src/net/lookup_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 (
 	"bytes"
 	"fmt"
 	"internal/testenv"
 	"runtime"
 	"strings"
 	"testing"
 	"time"
 )

 func lookupLocalhost(fn func(string) ([]IPAddr, error), host string) ([]IPAddr, error) {
 	switch host {
 	case "localhost":
 		return []IPAddr{
 			{IP: IPv4(127, 0, 0, 1)},
 			{IP: IPv6loopback},
 		}, nil
 	default:
 		return fn(host)
 	}
 }

 // The Lookup APIs use various sources such as local database, DNS or
 // mDNS, and may use platform-dependent DNS stub resolver if possible.
 // The APIs accept any of forms for a query; host name in various
 // encodings, UTF-8 encoded net name, domain name, FQDN or absolute
 // FQDN, but the result would be one of the forms and it depends on
 // the circumstances.

 var lookupGoogleSRVTests = []struct {
 	service, proto, name string
 	cname, target        string
 }{
 	{
 		"xmpp-server", "tcp", "google.com",
 		"google.com.", "google.com.",
 	},
 	{
 		"xmpp-server", "tcp", "google.com.",
 		"google.com.", "google.com.",
 	},

 	// non-standard back door
 	{
 		"", "", "_xmpp-server._tcp.google.com",
 		"google.com.", "google.com.",
 	},
 	{
 		"", "", "_xmpp-server._tcp.google.com.",
 		"google.com.", "google.com.",
 	},
 }

 func TestLookupGoogleSRV(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGoogleSRVTests {
 		cname, srvs, err := LookupSRV(tt.service, tt.proto, tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(srvs) == 0 {
 			t.Error("got no record")
 		}
 		if !strings.HasSuffix(cname, tt.cname) {
 			t.Errorf("got %s; want %s", cname, tt.cname)
 		}
 		for _, srv := range srvs {
 			if !strings.HasSuffix(srv.Target, tt.target) {
 				t.Errorf("got %v; want a record containing %s", srv, tt.target)
 			}
 		}
 	}
 }

 var lookupGmailMXTests = []struct {
 	name, host string
 }{
 	{"gmail.com", "google.com."},
 	{"gmail.com.", "google.com."},
 }

 func TestLookupGmailMX(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGmailMXTests {
 		mxs, err := LookupMX(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(mxs) == 0 {
 			t.Error("got no record")
 		}
 		for _, mx := range mxs {
 			if !strings.HasSuffix(mx.Host, tt.host) {
 				t.Errorf("got %v; want a record containing %s", mx, tt.host)
 			}
 		}
 	}
 }

 var lookupGmailNSTests = []struct {
 	name, host string
 }{
 	{"gmail.com", "google.com."},
 	{"gmail.com.", "google.com."},
 }

 func TestLookupGmailNS(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGmailNSTests {
 		nss, err := LookupNS(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(nss) == 0 {
 			t.Error("got no record")
 		}
 		for _, ns := range nss {
 			if !strings.HasSuffix(ns.Host, tt.host) {
 				t.Errorf("got %v; want a record containing %s", ns, tt.host)
 			}
 		}
 	}
 }

 var lookupGmailTXTTests = []struct {
 	name, txt, host string
 }{
 	{"gmail.com", "spf", "google.com"},
 	{"gmail.com.", "spf", "google.com"},
 }

 func TestLookupGmailTXT(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGmailTXTTests {
 		txts, err := LookupTXT(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(txts) == 0 {
 			t.Error("got no record")
 		}
 		for _, txt := range txts {
 			if !strings.Contains(txt, tt.txt) || (!strings.HasSuffix(txt, tt.host) && !strings.HasSuffix(txt, tt.host+".")) {
 				t.Errorf("got %s; want a record containing %s, %s", txt, tt.txt, tt.host)
 			}
 		}
 	}
 }

 var lookupGooglePublicDNSAddrTests = []struct {
 	addr, name string
 }{
 	{"8.8.8.8", ".google.com."},
 	{"8.8.4.4", ".google.com."},

