Re: [netmod] How to constrain a leaf to a read-only list of supported values?

[Balazs Lengyel]

Hello, Similarly to Andy's idea we are thinking about declaring data nodes static-data. This means that they can not be changed via the management interface e.g. CLI/Netconf/Restconf that they are changed very infrequently ( at upgrade) that they are considered part of the systems design time definition, meaning that the specific values must be subject to strict backwards compatibility rules, just as the models themselves need to stay backwards compatible This data can be config true or false, and the former allows must/when/leafref restrictions on them. regards Balazs On 2016-09-28 02:21, Andy Bierman wrote: On Tue, Sep 27, 2016 at 4:58 PM, Alex Campbell <alex.campb...@aviatnet.com> wrote: > Dale R. Worley <wor...@ariadne.com> writes: >> Ladislav Lhotka <lho...@nic.cz> writes: >>> typedef Compression-Method { >>>   ... >>> } >>> >>> list node { >>>   config true; >>>   key name; >>> >>>   string name; >>> >>>   leaf-list supported-compression-methods { >>>     type Compression-Method; >>>     config false; >>>   } >>> >>>   Compression-Method compression-method; >>>   must "compression-method ... supported-compression-methods"; >>> } >> The only technical problem with your mock-up is that "must" expressions >> on config nodes cannot refer to state data. > Ouch!  That means that any technique like the one I proposed isn't going > to work.  Indeed, it may be that there is no way to constrain a config > leaf based on value(s) provided by the implementation. It was my understanding was that this is a deliberate design decision, so that a configuration tree can always be validated offline. Back before there was YANG 1.0 I proposed the concept of constants in YANG but this was seen as too complicated.  This is the exact use-case I had in mind. The YANG module would #define the constants (maybe with a default or no value) and they could be used in statements. The vendors would set the constants at build or maybe the operators can set them at module load-time. I was thinking more about range/pattern statements at the time than bit-is-set() but I think the same concept could apply.    #define SUPPORTED_COMPRESSION_METHODS    must "compression-method ... SUPPORTED_COMPRESSION_METHODS"; This way config does not depend on operational state,which would be a really bad idea. > Dale Alex Andy   _______________________________________________ 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 -- Balazs Lengyel Ericsson Hungary Ltd. Senior Specialist Mobile: +36-70-330-7909 email: balazs.leng...@ericsson.com

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