Re: [netmod] [Technical Errata Reported] RFC7950 (6031)

Andy Bierman <andy@yumaworks.com> Fri, 03 April 2020 20:36 UTC

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From: Andy Bierman <andy@yumaworks.com>
Date: Fri, 3 Apr 2020 13:36:04 -0700
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To: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>, "Rob Wilton (rwilton)" <rwilton=40cisco.com@dmarc.ietf.org>, Ladislav Lhotka <lhotka@nic.cz>, "netmod@ietf.org" <netmod@ietf.org>
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Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
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On Fri, Apr 3, 2020 at 9:56 AM Juergen Schoenwaelder <
j.schoenwaelder@jacobs-university.de> wrote:

> I propose option 1) and add an issue on yang-next (if not already
> there yet).
>
>
+1  (Noting that neither pyang or yangdump-pro handles this correctly right
now)


> /js
>
>
Andy


> On Fri, Apr 03, 2020 at 04:24:35PM +0000, Rob Wilton (rwilton) wrote:
> > For the errata, it looks like there are two choices:
> >
> > 1) We reject this errata, on the grounds that it is unclear on what the
> behaviour was expected to be.  It is left unspecified as to whether
> require-instance is allowed in a typedef.  We add an issue on the YANG.Next
> issue tracker to sort this out in a future revision of YANG.
> >
> > 2) We agree on what the expected behaviour should be, in which case it
> may be possible that this can be "Hold for document update", although it
> still seems questionable whether this really fits as an errata.
> >
> > Regards,
> > Rob
> >
> >
> > > -----Original Message-----
> > > From: netmod <netmod-bounces@ietf.org> On Behalf Of Ladislav Lhotka
> > > Sent: 03 April 2020 15:52
> > > To: netmod@ietf.org
> > > Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
> > >
> > > On Fri, 2020-04-03 at 14:01 +0000, Sterne, Jason (Nokia - CA/Ottawa)
> > > wrote:
> > > > Hi Martin,
> > > >
> > > > I believe you that the technical "value space" doesn't change, but
> > > > that leaf would suddenly accept more values than it did before right?
> > > > I'm wondering if we want to follow the "spirit" here, or stick with
> the
> > > "value space" argument.
> > >
> > > I agree with Martin here. Moreover, if such a derived type is added, it
> > > doesn't change anything related to existing data, because they use the
> > > base type as before. New data nodes may use the new type but no
> confusion
> > > can arise - their type has "require-instance false", which is correct.
> > >
> > > Lada
> > >
> > > >
> > > > I'm not really certain what the implications are (and maybe someone
> > > > has an example of why it is better to allow it?) but overwriting
> > > > require-instance with 'false' doesn't feel right.
> > > >
> > > > Jason
> > > >
> > > > > -----Original Message-----
> > > > > From: Martin Björklund <mbj+ietf@4668.se>
> > > > > Sent: Friday, April 3, 2020 9:54 AM
> > > > > To: Sterne, Jason (Nokia - CA/Ottawa) <jason.sterne@nokia.com>
> > > > > Cc: rwilton=40cisco.com@dmarc.ietf.org; j.schoenwaelder@jacobs-
> > > > > university.de; mbj+ietf@4668.se; warren@kumari.net;
> netmod@ietf.org;
> > > > > rfc- editor@rfc-editor.org
> > > > > Subject: Re: [netmod] [Technical Errata Reported] RFC7950 (6031)
> > > > >
> > > > > Hi,
> > > > >
> > > > > "Sterne, Jason (Nokia - CA/Ottawa)" <jason.sterne@nokia.com>
> wrote:
> > > > > > I don't think we should allow overwriting a require-instance true
> > > > > > with a require-instance false in a derived type. It seems to go
> > > > > > against the spirit of avoiding expansion of allowable values.
> > > > >
> > > > > As I wrote earlier in this thread, the value space doesn't change
> > > > > with require-instance.
> > > > >
> > > > >
> > > > > /martin
> > > > >
> > > > >
> > > > >
> > > > > > From section 4.1 of RFC7950:
> > > > > >
> > > > > >         Derived types can restrict their base type's set of valid
> > > > > > values
> > > > > >
> > > > > > And this text in section 7.3.4 implies that derived types only do
> > > > > > further restriction:
> > > > > >
> > > > > >     If the type's default value is not valid according to the new
> > > > > >    restrictions specified in a derived type or leaf definition,
> the
> > > > > >    derived type or leaf definition MUST specify a new default
> value
> > > > > >    compatible with the restrictions.
> > > > > >
> > > > > > Going the other direction (overwriting with require-instance
> true)
> > > > > > seems OK to me.
> > > > > >
> > > > > > Jason
> > > > > >
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: netmod <netmod-bounces@ietf.org> On Behalf Of Rob Wilton
> > > > > > > (rwilton)
> > > > > > > Sent: Friday, April 3, 2020 8:06 AM
> > > > > > > To: Juergen Schoenwaelder
