Re: [netconf] RFC6241: "xs:QName" text values in <nc:rpc-error> instances

[Andy Bierman <[e-mail]>]

On Thu, Jun 1, 2023 at 2:13 AM Jernej Tuljak <[e-mail]>
wrote:

> Hi,
>
> RFC 6241 contains the following example in section 4.3.
>
>     Example:  An error is returned if an <rpc> element is received
>        without a "message-id" attribute.  Note that only in this case is
>        it acceptable for the NETCONF peer to omit the "message-id"
>        attribute in the <rpc-reply> element.
>
>       <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
>         <get-config>
>           <source>
>             <running/>
>           </source>
>         </get-config>
>       </rpc>
>
>       <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
>         <rpc-error>
>           <error-type>rpc</error-type>
>           <error-tag>missing-attribute</error-tag>
>           <error-severity>error</error-severity>
>           <error-info>
>             <bad-attribute>message-id</bad-attribute>
>             <bad-element>rpc</bad-element>
>           </error-info>
>         </rpc-error>
>       </rpc-reply>
>
> I think this <rpc-reply> is semantically incorrect. It should be
> corrected to:
>
>       <nc:rpc-reply xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
>         <nc:rpc-error>
>           <nc:error-type>rpc</nc:error-type>
>           <nc:error-tag>missing-attribute</nc:error-tag>
>           <nc:error-severity>error</nc:error-severity>
>           <nc:error-info>
> <nc:bad-attribute>message-id</nc:bad-attribute>
>             <nc:bad-element>nc:rpc</nc:bad-element>
>           </nc:error-info>
>         </nc:rpc-error>
>       </nc:rpc-reply>
>
>

You should file an Errata.

OLD:

    <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rpc-error>
         <error-type>rpc</error-type>
         <error-tag>missing-attribute</error-tag>
         <error-severity>error</error-severity>
         <error-info>
           <bad-attribute>message-id</bad-attribute>
           <bad-element>rpc</bad-element>
         </error-info>
       </rpc-error>
     </rpc-reply>



NEW:


    <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rpc-error>
         <error-type>rpc</error-type>
         <error-tag>missing-attribute</error-tag>
         <error-severity>error</error-severity>
         <error-info>

           <bad-attribute
            xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">nc:message-id</bad-attribute>
           <bad-element
            xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">nc:rpc</bad-element>
         </error-info>
       </rpc-error>
     </rpc-reply>



Andy





> NETCONF messages layer is modeled with XML Schema 1.1 (XSD 1.1) in
> Appendix B.
>
> While the <rpc-reply> in the original example is valid according to XML
> 1.1 Schema in Appendix B, it does not seem to be consistent with
> requirements described in Appendix A. The text value of XML elements
> <bad-attribute> and <bad-element> should be a valid "xs:QName" that
> references a known attribute or element by its name ({namepace-name,
> local-part} tuple, not a string literal). Since the "message-id"
> attribute and "rpc" element do not belong to the same namespace in an
> <rpc> message, one of the text values in the original <rpc-reply> cannot
> be semantically correct.
>
> It is also unclear which namespace unprefixed text values of XSD 1.1
> modeled data map to (and RFC 6241 says nothing about this), so my
> correction above is intentionally verbose in order to eliminate the
> default namespace. Note that the intention of the authors of XSD 1.1
> specification seems to be that such values are _always_ mapped to the
> null namespace, unlike in some other XML schema languages, where the
> default namespace would be used instead (if it exists), which would
> imply that only the value of <bad-element> in the original <rpc-reply>
> is problematic. The following could also be semantically correct:
>
>       <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
> xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
>         <rpc-error>
>           <error-type>rpc</error-type>
>           <error-tag>missing-attribute</error-tag>
>           <error-severity>error</error-severity>
>           <error-info>
>             <bad-attribute>message-id</bad-attribute>
>             <bad-element>nc:rpc</bad-element>
>           </error-info>
>         </rpc-error>
>       </rpc-reply>
>
> However, XSD 1.1 specification does not seem to explicitly confirm this
> anywhere.
>
> Can someone please clarify what the intention of RFC 6241 was here?
> Specifically, why was XSD 1.1 "xs:QName" chosen as the data type for
> such XML elements in Appendix B, and what does "name" in Appendix A
> refer to?
>
> Jernej
>
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