Link status not updating to "error" after nni attribute removal (Use Case 9)

[gretelliz]

--------------------------- New Description

According to Use Case 9, when OXPO sends a topology update where a previously valid NNI port is removed or changed to UNI (i.e., sdx_nni = ""), the affected link must be marked as status = "error" in the SDX-Controller, and any service using that link must be rerouted.

A test was added to validate this behavior test_091_port_missing_nni, but it currently fails: After updating the topology and removing the NNI designation from one side of the link, the SDX-Controller keeps the link in up status instead of transitioning it to error.

This indicates that the controller is not correctly handling topology updates where an NNI becomes missing or invalid.

Test Summary

1. Create an L2VPN using the link sax.net:Sax01:40 — ampath.net:Ampath1:40.
2. Confirm the link is up in the SDX topology.
3. Update the ampath port to sdx_nni = "".
4. Force a topology update to SDX-LC and wait for processing.
5. Retrieve the topology from the SDX-Controller.

Expected Result: The link status changes to error.

Actual Result: The link remains in up status.

---------------------------- Old Description
According to Use Case 9: When OXPO sends a topology update with a Port missing — if that Port was previously an NNI and is changed to UNI by one side (nni == ''), the link should be set to status = error.

A test was implemented to verify this behavior, but it fails because the link remains in "up" status after the change, instead of transitioning to "error".

Test Steps

1- Create an L2VPN that routes through the link sax.net:Sax01:40 — ampath.net:Ampath1:40.
2- Verify the link is operational via the SDX topology API.
3- Update the sdx_nni attribute on the ampath topology API to sdx_nni="".
4- Force the topology update to be sent to SDX-LC.
5- Wait a few seconds for the SDX-Controller to process and update the topology.
6- Retrieve the topology from the SDX-Controller and confirm the link is status="error".
7- Check if the L2VPN previously using that link has been rerouted to another link.

Expected Behavior

After step 5, the link should have status="error" in the SDX-Controller topology.
The L2VPN should be rerouted away from the affected link.

Actual Behavior

When retrieving the topology from the SDX-Controller after setting sdx_nni="", the link remains in "up" status (no change to "error").
The test fails at step 6.

[YufengXin]

@gretelliz two questions from fix/test:

1. I got the assert error earlier, not sure why the uni attribute was not removed
` if node['name'] == port_name.split('-')[0]:
for port in node['ports']:
if port['name'] == port_name:

                  assert port['nni'] == ''

E AssertionError: assert 'urn:sdx:port....net:Sax01:40' == ''
E + urn:sdx:port:sax.net:Sax01:40

tests/test_21_use_case_topology.py:348: AssertionError`

2 Should the link status be 'down' or 'error'?
for link in updated_topology['links']: if link['name'] == link_name: assert link['status'] == 'error' break

[YufengXin]

@gretelliz One more nuance to consider in this test:

In the new topology, if the 'nni' field of port is '', there will be NO link object being created. The current logic would treat it as a link 'down' event to trigger failure handling.

According to the spec, link 'error' only when the status of its port is 'error'

[YufengXin]

@italovalcy Just a note, pls review the description of this issue w/ @gretelliz based on the discussion we had in the meeting.
We probably need to split this to multiple issues:

1. distinguish between intra- and inter- OXP ports.
2. decide if the affected connections need to be re-routed or not, after marking the link to be 'error', in contrast to 'down'
3. if rerouted, do these connections need to be route back to the original link after it's 'UP' again.