTTP/2.
+// NewServerHandlerTransport returns a ServerTransport handling gRPC from
+// inside an http.Handler, or writes an HTTP error to w and returns an error.
+// It requires that the http Server supports HTTP/2.
 func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request, stats []stats.Handler) (ServerTransport, error) {
 	if r.ProtoMajor != 2 {
-		return nil, errors.New("gRPC requires HTTP/2")
+		msg := "gRPC requires HTTP/2"
+		http.Error(w, msg, http.StatusBadRequest)
+		return nil, errors.New(msg)
 	}
 	if r.Method != "POST" {
-		return nil, errors.New("invalid gRPC request method")
+		msg := fmt.Sprintf("invalid gRPC request method %q", r.Method)
+		http.Error(w, msg, http.StatusBadRequest)
+		return nil, errors.New(msg)
 	}
 	contentType := r.Header.Get("Content-Type")
 	// TODO: do we assume contentType is lowercase? we did before
 	contentSubtype, validContentType := grpcutil.ContentSubtype(contentType)
 	if !validContentType {
-		return nil, errors.New("invalid gRPC request content-type")
+		msg := fmt.Sprintf("invalid gRPC request content-type %q", contentType)
+		http.Error(w, msg, http.StatusBadRequest)
+		return nil, errors.New(msg)
 	}
 	if _, ok := w.(http.Flusher); !ok {
-		return nil, errors.New("gRPC requires a ResponseWriter supporting http.Flusher")
+		msg := "gRPC requires a ResponseWriter supporting http.Flusher"
+		http.Error(w, msg, http.StatusInternalServerError)
+		return nil, errors.New(msg)
 	}
 
 	st := &serverHandlerTransport{
@@ -79,7 +87,9 @@ func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request, stats []s
 	if v := r.Header.Get("grpc-timeout"); v != "" {
 		to, err := decodeTimeout(v)
 		if err != nil {
-			return nil, status.Errorf(codes.Internal, "malformed time-out: %v", err)
+			msg := fmt.Sprintf("malformed time-out: %v", err)
+			http.Error(w, msg, http.StatusBadRequest)
+			return nil, status.Error(codes.Internal, msg)
 		}
 		st.timeoutSet = true
 		st.timeout = to
@@ -97,7 +107,9 @@ func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request, stats []s
 		for _, v := range vv {
 			v, err := decodeMetadataHeader(k, v)
 			if err != nil {
-				return nil, status.Errorf(codes.Internal, "malformed binary metadata: %v", err)
+				msg := fmt.Sprintf("malformed binary metadata %q in header %q: %v", v, k, err)
+				http.Error(w, msg, http.StatusBadRequest)
+				return nil, status.Error(codes.Internal, msg)
 			}
 			metakv = append(metakv, k, v)
 		}
@@ -141,12 +153,15 @@ type serverHandlerTransport struct {
 	stats []stats.Handler
 }
 
-func (ht *serverHandlerTransport) Close() {
-	ht.closeOnce.Do(ht.closeCloseChanOnce)
+func (ht *serverHandlerTransport) Close(err error) {
+	ht.closeOnce.Do(func() {
+		if logger.V(logLevel) {
+			logger.Infof("Closing serverHandlerTransport: %v", err)
+		}
+		close(ht.closedCh)
+	})
 }
 
-func (ht *serverHandlerTransport) closeCloseChanOnce() { close(ht.closedCh) }
-
 func (ht *serverHandlerTransport) RemoteAddr() net.Addr { return strAddr(ht.req.RemoteAddr) }
 
 // strAddr is a net.Addr backed by either a TCP "ip:port" string, or
@@ -236,7 +251,7 @@ func (ht *serverHandlerTransport) WriteStatus(s *Stream, st *status.Status) erro
 			})
 		}
 	}
-	ht.Close()
+	ht.Close(errors.New("finished writing status"))
 	return err
 }
 
@@ -346,7 +361,7 @@ func (ht *serverHandlerTransport) HandleStreams(startStream func(*Stream), trace
 		case <-ht.req.Context().Done():
 		}
 		cancel()
-		ht.Close()
+		ht.Close(errors.New("request is done processing"))
 	}()
 
