From 74071a4fba0eeafab6202bbab2555df811265190 Mon Sep 17 00:00:00 2001
From: Fabio Falci <fabiofalci@gmail.com>
Date: Thu, 26 Jun 2014 12:03:23 +0100
Subject: [PATCH] Relax dns search to accept empty domain

In that case /etc/resolv.conf will be generated with no search
option. Usage: --dns-search=.

Docker-DCO-1.1-Signed-off-by: Fabio Falci <fabiofalci@gmail.com> (github: fabiofalci)
---
 networkfs/resolvconf/resolvconf.go      |  6 ++++--
 networkfs/resolvconf/resolvconf_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/networkfs/resolvconf/resolvconf.go b/networkfs/resolvconf/resolvconf.go
index d6854fb..38ae564 100644
--- a/networkfs/resolvconf/resolvconf.go
+++ b/networkfs/resolvconf/resolvconf.go
@@ -78,8 +78,10 @@ func Build(path string, dns, dnsSearch []string) error {
 		}
 	}
 	if len(dnsSearch) > 0 {
-		if _, err := content.WriteString("search " + strings.Join(dnsSearch, " ") + "\n"); err != nil {
-			return err
+		if searchString := strings.Join(dnsSearch, " "); strings.Trim(searchString, " ") != "." {
+			if _, err := content.WriteString("search " + searchString + "\n"); err != nil {
+				return err
+			}
 		}
 	}
 
diff --git a/networkfs/resolvconf/resolvconf_test.go b/networkfs/resolvconf/resolvconf_test.go
index fd20712..6187acb 100644
--- a/networkfs/resolvconf/resolvconf_test.go
+++ b/networkfs/resolvconf/resolvconf_test.go
@@ -131,3 +131,28 @@ func TestBuild(t *testing.T) {
 		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
 	}
 }
+
+func TestBuildWithZeroLengthDomainSearch(t *testing.T) {
+	file, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(file.Name())
+
+	err = Build(file.Name(), []string{"ns1", "ns2", "ns3"}, []string{"."})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	content, err := ioutil.ReadFile(file.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if expected := "nameserver ns1\nnameserver ns2\nnameserver ns3\n"; !bytes.Contains(content, []byte(expected)) {
+		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
+	}
+	if notExpected := "search ."; bytes.Contains(content, []byte(notExpected)) {
+		t.Fatalf("Expected to not find '%s' got '%s'", notExpected, content)
+	}
+}