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Merge pull request #10005 from estesp/fix-localhost-nameserver-cleanup

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Clean up localhost resolv logic and add IPv6 support to regexp
This commit is contained in:
Alexander Morozov 2015-01-20 10:30:06 -08:00
commit e9d3e237e5
5 changed files with 115 additions and 38 deletions
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8
daemon/container.go
View file

@ -964,8 +964,8 @@ func (container *Container) setupContainerDns() error {
log.Debugf("Check container (%s) for update to resolv.conf - UpdateDns flag was set", container.ID)
latestResolvConf, latestHash := resolvconf.GetLastModified()
// because the new host resolv.conf might have localhost nameservers..
updatedResolvConf, modified := resolvconf.RemoveReplaceLocalDns(latestResolvConf)
// clean container resolv.conf re: localhost nameservers and IPv6 NS (if IPv6 disabled)
updatedResolvConf, modified := resolvconf.FilterResolvDns(latestResolvConf, container.daemon.config.EnableIPv6)
if modified {
// changes have occurred during resolv.conf localhost cleanup: generate an updated hash
newHash, err := utils.HashData(bytes.NewReader(updatedResolvConf))
@ -1018,8 +1018,8 @@ func (container *Container) setupContainerDns() error {
return resolvconf.Build(container.ResolvConfPath, dns, dnsSearch)
}
// replace any localhost/127.* nameservers
resolvConf, _ = resolvconf.RemoveReplaceLocalDns(resolvConf)
// replace any localhost/127.*, and remove IPv6 nameservers if IPv6 disabled in daemon
resolvConf, _ = resolvconf.FilterResolvDns(resolvConf, daemon.config.EnableIPv6)
}
//get a sha256 hash of the resolv conf at this point so we can check
//for changes when the host resolv.conf changes (e.g. network update)

2
daemon/daemon.go
View file

@ -435,7 +435,7 @@ func (daemon *Daemon) setupResolvconfWatcher() error {
log.Debugf("Error retrieving updated host resolv.conf: %v", err)
} else if updatedResolvConf != nil {
// because the new host resolv.conf might have localhost nameservers..
updatedResolvConf, modified := resolvconf.RemoveReplaceLocalDns(updatedResolvConf)
updatedResolvConf, modified := resolvconf.FilterResolvDns(updatedResolvConf, daemon.config.EnableIPv6)
if modified {
// changes have occurred during localhost cleanup: generate an updated hash
newHash, err := utils.HashData(bytes.NewReader(updatedResolvConf))

34
integration-cli/docker_cli_run_test.go
View file

@ -1289,40 +1289,42 @@ func TestRunDisallowBindMountingRootToRoot(t *testing.T) {
logDone("run - bind mount /:/ as volume should fail")
}
// Verify that a container gets default DNS when only localhost resolvers exist
func TestRunDnsDefaultOptions(t *testing.T) {
// ci server has default resolv.conf
// so rewrite it for the test
// preserve original resolv.conf for restoring after test
origResolvConf, err := ioutil.ReadFile("/etc/resolv.conf")
if os.IsNotExist(err) {
t.Fatalf("/etc/resolv.conf does not exist")
}
// test with file
tmpResolvConf := []byte("nameserver 127.0.0.1")
if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
t.Fatal(err)
}
// put the old resolvconf back
// defer restored original conf
defer func() {
if err := ioutil.WriteFile("/etc/resolv.conf", origResolvConf, 0644); err != nil {
t.Fatal(err)
}
}()
// test 3 cases: standard IPv4 localhost, commented out localhost, and IPv6 localhost
// 2 are removed from the file at container start, and the 3rd (commented out) one is ignored by
// GetNameservers(), leading to a replacement of nameservers with the default set
tmpResolvConf := []byte("nameserver 127.0.0.1\n#nameserver 127.0.2.1\nnameserver ::1")
if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
t.Fatal(err)
}
cmd := exec.Command(dockerBinary, "run", "busybox", "cat", "/etc/resolv.conf")
actual, _, err := runCommandWithOutput(cmd)
if err != nil {
t.Error(err, actual)
return
t.Fatal(err, actual)
}
// check that the actual defaults are there
// if we ever change the defaults from google dns, this will break
expected := "\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
// check that the actual defaults are appended to the commented out
// localhost resolver (which should be preserved)
// NOTE: if we ever change the defaults from google dns, this will break
expected := "#nameserver 127.0.2.1\n\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
if actual != expected {
t.Errorf("expected resolv.conf be: %q, but was: %q", expected, actual)
return
t.Fatalf("expected resolv.conf be: %q, but was: %q", expected, actual)
}
deleteAllContainers()

