Re: [DNSOP] BCP on rrset ordering for round-robin? Also head's up on bind 9.12 bug (sorting rrsets by default)

Shumon Huque <shuque@gmail.com> Tue, 19 June 2018 19:22 UTC

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From: Shumon Huque <shuque@gmail.com>
Date: Tue, 19 Jun 2018 15:22:24 -0400
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Subject: Re: [DNSOP] BCP on rrset ordering for round-robin? Also head's up on bind 9.12 bug (sorting rrsets by default)
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On Tue, Jun 19, 2018 at 2:51 PM 神明達哉 <jinmei@wide.ad.jp> wrote:

> At Mon, 18 Jun 2018 17:51:26 -0400,
> Shumon Huque <shuque@gmail.com> wrote:
>
> > Client applications delegate address sorting to name resolution functions
> > like getaddrinfo() - correct?
> >
> > Doing some quick tests of getaddrinfo() just now on a recent *NIX
> machine,
> > it appears to return addresses sorted roughly in accordance with RFC
> > 6724, but rule 9 (longest prefix match) seems to be only applied to
> > IPv6 addresses. For IPv4 addresses (using an upstream resolver
> > that randomizes the response RRset), the order returned by getaddrinfo()
> > is ever changing - I assume presented in the order received.
>
> The very original implementation of BSD getaddrinfo() conformed to the
> RFC, but FreeBSD seems to have changed the behavior a few years ago so
> rule 9 wouldn't apply to IPv4 addresses:
>
> https://github.com/freebsd/freebsd/commit/1390d13ae69089142f6c6465dbb24438f295edee
> The commit log suggests the rrset round-robin was exactly the
> motivation for the change (whether it was good or bad).
>

Very useful information. Thanks for confirming!

My tests were on a Linux machine, so apparently they did the same ..

Shumon.