 	req := ht.req

vendor/google.golang.org/grpc/internal/transport/http2_client.go

@@ -59,11 +59,15 @@ var clientConnectionCounter uint64
 
 // http2Client implements the ClientTransport interface with HTTP2.
 type http2Client struct {
-	lastRead   int64 // Keep this field 64-bit aligned. Accessed atomically.
-	ctx        context.Context
-	cancel     context.CancelFunc
-	ctxDone    <-chan struct{} // Cache the ctx.Done() chan.
-	userAgent  string
+	lastRead  int64 // Keep this field 64-bit aligned. Accessed atomically.
+	ctx       context.Context
+	cancel    context.CancelFunc
+	ctxDone   <-chan struct{} // Cache the ctx.Done() chan.
+	userAgent string
+	// address contains the resolver returned address for this transport.
+	// If the `ServerName` field is set, it takes precedence over `CallHdr.Host`
+	// passed to `NewStream`, when determining the :authority header.
+	address    resolver.Address
 	md         metadata.MD
 	conn       net.Conn // underlying communication channel
 	loopy      *loopyWriter
@@ -238,8 +242,11 @@ func newHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts
 	go func(conn net.Conn) {
 		defer ctxMonitorDone.Fire() // Signal this goroutine has exited.
 		<-newClientCtx.Done()       // Block until connectCtx expires or the defer above executes.
-		if connectCtx.Err() != nil {
+		if err := connectCtx.Err(); err != nil {
 			// connectCtx expired before exiting the function.  Hard close the connection.
+			if logger.V(logLevel) {
+				logger.Infof("newClientTransport: aborting due to connectCtx: %v", err)
+			}
 			conn.Close()
 		}
 	}(conn)
@@ -314,6 +321,7 @@ func newHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts
 		cancel:                cancel,
 		userAgent:             opts.UserAgent,
 		registeredCompressors: grpcutil.RegisteredCompressors(),
+		address:               addr,
 		conn:                  conn,
 		remoteAddr:            conn.RemoteAddr(),
 		localAddr:             conn.LocalAddr(),
@@ -440,10 +448,8 @@ func newHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts
 	go func() {
 		t.loopy = newLoopyWriter(clientSide, t.framer, t.controlBuf, t.bdpEst)
 		err := t.loopy.run()
-		if err != nil {
-			if logger.V(logLevel) {
-				logger.Errorf("transport: loopyWriter.run returning. Err: %v", err)
-			}
+		if logger.V(logLevel) {
+			logger.Infof("transport: loopyWriter exited. Closing connection. Err: %v", err)
 		}
 		// Do not close the transport.  Let reader goroutine handle it since
 		// there might be data in the buffers.
@@ -702,6 +708,18 @@ func (e NewStreamError) Error() string {
 // streams.  All non-nil errors returned will be *NewStreamError.
 func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (*Stream, error) {
 	ctx = peer.NewContext(ctx, t.getPeer())
+
+	// ServerName field of the resolver returned address takes precedence over
+	// Host field of CallHdr to determine the :authority header. This is because,
+	// the ServerName field takes precedence for server authentication during
+	// TLS handshake, and the :authority header should match the value used
+	// for server authentication.
+	if t.address.ServerName != "" {
+		newCallHdr := *callHdr
+		newCallHdr.Host = t.address.ServerName
+		callHdr = &newCallHdr
+	}
+
 	headerFields, err := t.createHeaderFields(ctx, callHdr)
 	if err != nil {
 		return nil, &NewStreamError{Err: err, AllowTransparentRetry: false}
@@ -934,6 +952,9 @@ func (t *http2Client) Close(err error) {
 		t.mu.Unlock()
 		return
 	}
+	if logger.V(logLevel) {
+		logger.Infof("transport: closing: %v", err)
+	}
 	// Call t.onClose ASAP to prevent the client from attempting to create new
 	// streams.
 	t.onClose()
@@ -986,11 +1007,14 @@ func (t *http2Client) GracefulClose() {
 		t.mu.Unlock()
 		return
 	}
+	if logger.V(logLevel) {
+		logger.Infof("transport: GracefulClose called")
+	}
 	t.state = draining
 	active := len(t.activeStreams)
 	t.mu.Unlock()
 	if active == 0 {
-		t.Close(ErrConnClosing)
+		t.Close(connectionErrorf(true, nil, "no active streams left to process while draining"))
 		return
 	}
 	t.controlBuf.put(&incomingGoAway{})

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

@@ -21,6 +21,7 @@ package transport
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -41,6 +42,7 @@ import (
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/internal/channelz"
 	"google.golang.org/grpc/internal/grpcrand"
+	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/keepalive"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/peer"
@@ -101,13 +103,13 @@ type http2Server struct {
 
