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net: clean up builtin DNS stub resolver, fix tests
This change does clean up as preparation for fixing #11081. - renames cfg to resolvConf for clarification - adds a new type resolverConfig and its methods: init, update, tryAcquireSema, releaseSema for mutual exclusion of resolv.conf data - deflakes, simplifies tests for resolv.conf data; previously the tests sometimes left some garbage in the data Change-Id: I277ced853fddc3791dde40ab54dbd5c78114b78c Reviewed-on: https://go-review.googlesource.com/10931 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Mikio Hara
Brad Fitzpatrick
parent
d7a8d3eb08
commit
7ef6a9f38b
2 changed files with 185 additions and 156 deletions
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@ -7,11 +7,13 @@
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package net
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import (
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"io"
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"fmt"
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"io/ioutil"
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"os"
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"path"
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"reflect"
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"strings"
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"sync"
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"testing"
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"time"
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)
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@ -93,119 +95,135 @@ func TestSpecialDomainName(t *testing.T) {
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}
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type resolvConfTest struct {
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*testing.T
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dir string
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path string
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*resolverConfig
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}
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func newResolvConfTest(t *testing.T) *resolvConfTest {
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func newResolvConfTest() (*resolvConfTest, error) {
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dir, err := ioutil.TempDir("", "go-resolvconftest")
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if err != nil {
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t.Fatal(err)
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return nil, err
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}
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r := &resolvConfTest{
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T: t,
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dir: dir,
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path: path.Join(dir, "resolv.conf"),
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conf := &resolvConfTest{
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dir: dir,
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path: path.Join(dir, "resolv.conf"),
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resolverConfig: &resolvConf,
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}
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return r
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conf.initOnce.Do(conf.init)
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return conf, nil
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}
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func (r *resolvConfTest) SetConf(s string) {
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// Make sure the file mtime will be different once we're done here,
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// even on systems with coarse (1s) mtime resolution.
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time.Sleep(time.Second)
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f, err := os.OpenFile(r.path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600)
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func (conf *resolvConfTest) writeAndUpdate(lines []string) error {
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f, err := os.OpenFile(conf.path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600)
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if err != nil {
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r.Fatalf("failed to create temp file %s: %v", r.path, err)
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return err
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}
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if _, err := io.WriteString(f, s); err != nil {
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if _, err := f.WriteString(strings.Join(lines, "\n")); err != nil {
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f.Close()
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r.Fatalf("failed to write temp file: %v", err)
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return err
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}
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f.Close()
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cfg.lastChecked = time.Time{}
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loadConfig(r.path)
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}
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func (r *resolvConfTest) WantServers(want []string) {
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cfg.mu.RLock()
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defer cfg.mu.RUnlock()
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if got := cfg.dnsConfig.servers; !reflect.DeepEqual(got, want) {
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r.Fatalf("unexpected dns server loaded, got %v want %v", got, want)
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if err := conf.forceUpdate(conf.path); err != nil {
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return err
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}
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return nil
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}
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func (r *resolvConfTest) Close() {
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if err := os.RemoveAll(r.dir); err != nil {
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r.Logf("failed to remove temp dir %s: %v", r.dir, err)
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func (conf *resolvConfTest) forceUpdate(name string) error {
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dnsConf := dnsReadConfig(name)
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conf.mu.Lock()
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conf.dnsConfig = dnsConf
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conf.mu.Unlock()
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for i := 0; i < 5; i++ {
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if conf.tryAcquireSema() {
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conf.lastChecked = time.Time{}
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conf.releaseSema()
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return nil
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}
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}
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return fmt.Errorf("tryAcquireSema for %s failed", name)
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}
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func TestReloadResolvConfFail(t *testing.T) {
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func (conf *resolvConfTest) servers() []string {
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conf.mu.RLock()
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servers := conf.dnsConfig.servers
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conf.mu.RUnlock()
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return servers
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}
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func (conf *resolvConfTest) teardown() error {
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err := conf.forceUpdate("/etc/resolv.conf")
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os.RemoveAll(conf.dir)
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return err
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}
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var updateResolvConfTests = []struct {
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name string // query name
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lines []string // resolver configuration lines
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servers []string // expected name servers
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}{
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{
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name: "golang.org",
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lines: []string{"nameserver 8.8.8.8"},
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servers: []string{"8.8.8.8"},
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},
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{
