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

Andrew Sullivan <ajs@anvilwalrusden.com> Tue, 05 June 2018 22:24 UTC

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From: Andrew Sullivan <ajs@anvilwalrusden.com>
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References: <alpine.DEB.2.11.1806051604150.1809@grey.csi.cam.ac.uk> <20180605152355.6tlbeqvt7luklwjl@nic.fr> <alpine.DEB.2.11.1806051710290.1809@grey.csi.cam.ac.uk> <BYAPR19MB22489BE90FE768BCB13BD40B94660@BYAPR19MB2248.namprd19.prod.outlook.com> <alpine.DEB.2.11.1806051759430.1809@grey.csi.cam.ac.uk> <BYAPR19MB2248B0ADD763FF82E8C6C2E194660@BYAPR19MB2248.namprd19.prod.outlook.com> <alpine.DEB.2.11.1806051908040.1809@grey.csi.cam.ac.uk> <BYAPR19MB22489076D7E7A6780F78CCF094660@BYAPR19MB2248.namprd19.prod.outlook.com> <alpine.DEB.2.11.1806052125170.1809@grey.csi.cam.ac.uk> <8CB4E291-95D8-4AC2-9CBA-84D54A6E93DA@icann.org>
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Subject: Re: [Doh] [Ext] a tad confused on response sizes
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On Tue, Jun 05, 2018 at 10:10:33PM +0000, Paul Hoffman wrote: 
> Resolver 1 sends a query to a Resolver 2 (who allows forwarding) over TCP. Resolver 2 asks an authoritative,  gets a response with TC bit set on, tries on TCP, and gets a failure on TCP. Resolver 2 should send the partial answer it got over UDP to Resolver 1. That answer to Resolver 1 should have the TC bit set on, or not, depending on what you think that RFC 1035 "implies".
> 

Alternatively, maybe Resolver 2 should send some error (I'm guessing
SERVFAIL is the answer, though I suppose Vixie would be unhappy with
that guess).

The problem, of course, is that a TC'd answer is literally telling you
it's incomplete, and in principle you have an incomplete RRset, which
is maybe important.  It's not clear you should use it, and it's pretty
clear (at least to me) that you shouldn't cache it.

A

-- 
Andrew Sullivan
ajs@anvilwalrusden.com