Re: [Netconf] [Technical Errata Reported] RFC8040 (5565)

Martin Bjorklund <mbj@tail-f.com> Mon, 03 December 2018 10:38 UTC

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Subject: Re: [Netconf] [Technical Errata Reported] RFC8040 (5565)
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Qin Wu <bill.wu@huawei.com> wrote:
> -----邮件原件-----
> 发件人: Martin Bjorklund [mailto:mbj@tail-f.com] 
> 发送时间: 2018年12月3日 17:48
> 收件人: Qin Wu
> 抄送: rfc-editor@rfc-editor.org; andy@yumaworks.com; kwatsen@juniper.net; ibagdona@gmail.com; warren@kumari.net; mjethanandani@gmail.com; netconf@ietf.org
> 主题: Re: [Technical Errata Reported] RFC8040 (5565)
> 
> Qin Wu <bill.wu@huawei.com> wrote:
> > See data-missing definition in RFC6241:
> > "
> >    error-tag:      data-missing
> >    error-type:     application
> >    error-severity: error
> >    error-info:     none
> >    Description:    Request could not be completed because the relevant
> >                    data model content does not exist.  For example,
> >                    a "delete" operation was attempted on
> >                    data that does not exist.
> > 
> > "
> > And status code 409 definition in RFC7231 "
> > 6.5.8.  409 Conflict
> > 
> >    The 409 (Conflict) status code indicates that the request could not
> >    be completed due to a conflict with the current state of the target
> >    resource.  This code is used in situations where the user might be
> >    able to resolve the conflict and resubmit the request.  The server
> >    SHOULD generate a payload that includes enough information for a user
> >    to recognize the source of the conflict.
> > 
> > 6.5.4.  404 Not Found
> > 
> >    The 404 (Not Found) status code indicates that the origin server did
> >    not find a current representation for the target resource or is not
> >    willing to disclose that one exists.  A 404 status code does not
> >    indicate whether this lack of representation is temporary or
> >    permanent; the 410 (Gone) status code is preferred over 404 if the
> >    origin server knows, presumably through some configurable means, that
> >    the condition is likely to be permanent.
> > 
> > "
> > Which make me feel data missing is more related to 404 instead of 409. Wrong?
> 
> 404 means that *the requested resource* doesn't exist.
> 
> The example "delete" operation in 6241 refers to an edit-config with operation "delete".  The corresponding RESTCONF operation is "delete"
> within a YANG PATCH.  In this case, the requested resource exists, so a 404 would not be correct.
> 
> So there are certainly cases where "data-missing" does not mean 404.
> 
> But I guess there are also cases where "data-missing" will actually correspond to a 404.  For example an edit-config that just tries to delete a non-existing node will be a "data-missing", and if the corresponding RESTCONF request is a DELETE on the resource, it will be
> 404 - but if the corresponding RESTCONF request is a YANG PATCH with a "delete" edit, it will be 409.
> 
> So, maybe the proper fix is
> 
>                | data-missing            | 404, 409           |
> 
> 
> 
> /martin
> 
> [Qin]: Looks like status code 404 is given a different meaning in RFC8040
> See the following quoted text:
> "
> 4.  RESTCONF Methods
> The resource must exist or the DELETE method will fail. 
> 
> 4.6.  PATCH
> If the user is not authorized to alter the target resource, an error
>    response containing a "403 Forbidden" status-line SHOULD be returned.
>    A server MAY return a "404 Not Found" status-line, as described in
>    Section 6.5.4 in [RFC7231].  The error-tag value "invalid-value" is
>    used in this case. 
> 
> 
> 4.7.  DELETE
>    If the user is not authorized to delete the target resource, then an
>    error response containing a "403 Forbidden" status-line SHOULD be
>    returned.  The error-tag value "access-denied" is returned in this
>    case.  A server MAY return a "404 Not Found" status-line, as
>    described in Section 6.5.4 in [RFC7231].  The error-tag value
>    "invalid-value" is returned in this case.
> "
> If we allow mapping data-missing into 404, it seems to me more
> changes are required.

No, this is a different thing.  If "data-missing" can be mapped
to 404 it doesn't imply that 404 always means "data-missing".

See 6.5.4 in RFC 7231:

   The 404 (Not Found) status code indicates that the origin server did
   not find a current representation for the target resource or is not
   willing to disclose that one exists.


/martin


> > 
> > -Qin
> > -----邮件原件-----
> > 发件人: Martin Bjorklund [mailto:mbj@tail-f.com]
> > 发送时间: 2018年12月3日 16:54
> > 收件人: rfc-editor@rfc-editor.org
> > 抄送: andy@yumaworks.com; kwatsen@juniper.net; ibagdona@gmail.com; 
> > warren@kumari.net; mjethanandani@gmail.com; Qin Wu; netconf@ietf.org
> > 主题: Re: [Technical Errata Reported] RFC8040 (5565)
> > 
> > Hi,
> > 
> > I don't think this errata should be accepted.  404 means that the requested resource doesn't exist, but "data-missing" can be returned e.g. if you try to patch an existing resource of type leafref to point to a non-existing leaf.
> > 
> > 
> > /martin
> > 
> > 
> > RFC Errata System <rfc-editor@rfc-editor.org> wrote:
> > > The following errata report has been submitted for RFC8040, 
> > > "RESTCONF Protocol".
> > > 
> > > --------------------------------------
> > > You may review the report below and at:
> > > http://www.rfc-editor.org/errata/eid5565
> > > 
> > > --------------------------------------
> > > Type: Technical
> > > Reported by: Qin Wu <bill.wu@huawei.com>
> > > 
> > > Section: 7
> > > 
> > > Original Text
> > > -------------
> > >               +-------------------------+------------------+
> > >               | error-tag               | status code      |
> > >               +-------------------------+------------------+
> > >               | in-use                  | 409              |
> > >               | lock-denied             | 409              |
> > >               | resource-denied         | 409              |
> > >               | data-exists             | 409              |
> > >               | data-missing            | 409              |
> > > 
> > > 
> > > Corrected Text
> > > --------------
> > >               +-------------------------+------------------+
> > >               | error-tag               | status code      |
> > >               +-------------------------+------------------+
> > >               | in-use                  | 409              |
> > >               | lock-denied             | 409              |
> > >               | resource-denied         | 409              |
> > >               | data-exists             | 409              |
> > >               | data-missing            | 404              |
> > > 
> > > 
> > > Notes
> > > -----
> > > The <error-tag> data missing should be mapped to status code '404' instead of '409' to get consistent with the defintion of data-missing in RFC6241.
> > > 
> > > Instructions:
> > > -------------
> > > This erratum is currently posted as "Reported". If necessary, please 
> > > use "Reply All" to discuss whether it should be verified or rejected.
> > > When a decision is reached, the verifying party can log in to change 
> > > the status and edit the report, if necessary.
> > > 
> > > --------------------------------------
> > > RFC8040 (draft-ietf-netconf-restconf-18)
> > > --------------------------------------
> > > Title               : RESTCONF Protocol
> > > Publication Date    : January 2017
> > > Author(s)           : A. Bierman, M. Bjorklund, K. Watsen
> > > Category            : PROPOSED STANDARD
> > > Source              : Network Configuration
> > > Area                : Operations and Management
> > > Stream              : IETF
> > > Verifying Party     : IESG
> > >