Add test to zero rdata (for dyn updates)

This triggerd a bunch of failures, the most important one
is the packing and zero length domain name now works.

TODO.markdown

@@ -3,6 +3,8 @@
 * Support for on-the-fly-signing or check how to do it
 * Test all rdata packing with zero rdata -- allowed for dynamic updates
 * Actually mimic net/ ? Dial. Read/Write ?
+    - if I want this i need to work on something else than \*Client, because a single client
+      can have multiple oustanding qeuries
 * Ratelimiting? server side (rrl)
 * Ratelimiting? client side
 

dns_test.go

@@ -243,12 +243,12 @@ func TestToRFC3597(t *testing.T) {
 
 func TestNoRdata(t *testing.T) {
 	data := make([]byte, 1024)
-	for typ, _ := range TypeToString {
-		r := rr_mk[typ]()
+	for typ, fn := range rr_mk {
+		r := fn()
 		*r.Header() = RR_Header{Name: "miek.nl.", Rrtype: typ, Class: ClassINET, Ttl: 3600}
 		_, e := PackRR(r, data, 0, nil, false)
 		if e != nil {
-			t.Logf("Failed to pack rdata zero RR %d: %s\n", typ, e.Error())
+			t.Logf("Failed to pack rdata zero RR %s: %s\n", TypeToString[typ], e.Error())
 			t.Fail()
 		}
 	}

msg.go

@@ -214,8 +214,11 @@ var RcodeToString = map[int]string{
 func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
 	lenmsg := len(msg)
 	ls := len(s)
+	if ls == 0 { // Ok, for instance when dealing with update RR without any rdata.
+		return off, nil
+	}
 	// If not fully qualified, error out
-	if ls == 0 || s[ls-1] != '.' {
+	if s[ls-1] != '.' {
 		return lenmsg, ErrFqdn
 	}
 	// Each dot ends a segment of the name.
@@ -468,7 +471,9 @@ func packStructValue(val reflect.Value, msg []byte, off int, compression map[str
 					return lenmsg, &Error{err: "overflow packing a"}
 				}
 			case `dns:"aaaa"`:
-				// fv.Len TODO(mg) dynamic updates?
+				if fv.Len() == 0 {
+					break
+				}
 				if fv.Len() > net.IPv6len || off+fv.Len() > lenmsg {
 					return lenmsg, &Error{err: "overflow packing aaaa"}
 				}

types.go

@@ -884,8 +884,8 @@ func (rr *TA) len() int {
 
 type TALINK struct {
 	Hdr          RR_Header
-	PreviousName string `dns:"domain"`
-	NextName     string `dns:"domain"`
+	PreviousName string `dns:"domain-name"`
+	NextName     string `dns:"domain-name"`
 }
 
 func (rr *TALINK) Header() *RR_Header { return &rr.Hdr }