Number of additional records in queries

[Petr Špaček]

On 22. 10. 20 19:46, Brown, Chris via Unbound-users wrote:
> I appreciate both the replies.  I thank you and generally agree.  My question is more practical, though.  And there will be no judgement of the answer (at least by me).  
> 
> The state of things as I see it now in regards to the referenced additional section record check are:
> 
> - A strict reading of the RFCs does not generally prohibit records of any type or quantity in the additional section of queries.
> - A strict reading of the RFCs requires a FORMERR response if two or more OPT records exist in the additional section.
> - Google and other public DNS services generally answer queries with various records in the additional section.
> 
> - Unbound will attempt to process all queries with a single record in the additional section.  This record can have any type, including OPT.
> - Unbound will send a FORMERR response for any query that has more than one record in the additional section regardless of the type of any of the records.
> 
> Is this the desired behavior in the stock Unbound recursive DNS server?

I would say yes, it is very much desired.

Rationale:
If any future protocol extension makes use of new RR type in additional section and these are silently ignored then we have no way of detecting if the new extension is supported or not.

In other words FORMERR is the only future-proof thing to do.

Petr Špaček  @  CZ.NIC

> 
> Thank you for your time!
> 
> 
> -----Original Message-----
> From: Joe Abley <jabley at hopcount.ca> 
> Sent: Sunday, October 18, 2020 5:27 PM
> To: Tony Finch <dot at dotat.at>
> Cc: Brown, Chris <cbrown at akamai.com>; unbound-users at lists.nlnetlabs.nl
> Subject: Re: Number of additional records in queries
> 
> On 18 Oct 2020, at 16:04, Tony Finch via Unbound-users <unbound-users at lists.nlnetlabs.nl> wrote:
> 
>> Brown, Chris via Unbound-users <unbound-users at lists.nlnetlabs.nl> wrote:
>>
>>> So my question is...am I missing something in some RFC that would 
>>> break the rules to send non-opt records along with OPT records in the 
>>> ADDITIONAL section of queries?  Or is this just a sanity call Unbound 
>>> made for...well...some sanity and maybe safety.  Missing something else?
>>
>> I think the only other records you can legitimately put in a query are 
>> TSIG, TKEY, and SIG(0).
> 
> This feels like one of those situations where even if there's no prohibition on additional, arbitrary records being included in the additional section, there's also no known reason for a query to include them and hence no reliable behaviour that could be expected of a system processing that query and generating a response.
> 
> I don't think 1035 has any clear advice on the contents of the answer, authority or additional sections in messages with QR=0. That document is far from the final word on these matters, of course.
> 
> 
> Joe