 	mu sync.Mutex // guard the following
 
-	// drainChan is initialized when Drain() is called the first time.
-	// After which the server writes out the first GoAway(with ID 2^31-1) frame.
-	// Then an independent goroutine will be launched to later send the second GoAway.
-	// During this time we don't want to write another first GoAway(with ID 2^31 -1) frame.
-	// Thus call to Drain() will be a no-op if drainChan is already initialized since draining is
-	// already underway.
-	drainChan     chan struct{}
+	// drainEvent is initialized when Drain() is called the first time. After
+	// which the server writes out the first GoAway(with ID 2^31-1) frame. Then
+	// an independent goroutine will be launched to later send the second
+	// GoAway. During this time we don't want to write another first GoAway(with
+	// ID 2^31 -1) frame. Thus call to Drain() will be a no-op if drainEvent is
+	// already initialized since draining is already underway.
+	drainEvent    *grpcsync.Event
 	state         transportState
 	activeStreams map[uint32]*Stream
 	// idle is the time instant when the connection went idle.
@@ -293,7 +295,7 @@ func NewServerTransport(conn net.Conn, config *ServerConfig) (_ ServerTransport,
 
 	defer func() {
 		if err != nil {
-			t.Close()
+			t.Close(err)
 		}
 	}()
 
@@ -331,10 +333,9 @@ func NewServerTransport(conn net.Conn, config *ServerConfig) (_ ServerTransport,
 	go func() {
 		t.loopy = newLoopyWriter(serverSide, t.framer, t.controlBuf, t.bdpEst)
 		t.loopy.ssGoAwayHandler = t.outgoingGoAwayHandler
-		if err := t.loopy.run(); err != nil {
-			if logger.V(logLevel) {
-				logger.Errorf("transport: loopyWriter.run returning. Err: %v", err)
-			}
+		err := t.loopy.run()
+		if logger.V(logLevel) {
+			logger.Infof("transport: loopyWriter exited. Closing connection. Err: %v", err)
 		}
 		t.conn.Close()
 		t.controlBuf.finish()
@@ -344,8 +345,9 @@ func NewServerTransport(conn net.Conn, config *ServerConfig) (_ ServerTransport,
 	return t, nil
 }
 
-// operateHeader takes action on the decoded headers.
-func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(*Stream), traceCtx func(context.Context, string) context.Context) (fatal bool) {
+// operateHeaders takes action on the decoded headers. Returns an error if fatal
+// error encountered and transport needs to close, otherwise returns nil.
+func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(*Stream), traceCtx func(context.Context, string) context.Context) error {
 	// Acquire max stream ID lock for entire duration
 	t.maxStreamMu.Lock()
 	defer t.maxStreamMu.Unlock()
@@ -361,15 +363,12 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 			rstCode:  http2.ErrCodeFrameSize,
 			onWrite:  func() {},
 		})
-		return false
+		return nil
 	}
 
 	if streamID%2 != 1 || streamID <= t.maxStreamID {
 		// illegal gRPC stream id.
-		if logger.V(logLevel) {
-			logger.Errorf("transport: http2Server.HandleStreams received an illegal stream id: %v", streamID)
-		}
-		return true
+		return fmt.Errorf("received an illegal stream id: %v. headers frame: %+v", streamID, frame)
 	}
 	t.maxStreamID = streamID
 
@@ -453,7 +452,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 			status:         status.New(codes.Internal, errMsg),
 			rst:            !frame.StreamEnded(),
 		})
-		return false
+		return nil
 	}
 
 	if !isGRPC || headerError {
@@ -463,7 +462,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 			rstCode:  http2.ErrCodeProtocol,
 			onWrite:  func() {},
 		})
-		return false
+		return nil
 	}
 
 	// "If :authority is missing, Host must be renamed to :authority." - A41
@@ -503,7 +502,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 	if t.state != reachable {
 		t.mu.Unlock()
 		s.cancel()
-		return false
+		return nil
 	}
 	if uint32(len(t.activeStreams)) >= t.maxStreams {
 		t.mu.Unlock()
@@ -514,7 +513,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 			onWrite:  func() {},
 		})
 		s.cancel()
-		return false
+		return nil
 	}
 	if httpMethod != http.MethodPost {
 		t.mu.Unlock()
@@ -530,7 +529,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 			rst:            !frame.StreamEnded(),
 		})
 		s.cancel()
-		return false
+		return nil
 	}
 	if t.inTapHandle != nil {
 		var err error
@@ -550,7 +549,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 				status:         stat,
 				rst:            !frame.StreamEnded(),
 			})
-			return false
+			return nil
 		}
 	}
 	t.activeStreams[streamID] = s
@@ -597,7 +596,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 		wq:       s.wq,
 	})
 	handle(s)
-	return false
+	return nil
 }
 
