src/net/net_test.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package net

 import (
 	"errors"
 	"fmt"
 	"io"
 	"net/internal/socktest"
 	"os"
 	"runtime"
 	"testing"
 	"time"
 )

 func TestCloseRead(t *testing.T) {
 	switch runtime.GOOS {
 	case "plan9":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}

 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		ln, err := newLocalListener(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(ln.Addr().String())
 		}
 		defer ln.Close()

 		c, err := Dial(ln.Addr().Network(), ln.Addr().String())
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(c.LocalAddr().String())
 		}
 		defer c.Close()

 		switch c := c.(type) {
 		case *TCPConn:
 			err = c.CloseRead()
 		case *UnixConn:
 			err = c.CloseRead()
 		}
 		if err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		var b [1]byte
 		n, err := c.Read(b[:])
 		if n != 0 || err == nil {
 			t.Fatalf("got (%d, %v); want (0, error)", n, err)
 		}
 	}
 }

 func TestCloseWrite(t *testing.T) {
 	switch runtime.GOOS {
 	case "nacl", "plan9":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}

 	handler := func(ls *localServer, ln Listener) {
 		c, err := ln.Accept()
 		if err != nil {
 			t.Error(err)
 			return
 		}
 		defer c.Close()

 		var b [1]byte
 		n, err := c.Read(b[:])
 		if n != 0 || err != io.EOF {
 			t.Errorf("got (%d, %v); want (0, io.EOF)", n, err)
 			return
 		}
 		switch c := c.(type) {
 		case *TCPConn:
 			err = c.CloseWrite()
 		case *UnixConn:
 			err = c.CloseWrite()
 		}
 		if err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Error(err)
 			return
 		}
 		n, err = c.Write(b[:])
 		if err == nil {
 			t.Errorf("got (%d, %v); want (any, error)", n, err)
 			return
 		}
 	}

 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		ls, err := newLocalServer(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		defer ls.teardown()
 		if err := ls.buildup(handler); err != nil {
 			t.Fatal(err)
 		}

 		c, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(c.LocalAddr().String())
 		}
 		defer c.Close()

 		switch c := c.(type) {
 		case *TCPConn:
 			err = c.CloseWrite()
 		case *UnixConn:
 			err = c.CloseWrite()
 		}
 		if err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		var b [1]byte
 		n, err := c.Read(b[:])
 		if n != 0 || err != io.EOF {
 			t.Fatalf("got (%d, %v); want (0, io.EOF)", n, err)
 		}
 		n, err = c.Write(b[:])
 		if err == nil {
 			t.Fatalf("got (%d, %v); want (any, error)", n, err)
 		}
 	}
 }

 func TestConnClose(t *testing.T) {
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		ln, err := newLocalListener(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(ln.Addr().String())
 		}
 		defer ln.Close()

 		c, err := Dial(ln.Addr().Network(), ln.Addr().String())
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(c.LocalAddr().String())
 		}
 		defer c.Close()

 		if err := c.Close(); err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		var b [1]byte
 		n, err := c.Read(b[:])
 		if n != 0 || err == nil {
 			t.Fatalf("got (%d, %v); want (0, error)", n, err)
 		}
 	}
 }

 func TestListenerClose(t *testing.T) {
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		ln, err := newLocalListener(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unix", "unixpacket":
 			defer os.Remove(ln.Addr().String())
 		}

 		dst := ln.Addr().String()
 		if err := ln.Close(); err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		c, err := ln.Accept()
 		if err == nil {
 			c.Close()
 			t.Fatal("should fail")
 		}

 		if network == "tcp" {
 			// We will have two TCP FSMs inside the
 			// kernel here. There's no guarantee that a
 			// signal comes from the far end FSM will be
 			// delivered immediately to the near end FSM,
 			// especially on the platforms that allow
 			// multiple consumer threads to pull pending
 			// established connections at the same time by
 			// enabling SO_REUSEPORT option such as Linux,
 			// DragonFly BSD. So we need to give some time
 			// quantum to the kernel.
 			//
 			// Note that net.inet.tcp.reuseport_ext=1 by
 			// default on DragonFly BSD.
 			time.Sleep(time.Millisecond)