50
pkg/networkfs/resolvconf/resolvconf.go
View file

@ -12,9 +12,21 @@ import (
)
var (
defaultDns = []string{"8.8.8.8", "8.8.4.4"}
localHostRegexp = regexp.MustCompile(`(?m)^nameserver 127[^\n]+\n*`)
nsRegexp = regexp.MustCompile(`^\s*nameserver\s*(([0-9]+\.){3}([0-9]+))\s*$`)
// Note: the default IPv4 & IPv6 resolvers are set to Google's Public DNS
defaultIPv4Dns = []string{"nameserver 8.8.8.8", "nameserver 8.8.4.4"}
defaultIPv6Dns = []string{"nameserver 2001:4860:4860::8888", "nameserver 2001:4860:4860::8844"}
ipv4NumBlock = `(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)`
ipv4Address = `(` + ipv4NumBlock + `\.){3}` + ipv4NumBlock
// This is not an IPv6 address verifier as it will accept a super-set of IPv6, and also
// will *not match* IPv4-Embedded IPv6 Addresses (RFC6052), but that and other variants
// -- e.g. other link-local types -- either won't work in containers or are unnecessary.
// For readability and sufficiency for Docker purposes this seemed more reasonable than a
// 1000+ character regexp with exact and complete IPv6 validation
ipv6Address = `([0-9A-Fa-f]{0,4}:){2,7}([0-9A-Fa-f]{0,4})`
localhostRegexp = regexp.MustCompile(`(?m)^nameserver\s+((127\.([0-9]{1,3}.){2}[0-9]{1,3})|(::1))\s*\n*`)
nsIPv6Regexp = regexp.MustCompile(`(?m)^nameserver\s+` + ipv6Address + `\s*\n*`)
nsRegexp = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`)
searchRegexp = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`)
)
@ -65,17 +77,31 @@ func GetLastModified() ([]byte, string) {
return lastModified.contents, lastModified.sha256
}
// RemoveReplaceLocalDns looks for localhost (127.*) entries in the provided
// resolv.conf, removing local nameserver entries, and, if the resulting
// cleaned config has no defined nameservers left, adds default DNS entries
// FilterResolvDns has two main jobs:
// 1. It looks for localhost (127.*|::1) entries in the provided
// resolv.conf, removing local nameserver entries, and, if the resulting
// cleaned config has no defined nameservers left, adds default DNS entries
// 2. Given the caller provides the enable/disable state of IPv6, the filter
// code will remove all IPv6 nameservers if it is not enabled for containers
//
// It also returns a boolean to notify the caller if changes were made at all
func RemoveReplaceLocalDns(resolvConf []byte) ([]byte, bool) {
func FilterResolvDns(resolvConf []byte, ipv6Enabled bool) ([]byte, bool) {
changed := false
cleanedResolvConf := localHostRegexp.ReplaceAll(resolvConf, []byte{})
// if the resulting resolvConf is empty, use defaultDns
if !bytes.Contains(cleanedResolvConf, []byte("nameserver")) {
log.Infof("No non-localhost DNS nameservers are left in resolv.conf. Using default external servers : %v", defaultDns)
cleanedResolvConf = append(cleanedResolvConf, []byte("\nnameserver "+strings.Join(defaultDns, "\nnameserver "))...)
cleanedResolvConf := localhostRegexp.ReplaceAll(resolvConf, []byte{})
// if IPv6 is not enabled, also clean out any IPv6 address nameserver
if !ipv6Enabled {
cleanedResolvConf = nsIPv6Regexp.ReplaceAll(cleanedResolvConf, []byte{})
}
// if the resulting resolvConf has no more nameservers defined, add appropriate
// default DNS servers for IPv4 and (optionally) IPv6
if len(GetNameservers(cleanedResolvConf)) == 0 {
log.Infof("No non-localhost DNS nameservers are left in resolv.conf. Using default external servers : %v", defaultIPv4Dns)
dns := defaultIPv4Dns
if ipv6Enabled {
log.Infof("IPv6 enabled; Adding default IPv6 external servers : %v", defaultIPv6Dns)
dns = append(dns, defaultIPv6Dns...)
}
cleanedResolvConf = append(cleanedResolvConf, []byte("\n"+strings.Join(dns, "\n"))...)
}
if !bytes.Equal(resolvConf, cleanedResolvConf) {
changed = true

59
pkg/networkfs/resolvconf/resolvconf_test.go
View file

@ -157,33 +157,82 @@ func TestBuildWithZeroLengthDomainSearch(t *testing.T) {
}
}
func TestRemoveReplaceLocalDns(t *testing.T) {
func TestFilterResolvDns(t *testing.T) {
ns0 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\n"
if result, _ := RemoveReplaceLocalDns([]byte(ns0)); result != nil {
if result, _ := FilterResolvDns([]byte(ns0), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed No Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
ns1 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\nnameserver 127.0.0.1\n"
if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
ns1 = "nameserver 10.16.60.14\nnameserver 127.0.0.1\nnameserver 10.16.60.21\n"
if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
ns1 = "nameserver 127.0.1.1\nnameserver 10.16.60.14\nnameserver 10.16.60.21\n"
if result, _ := RemoveReplaceLocalDns([]byte(ns1)); result != nil {
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
ns1 = "nameserver ::1\nnameserver 10.16.60.14\nnameserver 127.0.2.1\nnameserver 10.16.60.21\n"
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
ns1 = "nameserver 10.16.60.14\nnameserver ::1\nnameserver 10.16.60.21\nnameserver ::1"
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
// with IPv6 disabled (false param), the IPv6 nameserver should be removed
ns1 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\nnameserver ::1"
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost+IPv6 off: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
// with IPv6 enabled, the IPv6 nameserver should be preserved
ns0 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\n"
ns1 = "nameserver 10.16.60.14\nnameserver 2002:dead:beef::1\nnameserver 10.16.60.21\nnameserver ::1"
if result, _ := FilterResolvDns([]byte(ns1), true); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost+IPv6 on: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
// with IPv6 enabled, and no non-localhost servers, Google defaults (both IPv4+IPv6) should be added
ns0 = "\nnameserver 8.8.8.8\nnameserver 8.8.4.4\nnameserver 2001:4860:4860::8888\nnameserver 2001:4860:4860::8844"
ns1 = "nameserver 127.0.0.1\nnameserver ::1\nnameserver 127.0.2.1"
if result, _ := FilterResolvDns([]byte(ns1), true); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed no Localhost+IPv6 enabled: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
// with IPv6 disabled, and no non-localhost servers, Google defaults (only IPv4) should be added
ns0 = "\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
ns1 = "nameserver 127.0.0.1\nnameserver ::1\nnameserver 127.0.2.1"
if result, _ := FilterResolvDns([]byte(ns1), false); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed no Localhost+IPv6 enabled: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
}