 	{"2001:4860:4860::8888", ".google.com."},
 	{"2001:4860:4860::8844", ".google.com."},
 }

 func TestLookupGooglePublicDNSAddr(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !supportsIPv6 || !*testIPv4 || !*testIPv6 {
 		t.Skip("both IPv4 and IPv6 are required")
 	}

 	for _, tt := range lookupGooglePublicDNSAddrTests {
 		names, err := LookupAddr(tt.addr)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(names) == 0 {
 			t.Error("got no record")
 		}
 		for _, name := range names {
 			if !strings.HasSuffix(name, tt.name) {
 				t.Errorf("got %s; want a record containing %s", name, tt.name)
 			}
 		}
 	}
 }

 func TestLookupIPv6LinkLocalAddr(t *testing.T) {
 	if !supportsIPv6 || !*testIPv6 {
 		t.Skip("IPv6 is required")
 	}

 	addrs, err := LookupHost("localhost")
 	if err != nil {
 		t.Fatal(err)
 	}
 	found := false
 	for _, addr := range addrs {
 		if addr == "fe80::1%lo0" {
 			found = true
 			break
 		}
 	}
 	if !found {
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if _, err := LookupAddr("fe80::1%lo0"); err != nil {
 		t.Error(err)
 	}
 }

 var lookupIANACNAMETests = []struct {
 	name, cname string
 }{
 	{"www.iana.org", "icann.org."},
 	{"www.iana.org.", "icann.org."},
 }

 func TestLookupIANACNAME(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupIANACNAMETests {
 		cname, err := LookupCNAME(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if !strings.HasSuffix(cname, tt.cname) {
 			t.Errorf("got %s; want a record containing %s", cname, tt.cname)
 		}
 	}
 }

 var lookupGoogleHostTests = []struct {
 	name string
 }{
 	{"google.com"},
 	{"google.com."},
 }

 func TestLookupGoogleHost(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGoogleHostTests {
 		addrs, err := LookupHost(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(addrs) == 0 {
 			t.Error("got no record")
 		}
 		for _, addr := range addrs {
 			if ParseIP(addr) == nil {
 				t.Errorf("got %q; want a literal IP address", addr)
 			}
 		}
 	}
 }

 var lookupGoogleIPTests = []struct {
 	name string
 }{
 	{"google.com"},
 	{"google.com."},
 }

 func TestLookupGoogleIP(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for _, tt := range lookupGoogleIPTests {
 		ips, err := LookupIP(tt.name)
 		if err != nil {
 			t.Fatal(err)
 		}
 		if len(ips) == 0 {
 			t.Error("got no record")
 		}
 		for _, ip := range ips {
 			if ip.To4() == nil && ip.To16() == nil {
 				t.Errorf("got %v; want an IP address", ip)
 			}
 		}
 	}
 }

 var revAddrTests = []struct {
 	Addr      string
 	Reverse   string
 	ErrPrefix string
 }{
 	{"1.2.3.4", "4.3.2.1.in-addr.arpa.", ""},
 	{"245.110.36.114", "114.36.110.245.in-addr.arpa.", ""},
 	{"::ffff:12.34.56.78", "78.56.34.12.in-addr.arpa.", ""},
 	{"::1", "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", ""},
 	{"1::", "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.ip6.arpa.", ""},
 	{"1234:567::89a:bcde", "e.d.c.b.a.9.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
 	{"1234:567:fefe:bcbc:adad:9e4a:89a:bcde", "e.d.c.b.a.9.8.0.a.4.e.9.d.a.d.a.c.b.c.b.e.f.e.f.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
 	{"1.2.3", "", "unrecognized address"},
 	{"1.2.3.4.5", "", "unrecognized address"},
 	{"1234:567:bcbca::89a:bcde", "", "unrecognized address"},
 	{"1234:567::bcbc:adad::89a:bcde", "", "unrecognized address"},
 }

 func TestReverseAddress(t *testing.T) {
 	for i, tt := range revAddrTests {
 		a, err := reverseaddr(tt.Addr)
 		if len(tt.ErrPrefix) > 0 && err == nil {
 			t.Errorf("#%d: expected %q, got <nil> (error)", i, tt.ErrPrefix)
 			continue
 		}
 		if len(tt.ErrPrefix) == 0 && err != nil {
 			t.Errorf("#%d: expected <nil>, got %q (error)", i, err)
 		}
 		if err != nil && err.(*DNSError).Err != tt.ErrPrefix {
 			t.Errorf("#%d: expected %q, got %q (mismatched error)", i, tt.ErrPrefix, err.(*DNSError).Err)
 		}
 		if a != tt.Reverse {
 			t.Errorf("#%d: expected %q, got %q (reverse address)", i, tt.Reverse, a)
 		}
 	}
 }

 func TestLookupIPDeadline(t *testing.T) {
 	if !*testDNSFlood {
 		t.Skip("test disabled; use -dnsflood to enable")
 	}

