Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1026 insertions, 0 deletions

diff --git a/src/net/dial_test.go b/src/net/dial_test.go
new file mode 100644
index 0000000..57cf555
--- /dev/null
+++ b/src/net/dial_test.go
@@ -0,0 +1,1026 @@
+// Copyright 2011 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.
+
+// +build !js
+
+package net
+
+import (
+	"bufio"
+	"context"
+	"internal/testenv"
+	"io"
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+var prohibitionaryDialArgTests = []struct {
+	network string
+	address string
+}{
+	{"tcp6", "127.0.0.1"},
+	{"tcp6", "::ffff:127.0.0.1"},
+}
+
+func TestProhibitionaryDialArg(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("not supported on %s", runtime.GOOS)
+	}
+	if !supportsIPv4map() {
+		t.Skip("mapping ipv4 address inside ipv6 address not supported")
+	}
+
+	ln, err := Listen("tcp", "[::]:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	_, port, err := SplitHostPort(ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for i, tt := range prohibitionaryDialArgTests {
+		c, err := Dial(tt.network, JoinHostPort(tt.address, port))
+		if err == nil {
+			c.Close()
+			t.Errorf("#%d: %v", i, err)
+		}
+	}
+}
+
+func TestDialLocal(t *testing.T) {
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	_, port, err := SplitHostPort(ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := Dial("tcp", JoinHostPort("", port))
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.Close()
+}
+
+func TestDialerDualStackFDLeak(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("%s does not have full support of socktest", runtime.GOOS)
+	case "windows":
+		t.Skipf("not implemented a way to cancel dial racers in TCP SYN-SENT state on %s", runtime.GOOS)
+	case "openbsd":
+		testenv.SkipFlaky(t, 15157)
+	}
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	before := sw.Sockets()
+	origTestHookLookupIP := testHookLookupIP
+	defer func() { testHookLookupIP = origTestHookLookupIP }()
+	testHookLookupIP = lookupLocalhost
+	handler := func(dss *dualStackServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}
+	dss, err := newDualStackServer()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := dss.buildup(handler); err != nil {
+		dss.teardown()
+		t.Fatal(err)
+	}
+
+	const N = 10
+	var wg sync.WaitGroup
+	wg.Add(N)
+	d := &Dialer{DualStack: true, Timeout: 5 * time.Second}
+	for i := 0; i < N; i++ {
+		go func() {
+			defer wg.Done()
+			c, err := d.Dial("tcp", JoinHostPort("localhost", dss.port))
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			c.Close()
+		}()
+	}
+	wg.Wait()
+	dss.teardown()
+	after := sw.Sockets()
+	if len(after) != len(before) {
+		t.Errorf("got %d; want %d", len(after), len(before))
+	}
+}
+
+// Define a pair of blackholed (IPv4, IPv6) addresses, for which dialTCP is
+// expected to hang until the timeout elapses. These addresses are reserved
+// for benchmarking by RFC 6890.
+const (
+	slowDst4 = "198.18.0.254"
+	slowDst6 = "2001:2::254"
+)
+
+// In some environments, the slow IPs may be explicitly unreachable, and fail
+// more quickly than expected. This test hook prevents dialTCP from returning
+// before the deadline.
+func slowDialTCP(ctx context.Context, network string, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	sd := &sysDialer{network: network, address: raddr.String()}
+	c, err := sd.doDialTCP(ctx, laddr, raddr)
+	if ParseIP(slowDst4).Equal(raddr.IP) || ParseIP(slowDst6).Equal(raddr.IP) {
+		// Wait for the deadline, or indefinitely if none exists.
+		<-ctx.Done()
+	}
+	return c, err
+}
+
+func dialClosedPort(t *testing.T) (actual, expected time.Duration) {
+	// Estimate the expected time for this platform.
+	// On Windows, dialing a closed port takes roughly 1 second,
+	// but other platforms should be instantaneous.
