Re: [netmod] yanglint and implemented versus imported YANG modules
Ladislav Lhotka <lhotka@nic.cz> Tue, 07 March 2017 11:53 UTC
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From: Ladislav Lhotka <lhotka@nic.cz>
To: Radek Krejčí <rkrejci@cesnet.cz>, Robert Wilton <rwilton@cisco.com>, William Lupton <wlupton@broadband-forum.org>, netmod@ietf.org
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Date: Tue, 07 Mar 2017 12:53:39 +0100
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Subject: Re: [netmod] yanglint and implemented versus imported YANG modules
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Radek Krejčí <rkrejci@cesnet.cz> writes: > Hi Lada, > > Dne 7.3.2017 v 10:30 Ladislav Lhotka napsal(a): >> Robert Wilton <rwilton@cisco.com> writes: >> >>> Hi William, >>> >>> I think that what yanglint is doing here is sane, i.e. I think that its >>> interpretation/split between imported vs implemented modules is >>> supported by the YANG RFC. >>> >>> However, for validation purposes it seems that it would be useful if >>> yanglint had an option to assume that all imported modules are >>> implicitly implemented without requiring them to be explicitly >>> specified. >> This will fail if a module just wants to use a grouping or typedef from >> an imported module but not data nodes that may also be there. > > but does it affect the validation of the module? Potentially it could - for example, the imported module may have some default content with "must" statements. Practically, it shouldn't be a problem most of the time. > >> It is exactly the problem that I mentioned in the discussion about >> NETMOD charter: we need a way to specify a complete data model. In my >> YANG/I-D development environment [1], a hello XML file is used for this >> purpose. >> >> Lada >> >> [1] https://github.com/llhotka/YANG-I-D > > we have this feature in TODO for yanglint, but I'm afraid that it does Now it's better to use yang-library, as Yangson does (but maybe this is your plan, right?). > not solve the issue - even now the script can read some additional > file with the specification which modules are expected to be loaded > before the module being validated (i.e. which imported module is > supposed to be implemented). The root of the issue is that this > information is not part of the importing module itself. This would be one option, otherwise this information can also be included in the document separately as metadata - validation instructions. This could BTW also solve the issue of what modules are supposed to be validated. Lada > > Radek > >> >>> Thanks, >>> Rob >>> >>> >>> On 06/03/2017 16:44, William Lupton wrote: >>>> All, >>>> >>>> This message arose from a yang-multicast@ietf.org >>>> <mailto:yang-multicast@ietf.org> “draft-ietf-pim-igmp-mld-yang-02.txt: >>>> YANG compilation isuse” (sic) thread >>>> <https://www.ietf.org/mail-archive/web/yang-multicast/current/threads.html#00232> initiated >>>> by Benoit. >>>> >>>> I thought it would be useful for NETMOD to see the part of the >>>> discussion that relates to implemented versus imported YANG modules. >>>> >>>> 1. Benoit Claise reported this warning: >>>> * warn: Schema node "ietf-ip:ipv4" not found >>>> (/ietf-interfaces:interfaces/ietf-interfaces:interface[ietf-interfaces:name >>>> = current()]/ietf-ip:ipv4) >>>> 2. Radek Krejčí replied: >>>> * These warnings are printed because in yanglint, until >>>> explicitly stated, the imported modules (such as >>>> ietf-interfaces and ietf-ip), are supposed to be only >>>> imported, not implemented. The data nodes in imported schemas >>>> are not available, which is the reason of these warnings. >>>> 3. William Lupton (that’s me!) asked / commented: >>>> * Why are the complaints only about ip:ipv4 (etc) and not about >>>> if:interfaces (etc), which are also referenced in the must >>>> statements? >>>> * This makes it hard for an automated tool (such as Benoit’s) >>>> because it needs to know which other YANG files to process in >>>> addition to the “file of interest”. >>>> 4. Radek Krejčí replied: >>>> * According to RFC 7950, sec 5.6.6 (3rd paragraph) [ED: 5.6.5?], >>>> when an implemented module augments another module >>>> (ietf-interfaces), the augmented module MUST be also >>>> implemented. So libyang automatically changes the augmented >>>> module from imported to the implemented. The same rule applies >>>> also in case of referring a module in path (leafref) and >>>> by deviating a module. But it does not apply when a module >>>> data is used in must or when conditions. That's the reason why >>>> it complains just about ietf-ip and not about ietf-interfaces. >>>> * YANG actually does not provide a way to specify that a >>>> particular import is also expected to be implemented. >>>> Therefore, libyang needs some help with setting modules >>>> implemented - all the explicitly loaded modules are supposed >>>> to be implemented, if the module is just implicitly loaded >>>> from the search directory and user did not expressed that it >>>> is supposed to be implemented, it is kept only imported to >>>> provide groupings or type definitions >>>> 5. Benoit Claise asked (referring to my reference to automated tools): >>>> * Would it be possible to improve the warning (and the related >>>> test, by testing implemented instead of import), basically >>>> telling that the module itself is fine? >>>> >>>> >>>> I’m interested to know that NETMOD thinks about this distinction >>>> between implemented versus imported (in the absence of any instance >>>> documents). I guess my (maybe naive) view is that if all I’m doing is >>>> checking for errors in my YANG model then I don’t care about this. If >>>> my YANG is good I want to see no warnings or errors, and if it’s bad >>>> then I want to be told this (and why). >>>> >>>> Thanks, >>>> William >>>> >>>> >>>> _______________________________________________ >>>> netmod mailing list >>>> netmod@ietf.org >>>> https://www.ietf.org/mailman/listinfo/netmod >>> _______________________________________________ >>> netmod mailing list >>> netmod@ietf.org >>> https://www.ietf.org/mailman/listinfo/netmod > > -- Ladislav Lhotka, CZ.NIC Labs PGP Key ID: 0xB8F92B08A9F76C67
- [netmod] yanglint and implemented versus imported… William Lupton
- Re: [netmod] yanglint and implemented versus impo… Robert Wilton
- Re: [netmod] yanglint and implemented versus impo… William Lupton
- Re: [netmod] yanglint and implemented versus impo… Ladislav Lhotka
- Re: [netmod] yanglint and implemented versus impo… Radek Krejčí
- Re: [netmod] yanglint and implemented versus impo… Radek Krejčí
- Re: [netmod] yanglint and implemented versus impo… Ladislav Lhotka
- Re: [netmod] yanglint and implemented versus impo… Ladislav Lhotka
- Re: [netmod] yanglint and implemented versus impo… William Lupton
- Re: [netmod] yanglint and implemented versus impo… Radek Krejčí