[PATCH v4 0/2] Fix build of forwarder, then improve it

[Demi Marie Obenour <demiobenour@gmail.com>]

The first patch fixes the build of the XDP forwarder and ensures it does
not include any libc headers.  The second patch is a significant
cleanup and also should improve performance a tiny amount.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
---
Changes in v4:
- Use find_program instead of passing clang path as Meson option.
- Use path to Linux kernel package instead of path to include directory.
- Split the patch into two parts: a minimal one that just fixes the
  build, and a bigger one that refactors the BPF programs.
- Link to v3: https://spectrum-os.org/lists/archives/spectrum-devel/20251008-fix-forwarder-build-v3-1-a93e5156fb6a@gmail.com

Changes in v3:
- Fix build.
- Clean up XDP programs.
- Link to v2: https://spectrum-os.org/lists/archives/spectrum-devel/20251006-fix-forwarder-build-v2-1-6fdd7e05cb14@gmail.com

Changes in v2:
- Rewrite the programs to not use the helpers.
- This doesn't build.
 Link to v1: https://spectrum-os.org/lists/archives/spectrum-devel/20251003-fix-forwarder-build-v1-1-856b78ae5656@gmail.com

---
Demi Marie Obenour (2):
      tools/xdp-forwarder: Do not include libc headers in eBPF programs
      tools/xdp-forwarder: Simplify forwarder programs

 tools/default.nix                     |  11 +-
 tools/meson.options                   |   4 +
 tools/xdp-forwarder/helpers.h         |  54 +++++++
 tools/xdp-forwarder/meson.build       |  11 +-
 tools/xdp-forwarder/parsing_helpers.h | 274 ----------------------------------
 tools/xdp-forwarder/prog_physical.c   |  52 ++++---
 tools/xdp-forwarder/prog_router.c     |  48 ++++--
 tools/xdp-forwarder/rewrite_helpers.h | 146 ------------------
 8 files changed, 138 insertions(+), 462 deletions(-)
---
base-commit: c5d5786d3dc938af0b279c542d1e43bce381b4b9
change-id: 20251003-fix-forwarder-build-2889ea9aec91

-- 
Sincerely,
Demi Marie Obenour (she/her/hers)