+	if runtime.GOOS == "windows" {
+		expected = 1500 * time.Millisecond
+	} else if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		expected = 150 * time.Millisecond
+	} else {
+		expected = 95 * time.Millisecond
+	}
+
+	l, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Logf("dialClosedPort: Listen failed: %v", err)
+		return 999 * time.Hour, expected
+	}
+	addr := l.Addr().String()
+	l.Close()
+	// On OpenBSD, interference from TestTCPSelfConnect is mysteriously
+	// causing the first attempt to hang for a few seconds, so we throw
+	// away the first result and keep the second.
+	for i := 1; ; i++ {
+		startTime := time.Now()
+		c, err := Dial("tcp", addr)
+		if err == nil {
+			c.Close()
+		}
+		elapsed := time.Now().Sub(startTime)
+		if i == 2 {
+			t.Logf("dialClosedPort: measured delay %v", elapsed)
+			return elapsed, expected
+		}
+	}
+}
+
+func TestDialParallel(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	closedPortDelay, expectClosedPortDelay := dialClosedPort(t)
+	if closedPortDelay > expectClosedPortDelay {
+		t.Errorf("got %v; want <= %v", closedPortDelay, expectClosedPortDelay)
+	}
+
+	const instant time.Duration = 0
+	const fallbackDelay = 200 * time.Millisecond
+
+	// Some cases will run quickly when "connection refused" is fast,
+	// or trigger the fallbackDelay on Windows. This value holds the
+	// lesser of the two delays.
+	var closedPortOrFallbackDelay time.Duration
+	if closedPortDelay < fallbackDelay {
+		closedPortOrFallbackDelay = closedPortDelay
+	} else {
+		closedPortOrFallbackDelay = fallbackDelay
+	}
+
+	origTestHookDialTCP := testHookDialTCP
+	defer func() { testHookDialTCP = origTestHookDialTCP }()
+	testHookDialTCP = slowDialTCP
+
+	nCopies := func(s string, n int) []string {
+		out := make([]string, n)
+		for i := 0; i < n; i++ {
+			out[i] = s
+		}
+		return out
+	}
+
+	var testCases = []struct {
+		primaries       []string
+		fallbacks       []string
+		teardownNetwork string
+		expectOk        bool
+		expectElapsed   time.Duration
+	}{
+		// These should just work on the first try.
+		{[]string{"127.0.0.1"}, []string{}, "", true, instant},
+		{[]string{"::1"}, []string{}, "", true, instant},
+		{[]string{"127.0.0.1", "::1"}, []string{slowDst6}, "tcp6", true, instant},
+		{[]string{"::1", "127.0.0.1"}, []string{slowDst4}, "tcp4", true, instant},
+		// Primary is slow; fallback should kick in.
+		{[]string{slowDst4}, []string{"::1"}, "", true, fallbackDelay},
+		// Skip a "connection refused" in the primary thread.
+		{[]string{"127.0.0.1", "::1"}, []string{}, "tcp4", true, closedPortDelay},
+		{[]string{"::1", "127.0.0.1"}, []string{}, "tcp6", true, closedPortDelay},
+		// Skip a "connection refused" in the fallback thread.
+		{[]string{slowDst4, slowDst6}, []string{"::1", "127.0.0.1"}, "tcp6", true, fallbackDelay + closedPortDelay},
+		// Primary refused, fallback without delay.
+		{[]string{"127.0.0.1"}, []string{"::1"}, "tcp4", true, closedPortOrFallbackDelay},
+		{[]string{"::1"}, []string{"127.0.0.1"}, "tcp6", true, closedPortOrFallbackDelay},
+		// Everything is refused.
+		{[]string{"127.0.0.1"}, []string{}, "tcp4", false, closedPortDelay},
+		// Nothing to do; fail instantly.
+		{[]string{}, []string{}, "", false, instant},
+		// Connecting to tons of addresses should not trip the deadline.
+		{nCopies("::1", 1000), []string{}, "", true, instant},
+	}
+
+	handler := func(dss *dualStackServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}
+
+	// Convert a list of IP strings into TCPAddrs.
