Enable skip_tcp_negotiated_mss_check for BGP TCP MSS path MTU test

[mukherso]

Files changed

• (M) feature/bgp/otg_tests/bgp_tcp_mss_path_mtu/metadata.textproto

Change Scope

Updated the featureprofiles BGP TCP MSS path MTU test behavior to account for the configured TCP MSS value being reported in transport/state, rather than the negotiated MSS value.

The tcp-mss leaf is defined only under the transport configuration in the OpenConfig public model, and the same value is reflected in the corresponding state container for both peer-groups and neighbors. As a result, the effective configured MSS value is being reported in transport/state, not the negotiated MSS derived from TCP session establishment :

container transport {  
  description  
    "Transport session parameters for the BGP neighbor";  
  container config {  
    description  
      "Configuration parameters relating to the transport  
      session(s) used for the BGP neighbor";  
    uses bgp-common-neighbor-group-transport-config;  
  }  
  container state {  
    config false;  
    description  
      "State information relating to the transport session(s)  
      used for the BGP neighbor";  
    uses bgp-common-neighbor-group-transport-config;  
    uses bgp-neighbor-transport-state;  
  }  
}

However, the following tests:

https://github.com/openconfig/featureprofiles/blob/main/feature/bgp/otg_tests/bgp_tcp_mss_path_mtu/bgp_tcp_mss_path_mtu_test.go#L382

https://github.com/openconfig/featureprofiles/blob/main/feature/bgp/otg_tests/bgp_tcp_mss_path_mtu/bgp_tcp_mss_path_mtu_test.go#L482

currently expects the negotiated MSS value when querying: /bgp/neighbors/neighbor/transport/tcp-mss/state

To align the test with OpenConfig implementation, the Arista-specific deviation skip_tcp_negotiated_mss_check is enabled. This allows the test suite to pass while preserving correct validation of TCP MSS configuration semantics.

[gemini-code-assist]

Summary of Changes

Hello @mukherso, 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 addresses an inconsistency in how the BGP TCP MSS path MTU test interprets the tcp-mss value reported in transport/state. The OpenConfig model specifies that transport/state reflects the configured MSS, whereas the existing test expected a negotiated MSS. To resolve this, an Arista-specific flag, skip_tcp_negotiated_mss_check, has been enabled. This modification ensures the test suite passes correctly without introducing any changes to the OpenConfig model or device operational behavior.

Highlights

• Test Behavior Alignment: The BGP TCP MSS path MTU test has been updated to correctly account for the configured TCP MSS value being reported in transport/state, rather than the negotiated MSS value, aligning with the OpenConfig model's implementation.
• Arista-Specific Deviation: To facilitate the test's passing while preserving correct validation of TCP MSS configuration semantics, the Arista-specific deviation skip_tcp_negotiated_mss_check has been enabled.
• Scope and Compatibility: This change is backward compatible and exclusively impacts test behavior; it does not alter the OpenConfig model or the behavior of network devices.

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[OpenConfigBot]

Pull Request Functional Test Report for #4934 / 5c71a82

Virtual Devices

Device	Test	Test Documentation	Job	Raw Log
Arista cEOS		RT-1.21: BGP TCP MSS and PMTUD
Cisco 8000E		RT-1.21: BGP TCP MSS and PMTUD
Cisco XRd		RT-1.21: BGP TCP MSS and PMTUD
Juniper ncPTX		RT-1.21: BGP TCP MSS and PMTUD
Nokia SR Linux		RT-1.21: BGP TCP MSS and PMTUD
Openconfig Lemming		RT-1.21: BGP TCP MSS and PMTUD

Hardware Devices

Device	Test	Test Documentation	Raw Log
Arista 7808		RT-1.21: BGP TCP MSS and PMTUD
Cisco 8808		RT-1.21: BGP TCP MSS and PMTUD
Juniper PTX10008		RT-1.21: BGP TCP MSS and PMTUD
Nokia 7250 IXR-10e		RT-1.21: BGP TCP MSS and PMTUD

Help

[gemini-code-assist]

Code Review

This pull request enables the skip_tcp_negotiated_mss_check deviation for the BGP TCP MSS path MTU test. The change is well-justified in the description, which correctly points out that the test was expecting a negotiated MSS value from a telemetry path that, according to the OpenConfig model structure, is intended to report the configured value. By enabling this deviation, the test behavior is aligned with the device's implementation, which appears to be compliant with the OpenConfig model. The change is minimal, targeted, and correct. I have no further comments.

[AmrNJ]

Please add a proper issue tracker ID in the deviations file.