add etchosts

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)

networkfs/MAINTAINERS

@@ -0,0 +1 @@
+Victor Vieux <victor.vieux@docker.com> (@vieux)

networkfs/etchosts/etchosts.go

@@ -0,0 +1,34 @@
+package etchosts
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+)
+
+var defaultContent = map[string]string{
+	"localhost":                            "127.0.0.1",
+	"localhost ip6-localhost ip6-loopback": "::1",
+	"ip6-localnet":                         "fe00::0",
+	"ip6-mcastprefix":                      "ff00::0",
+	"ip6-allnodes":                         "ff02::1",
+	"ip6-allrouters":                       "ff02::2",
+}
+
+func Build(path, IP, hostname, domainname string) error {
+	content := bytes.NewBuffer(nil)
+	if IP != "" {
+		if domainname != "" {
+			content.WriteString(fmt.Sprintf("%s\t%s.%s %s\n", IP, hostname, domainname, hostname))
+		} else {
+			content.WriteString(fmt.Sprintf("%s\t%s\n", IP, hostname))
+		}
+	}
+
+	for hosts, ip := range defaultContent {
+		if _, err := content.WriteString(fmt.Sprintf("%s\t%s\n", ip, hosts)); err != nil {
+			return err
+		}
+	}
+	return ioutil.WriteFile(path, content.Bytes(), 0644)
+}

networkfs/etchosts/etchosts_test.go

@@ -0,0 +1,74 @@
+package etchosts
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestBuildHostnameDomainname(t *testing.T) {
+	file, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(file.Name())
+
+	err = Build(file.Name(), "10.11.12.13", "testhostname", "testdomainname")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	content, err := ioutil.ReadFile(file.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if expected := "10.11.12.13\ttesthostname.testdomainname testhostname\n"; !bytes.Contains(content, []byte(expected)) {
+		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
+	}
+}
+
+func TestBuildHostname(t *testing.T) {
+	file, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(file.Name())
+
+	err = Build(file.Name(), "10.11.12.13", "testhostname", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	content, err := ioutil.ReadFile(file.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if expected := "10.11.12.13\ttesthostname\n"; !bytes.Contains(content, []byte(expected)) {
+		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
+	}
+}
+
+func TestBuildNoIP(t *testing.T) {
+	file, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(file.Name())
+
+	err = Build(file.Name(), "", "testhostname", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	content, err := ioutil.ReadFile(file.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if expected := ""; !bytes.Contains(content, []byte(expected)) {
+		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
+	}
+}