+	makeAddrs := func(ips []string, port string) addrList {
+		var out addrList
+		for _, ip := range ips {
+			addr, err := ResolveTCPAddr("tcp", JoinHostPort(ip, port))
+			if err != nil {
+				t.Fatal(err)
+			}
+			out = append(out, addr)
+		}
+		return out
+	}
+
+	for i, tt := range testCases {
+		dss, err := newDualStackServer()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer dss.teardown()
+		if err := dss.buildup(handler); err != nil {
+			t.Fatal(err)
+		}
+		if tt.teardownNetwork != "" {
+			// Destroy one of the listening sockets, creating an unreachable port.
+			dss.teardownNetwork(tt.teardownNetwork)
+		}
+
+		primaries := makeAddrs(tt.primaries, dss.port)
+		fallbacks := makeAddrs(tt.fallbacks, dss.port)
+		d := Dialer{
+			FallbackDelay: fallbackDelay,
+		}
+		startTime := time.Now()
+		sd := &sysDialer{
+			Dialer:  d,
+			network: "tcp",
+			address: "?",
+		}
+		c, err := sd.dialParallel(context.Background(), primaries, fallbacks)
+		elapsed := time.Since(startTime)
+
+		if c != nil {
+			c.Close()
+		}
+
+		if tt.expectOk && err != nil {
+			t.Errorf("#%d: got %v; want nil", i, err)
+		} else if !tt.expectOk && err == nil {
+			t.Errorf("#%d: got nil; want non-nil", i)
+		}
+
+		// We used to always use 95 milliseconds as the slop,
+		// but that was flaky on Windows.  See issue 35616.
+		slop := 95 * time.Millisecond
+		if fifth := tt.expectElapsed / 5; fifth > slop {
+			slop = fifth
+		}
+		expectElapsedMin := tt.expectElapsed - slop
+		expectElapsedMax := tt.expectElapsed + slop
+		if elapsed < expectElapsedMin {
+			t.Errorf("#%d: got %v; want >= %v", i, elapsed, expectElapsedMin)
+		} else if elapsed > expectElapsedMax {
+			t.Errorf("#%d: got %v; want <= %v", i, elapsed, expectElapsedMax)
+		}
+
+		// Repeat each case, ensuring that it can be canceled quickly.
+		ctx, cancel := context.WithCancel(context.Background())
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			time.Sleep(5 * time.Millisecond)
+			cancel()
+			wg.Done()
+		}()
+		startTime = time.Now()
+		c, err = sd.dialParallel(ctx, primaries, fallbacks)
+		if c != nil {
+			c.Close()
+		}
+		elapsed = time.Now().Sub(startTime)
+		if elapsed > 100*time.Millisecond {
+			t.Errorf("#%d (cancel): got %v; want <= 100ms", i, elapsed)
+		}
+		wg.Wait()
+	}
+}
+
+func lookupSlowFast(ctx context.Context, fn func(context.Context, string, string) ([]IPAddr, error), network, host string) ([]IPAddr, error) {
+	switch host {
+	case "slow6loopback4":
+		// Returns a slow IPv6 address, and a local IPv4 address.
+		return []IPAddr{
+			{IP: ParseIP(slowDst6)},
+			{IP: ParseIP("127.0.0.1")},
+		}, nil
+	default:
+		return fn(ctx, network, host)
+	}
+}
+
+func TestDialerFallbackDelay(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	origTestHookLookupIP := testHookLookupIP
+	defer func() { testHookLookupIP = origTestHookLookupIP }()
+	testHookLookupIP = lookupSlowFast
+
+	origTestHookDialTCP := testHookDialTCP
+	defer func() { testHookDialTCP = origTestHookDialTCP }()
+	testHookDialTCP = slowDialTCP
+
+	var testCases = []struct {
+		dualstack     bool
+		delay         time.Duration
+		expectElapsed time.Duration
+	}{
+		// Use a very brief delay, which should fallback immediately.
+		{true, 1 * time.Nanosecond, 0},
+		// Use a 200ms explicit timeout.
+		{true, 200 * time.Millisecond, 200 * time.Millisecond},
+		// The default is 300ms.
