Re: Middleboxes and EDNS(0)

I had a tough time interpreting this as well.
Finally closed in on:
If DNS gets OPT RR (A) in an incoming packet, it will return back the same OPT RR in the final response back to the sender.
If it needs to forward the query, DNS can chose to add new OPT RR as required for its own needs.  There is no mandate on the DNS server to keep the original OPT RR.
(needless to say the received and sent OPT RR can be also chosen to be same)

Ashu
Microsoft

-----Original Message-----
From: dnsext [mailto:[email protected]] On Behalf Of Warren Kumari
Sent: Monday, December 15, 2014 23:27
To: Paul Hoffman
Cc: DNSEXT Group Working
Subject: Re: [dnsext] Middleboxes and EDNS(0)

On Sun, Dec 14, 2014 at 5:30 PM, Paul Hoffman <[email protected]> wrote:
> Greetings again. Section 6.1.1.1 of RFC 6891 says:
>
>    OPT RRs MUST NOT be cached,
>    forwarded, or stored in or loaded from master files.
>
> Section 6.2.6 says:
>
>    Middleboxes that simply forward requests to a recursive resolver MUST
>    NOT modify and MUST NOT delete the OPT record contents in either
>    direction.
>
> If I'm a middlebox that is acting as a DNS forwarder, and I see an OPT RR on a query coming in my left side, what do I send that OPT RR out the right side? Do I follow the first or the second quote?

Based on observation, if you are a middlebox that is acting as a DNS forwarder, and you see an OPT RR on a query coming in your left side, you arbitrarily choose between:
A: the first
B: the second
C: a very small rock named Edgar.

I think that the Section 6.2.6 is more correct, but middleboxes seem to take perverse pleasure in ignoring "correct" as it related to the DNS....

W


>
> --Paul Hoffman
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> https://www.ietf.org/mailman/listinfo/dnsext



--
I don't think the execution is relevant when it was obviously a bad idea in the first place.
This is like putting rabid weasels in your pants, and later expressing regret at having chosen those particular rabid weasels and that pair of pants.
   ---maf

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