diff --git a/networkfs/resolvconf/resolvconf.go b/networkfs/resolvconf/resolvconf.go new file mode 100644 index 0000000..d6854fb --- /dev/null +++ b/networkfs/resolvconf/resolvconf.go @@ -0,0 +1,87 @@ +package resolvconf + +import ( + "bytes" + "io/ioutil" + "regexp" + "strings" +) + +func Get() ([]byte, error) { + resolv, err := ioutil.ReadFile("/etc/resolv.conf") + if err != nil { + return nil, err + } + return resolv, nil +} + +// getLines parses input into lines and strips away comments. +func getLines(input []byte, commentMarker []byte) [][]byte { + lines := bytes.Split(input, []byte("\n")) + var output [][]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 +} + +// GetNameservers returns nameservers (if any) listed in /etc/resolv.conf +func GetNameservers(resolvConf []byte) []string { + nameservers := []string{} + re := regexp.MustCompile(`^\s*nameserver\s*(([0-9]+\.){3}([0-9]+))\s*$`) + for _, line := range getLines(resolvConf, []byte("#")) { + var ns = re.FindSubmatch(line) + if len(ns) > 0 { + nameservers = append(nameservers, string(ns[1])) + } + } + return nameservers +} + +// GetNameserversAsCIDR returns nameservers (if any) listed in +// /etc/resolv.conf as CIDR blocks (e.g., "1.2.3.4/32") +// This function's output is intended for net.ParseCIDR +func GetNameserversAsCIDR(resolvConf []byte) []string { + nameservers := []string{} + for _, nameserver := range GetNameservers(resolvConf) { + nameservers = append(nameservers, nameserver+"/32") + } + return nameservers +} + +// GetSearchDomains returns search domains (if any) listed in /etc/resolv.conf +// If more than one search line is encountered, only the contents of the last +// one is returned. +func GetSearchDomains(resolvConf []byte) []string { + re := regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`) + domains := []string{} + for _, line := range getLines(resolvConf, []byte("#")) { + match := re.FindSubmatch(line) + if match == nil { + continue + } + domains = strings.Fields(string(match[1])) + } + return domains +} + +func Build(path string, dns, dnsSearch []string) error { + content := bytes.NewBuffer(nil) + for _, dns := range dns { + if _, err := content.WriteString("nameserver " + dns + "\n"); err != nil { + return err + } + } + if len(dnsSearch) > 0 { + if _, err := content.WriteString("search " + strings.Join(dnsSearch, " ") + "\n"); err != nil { + return err + } + } + + return ioutil.WriteFile(path, content.Bytes(), 0644) +} diff --git a/networkfs/resolvconf/resolvconf_test.go b/networkfs/resolvconf/resolvconf_test.go new file mode 100644 index 0000000..fd20712 --- /dev/null +++ b/networkfs/resolvconf/resolvconf_test.go @@ -0,0 +1,133 @@ +package resolvconf + +import ( + "bytes" + "io/ioutil" + "os" + "testing" +) + +func TestGet(t *testing.T) { + resolvConfUtils, err := Get() + if err != nil { + t.Fatal(err) + } + resolvConfSystem, err := ioutil.ReadFile("/etc/resolv.conf") + if err != nil { + t.Fatal(err) + } + if string(resolvConfUtils) != string(resolvConfSystem) { + t.Fatalf("/etc/resolv.conf and GetResolvConf have different content.") + } +} + +func TestGetNameservers(t *testing.T) { + for resolv, result := range map[string][]string{` +nameserver 1.2.3.4 +nameserver 40.3.200.10 +search example.com`: {"1.2.3.4", "40.3.200.10"}, + `search example.com`: {}, + `nameserver 1.2.3.4 +search example.com +nameserver 4.30.20.100`: {"1.2.3.4", "4.30.20.100"}, + ``: {}, + ` nameserver 1.2.3.4 `: {"1.2.3.4"}, + `search example.com +nameserver 1.2.3.4 +#nameserver 4.3.2.1`: {"1.2.3.4"}, + `search example.com +nameserver 1.2.3.4 # not 4.3.2.1`: {"1.2.3.4"}, + } { + test := GetNameservers([]byte(resolv)) + if !strSlicesEqual(test, result) { + t.Fatalf("Wrong nameserver string {%s} should be %v. Input: %s", test, result, resolv) + } + } +} + +func TestGetNameserversAsCIDR(t *testing.T) { + for resolv, result := range map[string][]string{` +nameserver 1.2.3.4 +nameserver 40.3.200.10 +search example.com`: {"1.2.3.4/32", "40.3.200.10/32"}, + `search example.com`: {}, + `nameserver 1.2.3.4 +search example.com +nameserver 4.30.20.100`: {"1.2.3.4/32", "4.30.20.100/32"}, + ``: {}, + ` nameserver 1.2.3.4 `: {"1.2.3.4/32"}, + `search example.com +nameserver 1.2.3.4 +#nameserver 4.3.2.1`: {"1.2.3.4/32"}, + `search example.com +nameserver 1.2.3.4 # not 4.3.2.1`: {"1.2.3.4/32"}, + } { + test := GetNameserversAsCIDR([]byte(resolv)) + if !strSlicesEqual(test, result) { + t.Fatalf("Wrong nameserver string {%s} should be %v. Input: %s", test, result, resolv) + } + } +} + +func TestGetSearchDomains(t *testing.T) { + for resolv, result := range map[string][]string{ + `search example.com`: {"example.com"}, + `search example.com # ignored`: {"example.com"}, + ` search example.com `: {"example.com"}, + ` search example.com # ignored`: {"example.com"}, + `search foo.example.com example.com`: {"foo.example.com", "example.com"}, + ` search foo.example.com example.com `: {"foo.example.com", "example.com"}, + ` search foo.example.com example.com # ignored`: {"foo.example.com", "example.com"}, + ``: {}, + `# ignored`: {}, + `nameserver 1.2.3.4 +search foo.example.com example.com`: {"foo.example.com", "example.com"}, + `nameserver 1.2.3.4 +search dup1.example.com dup2.example.com +search foo.example.com example.com`: {"foo.example.com", "example.com"}, + `nameserver 1.2.3.4 +search foo.example.com example.com +nameserver 4.30.20.100`: {"foo.example.com", "example.com"}, + } { + test := GetSearchDomains([]byte(resolv)) + if !strSlicesEqual(test, result) { + t.Fatalf("Wrong search domain string {%s} should be %v. Input: %s", test, result, resolv) + } + } +} + +func strSlicesEqual(a, b []string) bool { + if len(a) != len(b) { + return false + } + + for i, v := range a { + if v != b[i] { + return false + } + } + + return true +} + +func TestBuild(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{"search1"}) + 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\nsearch search1\n"; !bytes.Contains(content, []byte(expected)) { + t.Fatalf("Expected to find '%s' got '%s'", expected, content) + } +}