 // HandleStreams receives incoming streams using the given handler. This is
@@ -630,19 +629,16 @@ func (t *http2Server) HandleStreams(handle func(*Stream), traceCtx func(context.
 				continue
 			}
 			if err == io.EOF || err == io.ErrUnexpectedEOF {
-				t.Close()
+				t.Close(err)
 				return
 			}
-			if logger.V(logLevel) {
-				logger.Warningf("transport: http2Server.HandleStreams failed to read frame: %v", err)
-			}
-			t.Close()
+			t.Close(err)
 			return
 		}
 		switch frame := frame.(type) {
 		case *http2.MetaHeadersFrame:
-			if t.operateHeaders(frame, handle, traceCtx) {
-				t.Close()
+			if err := t.operateHeaders(frame, handle, traceCtx); err != nil {
+				t.Close(err)
 				break
 			}
 		case *http2.DataFrame:
@@ -843,8 +839,8 @@ const (
 
 func (t *http2Server) handlePing(f *http2.PingFrame) {
 	if f.IsAck() {
-		if f.Data == goAwayPing.data && t.drainChan != nil {
-			close(t.drainChan)
+		if f.Data == goAwayPing.data && t.drainEvent != nil {
+			t.drainEvent.Fire()
 			return
 		}
 		// Maybe it's a BDP ping.
@@ -886,10 +882,7 @@ func (t *http2Server) handlePing(f *http2.PingFrame) {
 
 	if t.pingStrikes > maxPingStrikes {
 		// Send goaway and close the connection.
-		if logger.V(logLevel) {
-			logger.Errorf("transport: Got too many pings from the client, closing the connection.")
-		}
-		t.controlBuf.put(&goAway{code: http2.ErrCodeEnhanceYourCalm, debugData: []byte("too_many_pings"), closeConn: true})
+		t.controlBuf.put(&goAway{code: http2.ErrCodeEnhanceYourCalm, debugData: []byte("too_many_pings"), closeConn: errors.New("got too many pings from the client")})
 	}
 }
 
@@ -1153,7 +1146,7 @@ func (t *http2Server) keepalive() {
 				if logger.V(logLevel) {
 					logger.Infof("transport: closing server transport due to maximum connection age.")
 				}
-				t.Close()
+				t.controlBuf.put(closeConnection{})
 			case <-t.done:
 			}
 			return
@@ -1169,10 +1162,7 @@ func (t *http2Server) keepalive() {
 				continue
 			}
 			if outstandingPing && kpTimeoutLeft <= 0 {
-				if logger.V(logLevel) {
-					logger.Infof("transport: closing server transport due to idleness.")
-				}
-				t.Close()
+				t.Close(fmt.Errorf("keepalive ping not acked within timeout %s", t.kp.Time))
 				return
 			}
 			if !outstandingPing {
@@ -1199,12 +1189,15 @@ func (t *http2Server) keepalive() {
 // 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() {
+func (t *http2Server) Close(err error) {
 	t.mu.Lock()
 	if t.state == closing {
 		t.mu.Unlock()
 		return
 	}
+	if logger.V(logLevel) {
+		logger.Infof("transport: closing: %v", err)
+	}
 	t.state = closing
 	streams := t.activeStreams
 	t.activeStreams = nil
@@ -1295,10 +1288,10 @@ func (t *http2Server) RemoteAddr() net.Addr {
 func (t *http2Server) Drain() {
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	if t.drainChan != nil {
+	if t.drainEvent != nil {
 		return
 	}
-	t.drainChan = make(chan struct{})
+	t.drainEvent = grpcsync.NewEvent()
 	t.controlBuf.put(&goAway{code: http2.ErrCodeNo, debugData: []byte{}, headsUp: true})
 }
 
@@ -1319,19 +1312,20 @@ func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
 		// Stop accepting more streams now.
 		t.state = draining
 		sid := t.maxStreamID
+		retErr := g.closeConn
 		if len(t.activeStreams) == 0 {
-			g.closeConn = true
+			retErr = errors.New("second GOAWAY written and no active streams left to process")
 		}
 		t.mu.Unlock()
 		t.maxStreamMu.Unlock()
 		if err := t.framer.fr.WriteGoAway(sid, g.code, g.debugData); err != nil {
 			return false, err
 		}
-		if g.closeConn {
+		if retErr != nil {
 			// Abruptly close the connection following the GoAway (via
 			// loopywriter).  But flush out what's inside the buffer first.
 			t.framer.writer.Flush()
-			return false, fmt.Errorf("transport: Connection closing")
+			return false, retErr
 		}
 		return true, nil
 	}
@@ -1353,7 +1347,7 @@ func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
 		timer := time.NewTimer(time.Minute)
 		defer timer.Stop()
 		select {
-		case <-t.drainChan:
+		case <-t.drainEvent.Done():
 		case <-timer.C:
 		case <-t.done:
 			return

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

@@ -701,7 +701,7 @@ type ServerTransport interface {
 	// Close tears down the transport. Once it is called, the transport
 	// should not be accessed any more. All the pending streams and their
 	// handlers will be terminated asynchronously.
-	Close()
+	Close(err error)
 
 	// RemoteAddr returns the remote network address.
 	RemoteAddr() net.Addr