[Doh] special meta QTYPEs
Tony Finch <dot@dotat.at> Wed, 06 June 2018 14:49 UTC
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Date: Wed, 06 Jun 2018 15:49:40 +0100
From: Tony Finch <dot@dotat.at>
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Subject: [Doh] special meta QTYPEs
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I think there needs to be some specific wording about query meta-types (i.e. 128 <= QTYPE <= 255). Meta-types can change the framing rules of the response, e.g. IXFR and AXFR, so a DoH server needs to understand them even if it is implemented as a mostly-blind proxy. My DoH implementation generates its own NOTIMP response if it gets a query with 128 <= QTYPE <= 254 (it allows QTYPE=*/ANY). The other meta type is OPT, but it isn't special-cased because it's safe to proxy. BIND returns FORMERR rather than NOTIMP for unknown meta-types; it seems to reserve NOTIMP for known but deprecated types. I think it is reasonable for an implementation to support TKEY or MAILA or MAILB if it wishes. I don't think it's possible to fit AXFR or IXFR into DoH because their responses involve multiple DNS messages. Suggested wording: A DoH server MUST return a DNS error response, either RCODE=1 (format error) or RCODE=4 (not implemented) if it receives a request with an unknown meta-QTYPE between 128 and 254 inclusive. The meta-QTYPE 255 (* or ANY) SHOULD be supported. The meta-QTYPEs 251 (IXFR) and 252 (AXFR) MUST NOT be supported and the DoH server MUST return an error response. This is because meta-QTYPEs can affect the way a DNS response is framed; for example, AXFR and IXFR responses can span multiple DNS messages, whereas A DoH response can only contain one DNS message. Tony. -- f.anthony.n.finch <dot@dotat.at> http://dotat.at/ Humber: Variable mainly north, 3 or 4. Moderate at first in northwest, otherwise slight. Fog patches. Moderate or good, occasionally very poor.
- [Doh] special meta QTYPEs Tony Finch
- Re: [Doh] special meta QTYPEs Ben Schwartz
- Re: [Doh] special meta QTYPEs Tony Finch
- Re: [Doh] special meta QTYPEs Dave Lawrence
- Re: [Doh] special meta QTYPEs Tony Finch
- Re: [Doh] special meta QTYPEs Martin Thomson
- Re: [Doh] special meta QTYPEs Tony Finch