Hi andy,

You only talk about the constraints on rpc operation’s parameter?

Do you have any opinion about my question?

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发件人: Andy Bierman [mailto:[email protected]]
发送时间: 2019年9月10日 1:14
收件人: Rob Wilton (rwilton) <[email protected]>
抄送: Fengchong (frank) <[email protected]>; [email protected]; Yangang 
<[email protected]>
主题: Re: [netmod] Please clarify implementation about ‘when’

Hi,

None of the operations that accept or return datastore contents expose the 
datastore objects
in the RPC parameters.  They are always anyxml or anydata. This means that
there are no descendant data nodes defined at all according to the RPC operation
and therefore the constraints on those nodes do not exist in the RPC operation 
either.



On Mon, Sep 9, 2019 at 6:41 AM Rob Wilton (rwilton) 
<[email protected]<mailto:[email protected]>> wrote:
Hi Frank,

My interpretation of what the expected behaviour is as follows.

For “scene 1”, the config change is accepted because the result of the config 
datastore after the edit-config has been applied is valid.

For “scene 2”, the config change is rejected because the result of the config 
datastore after the edit-config has been applied is invalid.

My interpretation is that the block of text in 8.3.1 payload parsing is primary 
intended to refer to RFC input.  E.g. if the RPC was defined something like 
below, then the ‘when’ rule in 8.3.1 would enforce that a zip-code can only be 
provided if the country is the USA.

       rpc rock-the-house {
         input {
           leaf country {
             type string;
           }
           leaf zip-code {
             when “../country = ‘usa’”;
             type string;
           }
         }
       }

Thanks,
Rob



From: netmod <[email protected]<mailto:[email protected]>> On 
Behalf Of Fengchong (frank)
Sent: 06 September 2019 08:19
To: [email protected]<mailto:[email protected]>
Cc: Yangang <[email protected]<mailto:[email protected]>>
Subject: [netmod] Please clarify implementation about ‘when’

Hi all,

In RFC7950 secton 8, several description about when:
In section 8.2<https://tools.ietf.org/html/rfc7950#section-8.2>.  Configuration 
Data Modifications
   o  If a request modifies a configuration data node such that any
      node's "when" expression becomes false, then the node in the data
      tree with the "when" expression is deleted by the server.
In 8.3.1<https://tools.ietf.org/html/rfc7950#section-8.3.1>.  Payload Parsing

   o  If data for a node tagged with "when" is present and the "when"

      condition evaluates to "false", the server MUST reply with an

      "unknown-element" <error-tag> in the <rpc-error>.

In 8.3.2<https://tools.ietf.org/html/rfc7950#section-8.3.2>.  NETCONF 
<edit-config> Processing

Modification requests for nodes tagged with "when", and the "when"

      condition evaluates to "false".  In this case, the server MUST

      reply with an "unknown-element" <error-tag> in the <rpc-error>.

YANG module:
module foo {
   namespace “http://foo.com”;
   prefix “foo”;
Leaf a {…}
Leaf b {
  When “a = 10”;
}
}
Scene 1:
The first edit-config request:
<edit-config>
   <target>
      <candidate/>
   </target>
   <config>
      <a xmlns= “http://foo.com”>3</a>
   </config>
</edit-config>
This request will set a = 3.

The second request:
<edit-config>
   <target>
      <candidate/>
   </target>
   <config>
      <a xmlns= “http://foo.com”>10</a>
      <b xmlns= “http://foo.com”>5</b>
   </config>
</edit-config>

According 8.3.1, in rpc payload parsing phase, the a’s value in candidate 
datastore is 3,so leaf b’s when condition is evaluated to false, server will 
report ‘unknown-element’ error.
Is it expected by user?
Scene 2:
The first edit-config request:
<edit-config>
   <target>
      <candidate/>
   </target>
   <config>
      <a xmlns= “http://foo.com”>10</a>
   </config>
</edit-config>
This request will set a = 10.

The second request:
<edit-config>
   <target>
      <candidate/>
   </target>
   <config>
      <a xmlns= “http://foo.com”>3</a>
      <b xmlns= “http://foo.com”>5</b>
   </config>
</edit-config>
According 8.3.1, in rpc payload parsing phase, the a’s value in candidate 
datastore is 10, so leaf b’s when condition is evaluated to true, server will 
accept this request in payload parsing phase.

In edit-config request processing phase, if leaf a’s modification is processed 
firstly, the a’s value will be changed to 3, so the b’s when condition will be 
false, when server process b’s modification, b will be treated as 
unknown-element, the edit-config request will fail.
If leaf b’s modification is processed firstly, server will accept this 
modification ,because b’s when condition is true, and when server process a’s 
modification , this modification will be accepted, and b’s when condition will 
be evaluated to false, leaf b will be deleted automatically, the edit-config 
request will be OK.

How server should process this situation?

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