experiment with generic xdp tx zerocopy

[mtfriesen]

Description

Describe the purpose of and changes within this Pull Request.

Let's see how much performance is bottlenecked by the TX bounce buffer for generic XDP.

Testing

Do any existing tests cover this change? Are new tests needed?

Documentation

Is there any documentation impact for this change?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.67%. Comparing base (54ced5e) to head (208eaee).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5086      +/-   ##
==========================================
- Coverage   85.92%   85.67%   -0.25%     
==========================================
  Files          59       59              
  Lines       18035    18035              
==========================================
- Hits        15496    15451      -45     
- Misses       2539     2584      +45     

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[mtfriesen]

No performance improvement in netperf.