> > > > > > > <j.schoenwaelder@jacobs-university.de>de>;
> > > > > > > Martin
> > > > > > > Björklund <mbj+ietf@4668.se>
> > > > > > > Cc: warren@kumari.net; netmod@ietf.org;
> > > > > > > rfc-editor@rfc-editor.org
> > > > > > > Subject: Re: [netmod] [Technical Errata Reported] RFC7950
> (6031)
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: netmod <netmod-bounces@ietf.org> On Behalf Of Juergen
> > > > > > > Schoenwaelder
> > > > > > > > Sent: 27 March 2020 16:13
> > > > > > > > To: Martin Björklund <mbj+ietf@4668.se>
> > > > > > > > Cc: ibagdona@gmail.com; warren@kumari.net; netmod@ietf.org;
> > > > > > > > rfc- editor@rfc-editor.org
> > > > > > > > Subject: Re: [netmod] [Technical Errata Reported] RFC7950
> > > > > > > > (6031)
> > > > > > > >
> > > > > > > > On Fri, Mar 27, 2020 at 04:35:44PM +0100, Martin Björklund
> > > wrote:
> > > > > > > > > [re-sent w/ correct address]
> > > > > > > > >
> > > > > > > > > Juergen Schoenwaelder <
> j.schoenwaelder@jacobs-university.de>
> > > > > wrote:
> > > > > > > > > > Hi,
> > > > > > > > > >
> > > > > > > > > > two comments:
> > > > > > > > > >
> > > > > > > > > > - It is unclear to me whether this really qualifies as an
> > > errata.
> > > > > > > > > >
> > > > > > > > > > - If we add this, then there should probably text about
> > > which
> > > > > > > > > >   combinations are allowed. For example, for pattern and
> > > > > > > > > > ranges,
> > > > > there
> > > > > > > > > >   is explicit text that says further restrictions of the
> > > > > > > > > > value space
> > > > > > > > > >   are possible, bot not expansions. If we follow that
> > > > > > > > > > logic, then
> > > > > > > > > >
> > > > > > > > > >   typedef a {
> > > > > > > > > >     type leaf-ref {
> > > > > > > > > >       path "/some/thing";
> > > > > > > > > >       require-instance true;
> > > > > > > > > >     }
> > > > > > > > > >   }
> > > > > > > > > >
> > > > > > > > > >   typedef b {
> > > > > > > > > >     type a {
> > > > > > > > > >       require-instance false;
> > > > > > > > > >     }
> > > > > > > > > >   }
> > > > > > > > > >
> > > > > > > > > >   might be illegal since b has a larger value space than
> a.
> > > > > > > > >
> > > > > > > > > The value space of b is the same as for a.
> "require-instance"
> > > > > > > > > doesn't
> > > > > > > > > change the value space; it changes semantic validation of
> > > > > > > > > the given values ((see my mail from 17 Mar,
> "Require-instance
> > > problem").
> > > > > > > > >
> > > > > > > > > /martin
> > > > > > > >
> > > > > > > > OK. If we consider require-instance a constraint and not a
> > > > > > > > restriction, then the motivation for this errata is at least
> > > > > > > > confusing:
> > > > > > > >
> > > > > > > >   Since no one argued against this understanding, this errata
> > > changes
> > > > > > > >   the text to the same form as in other restrictions
> applicable
> > > to
> > > > > > > >   derived types.
> > > > > > > >
> > > > > > > > Simply put: Do you think it is OK to overwrite a
> > > > > > > > require-instance true with a require-instance false in a
> derived
> > > type?
> > > > > > > [RW]
> > > > > > > I'm not sure, but going in the other direction seems plausible.
> > > > > > >
> > > > > > > E.g. you start with a typedef that is explicitly
> > > > > > > require-instance false that is then refined by a typedef to be
> > > > > > > require-instance true.
> > > > > > >
> > > > > > > Regards,
> > > > > > > Rob
> > > > > > >
> > > > > > >
> > > > > > > > /js
> > > > > > > >
> > > > > > > > --
> > > > > > > > Juergen Schoenwaelder           Jacobs University Bremen
> gGmbH
> > > > > > > > Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen
> |
> > > Germany
> > > > > > > > Fax:   +49 421 200 3103         <https://www.jacobs-
> > > university.de/>
> > > > > > > >
> > > > > > > > _______________________________________________
> > > > > > > > netmod mailing list
> > > > > > > > netmod@ietf.org
> > > > > > > > https://www.ietf.org/mailman/listinfo/netmod
> > > > > > >
> > > > > > > _______________________________________________
> > > > > > > netmod mailing list
> > > > > > > netmod@ietf.org
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> > > >
> > > > _______________________________________________
> > > > netmod mailing list
> > > > netmod@ietf.org
> > > > https://www.ietf.org/mailman/listinfo/netmod
> > > --
> > > Ladislav Lhotka
> > > Head, CZ.NIC Labs
> > > PGP Key ID: 0xB8F92B08A9F76C67
> > >
> > > _______________________________________________
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>
> --
> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
> Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>
>
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