Add error reporting as per section 7.1 from RFC-8040

[Patrick Dumais]

When returning an error with
// Option #2 - enhanced but still an 401 error return fmt.Errorf("Bad ACL %w", fc.UnauthorizedError)
It would be useful if restconf could create a payload according to the model of ietf-restconf:errors

{
  "ietf-restconf:errors": {
    "error": [
      {
        "error-type": "protocol",
        "error-tag": "lock-denied",
        "error-message": "Lock failed; lock already held"
      }
    ]
  }
}

[Douglas Hubler]

I presume spec is here
https://datatracker.ietf.org/doc/html/rfc8040#section-3.6.3

[sguay]

Hi @dhubler, I see that the response body is well formatted:

{"ietf-sztp-bootstrap-server:output":}{"ietf-restconf:errors":{"error":[{"error-type":"protocol","error-tag":"access-denied","error-path":"ietf-sztp-bootstrap-server:get-bootstrapping-data","error-message":"Bad ACL not authorized"}

But the response code is always 200 OK and it should be 401.

We are completely uploaded and fineTLSv1.3 (IN), TLS handshake, Newsession Ticket (4): Connection state changed (MAX_CONCURRENT_STREAMS == 250)! HTTP/2 200 access-control-allow-headers: origin, content-type, accept access-control-allow-methods: GET, POST, PUT, OPTIONS, DELETE, PATCH access-control-allow-origin: * content-type: application/json content-length: 236 date: Fri, 24 Feb 2023 19:34:07 GMT {"ietf-sztp-bootstrap-server:output":}{"ietf-restconf:errors":{"error":[{"error-type":"protocol","error-tag":"access-denied","error-path":"ietf-sztp-bootstrap-server:get-bootstrapping-data","error-message":"Bad ACL not authorized"} ]}}

Is it the right way to return an error:

return nil, fmt.Errorf("Bad ACL %w", fc.UnauthorizedError)

[Douglas Hubler]

It should be a 401 and it does look like you are wrapping the error correctly.

If you are sure you have haven't added more error wrapping beyond the above and running the latest code then there might be an issue.

BTW: The related code is here:
https://github.com/freeconf/restconf/blob/master/util.go#L71
https://github.com/freeconf/yang/blob/master/fc/err.go#L31
It would help if you can setup a debugger and step thru why the status code might be getting lost.