 	const N = 5000
 	const timeout = 3 * time.Second
 	c := make(chan error, 2*N)
 	for i := 0; i < N; i++ {
 		name := fmt.Sprintf("%d.net-test.golang.org", i)
 		go func() {
 			_, err := lookupIPDeadline(name, time.Now().Add(timeout/2))
 			c <- err
 		}()
 		go func() {
 			_, err := lookupIPDeadline(name, time.Now().Add(timeout))
 			c <- err
 		}()
 	}
 	qstats := struct {
 		succeeded, failed         int
 		timeout, temporary, other int
 		unknown                   int
 	}{}
 	deadline := time.After(timeout + time.Second)
 	for i := 0; i < 2*N; i++ {
 		select {
 		case <-deadline:
 			t.Fatal("deadline exceeded")
 		case err := <-c:
 			switch err := err.(type) {
 			case nil:
 				qstats.succeeded++
 			case Error:
 				qstats.failed++
 				if err.Timeout() {
 					qstats.timeout++
 				}
 				if err.Temporary() {
 					qstats.temporary++
 				}
 				if !err.Timeout() && !err.Temporary() {
 					qstats.other++
 				}
 			default:
 				qstats.failed++
 				qstats.unknown++
 			}
 		}
 	}

 	// A high volume of DNS queries for sub-domain of golang.org
 	// would be coordinated by authoritative or recursive server,
 	// or stub resolver which implements query-response rate
 	// limitation, so we can expect some query successes and more
 	// failures including timeout, temporary and other here.
 	// As a rule, unknown must not be shown but it might possibly
 	// happen due to issue 4856 for now.
 	t.Logf("%v succeeded, %v failed (%v timeout, %v temporary, %v other, %v unknown)", qstats.succeeded, qstats.failed, qstats.timeout, qstats.temporary, qstats.other, qstats.unknown)
 }

 func TestLookupDotsWithLocalSource(t *testing.T) {
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	for i, fn := range []func() func(){forceGoDNS, forceCgoDNS} {
 		fixup := fn()
 		if fixup == nil {
 			continue
 		}
 		names, err := LookupAddr("127.0.0.1")
 		fixup()
 		if err != nil {
 			t.Logf("#%d: %v", i, err)
 			continue
 		}
 		mode := "netgo"
 		if i == 1 {
 			mode = "netcgo"
 		}
 	loop:
 		for i, name := range names {
 			if strings.Index(name, ".") == len(name)-1 { // "localhost" not "localhost."
 				for j := range names {
 					if j == i {
 						continue
 					}
 					if names[j] == name[:len(name)-1] {
 						// It's OK if we find the name without the dot,
 						// as some systems say 127.0.0.1 localhost localhost.
 						continue loop
 					}
 				}
 				t.Errorf("%s: got %s; want %s", mode, name, name[:len(name)-1])
 			} else if strings.Contains(name, ".") && !strings.HasSuffix(name, ".") { // "localhost.localdomain." not "localhost.localdomain"
 				t.Errorf("%s: got %s; want name ending with trailing dot", mode, name)
 			}
 		}
 	}
 }

 func TestLookupDotsWithRemoteSource(t *testing.T) {
 	if testing.Short() && testenv.Builder() == "" || !*testExternal {
 		t.Skip("avoid external network")
 	}
 	if !supportsIPv4 || !*testIPv4 {
 		t.Skip("IPv4 is required")
 	}

 	if fixup := forceGoDNS(); fixup != nil {
 		testDots(t, "go")
 		fixup()
 	}
 	if fixup := forceCgoDNS(); fixup != nil {
 		testDots(t, "cgo")
 		fixup()
 	}
 }

 func testDots(t *testing.T, mode string) {
 	names, err := LookupAddr("8.8.8.8") // Google dns server
 	if err != nil {
 		t.Errorf("LookupAddr(8.8.8.8): %v (mode=%v)", err, mode)
 	} else {
 		for _, name := range names {
 			if !strings.HasSuffix(name, ".google.com.") {
 				t.Errorf("LookupAddr(8.8.8.8) = %v, want names ending in .google.com. with trailing dot (mode=%v)", names, mode)
 				break
 			}
 		}
 	}

 	cname, err := LookupCNAME("www.mit.edu")
 	if err != nil || !strings.HasSuffix(cname, ".") {
 		t.Errorf("LookupCNAME(www.mit.edu) = %v, %v, want cname ending in . with trailing dot (mode=%v)", cname, err, mode)
 	}

 	mxs, err := LookupMX("google.com")
 	if err != nil {
 		t.Errorf("LookupMX(google.com): %v (mode=%v)", err, mode)
 	} else {
 		for _, mx := range mxs {
 			if !strings.HasSuffix(mx.Host, ".google.com.") {
 				t.Errorf("LookupMX(google.com) = %v, want names ending in .google.com. with trailing dot (mode=%v)", mxString(mxs), mode)
 				break
 			}
 		}
 	}

