// check with what kind of RR header we are dealing with
        // I'm sitting on the start byte of the name, with off?
        // ifso I can check the. From RFC 1035 4.1.4
        //  The first two bits are ones.  This allows a pointer to be distinguished
        //  from a label, since the label must begin with two zero bits because
        //  labels are restricted to 63 octets or less.  (The 10 and 01 combinations
        //  are reserved for future use.)
        // EDNS takes 01
        c := int(msg[off])
        switch c & 0xC0 {
        case 0x00,0xC0:
               // normal name
                // pack twice, once to find end of header
                // and again to find end of packet.
                // a bit inefficient but this doesn't need to be fast.
                // off1 is end of header
                // off2 is end of rr
                off1, ok = packStruct(rr.Header(), msg, off)
                off2, ok = packStruct(rr, msg, off)
                if !ok {
                        return len(msg), false
                }   
                // pack a third time; redo header with correct data length
                rr.Header().Rdlength = uint16(off2 - off1)
                packStruct(rr.Header(), msg, off)
                return off2, true
         case 0x40:
                // EDNS0 header
                return 0,true
        }   
        return 0, true  // BUG in Go
}