Fix ignored last line of resolv.conf

When ClientConfigFromFile is given a file that is missing a newline
before EOF, then the last directive is completely ignored.

This also adds a very basic test for a normal resolv.conf parsing.

clientconfig.go

@@ -26,14 +26,19 @@ func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
 	}
 	defer file.Close()
 	c := new(ClientConfig)
-	b := bufio.NewReader(file)
+	scanner := bufio.NewScanner(file)
 	c.Servers = make([]string, 0)
 	c.Search = make([]string, 0)
 	c.Port = "53"
 	c.Ndots = 1
 	c.Timeout = 5
 	c.Attempts = 2
-	for line, ok := b.ReadString('\n'); ok == nil; line, ok = b.ReadString('\n') {
+
+	for scanner.Scan() {
+		if err := scanner.Err(); err != nil {
+			return nil, err
+		}
+		line := scanner.Text()
 		f := strings.Fields(line)
 		if len(f) < 1 {
 			continue

clientconfig_test.go

@@ -0,0 +1,61 @@
+package dns
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+const normal string = `
+# This file is automatically generated.
+#
+domain somedomain.com
+nameserver 10.28.10.2
+nameserver 11.28.10.1
+`
+
+const missingNewline string = `
+# This file is automatically generated.
+#
+domain somedomain.com
+nameserver 10.28.10.2
+nameserver 11.28.10.1` // <- NOTE: NO newline.
+
+func testConfig(t *testing.T, data string) {
+	tempDir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("TempDir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	path := filepath.Join(tempDir, "resolv.conf")
+	if err := ioutil.WriteFile(path, []byte(data), 0644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+	cc, err := ClientConfigFromFile(path)
+	if err != nil {
+		t.Errorf("error parsing resolv.conf: %s", err)
+	}
+	if l := len(cc.Servers); l != 2 {
+		t.Errorf("incorrect number of nameservers detected: %d", l)
+	}
+	if l := len(cc.Search); l != 1 {
+		t.Errorf("domain directive not parsed correctly: %v", cc.Search)
+	} else {
+		if cc.Search[0] != "somedomain.com" {
+			t.Errorf("domain is unexpected: %v", cc.Search[0])
+		}
+	}
+}
+
+// Test we can read a normally formed resolv.conf.
+func TestNameserver(t *testing.T) {
+	testConfig(t, normal)
+}
+
+// Don't drop the last line if there is no newline before EOF.
+func TestMissingFinalNewLine(t *testing.T) {
+	testConfig(t, missingNewline)
+
+}