 	nss, err := LookupNS("google.com")
 	if err != nil {
 		t.Errorf("LookupNS(google.com): %v (mode=%v)", err, mode)
 	} else {
 		for _, ns := range nss {
 			if !strings.HasSuffix(ns.Host, ".google.com.") {
 				t.Errorf("LookupNS(google.com) = %v, want names ending in .google.com. with trailing dot (mode=%v)", nsString(nss), mode)
 				break
 			}
 		}
 	}

 	cname, srvs, err := LookupSRV("xmpp-server", "tcp", "google.com")
 	if err != nil {
 		t.Errorf("LookupSRV(xmpp-server, tcp, google.com): %v (mode=%v)", err, mode)
 	} else {
 		if !strings.HasSuffix(cname, ".google.com.") {
 			t.Errorf("LookupSRV(xmpp-server, tcp, google.com) returned cname=%v, want name ending in .google.com. with trailing dot (mode=%v)", cname, mode)
 		}
 		for _, srv := range srvs {
 			if !strings.HasSuffix(srv.Target, ".google.com.") {
 				t.Errorf("LookupSRV(xmpp-server, tcp, google.com) returned addrs=%v, want names ending in .google.com. with trailing dot (mode=%v)", srvString(srvs), mode)
 				break
 			}
 		}
 	}
 }

 func mxString(mxs []*MX) string {
 	var buf bytes.Buffer
 	sep := ""
 	fmt.Fprintf(&buf, "[")
 	for _, mx := range mxs {
 		fmt.Fprintf(&buf, "%s%s:%d", sep, mx.Host, mx.Pref)
 		sep = " "
 	}
 	fmt.Fprintf(&buf, "]")
 	return buf.String()
 }

 func nsString(nss []*NS) string {
 	var buf bytes.Buffer
 	sep := ""
 	fmt.Fprintf(&buf, "[")
 	for _, ns := range nss {
 		fmt.Fprintf(&buf, "%s%s", sep, ns.Host)
 		sep = " "
 	}
 	fmt.Fprintf(&buf, "]")
 	return buf.String()
 }

 func srvString(srvs []*SRV) string {
 	var buf bytes.Buffer
 	sep := ""
 	fmt.Fprintf(&buf, "[")
 	for _, srv := range srvs {
 		fmt.Fprintf(&buf, "%s%s:%d:%d:%d", sep, srv.Target, srv.Port, srv.Priority, srv.Weight)
 		sep = " "
 	}
 	fmt.Fprintf(&buf, "]")
 	return buf.String()
 }

 var lookupPortTests = []struct {
 	network string
 	name    string
 	port    int
 	ok      bool
 }{
 	{"tcp", "0", 0, true},
 	{"tcp", "echo", 7, true},
 	{"tcp", "discard", 9, true},
 	{"tcp", "systat", 11, true},
 	{"tcp", "daytime", 13, true},
 	{"tcp", "chargen", 19, true},
 	{"tcp", "ftp-data", 20, true},
 	{"tcp", "ftp", 21, true},
 	{"tcp", "telnet", 23, true},
 	{"tcp", "smtp", 25, true},
 	{"tcp", "time", 37, true},
 	{"tcp", "domain", 53, true},
 	{"tcp", "finger", 79, true},
 	{"tcp", "42", 42, true},

 	{"udp", "0", 0, true},
 	{"udp", "echo", 7, true},
 	{"udp", "tftp", 69, true},
 	{"udp", "bootpc", 68, true},
 	{"udp", "bootps", 67, true},
 	{"udp", "domain", 53, true},
 	{"udp", "ntp", 123, true},
 	{"udp", "snmp", 161, true},
 	{"udp", "syslog", 514, true},
 	{"udp", "42", 42, true},

 	{"--badnet--", "zzz", 0, false},
 	{"tcp", "--badport--", 0, false},
 	{"tcp", "-1", 0, false},
 	{"tcp", "65536", 0, false},
 	{"udp", "-1", 0, false},
 	{"udp", "65536", 0, false},

