Fix Tsig parsing

msg.go

@@ -598,6 +598,25 @@ func unpackStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int,
 					fmt.Fprintf(os.Stderr, "dns: failure unpacking domain-name")
 					return len(msg), false
 				}
+			case "fixed-size":
+				// We should already know how many bytes we can expect
+				// TODO(mg) pack variant
+                                println(val.Type().Name())
+                                println(f.Name) // MAC Otherdata, then get back the 
+                                //f := val.Type().(*reflect.StructType).Field(i)
+                                //FieldByName(MACSize), Othersize to get the stuff we need
+				var size int
+				//	consumed += len(val.FieldByName("SignerName").(*reflect.StringValue).Get()) + 1
+				switch val.Type().Name() {
+				case "RR_TSIG":
+					// tsig has MACSize
+					size = 16 // TODO(mg) other hashes
+				}
+				if off+size > len(msg) {
+					fmt.Fprintf(os.Stderr, "dns: failure unpacking fixed-size string")
+					return len(msg), false
+				}
+				s = string(msg[off : off+size])
 			case "":
 				if off >= len(msg) || off+1+int(msg[off]) > len(msg) {
 					fmt.Fprintf(os.Stderr, "dns: failure unpacking string")

tsig.go

@@ -22,11 +22,11 @@ type RR_TSIG struct {
 	TimeSigned uint64
 	Fudge      uint16
 	MACSize    uint16
-	MAC        string
+	MAC        string "fixed-size"
 	OrigId     uint16
 	Error      uint16
 	OtherLen   uint16
-	OtherData  string
+	OtherData  string "fixed-size"
 }
 
 func (rr *RR_TSIG) Header() *RR_Header {
@@ -35,6 +35,7 @@ func (rr *RR_TSIG) Header() *RR_Header {
 
 func (rr *RR_TSIG) String() string {
 	// It has no official presentation format
+	println("mac len: ", rr.MACSize)
 	return rr.Hdr.String() +
 		" " + rr.Algorithm +
 		" " + tsigTimeToDate(rr.TimeSigned) +