Re: [DNSOP] draft-ietf-dnsop-extended-error code options

Tony Finch <dot@dotat.at> Mon, 13 November 2017 13:13 UTC

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Date: Mon, 13 Nov 2017 13:13:22 +0000
From: Tony Finch <dot@dotat.at>
To: Ray Bellis <ray@bellis.me.uk>
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Subject: Re: [DNSOP] draft-ietf-dnsop-extended-error code options
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Ray Bellis <ray@bellis.me.uk> wrote:
>
> Would it be feasible to reserve a standard RCODE value in the header
> that just means "see extended error"?

That would require client-to-server signalling, and the server would be
unable to simply unconditionally include the extended error in the OPT
record.

> It has always kinda surprised me that the EDNS RCODE didn't work that
> way, instead of the current situation where if you only read the bottom
> 4 bits of the extended 12-bit code you could completely misinterpret the
> status (e.g. treat BADVER[16] as NOERROR[0], since the bottom four bits
> are all zeros for both).

There can only be an EDNS RCODE if the client sent an EDNS OPT; if the
client forgot it sent the OPT then it's too broken to worry about.

Tony.
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