Re: [netmod] a question about 'when'

Ladislav Lhotka <lhotka@nic.cz> Mon, 05 August 2019 09:49 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: "Fengchong \(frank\)" <frank.fengchong@huawei.com>, "netmod\@ietf.org" <netmod@ietf.org>
Cc: "Zhangxiaoping \(C\)" <zhang.xiaoping@huawei.com>, liuzhiying <liuzhiying@huawei.com>
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Date: Mon, 05 Aug 2019 11:48:52 +0200
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Subject: Re: [netmod] a question about 'when'
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"Fengchong (frank)" <frank.fengchong@huawei.com>; writes:

> Hi all,
>
> I encounter a question about 'when', when I implement yang model associated when condition.
>
> Yang model:
>
> leaf password-type {
>    type enumeration {
>       enum null;
>       enum simple;
>       enum cipher;
>    }
> }
>
> leaf password-text {
> type string;
> when "../password-type != null";
> }
>
> I config these two leafs as below:
> <password-type>simple</password-type>
> <password-text>123456</password-text>
>
> And I changed password-type to null, I get the config like below:
> <password-type>null</password-type>
>
> And then, I reconfig the password-type to simple, what data should be returned?
>
> Is
>   <password-type>simple</password-type>

According to RFC 7950, sec. 8.2, the server deleted "password-text" after you changed "password-type" to null but the original value isn't recovered after you change the type back.

This server behaviour means that a typo or similar trivial error may have catastrophic consequences such as auto-deletion of entire configuration subtrees. That's why our RESTCONF implementation (jetconf) does something else: it won't permit you to change "password-type" to null as long as the "password-text" exists.

Lada

>
> Or
>
>   <password-type>simple</password-type>
>   <password-text>123456</password-type>
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> netmod@ietf.org
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-- 
Ladislav Lhotka 
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67