 	// Issue 13610: LookupPort("tcp", "")
 	{"tcp", "", 0, true},
 	{"tcp6", "", 0, true},
 	{"tcp4", "", 0, true},
 	{"udp", "", 0, true},
 }

 func TestLookupPort(t *testing.T) {
 	switch runtime.GOOS {
 	case "nacl":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	case "android":
 		if netGo {
 			t.Skipf("not supported on %s without cgo; see golang.org/issues/14576", runtime.GOOS)
 		}
 	}

 	for _, tt := range lookupPortTests {
 		if port, err := LookupPort(tt.network, tt.name); port != tt.port || (err == nil) != tt.ok {
 			t.Errorf("LookupPort(%q, %q) = %d, %v; want %d", tt.network, tt.name, port, err, tt.port)
 		}
 	}
 }
	// 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 (
	"bytes"
	"fmt"
	"internal/testenv"
	"runtime"
	"strings"
	"testing"
	"time"
	)

	func lookupLocalhost(fn func(string) ([]IPAddr, error), host string) ([]IPAddr, error) {
	switch host {
	case "localhost":
	return []IPAddr{
	{IP: IPv4(127, 0, 0, 1)},
	{IP: IPv6loopback},
	}, nil
	default:
	return fn(host)
	}
	}

	// The Lookup APIs use various sources such as local database, DNS or
	// mDNS, and may use platform-dependent DNS stub resolver if possible.
	// The APIs accept any of forms for a query; host name in various
	// encodings, UTF-8 encoded net name, domain name, FQDN or absolute
	// FQDN, but the result would be one of the forms and it depends on
	// the circumstances.

	var lookupGoogleSRVTests = []struct {
	service, proto, name string
	cname, target string
	}{
	{
	"xmpp-server", "tcp", "google.com",
	"google.com.", "google.com.",
	},
	{
	"xmpp-server", "tcp", "google.com.",
	"google.com.", "google.com.",
	},

	// non-standard back door
	{
	"", "", "_xmpp-server._tcp.google.com",
	"google.com.", "google.com.",
	},
	{
	"", "", "_xmpp-server._tcp.google.com.",
	"google.com.", "google.com.",
	},
	}

	func TestLookupGoogleSRV(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGoogleSRVTests {
	cname, srvs, err := LookupSRV(tt.service, tt.proto, tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(srvs) == 0 {
	t.Error("got no record")
	}
	if !strings.HasSuffix(cname, tt.cname) {
	t.Errorf("got %s; want %s", cname, tt.cname)
	}
	for _, srv := range srvs {
	if !strings.HasSuffix(srv.Target, tt.target) {
	t.Errorf("got %v; want a record containing %s", srv, tt.target)
	}
	}
	}
	}

	var lookupGmailMXTests = []struct {
	name, host string
	}{
	{"gmail.com", "google.com."},
	{"gmail.com.", "google.com."},
	}

	func TestLookupGmailMX(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGmailMXTests {
	mxs, err := LookupMX(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(mxs) == 0 {
	t.Error("got no record")
	}
	for _, mx := range mxs {
	if !strings.HasSuffix(mx.Host, tt.host) {
	t.Errorf("got %v; want a record containing %s", mx, tt.host)
	}
	}
	}
	}

	var lookupGmailNSTests = []struct {
	name, host string
	}{
	{"gmail.com", "google.com."},
	{"gmail.com.", "google.com."},
	}

	func TestLookupGmailNS(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGmailNSTests {
	nss, err := LookupNS(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(nss) == 0 {
	t.Error("got no record")
	}
	for _, ns := range nss {
	if !strings.HasSuffix(ns.Host, tt.host) {
	t.Errorf("got %v; want a record containing %s", ns, tt.host)
	}
	}
	}
	}

	var lookupGmailTXTTests = []struct {
	name, txt, host string
	}{
	{"gmail.com", "spf", "google.com"},
	{"gmail.com.", "spf", "google.com"},
	}

	func TestLookupGmailTXT(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGmailTXTTests {
	txts, err := LookupTXT(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(txts) == 0 {
	t.Error("got no record")
	}
	for _, txt := range txts {
	if !strings.Contains(txt, tt.txt) \|\| (!strings.HasSuffix(txt, tt.host) && !strings.HasSuffix(txt, tt.host+".")) {
	t.Errorf("got %s; want a record containing %s, %s", txt, tt.txt, tt.host)
	}
	}
	}
	}

	var lookupGooglePublicDNSAddrTests = []struct {
	addr, name string
	}{
	{"8.8.8.8", ".google.com."},
	{"8.8.4.4", ".google.com."},