+		{true, 0, 300 * time.Millisecond},
+	}
+
+	handler := func(dss *dualStackServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}
+	dss, err := newDualStackServer()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dss.teardown()
+	if err := dss.buildup(handler); err != nil {
+		t.Fatal(err)
+	}
+
+	for i, tt := range testCases {
+		d := &Dialer{DualStack: tt.dualstack, FallbackDelay: tt.delay}
+
+		startTime := time.Now()
+		c, err := d.Dial("tcp", JoinHostPort("slow6loopback4", dss.port))
+		elapsed := time.Now().Sub(startTime)
+		if err == nil {
+			c.Close()
+		} else if tt.dualstack {
+			t.Error(err)
+		}
+		expectMin := tt.expectElapsed - 1*time.Millisecond
+		expectMax := tt.expectElapsed + 95*time.Millisecond
+		if elapsed < expectMin {
+			t.Errorf("#%d: got %v; want >= %v", i, elapsed, expectMin)
+		}
+		if elapsed > expectMax {
+			t.Errorf("#%d: got %v; want <= %v", i, elapsed, expectMax)
+		}
+	}
+}
+
+func TestDialParallelSpuriousConnection(t *testing.T) {
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	var readDeadline time.Time
+	if td, ok := t.Deadline(); ok {
+		const arbitraryCleanupMargin = 1 * time.Second
+		readDeadline = td.Add(-arbitraryCleanupMargin)
+	} else {
+		readDeadline = time.Now().Add(5 * time.Second)
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(2)
+	handler := func(dss *dualStackServer, ln Listener) {
+		// Accept one connection per address.
+		c, err := ln.Accept()
+		if err != nil {
+			t.Fatal(err)
+		}
+		// The client should close itself, without sending data.
+		c.SetReadDeadline(readDeadline)
+		var b [1]byte
+		if _, err := c.Read(b[:]); err != io.EOF {
+			t.Errorf("got %v; want %v", err, io.EOF)
+		}
+		c.Close()
+		wg.Done()
+	}
+	dss, err := newDualStackServer()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dss.teardown()
+	if err := dss.buildup(handler); err != nil {
+		t.Fatal(err)
+	}
+
+	const fallbackDelay = 100 * time.Millisecond
+
+	origTestHookDialTCP := testHookDialTCP
+	defer func() { testHookDialTCP = origTestHookDialTCP }()
+	testHookDialTCP = func(ctx context.Context, net string, laddr, raddr *TCPAddr) (*TCPConn, error) {
+		// Sleep long enough for Happy Eyeballs to kick in, and inhibit cancellation.
+		// This forces dialParallel to juggle two successful connections.
+		time.Sleep(fallbackDelay * 2)
+
+		// Now ignore the provided context (which will be canceled) and use a
+		// different one to make sure this completes with a valid connection,
+		// which we hope to be closed below:
+		sd := &sysDialer{network: net, address: raddr.String()}
+		return sd.doDialTCP(context.Background(), laddr, raddr)
+	}
+
+	d := Dialer{
+		FallbackDelay: fallbackDelay,
+	}
+	sd := &sysDialer{
+		Dialer:  d,
+		network: "tcp",
+		address: "?",
+	}
+
+	makeAddr := func(ip string) addrList {
+		addr, err := ResolveTCPAddr("tcp", JoinHostPort(ip, dss.port))
+		if err != nil {
+			t.Fatal(err)
+		}
+		return addrList{addr}
+	}
+
+	// dialParallel returns one connection (and closes the other.)
+	c, err := sd.dialParallel(context.Background(), makeAddr("127.0.0.1"), makeAddr("::1"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.Close()
+
+	// The server should've seen both connections.
+	wg.Wait()
+}
+
+func TestDialerPartialDeadline(t *testing.T) {
+	now := time.Date(2000, time.January, 1, 0, 0, 0, 0, time.UTC)
+	var testCases = []struct {
+		now            time.Time
+		deadline       time.Time
+		addrs          int
+		expectDeadline time.Time
+		expectErr      error
+	}{
+		// Regular division.