 			cc, err := Dial("tcp", dst)
 			if err == nil {
 				t.Error("Dial to closed TCP listener succeeded.")
 				cc.Close()
 			}
 		}
 	}
 }

 func TestPacketConnClose(t *testing.T) {
 	for _, network := range []string{"udp", "unixgram"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		c, err := newLocalPacketListener(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		switch network {
 		case "unixgram":
 			defer os.Remove(c.LocalAddr().String())
 		}
 		defer c.Close()

 		if err := c.Close(); err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		var b [1]byte
 		n, _, err := c.ReadFrom(b[:])
 		if n != 0 || err == nil {
 			t.Fatalf("got (%d, %v); want (0, error)", n, err)
 		}
 	}
 }

 // nacl was previous failing to reuse an address.
 func TestListenCloseListen(t *testing.T) {
 	const maxTries = 10
 	for tries := 0; tries < maxTries; tries++ {
 		ln, err := newLocalListener("tcp")
 		if err != nil {
 			t.Fatal(err)
 		}
 		addr := ln.Addr().String()
 		if err := ln.Close(); err != nil {
 			if perr := parseCloseError(err); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		ln, err = Listen("tcp", addr)
 		if err == nil {
 			// Success. nacl couldn't do this before.
 			ln.Close()
 			return
 		}
 		t.Errorf("failed on try %d/%d: %v", tries+1, maxTries, err)
 	}
 	t.Fatalf("failed to listen/close/listen on same address after %d tries", maxTries)
 }

 // See golang.org/issue/6163, golang.org/issue/6987.
 func TestAcceptIgnoreAbortedConnRequest(t *testing.T) {
 	switch runtime.GOOS {
 	case "plan9":
 		t.Skipf("%s does not have full support of socktest", runtime.GOOS)
 	}

 	syserr := make(chan error)
 	go func() {
 		defer close(syserr)
 		for _, err := range abortedConnRequestErrors {
 			syserr <- err
 		}
 	}()
 	sw.Set(socktest.FilterAccept, func(so *socktest.Status) (socktest.AfterFilter, error) {
 		if err, ok := <-syserr; ok {
 			return nil, err
 		}
 		return nil, nil
 	})
 	defer sw.Set(socktest.FilterAccept, nil)

 	operr := make(chan error, 1)
 	handler := func(ls *localServer, ln Listener) {
 		defer close(operr)
 		c, err := ln.Accept()
 		if err != nil {
 			if perr := parseAcceptError(err); perr != nil {
 				operr <- perr
 			}
 			operr <- err
 			return
 		}
 		c.Close()
 	}
 	ls, err := newLocalServer("tcp")
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer ls.teardown()
 	if err := ls.buildup(handler); err != nil {
 		t.Fatal(err)
 	}

 	c, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
 	if err != nil {
 		t.Fatal(err)
 	}
 	c.Close()

 	for err := range operr {
 		t.Error(err)
 	}
 }

 func TestZeroByteRead(t *testing.T) {
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		if !testableNetwork(network) {
 			t.Logf("skipping %s test", network)
 			continue
 		}

 		ln, err := newLocalListener(network)
 		if err != nil {
 			t.Fatal(err)
 		}
 		connc := make(chan Conn, 1)
 		go func() {
 			defer ln.Close()
 			c, err := ln.Accept()
 			if err != nil {
 				t.Error(err)
 			}
 			connc <- c // might be nil
 		}()
 		c, err := Dial(network, ln.Addr().String())
 		if err != nil {
 			t.Fatal(err)
 		}
 		defer c.Close()
 		sc := <-connc
 		if sc == nil {
 			continue
 		}
 		defer sc.Close()

