DP-1.16.3: MPLS swap action code fix

[karthikeya-remilla]

Code changes to add the missing MPLS-specific plumbing needed to validate ingress classification and rewrite for MPLS traffic.

Diff:

1. Added MPLS classifier coverage to ingress_traffic_classification_and_rewrite_test:
   • defined MPLS EXP-based classifier terms
   • attached the MPLS input classifier on the ingress interface
   • added MPLS remark handling via set-mpls-tc
2. Updated the DP-1.16.3 flow to exercise MPLS swap behavior with the correct DUT interface context.
3. Added Cisco-specific MPLS static support:
   • new metadata deviation enable_mpls_static_on_interface
   • Cisco platform exception in test metadata
   • deviation accessor in internal/deviations
   • Cisco CLI add/remove handling for static MPLS swap LSPs in internal/cfgplugins/mpls.go

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements necessary MPLS-specific plumbing to validate ingress classification and rewrite functionality for MPLS traffic. It enhances the existing QoS test suite by adding MPLS classifier support and updates the flow testing logic to ensure correct DUT interface interaction, specifically addressing requirements for Cisco platforms through new metadata deviations and CLI configuration plugins.

Highlights

• MPLS Classifier Coverage: Added MPLS EXP-based classifier terms, attached the MPLS input classifier to the ingress interface, and implemented MPLS remark handling using set-mpls-tc.
• Flow Updates: Updated the DP-1.16.3 flow to properly exercise MPLS swap behavior with the correct DUT interface context.
• Cisco-Specific MPLS Support: Introduced metadata deviations for MPLS static support, added Cisco platform exceptions, and implemented CLI handling for static MPLS swap LSPs in the configuration plugins.

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[OpenConfigBot]

Pull Request Functional Test Report for #5344 / 74acc10

Virtual Devices

Device	Test	Test Documentation	Job	Raw Log
Arista cEOS		DP-1.16: Ingress traffic classification and rewrite
Cisco 8000E		DP-1.16: Ingress traffic classification and rewrite
Cisco XRd		DP-1.16: Ingress traffic classification and rewrite
Juniper ncPTX		DP-1.16: Ingress traffic classification and rewrite
Nokia SR Linux		DP-1.16: Ingress traffic classification and rewrite
Openconfig Lemming		DP-1.16: Ingress traffic classification and rewrite

Hardware Devices

Device	Test	Test Documentation	Raw Log
Arista 7808		DP-1.16: Ingress traffic classification and rewrite
Cisco 8808		DP-1.16: Ingress traffic classification and rewrite
Juniper PTX10008		DP-1.16: Ingress traffic classification and rewrite
Nokia 7250 IXR-10e		DP-1.16: Ingress traffic classification and rewrite

Help

[gemini-code-assist]

Code Review

This pull request introduces MPLS EXP-based traffic classification and remarking for QoS tests, adding support for Cisco devices through new deviations and CLI-based static MPLS configurations. Key updates include refactoring rewriteMplsSwapAction into a table-driven test and modifying ConfigureQoS to handle MPLS traffic classes. Review feedback recommends using t.Skip() instead of commenting out test cases, ensuring interface-level configurations are cleaned up to maintain test isolation, and refining the logic to prevent the creation of empty remark containers. Additionally, the reviewer suggested maintaining CLI string consistency and addressing a version mismatch in the generated protobuf code.

[karthikeya-remilla]

Team, in the original code I see that all classifier terms are configured that could match all EXP values per README, but only 1 value of EXP is being sent for verification in traffic flows. In my diff, 2 values are being sent.

Ideally, to fully satisfy the intent for MPLS classification+rewrite, shouldn't we send traffic for: 0,1,2,3,4,5,6,7 and expect remark outputs: 0,1,2,3,4,4,6,6 to exercise all of the classes?