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)
 	}
 	t.Parallel()

 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

 			ln := newLocalListener(t, network)
 			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, true); 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 "plan9":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}

 	t.Parallel()
 	deadline, _ := t.Deadline()
 	if !deadline.IsZero() {
 		// Leave 10% headroom on the deadline to report errors and clean up.
 		deadline = deadline.Add(-time.Until(deadline) / 10)
 	}

 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

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

 				// Workaround for https://go.dev/issue/49352.
 				// On arm64 macOS (current as of macOS 12.4),
 				// reading from a socket at the same time as the client
 				// is closing it occasionally hangs for 60 seconds before
 				// returning ECONNRESET. Sleep for a bit to give the
 				// socket time to close before trying to read from it.
 				if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
 					time.Sleep(10 * time.Millisecond)
 				}

 				if !deadline.IsZero() {
 					c.SetDeadline(deadline)
 				}
 				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, true); 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
 				}
 			}

 			ls := newLocalServer(t, network)
 			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)
 			}
 			if !deadline.IsZero() {
 				c.SetDeadline(deadline)
 			}
 			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, true); 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) {
 	t.Parallel()
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

 			ln := newLocalListener(t, network)
 			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, false); 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) {
 	t.Parallel()
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

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

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

 			// Note: we cannot ensure that a subsequent Dial does not succeed, because
 			// we do not in general have any guarantee that ln.Addr is not immediately
 			// reused. (TCP sockets enter a TIME_WAIT state when closed, but that only
 			// applies to existing connections for the port — it does not prevent the
 			// port itself from being used for entirely new connections in the
 			// meantime.)
 		})
 	}
 }

 func TestPacketConnClose(t *testing.T) {
 	t.Parallel()
 	for _, network := range []string{"udp", "unixgram"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

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

 			if err := c.Close(); err != nil {
 				if perr := parseCloseError(err, false); 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)
 			}
 		})
 	}
 }

 func TestListenCloseListen(t *testing.T) {
 	const maxTries = 10
 	for tries := 0; tries < maxTries; tries++ {
 		ln := newLocalListener(t, "tcp")
 		addr := ln.Addr().String()
 		// TODO: This is racy. The selected address could be reused in between this
 		// Close and the subsequent Listen.
 		if err := ln.Close(); err != nil {
 			if perr := parseCloseError(err, false); perr != nil {
 				t.Error(perr)
 			}
 			t.Fatal(err)
 		}
 		ln, err := Listen("tcp", addr)
 		if err == nil {
 			// Success. (This test didn't always make it here earlier.)
 			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 := newLocalServer(t, "tcp")
 	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) {
 	t.Parallel()
 	for _, network := range []string{"tcp", "unix", "unixpacket"} {
 		network := network
 		t.Run(network, func(t *testing.T) {
 			if !testableNetwork(network) {
 				t.Skipf("network %s is not testable on the current platform", network)
 			}
 			t.Parallel()

 			ln := newLocalListener(t, network)
 			connc := make(chan Conn, 1)
 			defer func() {
 				ln.Close()
 				for c := range connc {
 					if c != nil {
 						c.Close()
 					}
 				}
 			}()
 			go func() {
 				defer close(connc)
 				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 {
 				return
 			}
 			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) {
 	t.Helper()
 	ln := newLocalListener(t, "tcp")
 	defer ln.Close()
 	errc := make(chan error, 2)
 	go func() {
 		c1, err := ln.Accept()
 		if err != nil {
 			errc <- err
 			return
 		}
 		err = peer1(c1.(*TCPConn))
 		c1.Close()
 		errc <- err
 	}()
 	go func() {
 		c2, err := Dial("tcp", ln.Addr().String())
 		if err != nil {
 			errc <- err
 			return
 		}
 		err = peer2(c2.(*TCPConn))
 		c2.Close()
 		errc <- err
 	}()
 	for i := 0; i < 2; i++ {
 		if err := <-errc; err != nil {
 			t.Error(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)
 }

