Add option to parse resolv.conf for proxy upstreams (#353)

* Add option to parse resolv.conf for proxy upstreams

* Add test and README update for resolv.conf proxy

* Run gofmt

middleware/proxy/upstream_test.go

@@ -1,6 +1,10 @@
 package proxy
 
 import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -78,6 +82,19 @@ func TestAllowedPaths(t *testing.T) {
 	}
 }
 
+func writeTmpFile(t *testing.T, data string) (string, string) {
+	tempDir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("tempDir: %v", err)
+	}
+
+	path := filepath.Join(tempDir, "resolv.conf")
+	if err := ioutil.WriteFile(path, []byte(data), 0644); err != nil {
+		t.Fatalf("writeFile: %v", err)
+	}
+	return tempDir, path
+}
+
 func TestProxyParse(t *testing.T) {
 	tests := []struct {
 		inputUpstreams string
@@ -143,6 +160,11 @@ proxy . 8.8.8.8:53 {
 }`,
 			true,
 		},
+		{
+			`
+proxy . some_bogus_filename`,
+			true,
+		},
 	}
 	for i, test := range tests {
 		c := caddy.NewTestController("dns", test.inputUpstreams)
@@ -152,3 +174,79 @@ proxy . 8.8.8.8:53 {
 		}
 	}
 }
+
+func TestResolvParse(t *testing.T) {
+	tests := []struct {
+		inputUpstreams string
+		filedata       string
+		shouldErr      bool
+		expected       []string
+	}{
+		{
+			`
+proxy . FILE
+`,
+			`
+nameserver 1.2.3.4
+nameserver 4.3.2.1
+`,
+			false,
+			[]string{"1.2.3.4:53", "4.3.2.1:53"},
+		},
+		{
+			`
+proxy example.com 1.1.1.1:5000
+proxy . FILE
+proxy example.org 2.2.2.2:1234
+`,
+			`
+nameserver 1.2.3.4
+`,
+			false,
+			[]string{"1.1.1.1:5000", "1.2.3.4:53", "2.2.2.2:1234"},
+		},
+		{
+			`
+proxy example.com 1.1.1.1:5000
+proxy . FILE
+proxy example.org 2.2.2.2:1234
+`,
+			`
+junky resolve.conf
+`,
+			false,
+			[]string{"1.1.1.1:5000", "2.2.2.2:1234"},
+		},
+	}
+	for i, test := range tests {
+		tempDir, path := writeTmpFile(t, test.filedata)
+		defer os.RemoveAll(tempDir)
+		config := strings.Replace(test.inputUpstreams, "FILE", path, -1)
+		c := caddy.NewTestController("dns", config)
+		upstreams, err := NewStaticUpstreams(&c.Dispenser)
+		if (err != nil) != test.shouldErr {
+			t.Errorf("Test %d expected no error, got %v", i+1, err)
+		}
+		var hosts []string
+		for _, u := range upstreams {
+			for _, h := range u.(*staticUpstream).Hosts {
+				hosts = append(hosts, h.Name)
+			}
+		}
+		if !test.shouldErr {
+			if len(hosts) != len(test.expected) {
+				t.Errorf("Test %d expected %d hosts got %d", i+1, len(test.expected), len(upstreams))
+			} else {
+				ok := true
+				for i, v := range test.expected {
+					if v != hosts[i] {
+						ok = false
+					}
+				}
+				if !ok {
+					t.Errorf("Test %d expected %v got %v", i+1, test.expected, upstreams)
+				}
+			}
+		}
+	}
+}