	{"2001:4860:4860::8888", ".google.com."},
	{"2001:4860:4860::8844", ".google.com."},
	}

	func TestLookupGooglePublicDNSAddr(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !supportsIPv6 \|\| !testIPv4 \|\| !testIPv6 {
	t.Skip("both IPv4 and IPv6 are required")
	}

	for _, tt := range lookupGooglePublicDNSAddrTests {
	names, err := LookupAddr(tt.addr)
	if err != nil {
	t.Fatal(err)
	}
	if len(names) == 0 {
	t.Error("got no record")
	}
	for _, name := range names {
	if !strings.HasSuffix(name, tt.name) {
	t.Errorf("got %s; want a record containing %s", name, tt.name)
	}
	}
	}
	}

	func TestLookupIPv6LinkLocalAddr(t *testing.T) {
	if !supportsIPv6 \|\| !*testIPv6 {
	t.Skip("IPv6 is required")
	}

	addrs, err := LookupHost("localhost")
	if err != nil {
	t.Fatal(err)
	}
	found := false
	for _, addr := range addrs {
	if addr == "fe80::1%lo0" {
	found = true
	break
	}
	}
	if !found {
	t.Skipf("not supported on %s", runtime.GOOS)
	}
	if _, err := LookupAddr("fe80::1%lo0"); err != nil {
	t.Error(err)
	}
	}

	var lookupIANACNAMETests = []struct {
	name, cname string
	}{
	{"www.iana.org", "icann.org."},
	{"www.iana.org.", "icann.org."},
	}

	func TestLookupIANACNAME(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupIANACNAMETests {
	cname, err := LookupCNAME(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if !strings.HasSuffix(cname, tt.cname) {
	t.Errorf("got %s; want a record containing %s", cname, tt.cname)
	}
	}
	}

	var lookupGoogleHostTests = []struct {
	name string
	}{
	{"google.com"},
	{"google.com."},
	}

	func TestLookupGoogleHost(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGoogleHostTests {
	addrs, err := LookupHost(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(addrs) == 0 {
	t.Error("got no record")
	}
	for _, addr := range addrs {
	if ParseIP(addr) == nil {
	t.Errorf("got %q; want a literal IP address", addr)
	}
	}
	}
	}

	var lookupGoogleIPTests = []struct {
	name string
	}{
	{"google.com"},
	{"google.com."},
	}

	func TestLookupGoogleIP(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for _, tt := range lookupGoogleIPTests {
	ips, err := LookupIP(tt.name)
	if err != nil {
	t.Fatal(err)
	}
	if len(ips) == 0 {
	t.Error("got no record")
	}
	for _, ip := range ips {
	if ip.To4() == nil && ip.To16() == nil {
	t.Errorf("got %v; want an IP address", ip)
	}
	}
	}
	}

	var revAddrTests = []struct {
	Addr string
	Reverse string
	ErrPrefix string
	}{
	{"1.2.3.4", "4.3.2.1.in-addr.arpa.", ""},
	{"245.110.36.114", "114.36.110.245.in-addr.arpa.", ""},
	{"::ffff:12.34.56.78", "78.56.34.12.in-addr.arpa.", ""},
	{"::1", "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", ""},
	{"1::", "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.ip6.arpa.", ""},
	{"1234:567::89a:bcde", "e.d.c.b.a.9.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
	{"1234:567:fefe:bcbc:adad:9e4a:89a:bcde", "e.d.c.b.a.9.8.0.a.4.e.9.d.a.d.a.c.b.c.b.e.f.e.f.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
	{"1.2.3", "", "unrecognized address"},
	{"1.2.3.4.5", "", "unrecognized address"},
	{"1234:567:bcbca::89a:bcde", "", "unrecognized address"},
	{"1234:567::bcbc:adad::89a:bcde", "", "unrecognized address"},
	}

	func TestReverseAddress(t *testing.T) {
	for i, tt := range revAddrTests {
	a, err := reverseaddr(tt.Addr)
	if len(tt.ErrPrefix) > 0 && err == nil {
	t.Errorf("#%d: expected %q, got <nil> (error)", i, tt.ErrPrefix)
	continue
	}
	if len(tt.ErrPrefix) == 0 && err != nil {
	t.Errorf("#%d: expected <nil>, got %q (error)", i, err)
	}
	if err != nil && err.(*DNSError).Err != tt.ErrPrefix {
	t.Errorf("#%d: expected %q, got %q (mismatched error)", i, tt.ErrPrefix, err.(*DNSError).Err)
	}
	if a != tt.Reverse {
	t.Errorf("#%d: expected %q, got %q (reverse address)", i, tt.Reverse, a)
	}
	}
	}

	func TestLookupIPDeadline(t *testing.T) {
	if !*testDNSFlood {
	t.Skip("test disabled; use -dnsflood to enable")
	}

