Do DNS resolvers choke if a question contains RRs in the additional section? Are they supposed to?
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Replying to @jedisct1
EDNS stuff goes into the additional section. See https://en.wikipedia.org/wiki/Extension_mechanisms_for_DNS …
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That states unknown OPT records should ignored. No mention of what to do with other resource records.
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A resolver that does not understand EDNS (or when a clients sends a non-OPT RR in ADDITIONAL) should send FORMERR though
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Any reference for that?
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RFC 6891 section 7
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That one is specifically for OPT records.
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Any nameserver that doesn't understand the query for any reason can send FORMERR (RFC 1035 §4.1.1, RFC 8499 §3). paging
@nuthaven for a more specific reference regarding FORMERR on spurious records in the query.1 reply 0 retweets 0 likes -
Types defined for the additional section in a query are OPT, TKEY and TSIG. AFAIK, other types should be ignored. 2845 §4.1 says "Note that some older name servers will not accept requests with a nonempty additional data section" which I take to imply there was no clear rule.
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Sounds reasonable. Thanks for your input, Evan!
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