 		if runtime.GOOS == "windows" {
 			// A zero byte read on Windows caused a wait for readability first.
 			// Rather than change that behavior, satisfy it in this test.
 			// See Issue 15735.
 			go io.WriteString(sc, "a")
 		}

 		n, err := c.Read(nil)
 		if n != 0 || err != nil {
 			t.Errorf("%s: zero byte client read = %v, %v; want 0, nil", network, n, err)
 		}

 		if runtime.GOOS == "windows" {
 			// Same as comment above.
 			go io.WriteString(c, "a")
 		}
 		n, err = sc.Read(nil)
 		if n != 0 || err != nil {
 			t.Errorf("%s: zero byte server read = %v, %v; want 0, nil", network, n, err)
 		}
 	}
 }

 // withTCPConnPair sets up a TCP connection between two peers, then
 // runs peer1 and peer2 concurrently. withTCPConnPair returns when
 // both have completed.
 func withTCPConnPair(t *testing.T, peer1, peer2 func(c *TCPConn) error) {
 	ln, err := newLocalListener("tcp")
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer ln.Close()
 	errc := make(chan error, 2)
 	go func() {
 		c1, err := ln.Accept()
 		if err != nil {
 			errc <- err
 			return
 		}
 		defer c1.Close()
 		errc <- peer1(c1.(*TCPConn))
 	}()
 	go func() {
 		c2, err := Dial("tcp", ln.Addr().String())
 		if err != nil {
 			errc <- err
 			return
 		}
 		defer c2.Close()
 		errc <- peer2(c2.(*TCPConn))
 	}()
 	for i := 0; i < 2; i++ {
 		if err := <-errc; err != nil {
 			t.Fatal(err)
 		}
 	}
 }

 // Tests that a blocked Read is interrupted by a concurrent SetReadDeadline
 // modifying that Conn's read deadline to the past.
 // See golang.org/cl/30164 which documented this. The net/http package
 // depends on this.
 func TestReadTimeoutUnblocksRead(t *testing.T) {
 	serverDone := make(chan struct{})
 	server := func(cs *TCPConn) error {
 		defer close(serverDone)
 		errc := make(chan error, 1)
 		go func() {
 			defer close(errc)
 			go func() {
 				// TODO: find a better way to wait
 				// until we're blocked in the cs.Read
 				// call below. Sleep is lame.
 				time.Sleep(100 * time.Millisecond)

 				// Interrupt the upcoming Read, unblocking it:
 				cs.SetReadDeadline(time.Unix(123, 0)) // time in the past
 			}()
 			var buf [1]byte
 			n, err := cs.Read(buf[:1])
 			if n != 0 || err == nil {
 				errc <- fmt.Errorf("Read = %v, %v; want 0, non-nil", n, err)
 			}
 		}()
 		select {
 		case err := <-errc:
 			return err
 		case <-time.After(5 * time.Second):
 			buf := make([]byte, 2<<20)
 			buf = buf[:runtime.Stack(buf, true)]
 			println("Stacks at timeout:\n", string(buf))
 			return errors.New("timeout waiting for Read to finish")
 		}

 	}
 	// Do nothing in the client. Never write. Just wait for the
 	// server's half to be done.
 	client := func(*TCPConn) error {
 		<-serverDone
 		return nil
 	}
 	withTCPConnPair(t, client, server)
 }