 // Issue 24808: verify that ECONNRESET is not temporary for read.
 func TestNotTemporaryRead(t *testing.T) {
 	t.Parallel()

 	ln := newLocalListener(t, "tcp")
 	serverDone := make(chan struct{})
 	dialed := make(chan struct{})
 	go func() {
 		defer close(serverDone)

 		cs, err := ln.Accept()
 		if err != nil {
 			return
 		}
 		<-dialed
 		cs.(*TCPConn).SetLinger(0)
 		cs.Close()
 	}()
 	defer func() {
 		ln.Close()
 		<-serverDone
 	}()

 	ss, err := Dial("tcp", ln.Addr().String())
 	close(dialed)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer ss.Close()

 	_, err = ss.Read([]byte{0})
 	if err == nil {
 		t.Fatal("Read succeeded unexpectedly")
 	} else if err == io.EOF {
 		// This happens on Plan 9, but for some reason (prior to CL 385314) it was
 		// accepted everywhere else too.
 		if runtime.GOOS == "plan9" {
 			return
 		}
 		t.Fatal("Read unexpectedly returned io.EOF after socket was abruptly closed")
 	}
 	if ne, ok := err.(Error); !ok {
 		t.Errorf("Read error does not implement net.Error: %v", err)
 	} else if ne.Temporary() {
 		t.Errorf("Read error is unexpectedly temporary: %v", err)
 	}
 }

 // The various errors should implement the Error interface.
 func TestErrors(t *testing.T) {
 	var (
 		_ Error = &OpError{}
 		_ Error = &ParseError{}
 		_ Error = &AddrError{}
 		_ Error = UnknownNetworkError("")
 		_ Error = InvalidAddrError("")
 		_ Error = &timeoutError{}
 		_ Error = &DNSConfigError{}
 		_ Error = &DNSError{}
 	)

 	// ErrClosed was introduced as type error, so we can't check
 	// it using a declaration.
 	if _, ok := ErrClosed.(Error); !ok {
 		t.Fatal("ErrClosed does not implement Error")
 	}
 }
	// 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)
	}
	t.Parallel()

	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

	ln := newLocalListener(t, network)
	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, true); 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 "plan9":
	t.Skipf("not supported on %s", runtime.GOOS)
	}

	t.Parallel()
	deadline, _ := t.Deadline()
	if !deadline.IsZero() {
	// Leave 10% headroom on the deadline to report errors and clean up.
	deadline = deadline.Add(-time.Until(deadline) / 10)
	}

	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

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

	// Workaround for https://go.dev/issue/49352.
	// On arm64 macOS (current as of macOS 12.4),
	// reading from a socket at the same time as the client
	// is closing it occasionally hangs for 60 seconds before
	// returning ECONNRESET. Sleep for a bit to give the
	// socket time to close before trying to read from it.
	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
	time.Sleep(10 * time.Millisecond)
	}

	if !deadline.IsZero() {
	c.SetDeadline(deadline)
	}
	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, true); 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
	}
	}

	ls := newLocalServer(t, network)
	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)
	}
	if !deadline.IsZero() {
	c.SetDeadline(deadline)
	}
	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, true); 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) {
	t.Parallel()
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

	ln := newLocalListener(t, network)
	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, false); 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) {
	t.Parallel()
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

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

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

	// Note: we cannot ensure that a subsequent Dial does not succeed, because
	// we do not in general have any guarantee that ln.Addr is not immediately
	// reused. (TCP sockets enter a TIME_WAIT state when closed, but that only
	// applies to existing connections for the port — it does not prevent the
	// port itself from being used for entirely new connections in the
	// meantime.)
	})
	}
	}

	func TestPacketConnClose(t *testing.T) {
	t.Parallel()
	for _, network := range []string{"udp", "unixgram"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