+		{now, now.Add(12 * time.Second), 1, now.Add(12 * time.Second), nil},
+		{now, now.Add(12 * time.Second), 2, now.Add(6 * time.Second), nil},
+		{now, now.Add(12 * time.Second), 3, now.Add(4 * time.Second), nil},
+		// Bump against the 2-second sane minimum.
+		{now, now.Add(12 * time.Second), 999, now.Add(2 * time.Second), nil},
+		// Total available is now below the sane minimum.
+		{now, now.Add(1900 * time.Millisecond), 999, now.Add(1900 * time.Millisecond), nil},
+		// Null deadline.
+		{now, noDeadline, 1, noDeadline, nil},
+		// Step the clock forward and cross the deadline.
+		{now.Add(-1 * time.Millisecond), now, 1, now, nil},
+		{now.Add(0 * time.Millisecond), now, 1, noDeadline, errTimeout},
+		{now.Add(1 * time.Millisecond), now, 1, noDeadline, errTimeout},
+	}
+	for i, tt := range testCases {
+		deadline, err := partialDeadline(tt.now, tt.deadline, tt.addrs)
+		if err != tt.expectErr {
+			t.Errorf("#%d: got %v; want %v", i, err, tt.expectErr)
+		}
+		if !deadline.Equal(tt.expectDeadline) {
+			t.Errorf("#%d: got %v; want %v", i, deadline, tt.expectDeadline)
+		}
+	}
+}
+
+func TestDialerLocalAddr(t *testing.T) {
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	type test struct {
+		network, raddr string
+		laddr          Addr
+		error
+	}
+	var tests = []test{
+		{"tcp4", "127.0.0.1", nil, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{}, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("0.0.0.0")}, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("0.0.0.0").To4()}, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("::")}, &AddrError{Err: "some error"}},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To4()}, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To16()}, nil},
+		{"tcp4", "127.0.0.1", &TCPAddr{IP: IPv6loopback}, errNoSuitableAddress},
+		{"tcp4", "127.0.0.1", &UDPAddr{}, &AddrError{Err: "some error"}},
+		{"tcp4", "127.0.0.1", &UnixAddr{}, &AddrError{Err: "some error"}},
+
+		{"tcp6", "::1", nil, nil},
+		{"tcp6", "::1", &TCPAddr{}, nil},
+		{"tcp6", "::1", &TCPAddr{IP: ParseIP("0.0.0.0")}, nil},
+		{"tcp6", "::1", &TCPAddr{IP: ParseIP("0.0.0.0").To4()}, nil},
+		{"tcp6", "::1", &TCPAddr{IP: ParseIP("::")}, nil},
+		{"tcp6", "::1", &TCPAddr{IP: ParseIP("127.0.0.1").To4()}, errNoSuitableAddress},
+		{"tcp6", "::1", &TCPAddr{IP: ParseIP("127.0.0.1").To16()}, errNoSuitableAddress},
+		{"tcp6", "::1", &TCPAddr{IP: IPv6loopback}, nil},
+		{"tcp6", "::1", &UDPAddr{}, &AddrError{Err: "some error"}},
+		{"tcp6", "::1", &UnixAddr{}, &AddrError{Err: "some error"}},
+
+		{"tcp", "127.0.0.1", nil, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{}, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("0.0.0.0")}, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("0.0.0.0").To4()}, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To4()}, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To16()}, nil},
+		{"tcp", "127.0.0.1", &TCPAddr{IP: IPv6loopback}, errNoSuitableAddress},
+		{"tcp", "127.0.0.1", &UDPAddr{}, &AddrError{Err: "some error"}},
+		{"tcp", "127.0.0.1", &UnixAddr{}, &AddrError{Err: "some error"}},
+
+		{"tcp", "::1", nil, nil},
+		{"tcp", "::1", &TCPAddr{}, nil},
+		{"tcp", "::1", &TCPAddr{IP: ParseIP("0.0.0.0")}, nil},
+		{"tcp", "::1", &TCPAddr{IP: ParseIP("0.0.0.0").To4()}, nil},
+		{"tcp", "::1", &TCPAddr{IP: ParseIP("::")}, nil},
