Re: [DNSOP] [Ext] I-D Action: draft-ietf-dnsop-svcb-https-05.txt

John R Levine <johnl@taugh.com> Thu, 13 May 2021 17:59 UTC

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Date: 13 May 2021 13:59:47 -0400
Message-ID: <34e915e0-1146-9037-caf0-fd68cc7eccc1@taugh.com>
From: "John R Levine" <johnl@taugh.com>
To: "Ben Schwartz" <bemasc@google.com>, "Brian Dickson" <brian.peter.dickson@gmail.com>
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Subject: Re: [DNSOP] [Ext] I-D Action: draft-ietf-dnsop-svcb-https-05.txt
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On Thu, 13 May 2021, Ben Schwartz wrote:
> SVCB's key=value zone-file format is borrowed straight from DNS-SD (RFC
> 6763); it is not new to DNS users.

Hey, wait a minute.  DNS-SD just sticks the "key=value" strings as-is into 
text fields.  Now that I look closer, I see what Brian's objection is and 
I have a lot more sympathy for it.

No other RRTYPE has master file processing anywhere near as complicated as 
this:

~>  - sort the SvcParams by key
>  - verify their uniqueness
>  - deal with list of fields nested in other fields (this includes the
> discussed comma escaping)~

If you put the SvcParams into text strings and let the client sort it out, 
I think the objections would go away.  This would mean that there could be 
zone files with semantically invalid SVCB records, yes, but that's nothing 
new, and the client has to check for that anyway.

Look at NAPTR.  It has a reputation for being very complicated but the DNS 
part is trivial, just a few numbers and strings.  The heavy lifting of 
regular expression matching all happens in the client.  If someone 
publishes a NAPTR with an invalid regexp, that's not the master file or 
server's problem.  It's something to catch at a higher level.

Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly