confd: Add mount constraint for container config

[axkar]

This PR adds a validation rule to prevent incomplete container mount configurations. Ensures that either "source" or "content" is present when "target" is specified, avoiding runtime errors caused by undefined mount sources.

Fixes #1040

Checklist

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• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
  • YANG model change => revision updated?
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
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  • ChangeLog updated (for major changes)
• Other (please describe):

[wkz]

Did you verify that adding mandatory true; to the data and content leafs did not solve this issue without an explicit must expression?

[troglobit]

Did you verify that adding mandatory true; to the data and content leafs did not solve this issue without an explicit must expression?

My question too.

[axkar]

I have just checked.
Unfortunately it doesn't seem to work to have it this way:

choice data {
          case source {
            leaf source {
              mandatory true;
              description "...";
              type string {
                pattern '/.*';
              }
            }
          }
          case content {
            leaf content {
              mandatory true;
              description "...";
              type binary;
            }
          }
        }

This looked like the ideal solution, but it seems that libyang might not be handling this correctly.
Possibly a bug or a limitation in how it treats choice nodes with mandatory leaves.

[axkar]

It actually works by placing mandatory true; at the top level of choice data.

choice data {
          mandatory true;
          case source {
            leaf source {
              description "...";
              type string {
                pattern '/.*';
              }
            }
          }
          case content {
            leaf content {
              description "...";
              type binary;
            }
          }
        }

Error messages are not perfect though for CLI users who do not interact with YANG models:

admin@test-00-01-00:/config/> leave
Error: Mandatory choice "data" data do not exist. (path "/infix-containers:containers/container[name='xyz']/mount[name='abc']")
Error: Invalid candidate configuration
admin@test-00-01-00:/config/>

There is no mention of source or content.
However, this seems to be the way forward. It is minimal and correct :)

[mattiaswal]

It actually works by placing mandatory true; at the top level of choice data.

choice data {
          mandatory true;
          case source {
            leaf source {
              description "...";
              type string {
                pattern '/.*';
              }
            }
          }
          case content {
            leaf content {
              description "...";
              type binary;
            }
          }
        }

Error messages are not perfect though for CLI users who do not interact with YANG models:

admin@test-00-01-00:/config/> leave
Error: Mandatory choice "data" data do not exist. (path "/infix-containers:containers/container[name='xyz']/mount[name='abc']")
Error: Invalid candidate configuration
admin@test-00-01-00:/config/>

There is no mention of source or content. However, this seems to be the way forward. It is minimal and correct :)

data is a very general name, i really think the (choice) node should be renamed to source to more indicate what it is. But this is a separate issue IMHO.

But for now, the user may need to look at the model to know whats happening.