1. docker
  2. Commit 65640994fda8e1667de3642d8f4daf76dd3de302
Browse code

Remove nameserver 127.0.0.1 line rather then dumping resolv.conf

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)

Dan Walsh authored on 2014/09/16 04:43:21
Showing 3 changed files
daemon/daemon.go
History View file @ 6564099
... ... 
@@ -1044,6 +1044,7 @@ func (daemon *Daemon) checkLocaldns() error {
1044 1044 
 	if err != nil {
1045 1045 
 		return err
1046 1046 
 	}
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+	resolvConf = utils.RemoveLocalDns(resolvConf)
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 	if len(daemon.config.Dns) == 0 && utils.CheckLocalDns(resolvConf) {
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 		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)
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 		daemon.config.Dns = DefaultDns
daemon/utils_test.go
History View file @ 6564099
... ... 
@@ -27,3 +27,34 @@ func TestMergeLxcConfig(t *testing.T) {
27 27 
 		t.Fatalf("expected %s got %s", expected, cpuset)
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 	}
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 }
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+
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+func TestRemoveLocalDns(t *testing.T) {
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+	ns0 := "nameserver 10.16.60.14\nnameserver 10.16.60.21\n"
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+
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+	if result := utils.RemoveLocalDns([]byte(ns0)); 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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+
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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 := utils.RemoveLocalDns([]byte(ns1)); 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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+
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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 := utils.RemoveLocalDns([]byte(ns1)); 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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+
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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 := utils.RemoveLocalDns([]byte(ns1)); 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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+}
utils/utils.go
History View file @ 6564099
... ... 
@@ -13,6 +13,7 @@ import (
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 	"os"
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 	"os/exec"
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 	"path/filepath"
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+	"regexp"
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 	"runtime"
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 	"strconv"
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 	"strings"
... ... 
@@ -332,6 +333,16 @@ func CheckLocalDns(resolvConf []byte) bool {
332 332 
 	return true
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 }
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+var (
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+	localHostRx = regexp.MustCompile(`(?m)^nameserver 127[^\n]+\n*`)
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+)
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+
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+// RemoveLocalDns looks into the /etc/resolv.conf,
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+// and removes any local nameserver entries.
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+func RemoveLocalDns(resolvConf []byte) []byte {
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+	return localHostRx.ReplaceAll(resolvConf, []byte{})
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+}
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+
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 // GetLines parses input into lines and strips away comments.
336 346 
 func GetLines(input []byte, commentMarker []byte) [][]byte {
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 	lines := bytes.Split(input, []byte("\n"))