зеркало из https://github.com/microsoft/docker.git
Merge pull request #10005 from estesp/fix-localhost-nameserver-cleanup
Clean up localhost resolv logic and add IPv6 support to regexp
This commit is contained in:
Alexander Morozov
Коммит
e9d3e237e5
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@ -964,8 +964,8 @@ func (container *Container) setupContainerDns() error {
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log.Debugf("Check container (%s) for update to resolv.conf - UpdateDns flag was set", container.ID)
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latestResolvConf, latestHash := resolvconf.GetLastModified()
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// because the new host resolv.conf might have localhost nameservers..
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updatedResolvConf, modified := resolvconf.RemoveReplaceLocalDns(latestResolvConf)
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// clean container resolv.conf re: localhost nameservers and IPv6 NS (if IPv6 disabled)
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updatedResolvConf, modified := resolvconf.FilterResolvDns(latestResolvConf, container.daemon.config.EnableIPv6)
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if modified {
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// changes have occurred during resolv.conf localhost cleanup: generate an updated hash
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newHash, err := utils.HashData(bytes.NewReader(updatedResolvConf))
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@ -1018,8 +1018,8 @@ func (container *Container) setupContainerDns() error {
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return resolvconf.Build(container.ResolvConfPath, dns, dnsSearch)
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}
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// replace any localhost/127.* nameservers
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resolvConf, _ = resolvconf.RemoveReplaceLocalDns(resolvConf)
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// replace any localhost/127.*, and remove IPv6 nameservers if IPv6 disabled in daemon
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resolvConf, _ = resolvconf.FilterResolvDns(resolvConf, daemon.config.EnableIPv6)
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}
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//get a sha256 hash of the resolv conf at this point so we can check
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//for changes when the host resolv.conf changes (e.g. network update)
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@ -435,7 +435,7 @@ func (daemon *Daemon) setupResolvconfWatcher() error {
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log.Debugf("Error retrieving updated host resolv.conf: %v", err)
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} else if updatedResolvConf != nil {
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// because the new host resolv.conf might have localhost nameservers..
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updatedResolvConf, modified := resolvconf.RemoveReplaceLocalDns(updatedResolvConf)
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updatedResolvConf, modified := resolvconf.FilterResolvDns(updatedResolvConf, daemon.config.EnableIPv6)
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if modified {
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// changes have occurred during localhost cleanup: generate an updated hash
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newHash, err := utils.HashData(bytes.NewReader(updatedResolvConf))
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@ -1289,40 +1289,42 @@ func TestRunDisallowBindMountingRootToRoot(t *testing.T) {
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logDone("run - bind mount /:/ as volume should fail")
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}
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// Verify that a container gets default DNS when only localhost resolvers exist
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func TestRunDnsDefaultOptions(t *testing.T) {
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// ci server has default resolv.conf
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// so rewrite it for the test
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// preserve original resolv.conf for restoring after test
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origResolvConf, err := ioutil.ReadFile("/etc/resolv.conf")
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if os.IsNotExist(err) {
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t.Fatalf("/etc/resolv.conf does not exist")
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}
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// test with file
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tmpResolvConf := []byte("nameserver 127.0.0.1")
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if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
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t.Fatal(err)
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}
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// put the old resolvconf back
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// defer restored original conf
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defer func() {
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if err := ioutil.WriteFile("/etc/resolv.conf", origResolvConf, 0644); err != nil {
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t.Fatal(err)
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}
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}()
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// test 3 cases: standard IPv4 localhost, commented out localhost, and IPv6 localhost
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// 2 are removed from the file at container start, and the 3rd (commented out) one is ignored by
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// GetNameservers(), leading to a replacement of nameservers with the default set
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tmpResolvConf := []byte("nameserver 127.0.0.1\n#nameserver 127.0.2.1\nnameserver ::1")
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if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
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t.Fatal(err)
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}
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cmd := exec.Command(dockerBinary, "run", "busybox", "cat", "/etc/resolv.conf")
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actual, _, err := runCommandWithOutput(cmd)
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if err != nil {
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t.Error(err, actual)
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return
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t.Fatal(err, actual)
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}
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// check that the actual defaults are there
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// if we ever change the defaults from google dns, this will break
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expected := "\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
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// check that the actual defaults are appended to the commented out
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// localhost resolver (which should be preserved)
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// NOTE: if we ever change the defaults from google dns, this will break
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expected := "#nameserver 127.0.2.1\n\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
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if actual != expected {
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t.Errorf("expected resolv.conf be: %q, but was: %q", expected, actual)
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return
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t.Fatalf("expected resolv.conf be: %q, but was: %q", expected, actual)
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}
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deleteAllContainers()
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@ -12,9 +12,21 @@ import (
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)
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var (
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defaultDns = []string{"8.8.8.8", "8.8.4.4"}
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localHostRegexp = regexp.MustCompile(`(?m)^nameserver 127[^\n]+\n*`)
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nsRegexp = regexp.MustCompile(`^\s*nameserver\s*(([0-9]+\.){3}([0-9]+))\s*$`)
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// Note: the default IPv4 & IPv6 resolvers are set to Google's Public DNS
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defaultIPv4Dns = []string{"nameserver 8.8.8.8", "nameserver 8.8.4.4"}
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defaultIPv6Dns = []string{"nameserver 2001:4860:4860::8888", "nameserver 2001:4860:4860::8844"}
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ipv4NumBlock = `(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)`
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ipv4Address = `(` + ipv4NumBlock + `\.){3}` + ipv4NumBlock
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// This is not an IPv6 address verifier as it will accept a super-set of IPv6, and also
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// will *not match* IPv4-Embedded IPv6 Addresses (RFC6052), but that and other variants
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// -- e.g. other link-local types -- either won't work in containers or are unnecessary.