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name: "",
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lines: nil, // an empty resolv.conf should use defaultNS as name servers
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servers: defaultNS,
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},
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{
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name: "www.example.com",
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lines: []string{"nameserver 8.8.4.4"},
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servers: []string{"8.8.4.4"},
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},
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}
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func TestUpdateResolvConf(t *testing.T) {
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if testing.Short() || !*testExternal {
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t.Skip("avoid external network")
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}
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r := newResolvConfTest(t)
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defer r.Close()
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r.SetConf("nameserver 8.8.8.8")
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if _, err := goLookupIP("golang.org"); err != nil {
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conf, err := newResolvConfTest()
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if err != nil {
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t.Fatal(err)
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}
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defer conf.teardown()
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// Using an empty resolv.conf should use localhost as servers
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r.SetConf("")
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if len(cfg.dnsConfig.servers) != len(defaultNS) {
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t.Fatalf("goLookupIP(missing; good; bad) failed: servers=%v, want: %v", cfg.dnsConfig.servers, defaultNS)
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}
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for i := range cfg.dnsConfig.servers {
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if cfg.dnsConfig.servers[i] != defaultNS[i] {
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t.Fatalf("goLookupIP(missing; good; bad) failed: servers=%v, want: %v", cfg.dnsConfig.servers, defaultNS)
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for i, tt := range updateResolvConfTests {
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if err := conf.writeAndUpdate(tt.lines); err != nil {
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t.Error(err)
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continue
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}
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if tt.name != "" {
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var wg sync.WaitGroup
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const N = 10
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wg.Add(N)
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for j := 0; j < N; j++ {
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go func(name string) {
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defer wg.Done()
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ips, err := goLookupIP(name)
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if err != nil {
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t.Error(err)
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return
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}
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if len(ips) == 0 {
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t.Errorf("no records for %s", name)
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return
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}
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}(tt.name)
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}
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wg.Wait()
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}
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servers := conf.servers()
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if !reflect.DeepEqual(servers, tt.servers) {
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t.Errorf("#%d: got %v; want %v", i, servers, tt.servers)
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continue
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}
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}
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}
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func TestReloadResolvConfChange(t *testing.T) {
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if testing.Short() || !*testExternal {
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t.Skip("avoid external network")
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}
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r := newResolvConfTest(t)
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defer r.Close()
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r.SetConf("nameserver 8.8.8.8")
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if _, err := goLookupIP("golang.org"); err != nil {
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t.Fatal(err)
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}
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r.WantServers([]string{"8.8.8.8"})
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// Using an empty resolv.conf should use localhost as servers
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r.SetConf("")
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if len(cfg.dnsConfig.servers) != len(defaultNS) {
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t.Fatalf("goLookupIP(missing; good; bad) failed: servers=%v, want: %v", cfg.dnsConfig.servers, defaultNS)
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}
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for i := range cfg.dnsConfig.servers {
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if cfg.dnsConfig.servers[i] != defaultNS[i] {
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t.Fatalf("goLookupIP(missing; good; bad) failed: servers=%v, want: %v", cfg.dnsConfig.servers, defaultNS)
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}
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}
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// A new good config should get picked up
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r.SetConf("nameserver 8.8.4.4")
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r.WantServers([]string{"8.8.4.4"})
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}
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func BenchmarkGoLookupIP(b *testing.B) {
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testHookUninstaller.Do(uninstallTestHooks)
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@ -225,14 +243,21 @@ func BenchmarkGoLookupIPNoSuchHost(b *testing.B) {
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func BenchmarkGoLookupIPWithBrokenNameServer(b *testing.B) {
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testHookUninstaller.Do(uninstallTestHooks)
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// This looks ugly but it's safe as long as benchmarks are run
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// sequentially in package testing.
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<-cfg.ch // keep config from being reloaded upon lookup
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orig := cfg.dnsConfig
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cfg.dnsConfig.servers = append([]string{"203.0.113.254"}, cfg.dnsConfig.servers...) // use TEST-NET-3 block, see RFC 5737
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conf, err := newResolvConfTest()
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if err != nil {
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b.Fatal(err)
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}
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defer conf.teardown()
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lines := []string{
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"nameserver 203.0.113.254", // use TEST-NET-3 block, see RFC 5737
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"nameserver 8.8.8.8",
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}
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if err := conf.writeAndUpdate(lines); err != nil {
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b.Fatal(err)
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}
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for i := 0; i < b.N; i++ {
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goLookupIP("www.example.com")
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}
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cfg.dnsConfig = orig
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cfg.ch <- struct{}{}
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}
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