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

	if err := c.Close(); err != nil {
	if perr := parseCloseError(err, false); 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)
	}
	})
	}
	}

	func TestListenCloseListen(t *testing.T) {
	const maxTries = 10
	for tries := 0; tries < maxTries; tries++ {
	ln := newLocalListener(t, "tcp")
	addr := ln.Addr().String()
	// TODO: This is racy. The selected address could be reused in between this
	// Close and the subsequent Listen.
	if err := ln.Close(); err != nil {
	if perr := parseCloseError(err, false); perr != nil {
	t.Error(perr)
	}
	t.Fatal(err)
	}
	ln, err := Listen("tcp", addr)
	if err == nil {
	// Success. (This test didn't always make it here earlier.)
	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 := newLocalServer(t, "tcp")
	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) {
	t.Parallel()
	for _, network := range []string{"tcp", "unix", "unixpacket"} {
	network := network
	t.Run(network, func(t *testing.T) {
	if !testableNetwork(network) {
	t.Skipf("network %s is not testable on the current platform", network)
	}
	t.Parallel()

	ln := newLocalListener(t, network)
	connc := make(chan Conn, 1)
	defer func() {
	ln.Close()
	for c := range connc {
	if c != nil {
	c.Close()
	}
	}
	}()
	go func() {
	defer close(connc)
	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 {
	return
	}
	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) {
	t.Helper()
	ln := newLocalListener(t, "tcp")
	defer ln.Close()
	errc := make(chan error, 2)
	go func() {
	c1, err := ln.Accept()
	if err != nil {
	errc <- err
	return
	}
	err = peer1(c1.(*TCPConn))
	c1.Close()
	errc <- err
	}()
	go func() {
	c2, err := Dial("tcp", ln.Addr().String())
	if err != nil {
	errc <- err
	return
	}
	err = peer2(c2.(*TCPConn))
	c2.Close()
	errc <- err
	}()
	for i := 0; i < 2; i++ {
	if err := <-errc; err != nil {
	t.Error(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)
	}

	// Issue 24808: verify that ECONNRESET is not temporary for read.
	func TestNotTemporaryRead(t *testing.T) {
	t.Parallel()

	ln := newLocalListener(t, "tcp")
	serverDone := make(chan struct{})
	dialed := make(chan struct{})
	go func() {
	defer close(serverDone)

	cs, err := ln.Accept()
	if err != nil {
	return
	}
	<-dialed
	cs.(*TCPConn).SetLinger(0)
	cs.Close()
	}()
	defer func() {
	ln.Close()
	<-serverDone
	}()

	ss, err := Dial("tcp", ln.Addr().String())
	close(dialed)
	if err != nil {
	t.Fatal(err)
	}
	defer ss.Close()

	_, err = ss.Read([]byte{0})
	if err == nil {
	t.Fatal("Read succeeded unexpectedly")
	} else if err == io.EOF {
	// This happens on Plan 9, but for some reason (prior to CL 385314) it was
	// accepted everywhere else too.
	if runtime.GOOS == "plan9" {
	return
	}
	t.Fatal("Read unexpectedly returned io.EOF after socket was abruptly closed")
	}
	if ne, ok := err.(Error); !ok {
	t.Errorf("Read error does not implement net.Error: %v", err)
	} else if ne.Temporary() {
	t.Errorf("Read error is unexpectedly temporary: %v", err)
	}
	}

	// The various errors should implement the Error interface.
	func TestErrors(t *testing.T) {
	var (
	_ Error = &OpError{}
	_ Error = &ParseError{}
	_ Error = &AddrError{}
	_ Error = UnknownNetworkError("")
	_ Error = InvalidAddrError("")
	_ Error = &timeoutError{}
	_ Error = &DNSConfigError{}
	_ Error = &DNSError{}
	)

	// ErrClosed was introduced as type error, so we can't check
	// it using a declaration.
	if _, ok := ErrClosed.(Error); !ok {
	t.Fatal("ErrClosed does not implement Error")
	}
	}