+		{"tcp", "::1", &TCPAddr{IP: ParseIP("127.0.0.1").To4()}, errNoSuitableAddress},
+		{"tcp", "::1", &TCPAddr{IP: ParseIP("127.0.0.1").To16()}, errNoSuitableAddress},
+		{"tcp", "::1", &TCPAddr{IP: IPv6loopback}, nil},
+		{"tcp", "::1", &UDPAddr{}, &AddrError{Err: "some error"}},
+		{"tcp", "::1", &UnixAddr{}, &AddrError{Err: "some error"}},
+	}
+
+	if supportsIPv4map() {
+		tests = append(tests, test{
+			"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("::")}, nil,
+		})
+	} else {
+		tests = append(tests, test{
+			"tcp", "127.0.0.1", &TCPAddr{IP: ParseIP("::")}, &AddrError{Err: "some error"},
+		})
+	}
+
+	origTestHookLookupIP := testHookLookupIP
+	defer func() { testHookLookupIP = origTestHookLookupIP }()
+	testHookLookupIP = lookupLocalhost
+	handler := func(ls *localServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}
+	var err error
+	var lss [2]*localServer
+	for i, network := range []string{"tcp4", "tcp6"} {
+		lss[i], err = newLocalServer(network)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer lss[i].teardown()
+		if err := lss[i].buildup(handler); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	for _, tt := range tests {
+		d := &Dialer{LocalAddr: tt.laddr}
+		var addr string
+		ip := ParseIP(tt.raddr)
+		if ip.To4() != nil {
+			addr = lss[0].Listener.Addr().String()
+		}
+		if ip.To16() != nil && ip.To4() == nil {
+			addr = lss[1].Listener.Addr().String()
+		}
+		c, err := d.Dial(tt.network, addr)
+		if err == nil && tt.error != nil || err != nil && tt.error == nil {
+			// A suspected kernel bug in macOS 10.12 occasionally results in
+			// timeout errors when dialing address ::1. The errors have not
+			// been observed on newer versions of the OS, so we don't plan to work
+			// around them. See https://golang.org/issue/22019.
+			if tt.raddr == "::1" && os.Getenv("GO_BUILDER_NAME") == "darwin-amd64-10_12" && os.IsTimeout(err) {
+				t.Logf("ignoring timeout error on Darwin; see https://golang.org/issue/22019")
+			} else {
+				t.Errorf("%s %v->%s: got %v; want %v", tt.network, tt.laddr, tt.raddr, err, tt.error)
+			}
+		}
+		if err != nil {
+			if perr := parseDialError(err); perr != nil {
+				t.Error(perr)
+			}
+			continue
+		}
+		c.Close()
+	}
+}
+
+func TestDialerDualStack(t *testing.T) {
+	testenv.SkipFlaky(t, 13324)
+
+	if !supportsIPv4() || !supportsIPv6() {
+		t.Skip("both IPv4 and IPv6 are required")
+	}
+
+	closedPortDelay, expectClosedPortDelay := dialClosedPort(t)
+	if closedPortDelay > expectClosedPortDelay {
+		t.Errorf("got %v; want <= %v", closedPortDelay, expectClosedPortDelay)
+	}
+
+	origTestHookLookupIP := testHookLookupIP
+	defer func() { testHookLookupIP = origTestHookLookupIP }()
+	testHookLookupIP = lookupLocalhost
+	handler := func(dss *dualStackServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}
+
+	var timeout = 150*time.Millisecond + closedPortDelay
+	for _, dualstack := range []bool{false, true} {
+		dss, err := newDualStackServer()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer dss.teardown()
+		if err := dss.buildup(handler); err != nil {
+			t.Fatal(err)
+		}
+
+		d := &Dialer{DualStack: dualstack, Timeout: timeout}
+		for range dss.lns {
+			c, err := d.Dial("tcp", JoinHostPort("localhost", dss.port))
+			if err != nil {
+				t.Error(err)
+				continue
+			}
+			switch addr := c.LocalAddr().(*TCPAddr); {
+			case addr.IP.To4() != nil:
+				dss.teardownNetwork("tcp4")
