Merge pull request #8047 from rhatdan/RemoveLocalDns

Remove nameserver 127.0.0.1 line rather then dumping resolv.conf

daemon/daemon.go

@@ -1,6 +1,7 @@
 package daemon
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -1044,8 +1045,10 @@ func (daemon *Daemon) checkLocaldns() error {
 	if err != nil {
 		return err
 	}
-	if len(daemon.config.Dns) == 0 && utils.CheckLocalDns(resolvConf) {
+	resolvConf = utils.RemoveLocalDns(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)
+
+	if len(daemon.config.Dns) == 0 && !bytes.Contains(resolvConf, []byte("nameserver")) {
+		log.Infof("No non localhost DNS resolver found in resolv.conf and containers can't use it. Using default external servers : %v", DefaultDns)
 		daemon.config.Dns = DefaultDns
 	}
 	return nil

daemon/utils_test.go

@@ -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))
+		}
+	}
+}

docs/sources/contributing/devenvironment.md

@@ -101,8 +101,6 @@ something like this
     --- PASS: TestParseRepositoryTag (0.00 seconds)
     === RUN TestGetResolvConf
     --- PASS: TestGetResolvConf (0.00 seconds)
-    === RUN TestCheckLocalDns
-    --- PASS: TestCheckLocalDns (0.00 seconds)
     === RUN TestParseRelease
     --- PASS: TestParseRelease (0.00 seconds)
     === RUN TestDependencyGraphCircular

utils/utils.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
@@ -312,39 +313,14 @@ func IsGIT(str string) bool {
 	return strings.HasPrefix(str, "git://") || strings.HasPrefix(str, "github.com/") || strings.HasPrefix(str, "git@github.com:") || (strings.HasSuffix(str, ".git") && IsURL(str))
 }
 
-// CheckLocalDns looks into the /etc/resolv.conf,
+var (
-// it returns true if there is a local nameserver or if there is no nameserver.
+	localHostRx = regexp.MustCompile(`(?m)^nameserver 127[^\n]+\n*`)
-func CheckLocalDns(resolvConf []byte) bool {
+)
-	for _, line := range GetLines(resolvConf, []byte("#")) {
-		if !bytes.Contains(line, []byte("nameserver")) {
-			continue
-		}
-		for _, ip := range [][]byte{
-			[]byte("127.0.0.1"),
-			[]byte("127.0.1.1"),
-		} {
-			if bytes.Contains(line, ip) {
-				return true
-			}
-		}
-		return false
-	}
-	return true
-}
 
-// GetLines parses input into lines and strips away comments.
+// RemoveLocalDns looks into the /etc/resolv.conf,
-func GetLines(input []byte, commentMarker []byte) [][]byte {
+// and removes any local nameserver entries.
-	lines := bytes.Split(input, []byte("\n"))
+func RemoveLocalDns(resolvConf []byte) []byte {
-	var output [][]byte
+	return localHostRx.ReplaceAll(resolvConf, []byte{})
-	for _, currentLine := range lines {
-		var commentIndex = bytes.Index(currentLine, commentMarker)
-		if commentIndex == -1 {
-			output = append(output, currentLine)
-		} else {
-			output = append(output, currentLine[:commentIndex])
-		}
-	}
-	return output
 }
 
 // An StatusError reports an unsuccessful exit by a command.

utils/utils_test.go

@@ -5,35 +5,6 @@ import (
 	"testing"
 )
 
-func TestCheckLocalDns(t *testing.T) {
-	for resolv, result := range map[string]bool{`# Dynamic
-nameserver 10.0.2.3
-search docker.com`: false,
-		`# Dynamic
-#nameserver 127.0.0.1
-nameserver 10.0.2.3
-search docker.com`: false,
-		`# Dynamic
-nameserver 10.0.2.3 #not used 127.0.1.1
-search docker.com`: false,
-		`# Dynamic
-#nameserver 10.0.2.3
-#search docker.com`: true,
-		`# Dynamic
-nameserver 127.0.0.1
-search docker.com`: true,
-		`# Dynamic
-nameserver 127.0.1.1
-search docker.com`: true,
-		`# Dynamic
-`: true,
-		``: true,
-	} {
-		if CheckLocalDns([]byte(resolv)) != result {
-			t.Fatalf("Wrong local dns detection: {%s} should be %v", resolv, result)
-		}
-	}
-}
 func TestReplaceAndAppendEnvVars(t *testing.T) {
 	var (
 		d = []string{"HOME=/"}