Re: question about net address

From	David Wright <deblis@lionunicorn.co.uk>
Newsgroups	linux.debian.user
Subject	Re: question about net address
Date	2023-03-22 00:50 +0100
Message-ID	<GbTTP-eaO0-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <GaZeW-dyjr-5@gated-at.bofh.it> <GaZyh-dyqA-3@gated-at.bofh.it> <GaZyh-dyqA-1@gated-at.bofh.it> <Gb6gp-dCzE-3@gated-at.bofh.it> <GbaN3-dFq6-1@gated-at.bofh.it>
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On Mon 20 Mar 2023 at 07:36:41 (+0800), Jeremy Ardley wrote:
> On 20/3/23 02:48, David Wright wrote:
> > > Checking the RFC. To my reading the final stanza is not checked
> > > " The <ip> is compared to the given network. If CIDR prefix length
> > > 
> > >     high-order bits match, the mechanism matches."
> > > 
> > > https://datatracker.ietf.org/doc/html/rfc7208#section-5.6
> > > 
> > > So in this case AI got it right.
> > I don't follow. What's your "final stanza" referring to, and
> > what's wrong with the RFC in connection with it?
> > 
> I should have used the term 'final qnum' but I think that would be obscure.
> 
> I meant the fourth number in the IPv4 dotted-quad notation.

Ah, I see now. I was trying to apply "stanza" to a bullet point in
the AI, or a section/paragraph from the RFC.

> As for the RFC? It's precise and definitive. My only concern is that
> some mail system implementer may 'improve' the RFC and restrict the
> acceptable address range to a /32 when they see a non zero final qnum
> in a /24

I don't know whether there are regression tests knocking around
for checking check_host(), but they would definitely fail in
that case. Hopefully some of the users (those affected) would
complain.

I assume the reason that host-ip-address/cidr-length is a permitted
domain-spec for ipv4: is by analogy with host-domain/cidr-length for
a:. So a:colo.example.com/28 could, if colo.example.com had an A
record with 93.184.216.34, be written 93.184.216.34/28. If you had
to write a strict network address, you'd have to figure out that it's
93.184.216.32/28. Easy in this case, but error-prone when you're
obliged to convert, say, a looked-up x.y.z.185/28 to its network
address of x.y.z.176/28.

A minor point that I noticed was included in the AI output, which
AFAIK would have to be found elsewhere than in the SPF specification
or RFC7208, are the range extremities, which correctly exclude the
network and broadcast addresses.

Cheers,
David.

Thread

question about net address coreyh@free.fr - 2023-03-18 12:30 +0100
  Re: question about net address Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2023-03-18 13:40 +0100
  Re: question about net address Timothy M Butterworth <timothy.m.butterworth@gmail.com> - 2023-03-18 14:30 +0100
  Re: question about net address Kushal Kumaran <kushal@locationd.net> - 2023-03-18 23:20 +0100
    Re: question about net address coreyh@free.fr - 2023-03-19 00:40 +0100
      Re: question about net address David Christensen <dpchrist@holgerdanske.com> - 2023-03-19 11:10 +0100
        Re: question about net address coreyh@free.fr - 2023-03-19 11:30 +0100
          Re: question about net address Joe <joe@jretrading.com> - 2023-03-19 11:40 +0100
          Re: question about net address Jeremy Ardley <jeremy@ardley.org> - 2023-03-19 11:40 +0100
            Re: question about net address coreyh@free.fr - 2023-03-19 11:40 +0100
              Re: question about net address jeremy ardley <jeremy@ardley.org> - 2023-03-19 11:50 +0100
              Re: question about net address <tomas@tuxteam.de> - 2023-03-19 12:10 +0100
              Re: question about net address Greg Wooledge <greg@wooledge.org> - 2023-03-19 13:20 +0100
                Re: question about net address Curt <curty@free.fr> - 2023-03-19 18:20 +0100
                Re: question about net address David Wright <deblis@lionunicorn.co.uk> - 2023-03-19 19:50 +0100
              Re: question about net address Stefan Monnier <monnier@iro.umontreal.ca> - 2023-03-19 16:00 +0100
            Re: question about net address Yassine Chaouche <a.chaouche@algerian-radio.dz> - 2023-03-19 12:10 +0100
              Re: question about net address <tomas@tuxteam.de> - 2023-03-19 12:20 +0100
              Re: question about net address <tomas@tuxteam.de> - 2023-03-19 12:20 +0100
                Re: question about net address Nicolas George <george@nsup.org> - 2023-03-19 12:20 +0100
                Re: question about net address Jeremy Ardley <jeremy@ardley.org> - 2023-03-19 12:40 +0100
                Re: question about net address Nicolas George <george@nsup.org> - 2023-03-19 12:50 +0100
                Re: question about net address Greg Wooledge <greg@wooledge.org> - 2023-03-19 13:30 +0100
                Re: question about net address David Wright <deblis@lionunicorn.co.uk> - 2023-03-19 18:30 +0100
                Re: question about net address David Wright <deblis@lionunicorn.co.uk> - 2023-03-19 19:50 +0100
                Re: question about net address Jeremy Ardley <jeremy@ardley.org> - 2023-03-20 00:40 +0100
                Re: question about net address fh@dnsbed.com - 2023-03-20 01:30 +0100
                Re: question about net address Stefan Monnier <monnier@iro.umontreal.ca> - 2023-03-21 23:30 +0100
                Re: question about net address Jeremy Ardley <jeremy@ardley.org> - 2023-03-22 00:00 +0100
                Re: question about net address David Wright <deblis@lionunicorn.co.uk> - 2023-03-22 00:50 +0100
                Re: question about net address David Wright <deblis@lionunicorn.co.uk> - 2023-03-22 15:50 +0100
                Re: question about net address Jeremy Ardley <jeremy@ardley.org> - 2023-03-19 12:40 +0100
                Re: question about net address Yassine Chaouche <a.chaouche@algerian-radio.dz> - 2023-03-19 13:10 +0100
                Re: question about net address Curt <curty@free.fr> - 2023-03-19 18:10 +0100
              Re: question about net address fh@dnsbed.com - 2023-03-19 12:40 +0100
                Re: question about net address <tomas@tuxteam.de> - 2023-03-19 13:00 +0100
              Re: artifiial intelligence (was: Re: question about net address) Yassine Chaouche <a.chaouche@algerian-radio.dz> - 2023-03-20 10:30 +0100
          Re: question about net address David Christensen <dpchrist@holgerdanske.com> - 2023-03-19 23:20 +0100
  Re: question about net address Yassine Chaouche <a.chaouche@algerian-radio.dz> - 2023-03-19 10:00 +0100
    Re: question about net address Yassine Chaouche <a.chaouche@algerian-radio.dz> - 2023-03-19 10:10 +0100
    Re: question about net address debian-user@howorth.org.uk - 2023-03-19 17:50 +0100

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