patches and low-level development discussion

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 # SPDX-License-Identifier: MIT
# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>

{ lib, runCommand, stdenv, llvmPackages, libbpf, linux, bpftools }:

stdenv.mkDerivation {
  pname = "xdp-forwarder";
  version = "0";

  src = lib.fileset.toSource {
    root = ./.;
    fileset = lib.fileset.fileFilter
      ({ hasExt, ... }: !(hasExt "nix") && !(hasExt "md")) ./.;
  };

  buildInputs = [ libbpf ];
  nativeBuildInputs = [ llvmPackages.clang-unwrapped bpftools ];

  buildPhase = ''
    bpftool btf dump file ${linux.dev}/vmlinux format c > include/vmlinux.h
    for prog in physical router; do
      clang $NIX_CFLAGS_COMPILE -O2 -g -Wall -target bpf -I include -c prog_$prog.c -o prog_$prog.o
      substituteInPlace load_$prog --replace-fail prog_$prog.o $out/lib/prog_$prog.o
    done
    $CC -lbpf -I include -o set_router_iface set_router_iface.c
  '';

  installPhase = ''
    for prog in physical router; do
      install -Dm644 prog_$prog.o $out/lib/prog_$prog.o
      install -Dm755 load_$prog $out/bin/load_$prog
    done
    install -Dm755 set_router_iface $out/bin/set_router_iface
  '';
}