 // Issue 17695: verify that a blocked Read is woken up by a Close.
 func TestCloseUnblocksRead(t *testing.T) {
 	t.Parallel()
 	server := func(cs *TCPConn) error {
 		// Give the client time to get stuck in a Read:
 		time.Sleep(20 * time.Millisecond)
 		cs.Close()
 		return nil
 	}
 	client := func(ss *TCPConn) error {
 		n, err := ss.Read([]byte{0})
 		if n != 0 || err != io.EOF {
 			return fmt.Errorf("Read = %v, %v; want 0, EOF", n, err)
 		}
 		return nil
 	}
 	withTCPConnPair(t, client, server)
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package net

	import (
	"errors"
	"fmt"
	"io"
	"net/internal/socktest"
	"os"
	"runtime"
	"testing"
	"time"
	)

	func TestCloseRead(t *testing.T) {
	switch runtime.GOOS {
	case "plan9":
	t.Skipf("not supported on %s", runtime.GOOS)
	}

	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	ln, err := newLocalListener(network)
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(ln.Addr().String())
	}
	defer ln.Close()

	c, err := Dial(ln.Addr().Network(), ln.Addr().String())
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(c.LocalAddr().String())
	}
	defer c.Close()

	switch c := c.(type) {
	case *TCPConn:
	err = c.CloseRead()
	case *UnixConn:
	err = c.CloseRead()
	}
	if err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	var b [1]byte
	n, err := c.Read(b[:])
	if n != 0 \|\| err == nil {
	t.Fatalf("got (%d, %v); want (0, error)", n, err)
	}
	}
	}

	func TestCloseWrite(t *testing.T) {
	switch runtime.GOOS {
	case "nacl", "plan9":
	t.Skipf("not supported on %s", runtime.GOOS)
	}

	handler := func(ls *localServer, ln Listener) {
	c, err := ln.Accept()
	if err != nil {
	t.Error(err)
	return
	}
	defer c.Close()

	var b [1]byte
	n, err := c.Read(b[:])
	if n != 0 \|\| err != io.EOF {
	t.Errorf("got (%d, %v); want (0, io.EOF)", n, err)
	return
	}
	switch c := c.(type) {
	case *TCPConn:
	err = c.CloseWrite()
	case *UnixConn:
	err = c.CloseWrite()
	}
	if err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Error(err)
	return
	}
	n, err = c.Write(b[:])
	if err == nil {
	t.Errorf("got (%d, %v); want (any, error)", n, err)
	return
	}
	}

	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	ls, err := newLocalServer(network)
	if err != nil {
	t.Fatal(err)
	}
	defer ls.teardown()
	if err := ls.buildup(handler); err != nil {
	t.Fatal(err)
	}

	c, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(c.LocalAddr().String())
	}
	defer c.Close()

	switch c := c.(type) {
	case *TCPConn:
	err = c.CloseWrite()
	case *UnixConn:
	err = c.CloseWrite()
	}
	if err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	var b [1]byte
	n, err := c.Read(b[:])
	if n != 0 \|\| err != io.EOF {
	t.Fatalf("got (%d, %v); want (0, io.EOF)", n, err)
	}
	n, err = c.Write(b[:])
	if err == nil {
	t.Fatalf("got (%d, %v); want (any, error)", n, err)
	}
	}
	}

	func TestConnClose(t *testing.T) {
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	ln, err := newLocalListener(network)
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(ln.Addr().String())
	}
	defer ln.Close()

	c, err := Dial(ln.Addr().Network(), ln.Addr().String())
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(c.LocalAddr().String())
	}
	defer c.Close()

	if err := c.Close(); err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	var b [1]byte
	n, err := c.Read(b[:])
	if n != 0 \|\| err == nil {
	t.Fatalf("got (%d, %v); want (0, error)", n, err)
	}
	}
	}

	func TestListenerClose(t *testing.T) {
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	ln, err := newLocalListener(network)
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unix", "unixpacket":
	defer os.Remove(ln.Addr().String())
	}

	dst := ln.Addr().String()
	if err := ln.Close(); err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	c, err := ln.Accept()
	if err == nil {
	c.Close()
	t.Fatal("should fail")
	}

