Re: [Doh] [Ext] a tad confused on response sizes

Tony Finch <dot@dotat.at> Tue, 05 June 2018 18:12 UTC

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Date: Tue, 5 Jun 2018 19:12:31 +0100
From: Tony Finch <dot@dotat.at>
To: Star Brilliant <m13253@hotmail.com>
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Subject: Re: [Doh] [Ext] a tad confused on response sizes
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Star Brilliant <m13253@hotmail.com>; wrote:
>
> The DoH client does not need to understand the TC bit. It just pass the TC bit to downstream.
> Let me explain how this work:
>
> When the downstream finds the TC bit, it should retry with TCP to the DoH client.
> And the DoH client should return the exactly same answer with TC.
> The downstream should stop retrying with the second TC (since there are no more methods to retry).

I'm afraid I don't understand that at all.

In many cases, the DoH client will be embedded in an application as an
alternative to a traditional stub resolver, so it doesn't have a
downstream that can retry.

> > My trivial DoH code makes upstream queries over TCP, so the EDNS buffer
> > size is ignored.
>
> Just a friendly warning:
> I have done this thing in my productive server, and soon get banned by
> some authoritative servers.

My DoH server is a proxy that talks to a full-service resolver that I
control.

Tony.
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