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Remove nameserver 127.0.0.1 line rather then dumping resolv.conf

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We have a bug report complaining about docker dumping the contents of the
hosts resolv.conf if it container 127.0.0.1.  They asked that instead
of dropping the file altogether, that we just remove the line.

This patch removes the 127.0.0.1 lines, if they exist and then
checks if any nameserver lines exist.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
This commit is contained in:
Dan Walsh 2014-09-15 15:43:21 -04:00
parent d142b18aab
commit 65640994fd
3 changed files with 43 additions and 0 deletions
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1
daemon/daemon.go
View file

@ -1044,6 +1044,7 @@ func (daemon *Daemon) checkLocaldns() error {
if err != nil {
return err
}
resolvConf = utils.RemoveLocalDns(resolvConf)
if len(daemon.config.Dns) == 0 && utils.CheckLocalDns(resolvConf) {
log.Infof("Local (127.0.0.1) DNS resolver found in resolv.conf and containers can't use it. Using default external servers : %v", DefaultDns)
daemon.config.Dns = DefaultDns

31
daemon/utils_test.go
View file

@ -27,3 +27,34 @@ func TestMergeLxcConfig(t *testing.T) {
t.Fatalf("expected %s got %s", expected, cpuset)
}
}
func TestRemoveLocalDns(t *testing.T) {
ns0 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\n"
if result := utils.RemoveLocalDns([]byte(ns0)); 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 := utils.RemoveLocalDns([]byte(ns1)); 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 := utils.RemoveLocalDns([]byte(ns1)); 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 := utils.RemoveLocalDns([]byte(ns1)); result != nil {
if ns0 != string(result) {
t.Fatalf("Failed Localhost: expected \n<%s> got \n<%s>", ns0, string(result))
}
}
}

11
utils/utils.go
View file

@ -13,6 +13,7 @@ import (
"os"
"os/exec"
"path/filepath"
"regexp"
"runtime"
"strconv"
"strings"
@ -332,6 +333,16 @@ func CheckLocalDns(resolvConf []byte) bool {
return true
}
var (
localHostRx = regexp.MustCompile(`(?m)^nameserver 127[^\n]+\n*`)
)
// RemoveLocalDns looks into the /etc/resolv.conf,
// and removes any local nameserver entries.
func RemoveLocalDns(resolvConf []byte) []byte {
return localHostRx.ReplaceAll(resolvConf, []byte{})
}
// GetLines parses input into lines and strips away comments.
func GetLines(input []byte, commentMarker []byte) [][]byte {
lines := bytes.Split(input, []byte("\n"))