Re: [netmod] 6021 ipv4-prefix

Ladislav Lhotka <lhotka@nic.cz> Fri, 26 April 2019 07:44 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: netmod@ietf.org
Date: Fri, 26 Apr 2019 09:44:43 +0200
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References: <003301d4f498$4f593640$ee0ba2c0$@gmail.com> <alpine.DEB.2.20.1904180906360.3490@uplift.swm.pp.se> <20190418080643.gcdi5x4dtn64adwc@anna.jacobs.jacobs-university.de> <alpine.DEB.2.20.1904181128480.3490@uplift.swm.pp.se> <20190418102604.y5wyqflcudiywj2i@anna.jacobs.jacobs-university.de> <alpine.DEB.2.20.1904181251000.3490@uplift.swm.pp.se> <20190418111241.5csf5kkgwgxwtsnm@anna.jacobs.jacobs-university.de> <227a2452-69f9-6786-2643-822e70dc636d@spritelink.net> <20190425215134.pabdl3bbbjoivbaj@anna.jacobs.jacobs-university.de> <01894841-bbf5-ce19-1a60-4737bc717311@spritelink.net>
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Subject: Re: [netmod] 6021 ipv4-prefix
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On Fri, 2019-04-26 at 00:07 +0200, Kristian Larsson wrote:
> 
> On 2019-04-25 23:51, Juergen Schoenwaelder wrote:
> > On Thu, Apr 25, 2019 at 11:20:57PM +0200, Kristian Larsson wrote:
> > > 
> > > On 2019-04-18 13:12, Juergen Schoenwaelder wrote:
> > > > On Thu, Apr 18, 2019 at 12:53:22PM +0200, Mikael Abrahamsson wrote:
> > > > > On Thu, 18 Apr 2019, Juergen Schoenwaelder wrote:
> > > > > > On Thu, Apr 18, 2019 at 11:43:05AM +0200, Mikael Abrahamsson wrote:
> > > > > > +17.4 is not an integer, so this is an error (not because of the +
> > > > > > but
> > > > > > because of the . followed by additional digits). +17 is I think a
> > > > > > valid
> > > > > > integer value but the + will be dropped in the canonical
> > > > > > representation.
> > > > > 
> > > > > Yes, but 2001:db8::1/64 isn't valid prefix (because the host portion
> > > > > of the
> > > > > prefix isn't 0) so why should it be "rounded" when 17.4 shouldn't be
> > > > > rounded
> > > > > if an integer input is expected?
> > > > 
> > > > The non-prefix bits are irrelevant for the prefix and the canonical
> > > > format has the non-prefix bits all set to zero. I understand that you
> > > > prefer 2001:db8::1/64 to be an error but RFC 6021 and RFC 6991
> > > > consider this as valid input that can be safely interpreted to mean
> > > > 2001:db8::0/64.
> > > 
> > > Vice versa, if an implementation does treat 2001:db8::1/64 as a syntax
> > > error, is that implementation incorrect?
> > > 
> > 
> > I think so. The types do not require that non-prefix bits are zero
> > when a value is received. However, a server must report the canonical
> > value, in this case 2001:db8::/64.
> 
> Cisco NSO treats 2001:db8::1/64 as a syntax error for a leaf of type 
> ip-prefix (or ip6-prefix).

It is a server backend job to take care about this, the YANG type can stay more
liberal. Similar differences in implementations are rather typical.

Lada

> 
> It would be interesting to hear Martins opinion on this.
> 
> Kind regards,
>     Kristian.
> 
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Ladislav Lhotka
Head, CZ.NIC Labs
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