plugin/template: fix CNAME upstream handling (#1886)

plugin/template/setup.go

@@ -149,7 +149,7 @@ func templateParse(c *caddy.Controller) (handler Handler, err error) {
 				if err != nil {
 					return handler, err
 				}
-				t.upstream = u
+				t.upstream = &u
 			default:
 				return handler, c.ArgErr()
 			}

plugin/template/template.go

@@ -34,7 +34,7 @@ type template struct {
 	qclass     uint16
 	qtype      uint16
 	fall       fall.F
-	upstream   upstream.Upstream
+	upstream   *upstream.Upstream
 }
 
 type templateData struct {
@@ -84,8 +84,8 @@ func (h Handler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 				return dns.RcodeServerFailure, err
 			}
 			msg.Answer = append(msg.Answer, rr)
-			if rr.Header().Rrtype == dns.TypeCNAME {
-				up, _ := template.upstream.Lookup(state, rr.(*dns.CNAME).Target, dns.TypeA)
+			if template.upstream != nil && (state.QType() == dns.TypeA || state.QType() == dns.TypeAAAA) && rr.Header().Rrtype == dns.TypeCNAME {
+				up, _ := template.upstream.Lookup(state, rr.(*dns.CNAME).Target, state.QType())
 				msg.Answer = append(msg.Answer, up.Answer...)
 			}
 		}

plugin/template/template_test.go

@@ -92,6 +92,14 @@ func TestHandler(t *testing.T) {
 		fall:      fall.Root,
 		zones:     []string{"."},
 	}
+	cnameTemplate := template{
+		regex:  []*regexp.Regexp{regexp.MustCompile("example[.]net[.]")},
+		answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("example.net 60 IN CNAME target.example.com"))},
+		qclass: dns.ClassANY,
+		qtype:  dns.TypeANY,
+		fall:   fall.Root,
+		zones:  []string{"."},
+	}
 
 	tests := []struct {
 		tmpl           template
@@ -254,6 +262,20 @@ func TestHandler(t *testing.T) {
 				return nil
 			},
 		},
+		{
+			name:         "CNAMEWithoutUpstream",
+			tmpl:         cnameTemplate,
+			qclass:       dns.ClassINET,
+			qtype:        dns.TypeA,
+			qname:        "example.net.",
+			expectedCode: dns.RcodeSuccess,
+			verifyResponse: func(r *dns.Msg) error {
+				if len(r.Answer) != 1 {
+					return fmt.Errorf("expected 1 answer, got %v", len(r.Answer))
+				}
+				return nil
+			},
+		},
 	}
 
 	ctx := context.TODO()

test/template_upstream_test.go

+package test
+
+import (
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+func TestTemplateUpstream(t *testing.T) {
+	corefile := `.:0 {
+ 		# CNAME
+		template IN ANY cname.example.net. {
+			match ".*"
+			answer "cname.example.net. 60 IN CNAME target.example.net."
+			upstream
+		}
+
+		# Target
+		template IN A target.example.net. {
+			match ".*"
+			answer "target.example.net. 60 IN A 1.2.3.4"
+		}
+}
+`
+	i, udp, _, err := CoreDNSServerAndPorts(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+	defer i.Stop()
+
+	// Test that an A query returns a CNAME and an A record
+	m := new(dns.Msg)
+	m.SetQuestion("cname.example.net.", dns.TypeA)
+	m.SetEdns0(4096, true) // need this?
+
+	r, err := dns.Exchange(m, udp)
+	if err != nil {
+		t.Fatalf("Could not send msg: %s", err)
+	}
+	if r.Rcode == dns.RcodeServerFailure {
+		t.Fatalf("Rcode should not be dns.RcodeServerFailure")
+	}
+	if len(r.Answer) < 2 {
+		t.Fatalf("Expected 2 answers, got %v", len(r.Answer))
+	}
+	if x := r.Answer[0].(*dns.CNAME).Target; x != "target.example.net." {
+		t.Fatalf("Failed to get address for CNAME, expected target.example.net. got %s", x)
+	}
+	if x := r.Answer[1].(*dns.A).A.String(); x != "1.2.3.4" {
+		t.Fatalf("Failed to get address for CNAME, expected 1.2.3.4 got %s", x)
+	}
+
+	// Test that a CNAME query only returns a CNAME
+	m = new(dns.Msg)
+	m.SetQuestion("cname.example.net.", dns.TypeCNAME)
+	m.SetEdns0(4096, true) // need this?
+
+	r, err = dns.Exchange(m, udp)
+	if err != nil {
+		t.Fatalf("Could not send msg: %s", err)
+	}
+	if r.Rcode == dns.RcodeServerFailure {
+		t.Fatalf("Rcode should not be dns.RcodeServerFailure")
+	}
+	if len(r.Answer) < 1 {
+		t.Fatalf("Expected 1 answer, got %v", len(r.Answer))
+	}
+	if x := r.Answer[0].(*dns.CNAME).Target; x != "target.example.net." {
+		t.Fatalf("Failed to get address for CNAME, expected target.example.net. got %s", x)
+	}
+}