+			case addr.IP.To16() != nil && addr.IP.To4() == nil:
+				dss.teardownNetwork("tcp6")
+			}
+			c.Close()
+		}
+	}
+}
+
+func TestDialerKeepAlive(t *testing.T) {
+	handler := func(ls *localServer, ln Listener) {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				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)
+	}
+	defer func() { testHookSetKeepAlive = func(time.Duration) {} }()
+
+	tests := []struct {
+		ka       time.Duration
+		expected time.Duration
+	}{
+		{-1, -1},
+		{0, 15 * time.Second},
+		{5 * time.Second, 5 * time.Second},
+		{30 * time.Second, 30 * time.Second},
+	}
+
+	for _, test := range tests {
+		var got time.Duration = -1
+		testHookSetKeepAlive = func(d time.Duration) { got = d }
+		d := Dialer{KeepAlive: test.ka}
+		c, err := d.Dial("tcp", ls.Listener.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+		c.Close()
+		if got != test.expected {
+			t.Errorf("Dialer.KeepAlive = %v: SetKeepAlive set to %v, want %v", d.KeepAlive, got, test.expected)
+		}
+	}
+}
+
+func TestDialCancel(t *testing.T) {
+	mustHaveExternalNetwork(t)
+
+	blackholeIPPort := JoinHostPort(slowDst4, "1234")
+	if !supportsIPv4() {
+		blackholeIPPort = JoinHostPort(slowDst6, "1234")
+	}
+
+	ticker := time.NewTicker(10 * time.Millisecond)
+	defer ticker.Stop()
+
+	const cancelTick = 5 // the timer tick we cancel the dial at
+	const timeoutTick = 100
+
+	var d Dialer
+	cancel := make(chan struct{})
+	d.Cancel = cancel
+	errc := make(chan error, 1)
+	connc := make(chan Conn, 1)
+	go func() {
+		if c, err := d.Dial("tcp", blackholeIPPort); err != nil {
+			errc <- err
+		} else {
+			connc <- c
+		}
+	}()
+	ticks := 0
+	for {
+		select {
+		case <-ticker.C:
+			ticks++
+			if ticks == cancelTick {
+				close(cancel)
+			}
+			if ticks == timeoutTick {
+				t.Fatal("timeout waiting for dial to fail")
+			}
+		case c := <-connc:
+			c.Close()
+			t.Fatal("unexpected successful connection")
+		case err := <-errc:
+			if perr := parseDialError(err); perr != nil {
+				t.Error(perr)
+			}
+			if ticks < cancelTick {
+				// Using strings.Contains is ugly but
+				// may work on plan9 and windows.
+				if strings.Contains(err.Error(), "connection refused") {
+					t.Skipf("connection to %v failed fast with %v", blackholeIPPort, err)
+				}
+				t.Fatalf("dial error after %d ticks (%d before cancel sent): %v",
+					ticks, cancelTick-ticks, err)
+			}
+			if oe, ok := err.(*OpError); !ok || oe.Err != errCanceled {
+				t.Fatalf("dial error = %v (%T); want OpError with Err == errCanceled", err, err)
+			}
+			return // success.
+		}
+	}
+}
+
+func TestCancelAfterDial(t *testing.T) {
+	if testing.Short() {
+		t.Skip("avoiding time.Sleep")
+	}
+
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	defer func() {
+		ln.Close()
+		wg.Wait()
+	}()
+
+	// Echo back the first line of each incoming connection.
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				break
+			}
+			rb := bufio.NewReader(c)
+			line, err := rb.ReadString('\n')
+			if err != nil {
+				t.Error(err)
+				c.Close()
+				continue
+			}
+			if _, err := c.Write([]byte(line)); err != nil {
+				t.Error(err)
+			}
+			c.Close()
+		}
+		wg.Done()
+	}()
+
+	try := func() {
+		cancel := make(chan struct{})
+		d := &Dialer{Cancel: cancel}
+		c, err := d.Dial("tcp", ln.Addr().String())
+
+		// Immediately after dialing, request cancellation and sleep.