	const N = 5000
	const timeout = 3 * time.Second
	c := make(chan error, 2*N)
	for i := 0; i < N; i++ {
	name := fmt.Sprintf("%d.net-test.golang.org", i)
	go func() {
	_, err := lookupIPDeadline(name, time.Now().Add(timeout/2))
	c <- err
	}()
	go func() {
	_, err := lookupIPDeadline(name, time.Now().Add(timeout))
	c <- err
	}()
	}
	qstats := struct {
	succeeded, failed int
	timeout, temporary, other int
	unknown int
	}{}
	deadline := time.After(timeout + time.Second)
	for i := 0; i < 2*N; i++ {
	select {
	case <-deadline:
	t.Fatal("deadline exceeded")
	case err := <-c:
	switch err := err.(type) {
	case nil:
	qstats.succeeded++
	case Error:
	qstats.failed++
	if err.Timeout() {
	qstats.timeout++
	}
	if err.Temporary() {
	qstats.temporary++
	}
	if !err.Timeout() && !err.Temporary() {
	qstats.other++
	}
	default:
	qstats.failed++
	qstats.unknown++
	}
	}
	}

	// A high volume of DNS queries for sub-domain of golang.org
	// would be coordinated by authoritative or recursive server,
	// or stub resolver which implements query-response rate
	// limitation, so we can expect some query successes and more
	// failures including timeout, temporary and other here.
	// As a rule, unknown must not be shown but it might possibly
	// happen due to issue 4856 for now.
	t.Logf("%v succeeded, %v failed (%v timeout, %v temporary, %v other, %v unknown)", qstats.succeeded, qstats.failed, qstats.timeout, qstats.temporary, qstats.other, qstats.unknown)
	}

	func TestLookupDotsWithLocalSource(t *testing.T) {
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	for i, fn := range []func() func(){forceGoDNS, forceCgoDNS} {
	fixup := fn()
	if fixup == nil {
	continue
	}
	names, err := LookupAddr("127.0.0.1")
	fixup()
	if err != nil {
	t.Logf("#%d: %v", i, err)
	continue
	}
	mode := "netgo"
	if i == 1 {
	mode = "netcgo"
	}
	loop:
	for i, name := range names {
	if strings.Index(name, ".") == len(name)-1 { // "localhost" not "localhost."
	for j := range names {
	if j == i {
	continue
	}
	if names[j] == name[:len(name)-1] {
	// It's OK if we find the name without the dot,
	// as some systems say 127.0.0.1 localhost localhost.
	continue loop
	}
	}
	t.Errorf("%s: got %s; want %s", mode, name, name[:len(name)-1])
	} else if strings.Contains(name, ".") && !strings.HasSuffix(name, ".") { // "localhost.localdomain." not "localhost.localdomain"
	t.Errorf("%s: got %s; want name ending with trailing dot", mode, name)
	}
	}
	}
	}

	func TestLookupDotsWithRemoteSource(t *testing.T) {
	if testing.Short() && testenv.Builder() == "" \|\| !*testExternal {
	t.Skip("avoid external network")
	}
	if !supportsIPv4 \|\| !*testIPv4 {
	t.Skip("IPv4 is required")
	}

	if fixup := forceGoDNS(); fixup != nil {
	testDots(t, "go")
	fixup()
	}
	if fixup := forceCgoDNS(); fixup != nil {
	testDots(t, "cgo")
	fixup()
	}
	}

	func testDots(t *testing.T, mode string) {
	names, err := LookupAddr("8.8.8.8") // Google dns server
	if err != nil {
	t.Errorf("LookupAddr(8.8.8.8): %v (mode=%v)", err, mode)
	} else {
	for _, name := range names {
	if !strings.HasSuffix(name, ".google.com.") {
	t.Errorf("LookupAddr(8.8.8.8) = %v, want names ending in .google.com. with trailing dot (mode=%v)", names, mode)
	break
	}
	}
	}

	cname, err := LookupCNAME("www.mit.edu")
	if err != nil \|\| !strings.HasSuffix(cname, ".") {
	t.Errorf("LookupCNAME(www.mit.edu) = %v, %v, want cname ending in . with trailing dot (mode=%v)", cname, err, mode)
	}

	mxs, err := LookupMX("google.com")
	if err != nil {
	t.Errorf("LookupMX(google.com): %v (mode=%v)", err, mode)
	} else {
	for _, mx := range mxs {
	if !strings.HasSuffix(mx.Host, ".google.com.") {
	t.Errorf("LookupMX(google.com) = %v, want names ending in .google.com. with trailing dot (mode=%v)", mxString(mxs), mode)
	break
	}
	}
	}

