Add test covering unpacking 0-length rdatas

update_test.go

@@ -1,8 +1,6 @@
 package dns
 
-import (
-	"testing"
-)
+import "testing"
 
 func TestDynamicUpdateParsing(t *testing.T) {
 	prefix := "example.com. IN "
@@ -34,3 +32,23 @@ func TestDynamicUpdateUnpack(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func TestDynamicUpdateZeroRdataUnpack(t *testing.T) {
+	m := new(Msg)
+	rr := &RR_Header{Name: ".", Rrtype: 0, Class: 1, Ttl: ^uint32(0), Rdlength: 0}
+	m.Answer = []RR{rr, rr, rr, rr, rr}
+	m.Ns = m.Answer
+	for n, s := range TypeToString {
+		rr.Rrtype = n
+		bytes, err := m.Pack()
+		if err != nil {
+			t.Logf("failed to pack %s: %v", s, err)
+			t.Fail()
+			continue
+		}
+		if err := new(Msg).Unpack(bytes); err != nil {
+			t.Logf("failed to unpack %s: %v", s, err)
+			t.Fail()
+		}
+	}
+}