Re: [DNSOP] Any website publishers who use CDNs on the list?

Tony Finch <dot@dotat.at> Wed, 07 November 2018 17:48 UTC

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Date: Wed, 7 Nov 2018 17:48:44 +0000
From: Tony Finch <dot@dotat.at>
To: =?UTF-8?Q?Vladim=C3=ADr_=C4=8Cun=C3=A1t?= <vladimir.cunat+ietf@nic.cz>
cc: Matthew Pounsett <matt@conundrum.com>, dnsop <dnsop@ietf.org>
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Subject: Re: [DNSOP] Any website publishers who use CDNs on the list?
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Vladimír Čunát <vladimir.cunat+ietf@nic.cz> wrote:
> On 11/7/18 4:00 PM, Matthew Pounsett wrote:
> > Can you point to a major browser that does *not* implement its own
> > resolver already?
>
> I believe Firefox on Linux uses libc call (in my basically default
> setup).

There's a problem on Unix that there isn't a way to get the recursive
server IP addresses from the libc resolver. In the IPv4 era it was often
possible to dig around in the _res struct in a moderately portable way, if
the libc resolver was derived from BIND, but that was thoroughly broken by
the divergence in IPv6 support.

And even if you can get the recursive server addresses, you should still
go through the name service switch to deal with names that aren't in the
DNS.

The custom DNS stub resolvers that I know about (adns, ldns, libevent)
reimplement the libc resolver, with their own parsers for /etc/resolv.conf
and all the rest.

Tony.
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