	nss, err := LookupNS("google.com")
	if err != nil {
	t.Errorf("LookupNS(google.com): %v (mode=%v)", err, mode)
	} else {
	for _, ns := range nss {
	if !strings.HasSuffix(ns.Host, ".google.com.") {
	t.Errorf("LookupNS(google.com) = %v, want names ending in .google.com. with trailing dot (mode=%v)", nsString(nss), mode)
	break
	}
	}
	}

	cname, srvs, err := LookupSRV("xmpp-server", "tcp", "google.com")
	if err != nil {
	t.Errorf("LookupSRV(xmpp-server, tcp, google.com): %v (mode=%v)", err, mode)
	} else {
	if !strings.HasSuffix(cname, ".google.com.") {
	t.Errorf("LookupSRV(xmpp-server, tcp, google.com) returned cname=%v, want name ending in .google.com. with trailing dot (mode=%v)", cname, mode)
	}
	for _, srv := range srvs {
	if !strings.HasSuffix(srv.Target, ".google.com.") {
	t.Errorf("LookupSRV(xmpp-server, tcp, google.com) returned addrs=%v, want names ending in .google.com. with trailing dot (mode=%v)", srvString(srvs), mode)
	break
	}
	}
	}
	}

	func mxString(mxs []*MX) string {
	var buf bytes.Buffer
	sep := ""
	fmt.Fprintf(&buf, "[")
	for _, mx := range mxs {
	fmt.Fprintf(&buf, "%s%s:%d", sep, mx.Host, mx.Pref)
	sep = " "
	}
	fmt.Fprintf(&buf, "]")
	return buf.String()
	}

	func nsString(nss []*NS) string {
	var buf bytes.Buffer
	sep := ""
	fmt.Fprintf(&buf, "[")
	for _, ns := range nss {
	fmt.Fprintf(&buf, "%s%s", sep, ns.Host)
	sep = " "
	}
	fmt.Fprintf(&buf, "]")
	return buf.String()
	}

	func srvString(srvs []*SRV) string {
	var buf bytes.Buffer
	sep := ""
	fmt.Fprintf(&buf, "[")
	for _, srv := range srvs {
	fmt.Fprintf(&buf, "%s%s:%d:%d:%d", sep, srv.Target, srv.Port, srv.Priority, srv.Weight)
	sep = " "
	}
	fmt.Fprintf(&buf, "]")
	return buf.String()
	}

	var lookupPortTests = []struct {
	network string
	name string
	port int
	ok bool
	}{
	{"tcp", "0", 0, true},
	{"tcp", "echo", 7, true},
	{"tcp", "discard", 9, true},
	{"tcp", "systat", 11, true},
	{"tcp", "daytime", 13, true},
	{"tcp", "chargen", 19, true},
	{"tcp", "ftp-data", 20, true},
	{"tcp", "ftp", 21, true},
	{"tcp", "telnet", 23, true},
	{"tcp", "smtp", 25, true},
	{"tcp", "time", 37, true},
	{"tcp", "domain", 53, true},
	{"tcp", "finger", 79, true},
	{"tcp", "42", 42, true},

	{"udp", "0", 0, true},
	{"udp", "echo", 7, true},
	{"udp", "tftp", 69, true},
	{"udp", "bootpc", 68, true},
	{"udp", "bootps", 67, true},
	{"udp", "domain", 53, true},
	{"udp", "ntp", 123, true},
	{"udp", "snmp", 161, true},
	{"udp", "syslog", 514, true},
	{"udp", "42", 42, true},

	{"--badnet--", "zzz", 0, false},
	{"tcp", "--badport--", 0, false},
	{"tcp", "-1", 0, false},
	{"tcp", "65536", 0, false},
	{"udp", "-1", 0, false},
	{"udp", "65536", 0, false},

	// Issue 13610: LookupPort("tcp", "")
	{"tcp", "", 0, true},
	{"tcp6", "", 0, true},
	{"tcp4", "", 0, true},
	{"udp", "", 0, true},
	}

	func TestLookupPort(t *testing.T) {
	switch runtime.GOOS {
	case "nacl":
	t.Skipf("not supported on %s", runtime.GOOS)
	case "android":
	if netGo {
	t.Skipf("not supported on %s without cgo; see golang.org/issues/14576", runtime.GOOS)
	}
	}

	for _, tt := range lookupPortTests {
	if port, err := LookupPort(tt.network, tt.name); port != tt.port \|\| (err == nil) != tt.ok {
	t.Errorf("LookupPort(%q, %q) = %d, %v; want %d", tt.network, tt.name, port, err, tt.port)
	}
	}
	}