Re: [netmod] Issue with path statements in RPC

tom petch <ietfc@btconnect.com> wrote:
> From: netmod <netmod-bounces@ietf.org> on behalf of Martin Björklund <mbj+ietf@4668.se>
> Sent: 10 August 2020 10:24
> 
> Italo Busi <Italo.Busi@huawei.com> wrote:
> > We have found some issues with RPC XPaths when developing the YANG
> > code for
> > https://tools.ietf.org/html/draft-ietf-teas-yang-path-computation
> >
> > As discussed during the TEAS WG session in IETF 108, this issue has
> > been raised on pyang github:
> > https://github.com/mbj4668/pyang/issues/662
> >
> > It was also suggested to check with Netmod WG what should be the
> > correct behavior according to RFC7950.
> >
> > The following code is accepted by pyang 1.75 but not by pyang 2.1:
> >
> >     type leafref {
> >       path "/te:tunnels-path-compute/te:input/"
> >          + "te:path-compute-info/"
> >         + "te-pc:tunnel-attributes/te-pc:tunnel-name";
> >     }
> >
> > The following code instead is accepted by pyang 2.1 but not by pyang
> > 1.7.5:
> >
> >     type leafref {
> >       path "/te:tunnels-path-compute/"
> >          + "te:path-compute-info/"
> >         + "te-pc:tunnel-attributes/te-pc:tunnel-name";
> >     }
> 
> The leafref path is an XPath expression, which operates on the data
> tree (instance data).  The "input" node is not present in the instance
> data / data tree.  See section 6.4.1 of RFC 7950.
> 
> So the latter path (as verfied by pyang 2.1) is correct.
> 
> <tp>
> Martin,
> 
> Thank you for the clarifications.  Just looking at the first issue, what gave me pause was section 9.9; the path statement is used to identify the referred leaf in the schema tree and 'input' is in the schema tree.  But I can see that 6.4.1 overrides that implication.

Hmm, yes that text can certainly be improved.  9.9.2 however refers to
6.4.1.

/martin

> 
> Tom Petch
> 
> 
> 
> > Moreover the following when statement, which is quite useful to
> > constraint which information is provided by the RPC output based on
> > some attributes in the RPC input, is accepted by pyang 1.7.5 but not
> > accepted by pyang 2.1;
> >
> >   augment "/te:tunnels-actions/te:output" {
> >     description
> >       "Augment Tunnels Action RPC input with path delete result";
> >
> >     container path-computed-delete-result {
> >       when "derived-from-or-self(../../te:input/te:action-info/"
> >          + "te:action, 'tunnel-action-path-compute-delete')";
> >       description "Path Delete RPC output";
> >       leaf-list path-compute-transaction-id {
> >         type string;
> >         description
> >           "The list of the transaction-id values of the
> >            transient states that have been successfully deleted";
> >       }
> >     }   // container path-computed-delete-result
> >   }   // path-delete rpc output
> >
> >
> > Could you please help us to understand what is the correct behavior?
> >
> > In case the correct behavior is the one of pyang 2.1, our
> > understanding is that it would not be possible to provide in YANG when
> > constraints for the data nodes in the RPC output depending on specific
> > values of the data nodes used in the RPC input. Therefore these
> > constraints should be specified as behavior and implemented in the
> > back-end.
> >
> > Is our understanding correct?
> 
> Yes, this is correct.  It is not possible to refer to the
> corresponding "input" instance data in the XPath expressions for the
> "output".
> 
> 
> /martin
> 
> 
> >
> > Thanks for your help
> >
> > Sergio and Italo (on behalf of co-authors/contributors)
> >
> > Italo Busi
> > Principal Optical Transport Network Research Engineer
> >
> > [cid:image001.jpg@01D5AC11.9575BB40]
> > ____________________________________________________________________
> >
> > Huawei Technologies Italia S.r.l.
> > Address: Centro Direzionale Milano 2, Palazzo Verrocchio, 20090
> > Segrate (MI)
> > Tel: +39 345 4721946 - Mobile:
> > Italo.busi@huawei.com<mailto:Italo.busi@huawei.com>
> >
> > __________________________________________________________________________________
> > Huawei Technologies Italia S.r.l. is a company registered in Italy at
> > the Company Registration Office of Milan, with registered number
> > 04501190963 and equity capital €3,000,000 fully paid up, whose
> > registered office is in Milan, Via Lorenteggio 240, Tower A, 20147
> > Milan, Italy. Huawei Technologies Italia S.r.l. is 100% owned by
> > Huawei Technologies Cooperatief U.A.
> > CONAI Reg. No. cc 12639454 - A.E.E. Registry No. IT10010000006521 -
> > Batteries and Accumulators Registry No. IT12050P00002839.
> > ________________________________________________________________________________________________________________________
> > This e-mail and its attachments contain confidential information from
> > HUAWEI, which is intended only for the person or entity whose address
> > is listed above. Any use of the information contained herein in any
> > way (including, but not limited to, total or partial disclosure,
> > reproduction, or dissemination) by persons other than the intended
> > recipient(s) is prohibited. If you receive this e-mail in error,
> > please notify the sender by phone or email immediately and delete it!
> > Thank you.
> > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> > PRIVACY NOTICE: Pursuant to Art. 13 of the General Data Protection
> > Regulation 2016/679 (GDPR), Huawei Technologies Italia S.r.l. informs
> > you that the personal data contained in this email will be collected
> > and treated for the acquisition of information preliminary to the
> > conclusion of contracts, for the definition of the contractual
> > relationship, as well as for the fulfillment of legal requirements
> > related to civil, tax and accounting law or any other legal obligation
> > to which Huawei may be subject. Personal data will not be subject to
> > disclosure and spread unless otherwise required by law. Huawei will
> > take appropriate security measures to protect personal data against
> > loss, misuse disclosure or destruction of the information. Personal
> > Data held may be transferred to countries outside the European Union,
> > however Huawei Italia has put in place appropriate safeguards for the
> > transfer of personal data to third countries by adopting the standard
> > data protection clauses of the EU Commission. Personal Data are kept
> > for a period necessary for the fulfillment of contract obligations
> > unless otherwise required by law. You can exercise your rights under
> > Art. 15 and following of the GDPR (i.e. right of access,
> > rectification, erasure, restriction, portability, object) by
> > contacting Huawei at this email address:
> > dataprotection@huawei.com<mailto:dataprotection@huawei.com> or through
> > the following channel:
> > www.huawei.com/en/personal-data-request<http://www.huawei.com/en/personal-data-request>. You
> > have also the right to lodge a complaint with the competent
> > supervisory authorities. If you need any further information or have
> > any queries on how Huawei process your personal data, please send an
> > email to our Data Protection Officer at
> > dpo@huawei.com<mailto:dpo@huawei.com>.The Data Controller is Huawei
> > Technologies Italia S.r.l. with registered office in Milan, Via
> > Lorenteggio 240 Tower A, 20147.
> >
> >
> _______________________________________________
> netmod mailing list
> netmod@ietf.org
> https://www.ietf.org/mailman/listinfo/netmod