Revert "crypto/tls: add CloseWrite method to Conn"

This reverts commit c6185aa63217c84a1a73c578c155e7d4dec6cec8. That
commit seems to be causing flaky failures on the builders. See
discussion on the original thread: https://golang.org/cl/25159.

Change-Id: I26e72d962d4efdcee28a0bc61a53f246b046df77
Reviewed-on: https://go-review.googlesource.com/31316
Run-TryBot: Adam Langley <agl@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

conn.go

@@ -64,13 +64,6 @@ type Conn struct {
 	// the first transmitted Finished message is the tls-unique
 	// channel-binding value.
 	clientFinishedIsFirst bool
-
-	// closeNotifyErr is any error from sending the alertCloseNotify record.
-	closeNotifyErr error
-	// closeNotifySent is true if the Conn attempted to send an
-	// alertCloseNotify record.
-	closeNotifySent bool
-
 	// clientFinished and serverFinished contain the Finished message sent
 	// by the client or server in the most recent handshake. This is
 	// retained to support the renegotiation extension and tls-unique
@@ -1007,10 +1000,7 @@ func (c *Conn) readHandshake() (interface{}, error) {
 	return m, nil
 }
 
-var (
+var errClosed = errors.New("tls: use of closed connection")
-	errClosed   = errors.New("tls: use of closed connection")
-	errShutdown = errors.New("tls: protocol is shutdown")
-)
 
 // Write writes data to the connection.
 func (c *Conn) Write(b []byte) (int, error) {
@@ -1041,10 +1031,6 @@ func (c *Conn) Write(b []byte) (int, error) {
 		return 0, alertInternalError
 	}
 
-	if c.closeNotifySent {
-		return 0, errShutdown
-	}
-
 	// SSL 3.0 and TLS 1.0 are susceptible to a chosen-plaintext
 	// attack when using block mode ciphers due to predictable IVs.
 	// This can be prevented by splitting each Application Data
@@ -1208,7 +1194,7 @@ func (c *Conn) Close() error {
 	c.handshakeMutex.Lock()
 	defer c.handshakeMutex.Unlock()
 	if c.handshakeComplete {
-		alertErr = c.closeNotify()
+		alertErr = c.sendAlert(alertCloseNotify)
 	}
 
 	if err := c.conn.Close(); err != nil {
@@ -1217,32 +1203,6 @@ func (c *Conn) Close() error {
 	return alertErr
 }
 
-var errEarlyCloseWrite = errors.New("tls: CloseWrite called before handshake complete")
-
-// CloseWrite shuts down the writing side of the connection. It should only be
-// called once the handshake has completed and does not call CloseWrite on the
-// underlying connection. Most callers should just use Close.
-func (c *Conn) CloseWrite() error {
-	c.handshakeMutex.Lock()
-	defer c.handshakeMutex.Unlock()
-	if !c.handshakeComplete {
-		return errEarlyCloseWrite
-	}
-
-	return c.closeNotify()
-}
-
-func (c *Conn) closeNotify() error {
-	c.out.Lock()
-	defer c.out.Unlock()
-
-	if !c.closeNotifySent {
-		c.closeNotifyErr = c.sendAlertLocked(alertCloseNotify)
-		c.closeNotifySent = true
-	}
-	return c.closeNotifyErr
-}
-
 // Handshake runs the client or server handshake
 // protocol if it has not yet been run.
 // Most uses of this package need not call Handshake

tls_test.go

@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"internal/testenv"
 	"io"
-	"io/ioutil"
 	"math"
 	"math/rand"
 	"net"
@@ -459,91 +458,6 @@ func TestConnCloseBreakingWrite(t *testing.T) {
 	}
 }
 
-func TestConnCloseWrite(t *testing.T) {
-	ln := newLocalListener(t)
-	defer ln.Close()
-
-	go func() {
-		sconn, err := ln.Accept()
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		serverConfig := testConfig.Clone()
-		srv := Server(sconn, serverConfig)
-		if err := srv.Handshake(); err != nil {
-			t.Fatalf("handshake: %v", err)
-		}
-		defer srv.Close()
-
-		data, err := ioutil.ReadAll(srv)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if len(data) > 0 {
-			t.Errorf("Read data = %q; want nothing", data)
-		}
-
-		if err = srv.CloseWrite(); err != nil {
-			t.Errorf("server CloseWrite: %v", err)
-		}
-	}()
-
-	clientConfig := testConfig.Clone()
-	conn, err := Dial("tcp", ln.Addr().String(), clientConfig)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if err = conn.Handshake(); err != nil {
-		t.Fatal(err)
-	}
-	defer conn.Close()
-
-	if err = conn.CloseWrite(); err != nil {
-		t.Errorf("client CloseWrite: %v", err)
-	}
-
-	if _, err := conn.Write([]byte{0}); err != errShutdown {
-		t.Errorf("CloseWrite error = %v; want errShutdown", err)
-	}
-
-	data, err := ioutil.ReadAll(conn)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if len(data) > 0 {
-		t.Errorf("Read data = %q; want nothing", data)
-	}
-
-	// test CloseWrite called before handshake finished
-
-	ln2 := newLocalListener(t)
-	defer ln2.Close()
-
-	go func() {
-		sconn, err := ln2.Accept()
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		serverConfig := testConfig.Clone()
-		srv := Server(sconn, serverConfig)
-
-		srv.Handshake()
-		srv.Close()
-	}()
-
-	netConn, err := net.Dial("tcp", ln2.Addr().String())
-	if err != nil {
-		t.Fatal(err)
-	}
-	conn = Client(netConn, clientConfig)
-
-	if err = conn.CloseWrite(); err != errEarlyCloseWrite {
-		t.Errorf("CloseWrite error = %v; want errEarlyCloseWrite", err)
-	}
-}
-
 func TestClone(t *testing.T) {
 	var c1 Config
 	v := reflect.ValueOf(&c1).Elem()