Re: [netmod] features in import

Andy Bierman <andy@yumaworks.com> wrote:
> On Thu, Jan 31, 2019 at 12:44 AM Martin Bjorklund <mbj@tail-f.com> wrote:
> 
> > Andy Bierman <andy@yumaworks.com> wrote:
> > > Hi,
> > >
> > > I do not agree these changes should be made at this late date.
> > > It seems to me that in order to support a feature you have to implement
> > it,
> > > and therefore if any features are set then the module is implemented, not
> > > imported.
> >
> > But this is not what RFC 7950 says about implement:
> >
> >    A server implements a module if it implements the module's data
> >    nodes, RPCs, actions, notifications, and deviations.
> >
> > > All features should be set to false in an import-only module.
> > >
> > > IMO this interpretation holds for typedef modules like iana-crypt-hash.
> > > We list that as implemented (because it is) and the features that are
> > > supported are set.
> >
> > If a module consists only of typedefs, there is no problem.
> > Conformance "import" or "import-only" modules exist in YL b/c modules
> > may have a mix of typedefs and data nodes etc.
> >
> > So in the case that Lada brought up, a server would have to list the
> > module as implemented with a certain set of features; and then also
> > deviate all nodes/rpc/notifc etc as 'not-implemented'.
> >
> >
> So what. Using deviate(not-supported) to cherry-pick what you want to
> implement
> out of a module is how it is supposed to work.
> 
> A server has to implement a feature to advertise it.

As per 7950, this is not true, as I pointed out earlier.

Note that with current YL (RFC 7895), it *is* in fact possible to
handle this case; you can list the features supported for an
import-only module.  The new YL removes this possibility (by
mistake).

/martin

> Therefore the module containing the feature cannot be import-only.
> 
> 
> 
> > /martin
> >
> >
> Andy
> 
> 
> > >
> > >
> > > Andy
> > >
> > > On Wed, Jan 30, 2019 at 11:03 AM Martin Bjorklund <mbj@tail-f.com>
> > wrote:
> > >
> > > > Hi,
> > > >
> > > > Ladislav Lhotka <lhotka@nic.cz> wrote:
> > > > > Hi,
> > > > >
> > > > > unlike RFC 7895, 7895bis doesn't provide the "feature" leaf list for
> > > > > import-only modules. But is it really so that features have no use in
> > > > > such modules?
> > > > >
> > > > > For example, an enum can depend on a feature, and if it is inside a
> > > > > typedef, it can also be in an import-only module. What if that
> > feature
> > > > > is defined in the same module?
> > > >
> > > > I think you're right, and that this is an unfortunate omission.
> > > >
> > > > The fix is simple though; we would have to add the leaf-list features
> > > > to import-only.  Probably refactor the "feature" leaf-list into a
> > > > grouping so it works like the grouping location-leaf-list:
> > > >
> > > >   grouping feature-leaf-list {
> > > >     leaf-list feature {
> > > >       type yang:yang-identifier;
> > > >       description
> > > >         "List of all YANG feature names from this module that are
> > > >          supported by the server, regardless whether they are defined
> > > >          in the module or any included submodule.";
> > > >     }
> > > >   }
> > > >
> > > > And then "uses feature-leaf-list":
> > > >
> > > > OLD:
> > > >
> > > >   grouping module-implementation-parameters {
> > > >     description
> > > >       "Parameters for describing the implementation of a module.";
> > > >
> > > >     leaf-list feature {
> > > >       type yang:yang-identifier;
> > > >       description
> > > >         "List of all YANG feature names from this module that are
> > > >          supported by the server, regardless whether they are defined
> > > >          in the module or any included submodule.";
> > > >     }
> > > >
> > > > NEW:
> > > >
> > > >   grouping module-implementation-parameters {
> > > >     description
> > > >       "Parameters for describing the implementation of a module.";
> > > >
> > > >     uses feature-leaf-list;
> > > >
> > > >
> > > > And in the list "import-only":
> > > >
> > > > OLD:
> > > >
> > > >       uses location-leaf-list;
> > > >
> > > >       uses feature-leaf-list;
> > > >
> > > >
> > > >
> > > > /martin
> > > >
> > > > _______________________________________________
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> > > > netmod@ietf.org
> > > > https://www.ietf.org/mailman/listinfo/netmod
> > > >
> >