+		// Before Issue 15078 was fixed, this would cause subsequent operations
+		// to fail with an i/o timeout roughly 50% of the time.
+		close(cancel)
+		time.Sleep(10 * time.Millisecond)
+
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer c.Close()
+
+		// Send some data to confirm that the connection is still alive.
+		const message = "echo!\n"
+		if _, err := c.Write([]byte(message)); err != nil {
+			t.Fatal(err)
+		}
+
+		// The server should echo the line, and close the connection.
+		rb := bufio.NewReader(c)
+		line, err := rb.ReadString('\n')
+		if err != nil {
+			t.Fatal(err)
+		}
+		if line != message {
+			t.Errorf("got %q; want %q", line, message)
+		}
+		if _, err := rb.ReadByte(); err != io.EOF {
+			t.Errorf("got %v; want %v", err, io.EOF)
+		}
+	}
+
+	// This bug manifested about 50% of the time, so try it a few times.
+	for i := 0; i < 10; i++ {
+		try()
+	}
+}
+
+// Issue 18806: it should always be possible to net.Dial a
+// net.Listener().Addr().String when the listen address was ":n", even
+// if the machine has halfway configured IPv6 such that it can bind on
+// "::" not connect back to that same address.
+func TestDialListenerAddr(t *testing.T) {
+	mustHaveExternalNetwork(t)
+	ln, err := Listen("tcp", ":0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	addr := ln.Addr().String()
+	c, err := Dial("tcp", addr)
+	if err != nil {
+		t.Fatalf("for addr %q, dial error: %v", addr, err)
+	}
+	c.Close()
+}
+
+func TestDialerControl(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("not supported on %s", runtime.GOOS)
+	}
+
+	t.Run("StreamDial", func(t *testing.T) {
+		for _, network := range []string{"tcp", "tcp4", "tcp6", "unix", "unixpacket"} {
+			if !testableNetwork(network) {
+				continue
+			}
+			ln, err := newLocalListener(network)
+			if err != nil {
+				t.Error(err)
+				continue
+			}
+			defer ln.Close()
+			d := Dialer{Control: controlOnConnSetup}
+			c, err := d.Dial(network, ln.Addr().String())
+			if err != nil {
+				t.Error(err)
+				continue
+			}
+			c.Close()
+		}
+	})
+	t.Run("PacketDial", func(t *testing.T) {
+		for _, network := range []string{"udp", "udp4", "udp6", "unixgram"} {
+			if !testableNetwork(network) {
+				continue
+			}
+			c1, err := newLocalPacketListener(network)
+			if err != nil {
+				t.Error(err)
+				continue
+			}
+			if network == "unixgram" {
+				defer os.Remove(c1.LocalAddr().String())
+			}
+			defer c1.Close()
+			d := Dialer{Control: controlOnConnSetup}
+			c2, err := d.Dial(network, c1.LocalAddr().String())
+			if err != nil {
+				t.Error(err)
+				continue
+			}
+			c2.Close()
+		}
+	})
+}
+
+// mustHaveExternalNetwork is like testenv.MustHaveExternalNetwork
+// except that it won't skip testing on non-mobile builders.
+func mustHaveExternalNetwork(t *testing.T) {
+	t.Helper()
+	mobile := runtime.GOOS == "android" || runtime.GOOS == "ios"
+	if testenv.Builder() == "" || mobile {
+		testenv.MustHaveExternalNetwork(t)
+	}
+}
+
+type contextWithNonZeroDeadline struct {
+	context.Context
+}
+
+func (contextWithNonZeroDeadline) Deadline() (time.Time, bool) {
+	// Return non-zero time.Time value with false indicating that no deadline is set.
+	return time.Unix(0, 0), false
+}
+
+func TestDialWithNonZeroDeadline(t *testing.T) {
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	_, port, err := SplitHostPort(ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := contextWithNonZeroDeadline{Context: context.Background()}
+	var dialer Dialer
+	c, err := dialer.DialContext(ctx, "tcp", JoinHostPort("", port))
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.Close()
+}