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// For readability and sufficiency for Docker purposes this seemed more reasonable than a
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// 1000+ character regexp with exact and complete IPv6 validation
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ipv6Address = `([0-9A-Fa-f]{0,4}:){2,7}([0-9A-Fa-f]{0,4})`
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localhostRegexp = regexp.MustCompile(`(?m)^nameserver\s+((127\.([0-9]{1,3}.){2}[0-9]{1,3})|(::1))\s*\n*`)
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nsIPv6Regexp = regexp.MustCompile(`(?m)^nameserver\s+` + ipv6Address + `\s*\n*`)
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nsRegexp = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`)
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searchRegexp = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`)
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)
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@ -65,17 +77,31 @@ func GetLastModified() ([]byte, string) {
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return lastModified.contents, lastModified.sha256
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}
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// RemoveReplaceLocalDns looks for localhost (127.*) entries in the provided
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// resolv.conf, removing local nameserver entries, and, if the resulting
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// cleaned config has no defined nameservers left, adds default DNS entries
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// FilterResolvDns has two main jobs:
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// 1. It looks for localhost (127.*|::1) entries in the provided
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// resolv.conf, removing local nameserver entries, and, if the resulting
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// cleaned config has no defined nameservers left, adds default DNS entries
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// 2. Given the caller provides the enable/disable state of IPv6, the filter
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// code will remove all IPv6 nameservers if it is not enabled for containers
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//
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// It also returns a boolean to notify the caller if changes were made at all
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func RemoveReplaceLocalDns(resolvConf []byte) ([]byte, bool) {
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func FilterResolvDns(resolvConf []byte, ipv6Enabled bool) ([]byte, bool) {
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changed := false
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cleanedResolvConf := localHostRegexp.ReplaceAll(resolvConf, []byte{})
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// if the resulting resolvConf is empty, use defaultDns
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if !bytes.Contains(cleanedResolvConf, []byte("nameserver")) {
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log.Infof("No non-localhost DNS nameservers are left in resolv.conf. Using default external servers : %v", defaultDns)
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cleanedResolvConf = append(cleanedResolvConf, []byte("\nnameserver "+strings.Join(defaultDns, "\nnameserver "))...)
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cleanedResolvConf := localhostRegexp.ReplaceAll(resolvConf, []byte{})
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// if IPv6 is not enabled, also clean out any IPv6 address nameserver
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if !ipv6Enabled {
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cleanedResolvConf = nsIPv6Regexp.ReplaceAll(cleanedResolvConf, []byte{})
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}
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// if the resulting resolvConf has no more nameservers defined, add appropriate
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// default DNS servers for IPv4 and (optionally) IPv6
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if len(GetNameservers(cleanedResolvConf)) == 0 {
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log.Infof("No non-localhost DNS nameservers are left in resolv.conf. Using default external servers : %v", defaultIPv4Dns)
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dns := defaultIPv4Dns
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if ipv6Enabled {
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log.Infof("IPv6 enabled; Adding default IPv6 external servers : %v", defaultIPv6Dns)
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dns = append(dns, defaultIPv6Dns...)
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}
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cleanedResolvConf = append(cleanedResolvConf, []byte("\n"+strings.Join(dns, "\n"))...)
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}
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if !bytes.Equal(resolvConf, cleanedResolvConf) {
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changed = true
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@ -157,33 +157,82 @@ func TestBuildWithZeroLengthDomainSearch(t *testing.T) {
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}
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}
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func TestRemoveReplaceLocalDns(t *testing.T) {
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func TestFilterResolvDns(t *testing.T) {
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ns0 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\n"
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if result, _ := RemoveReplaceLocalDns([]byte(ns0)); result != nil {
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if result, _ := FilterResolvDns([]byte(ns0), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed No Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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ns1 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\nnameserver 127.0.0.1\n"
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if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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ns1 = "nameserver 10.16.60.14\nnameserver 127.0.0.1\nnameserver 10.16.60.21\n"
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if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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ns1 = "nameserver 127.0.1.1\nnameserver 10.16.60.14\nnameserver 10.16.60.21\n"
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if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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ns1 = "nameserver ::1\nnameserver 10.16.60.14\nnameserver 127.0.2.1\nnameserver 10.16.60.21\n"
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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ns1 = "nameserver 10.16.60.14\nnameserver ::1\nnameserver 10.16.60.21\nnameserver ::1"
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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// with IPv6 disabled (false param), the IPv6 nameserver should be removed
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ns1 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\nnameserver ::1"
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost+IPv6 off: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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// with IPv6 enabled, the IPv6 nameserver should be preserved
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ns0 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\n"
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ns1 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\nnameserver ::1"
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if result, _ := FilterResolvDns([]byte(ns1), true); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed Localhost+IPv6 on: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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// with IPv6 enabled, and no non-localhost servers, Google defaults (both IPv4+IPv6) should be added
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ns0 = "\nnameserver 8.8.8.8\nnameserver 8.8.4.4\nnameserver 2001:4860:4860::8888\nnameserver 2001:4860:4860::8844"
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ns1 = "nameserver 127.0.0.1\nnameserver ::1\nnameserver 127.0.2.1"
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if result, _ := FilterResolvDns([]byte(ns1), true); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed no Localhost+IPv6 enabled: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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// with IPv6 disabled, and no non-localhost servers, Google defaults (only IPv4) should be added
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ns0 = "\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
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ns1 = "nameserver 127.0.0.1\nnameserver ::1\nnameserver 127.0.2.1"
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if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
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if ns0 != string(result) {
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t.Fatalf("Failed no Localhost+IPv6 enabled: expected \n<%s> got \n<%s>", ns0, string(result))
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}
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}
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}
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