	if network == "tcp" {
	// We will have two TCP FSMs inside the
	// kernel here. There's no guarantee that a
	// signal comes from the far end FSM will be
	// delivered immediately to the near end FSM,
	// especially on the platforms that allow
	// multiple consumer threads to pull pending
	// established connections at the same time by
	// enabling SO_REUSEPORT option such as Linux,
	// DragonFly BSD. So we need to give some time
	// quantum to the kernel.
	//
	// Note that net.inet.tcp.reuseport_ext=1 by
	// default on DragonFly BSD.
	time.Sleep(time.Millisecond)

	cc, err := Dial("tcp", dst)
	if err == nil {
	t.Error("Dial to closed TCP listener succeeded.")
	cc.Close()
	}
	}
	}
	}

	func TestPacketConnClose(t *testing.T) {
	for _, network := range []string{"udp", "unixgram"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	c, err := newLocalPacketListener(network)
	if err != nil {
	t.Fatal(err)
	}
	switch network {
	case "unixgram":
	defer os.Remove(c.LocalAddr().String())
	}
	defer c.Close()

	if err := c.Close(); err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	var b [1]byte
	n, _, err := c.ReadFrom(b[:])
	if n != 0 \|\| err == nil {
	t.Fatalf("got (%d, %v); want (0, error)", n, err)
	}
	}
	}

	// nacl was previous failing to reuse an address.
	func TestListenCloseListen(t *testing.T) {
	const maxTries = 10
	for tries := 0; tries < maxTries; tries++ {
	ln, err := newLocalListener("tcp")
	if err != nil {
	t.Fatal(err)
	}
	addr := ln.Addr().String()
	if err := ln.Close(); err != nil {
	if perr := parseCloseError(err); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	ln, err = Listen("tcp", addr)
	if err == nil {
	// Success. nacl couldn't do this before.
	ln.Close()
	return
	}
	t.Errorf("failed on try %d/%d: %v", tries+1, maxTries, err)
	}
	t.Fatalf("failed to listen/close/listen on same address after %d tries", maxTries)
	}

	// See golang.org/issue/6163, golang.org/issue/6987.
	func TestAcceptIgnoreAbortedConnRequest(t *testing.T) {
	switch runtime.GOOS {
	case "plan9":
	t.Skipf("%s does not have full support of socktest", runtime.GOOS)
	}

	syserr := make(chan error)
	go func() {
	defer close(syserr)
	for _, err := range abortedConnRequestErrors {
	syserr <- err
	}
	}()
	sw.Set(socktest.FilterAccept, func(so *socktest.Status) (socktest.AfterFilter, error) {
	if err, ok := <-syserr; ok {
	return nil, err
	}
	return nil, nil
	})
	defer sw.Set(socktest.FilterAccept, nil)

	operr := make(chan error, 1)
	handler := func(ls *localServer, ln Listener) {
	defer close(operr)
	c, err := ln.Accept()
	if err != nil {
	if perr := parseAcceptError(err); perr != nil {
	operr <- perr
	}
	operr <- err
	return
	}
	c.Close()
	}
	ls, err := newLocalServer("tcp")
	if err != nil {
	t.Fatal(err)
	}
	defer ls.teardown()
	if err := ls.buildup(handler); err != nil {
	t.Fatal(err)
	}

	c, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
	if err != nil {
	t.Fatal(err)
	}
	c.Close()

	for err := range operr {
	t.Error(err)
	}
	}

	func TestZeroByteRead(t *testing.T) {
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	if !testableNetwork(network) {
	t.Logf("skipping %s test", network)
	continue
	}

	ln, err := newLocalListener(network)
	if err != nil {
	t.Fatal(err)
	}
	connc := make(chan Conn, 1)
	go func() {
	defer ln.Close()
	c, err := ln.Accept()
	if err != nil {
	t.Error(err)
	}
	connc <- c // might be nil
	}()
	c, err := Dial(network, ln.Addr().String())
	if err != nil {
	t.Fatal(err)
	}
	defer c.Close()
	sc := <-connc
	if sc == nil {
	continue
	}
	defer sc.Close()

