From 62e84785b6ffec04a39cf611d7eaff21f2532195 Mon Sep 17 00:00:00 2001
From: Thijs Terlouw <thijsterlouw@gmail.com>
Date: Wed, 21 Aug 2013 15:23:12 +0200
Subject: [PATCH] proper resolv.conf parsing

---
 utils/utils.go      | 22 +++++++++++++++++++---
 utils/utils_test.go | 10 ++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/utils/utils.go b/utils/utils.go
index 6a5beb8e48..a8ed1deebc 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -772,21 +772,37 @@ func GetResolvConf() ([]byte, error) {
 // CheckLocalDns looks into the /etc/resolv.conf,
 // it returns true if there is a local nameserver or if there is no nameserver.
 func CheckLocalDns(resolvConf []byte) bool {
-	if !bytes.Contains(resolvConf, []byte("nameserver")) {
+	var parsedResolvConf = ParseResolvConf(resolvConf)
+	if !bytes.Contains(parsedResolvConf, []byte("nameserver")) {
 		return true
 	}
-
 	for _, ip := range [][]byte{
 		[]byte("127.0.0.1"),
 		[]byte("127.0.1.1"),
 	} {
-		if bytes.Contains(resolvConf, ip) {
+		if bytes.Contains(parsedResolvConf, ip) {
 			return true
 		}
 	}
 	return false
 }
 
+// ParseResolvConf parses the resolv.conf file into lines and strips away comments.
+func ParseResolvConf(resolvConf []byte) []byte {
+	lines := bytes.Split(resolvConf, []byte("\n"))
+	var noCommentsResolvConf []byte
+	for _, currentLine := range lines {
+		var cleanLine = bytes.TrimLeft(currentLine, " \t")
+		var commentIndex = bytes.Index(cleanLine, []byte("#"))
+		if ( commentIndex == -1 ) {
+			noCommentsResolvConf = append(noCommentsResolvConf, cleanLine...)
+		} else {
+			noCommentsResolvConf = append(noCommentsResolvConf, cleanLine[:commentIndex]...)
+		}
+	}
+	return noCommentsResolvConf
+}
+
 func ParseHost(host string, port int, addr string) string {
 	if strings.HasPrefix(addr, "unix://") {
 		return addr
diff --git a/utils/utils_test.go b/utils/utils_test.go
index 1030b2902a..cdf9c87073 100644
--- a/utils/utils_test.go
+++ b/utils/utils_test.go
@@ -323,6 +323,16 @@ func TestCheckLocalDns(t *testing.T) {
 nameserver 10.0.2.3
 search dotcloud.net`: false,
 		`# Dynamic
+#nameserver 127.0.0.1
+nameserver 10.0.2.3
+search dotcloud.net`: false,
+		`# Dynamic
+nameserver 10.0.2.3 #not used 127.0.1.1
+search dotcloud.net`: false,
+		`# Dynamic
+#nameserver 10.0.2.3
+#search dotcloud.net`: true,
+		`# Dynamic
 nameserver 127.0.0.1
 search dotcloud.net`: true,
 		`# Dynamic