middleware/log: allows logging based on response classes (#325)

Add the ability to add a class of responses to be logged; success,
denial or error. The default is to log everything (all).

Fixes #258

middleware/log/log_test.go

@@ -7,21 +7,15 @@ import (
 	"testing"
 
 	"github.com/miekg/coredns/middleware/pkg/dnsrecorder"
+	"github.com/miekg/coredns/middleware/pkg/response"
 	"github.com/miekg/coredns/middleware/test"
 
 	"github.com/miekg/dns"
 	"golang.org/x/net/context"
 )
 
-type erroringMiddleware struct{}
-
-func (erroringMiddleware) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
-	return dns.RcodeServerFailure, nil
-}
-
 func TestLoggedStatus(t *testing.T) {
 	var f bytes.Buffer
-	var next erroringMiddleware
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
@@ -30,7 +24,7 @@ func TestLoggedStatus(t *testing.T) {
 
 	logger := Logger{
 		Rules: []Rule{rule},
-		Next:  next,
+		Next:  test.ErrorHandler(),
 	}
 
 	ctx := context.TODO()
@@ -41,11 +35,67 @@ func TestLoggedStatus(t *testing.T) {
 
 	rcode, _ := logger.ServeDNS(ctx, rec, r)
 	if rcode != 0 {
-		t.Error("Expected rcode to be 0 - was", rcode)
+		t.Errorf("Expected rcode to be 0 - was: %d", rcode)
 	}
 
 	logged := f.String()
 	if !strings.Contains(logged, "A IN example.org. udp false 512") {
-		t.Error("Expected it to be logged. Logged string -", logged)
+		t.Errorf("Expected it to be logged. Logged string: %s", logged)
+	}
+}
+
+func TestLoggedClassDenial(t *testing.T) {
+	var f bytes.Buffer
+	rule := Rule{
+		NameScope: ".",
+		Format:    DefaultLogFormat,
+		Log:       log.New(&f, "", 0),
+		Class:     response.Denial,
+	}
+
+	logger := Logger{
+		Rules: []Rule{rule},
+		Next:  test.ErrorHandler(),
+	}
+
+	ctx := context.TODO()
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnsrecorder.New(&test.ResponseWriter{})
+
+	logger.ServeDNS(ctx, rec, r)
+
+	logged := f.String()
+	if len(logged) != 0 {
+		t.Errorf("Expected it not to be logged, but got string: %s", logged)
+	}
+}
+
+func TestLoggedClassError(t *testing.T) {
+	var f bytes.Buffer
+	rule := Rule{
+		NameScope: ".",
+		Format:    DefaultLogFormat,
+		Log:       log.New(&f, "", 0),
+		Class:     response.Error,
+	}
+
+	logger := Logger{
+		Rules: []Rule{rule},
+		Next:  test.ErrorHandler(),
+	}
+
+	ctx := context.TODO()
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnsrecorder.New(&test.ResponseWriter{})
+
+	logger.ServeDNS(ctx, rec, r)
+
+	logged := f.String()
+	if !strings.Contains(logged, "SERVFAIL") {
+		t.Errorf("Expected it to be logged. Logged string: %s", logged)
 	}
 }