|SUCCESS| net/mlx5: reject unsupported layers before GRE and NVGRE

[dpdklab at iol.unh.edu]

Test-Label: ai-code-review
Test-Status: SUCCESS
https://dpdk.org/patch/172728

_AI Code Review_

=== Patch Review: series.patch (via Claude) ===
Review date: 2026-11-08

# DPDK Patch Review

## Summary

This patch adds validation to reject unsupported protocol combinations in mlx5 flow patterns. Specifically, it prevents GRE and NVGRE from being matched after UDP, TCP, ICMP, ICMPv6, or ESP layers, which were previously accepted silently but produced incorrect matching behavior.

## ERRORS

None identified.

## WARNINGS

None identified.

## INFO

1. **Error message grammar** (line 3530-3531, 3915-3916):
   ```c
   "NVGRE cannot follow TCP, ICMP or ESP layer");
   ```
   The error message says "or ESP layer" but the check also includes ICMPv6. Consider:
   ```c
   "NVGRE cannot follow TCP, ICMP, ICMPv6, or ESP layer");
   ```
   This applies to both the GRE and NVGRE error messages. Minor clarity improvement for user-facing diagnostics.

2. **Style note on brace placement** (lines 3526-3528, 3910-3912):
   The multi-line `if` condition places the opening brace on the next line after the closing parenthesis. While this is acceptable in DPDK style, the more common pattern in the existing file is to place the brace immediately after the condition. This is consistent with the surrounding code and is not an error--just an observation for consistency.

Review-Result: CLEAN