On Thu, Jul 27, 2023 at 09:11:33AM +1000, George Michaelson wrote:
> if QDCOUNT is defined as [0|1] then we have 15 new bits of freedom in
> the header.
We don't actually have that freedom. There's no mechanism to make those
bits mean something other than a larger (invalid QDCOUNT) for a normal
query.
> maybe the truth is, we've got 15 bits of zero in the header forever, amen.
This. There's nothing we can do with the "extra bits" (and even if we
could, that wouldn't better be done with a suitable EDNS(0) extension).
The meaning of the message of course depends on the OPCODE. A new
OPCODE can bring in new semantics for the rest of the packet.
--
Viktor.
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