fix(xdp): use xdp off for stale cleanup

[simonmorley]

Summary

• Changes xdpgeneric off → xdp off in the stale XDP cleanup fallback
• xdpgeneric off only works if the stale program was attached in generic mode — fails silently otherwise, causing -EBUSY on next attachment
• xdp off detaches regardless of attachment mode (generic, driver, offloaded)

Test plan

• cargo test -- test_xdp_cleanup passes (updated assertions)
• Kill limpet with SIGKILL on scanner, verify restart succeeds

[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 improves the reliability of XDP program cleanup by adopting a more universal command for detaching stale programs. This change addresses a limitation where previous cleanup attempts might fail silently, leading to resource contention and errors when new XDP programs are deployed. The updated approach ensures consistent and successful detachment across all XDP attachment modes.

Highlights

• XDP Cleanup Command Update: The command used for cleaning up stale XDP programs has been changed from xdpgeneric off to xdp off.
• Enhanced Robustness: The xdpgeneric off command was limited, only working for programs attached in generic mode and failing silently otherwise. The new xdp off command ensures detachment regardless of the XDP program's attachment mode (generic, driver, or offloaded), preventing -EBUSY errors on subsequent attachments.

Changelog

• src/timing/xdp.rs
  • Modified the xdp_cleanup_command function to use xdp off instead of xdpgeneric off for detaching XDP programs.
  • Updated the unit tests for xdp_cleanup_command to reflect the change in the expected arguments.

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[gemini-code-assist]

Code Review

This pull request correctly updates the stale XDP cleanup command to use xdp off instead of xdpgeneric off, which improves the robustness of the cleanup logic. The corresponding unit tests are also correctly updated. The changes are sound. One minor point: for consistency, you might also want to update the user-facing error message at src/timing/xdp.rs:200, which still suggests using xdpgeneric off for manual cleanup.