	if runtime.GOOS == "windows" {
	// A zero byte read on Windows caused a wait for readability first.
	// Rather than change that behavior, satisfy it in this test.
	// See Issue 15735.
	go io.WriteString(sc, "a")
	}

	n, err := c.Read(nil)
	if n != 0 \|\| err != nil {
	t.Errorf("%s: zero byte client read = %v, %v; want 0, nil", network, n, err)
	}

	if runtime.GOOS == "windows" {
	// Same as comment above.
	go io.WriteString(c, "a")
	}
	n, err = sc.Read(nil)
	if n != 0 \|\| err != nil {
	t.Errorf("%s: zero byte server read = %v, %v; want 0, nil", network, n, err)
	}
	}
	}

	// withTCPConnPair sets up a TCP connection between two peers, then
	// runs peer1 and peer2 concurrently. withTCPConnPair returns when
	// both have completed.
	func withTCPConnPair(t testing.T, peer1, peer2 func(c TCPConn) error) {
	ln, err := newLocalListener("tcp")
	if err != nil {
	t.Fatal(err)
	}
	defer ln.Close()
	errc := make(chan error, 2)
	go func() {
	c1, err := ln.Accept()
	if err != nil {
	errc <- err
	return
	}
	defer c1.Close()
	errc <- peer1(c1.(*TCPConn))
	}()
	go func() {
	c2, err := Dial("tcp", ln.Addr().String())
	if err != nil {
	errc <- err
	return
	}
	defer c2.Close()
	errc <- peer2(c2.(*TCPConn))
	}()
	for i := 0; i < 2; i++ {
	if err := <-errc; err != nil {
	t.Fatal(err)
	}
	}
	}

	// Tests that a blocked Read is interrupted by a concurrent SetReadDeadline
	// modifying that Conn's read deadline to the past.
	// See golang.org/cl/30164 which documented this. The net/http package
	// depends on this.
	func TestReadTimeoutUnblocksRead(t *testing.T) {
	serverDone := make(chan struct{})
	server := func(cs *TCPConn) error {
	defer close(serverDone)
	errc := make(chan error, 1)
	go func() {
	defer close(errc)
	go func() {
	// TODO: find a better way to wait
	// until we're blocked in the cs.Read
	// call below. Sleep is lame.
	time.Sleep(100 * time.Millisecond)

	// Interrupt the upcoming Read, unblocking it:
	cs.SetReadDeadline(time.Unix(123, 0)) // time in the past
	}()
	var buf [1]byte
	n, err := cs.Read(buf[:1])
	if n != 0 \|\| err == nil {
	errc <- fmt.Errorf("Read = %v, %v; want 0, non-nil", n, err)
	}
	}()
	select {
	case err := <-errc:
	return err
	case <-time.After(5 * time.Second):
	buf := make([]byte, 2<<20)
	buf = buf[:runtime.Stack(buf, true)]
	println("Stacks at timeout:\n", string(buf))
	return errors.New("timeout waiting for Read to finish")
	}

	}
	// Do nothing in the client. Never write. Just wait for the
	// server's half to be done.
	client := func(*TCPConn) error {
	<-serverDone
	return nil
	}
	withTCPConnPair(t, client, server)
	}

	// Issue 17695: verify that a blocked Read is woken up by a Close.
	func TestCloseUnblocksRead(t *testing.T) {
	t.Parallel()
	server := func(cs *TCPConn) error {
	// Give the client time to get stuck in a Read:
	time.Sleep(20 * time.Millisecond)
	cs.Close()
	return nil
	}
	client := func(ss *TCPConn) error {
	n, err := ss.Read([]byte{0})
	if n != 0 \|\| err != io.EOF {
	return fmt.Errorf("Read = %v, %v; want 0, EOF", n, err)
	}
	return nil
	}
	withTCPConnPair(t, client, server)
	}