PF-1.9: Egress handling of TTL - Readme update

[keysightgems]

Readme Location: https://github.com/openconfig/featureprofiles/blob/main/feature/ttl/otg_tests/egress/README.md

Attached logs here: https://partnerissuetracker.corp.google.com/u/2/issues/559476791

[OpenConfigBot]

Pull Request Functional Test Report for #6017 / 796c2fd

Virtual Devices

Device	Test	Test Documentation	Job	Raw Log
Arista cEOS		PF-1.9: Egress handling of TTL
Cisco 8000E		PF-1.9: Egress handling of TTL
Cisco XRd		PF-1.9: Egress handling of TTL
Juniper ncPTX		PF-1.9: Egress handling of TTL
Nokia SR Linux		PF-1.9: Egress handling of TTL
Openconfig Lemming		PF-1.9: Egress handling of TTL

Hardware Devices

Device	Test	Test Documentation	Raw Log
Arista		PF-1.9: Egress handling of TTL
Cisco		PF-1.9: Egress handling of TTL
Juniper		PF-1.9: Egress handling of TTL
Nokia		PF-1.9: Egress handling of TTL

Help

[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 expands the egress TTL handling test suite for OpenConfig feature profiles. It introduces new test scenarios for encapsulated traffic (GRE, GUE, MPLS-over-UDP) and enhances the test infrastructure to support more robust hardware initialization, packet capture validation, and policy-forwarding counter verification. Additionally, it adds a new deviation to account for platform-specific limitations regarding ICMP TTL Exceeded message generation.

Highlights

• Test Coverage Expansion: Added multiple new test cases (PF-1.9.29 to PF-1.9.34) to verify IPv4/IPv6 over MPLS-over-UDP decapsulation with various TTL combinations.
• Infrastructure Updates: Introduced configureHardwareInit to support ICMP forwarding, and updated configureDUTPort and configureATE to improve test setup flexibility.
• Deviation Management: Added decap_icmp_ttl_exceeded_unsupported deviation to metadata to handle devices that do not generate ICMP TTL Exceeded messages after decapsulation.
• Utility Enhancements: Improved processCapture with retry logic to handle truncated PCAP files and updated validateDUTPkts to support policy-forwarding counter validation.

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[gemini-code-assist]

Code Review

This pull request introduces a comprehensive set of test cases for TTL handling in egress traffic, specifically covering various encapsulation scenarios like GRE, GUE, and MPLS-in-UDP. It adds necessary hardware initialization and decapsulation configuration plugins, along with new deviation definitions to handle device-specific limitations. The review identified a logical error in the expected TTL calculation for MPLS decapsulation and an incorrect parameter in the GUE decapsulation test case, both of which have been addressed in the code.