nxdns/flake.nix

{
  description = "nxdns: DNS sinkhole with per-client policy groups";

  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

  outputs =
    { nixpkgs, ... }:
    let
      # `zig build cut` rewrites the lines between the delimiters by text replacement.
      # BEGIN GENERATED BY zig build cut
      version = "0.0.20";
      hashes = {
        "aarch64-linux" = "sha256-2p86FImDgi4SDDzmV6w0qkrkp9dtDRyi/ZMOZ8WAEm4=";
        "x86_64-linux" = "sha256-rnTpjo7J9uY+pINxJ4ZgwbqU7E2o7N0gr9z7VRhQiZ0=";
      };
      # END GENERATED BY zig build cut

      triples = {
        "aarch64-linux" = "aarch64-linux-musl";
        "x86_64-linux" = "x86_64-linux-musl";
      };

      systems = builtins.attrNames hashes;

      package =
        system:
        let
          pkgs = nixpkgs.legacyPackages.${system};
          lib = pkgs.lib;
          triple = triples.${system};
        in
        pkgs.stdenv.mkDerivation {
          pname = "nxdns";
          inherit version;

          src = pkgs.fetchurl {
            url = "https://git.mial.net/mokhtar/nxdns/releases/download/v${version}/nxdns-${version}-${triple}.tar.gz";
            hash = hashes.${system};
          };

          # Static musl binary: the install check asserts that no interpreter was patched in.
          dontPatchELF = true;
          dontStrip = true;

          installPhase = ''
            runHook preInstall

            install -Dm755 nxdns $out/bin/nxdns
            install -Dm644 LICENSE $out/share/doc/nxdns/LICENSE
            install -Dm644 THIRD-PARTY-NOTICES $out/share/doc/nxdns/THIRD-PARTY-NOTICES

            runHook postInstall
          '';

          doInstallCheck = true;

          # GNU readelf prints `INTERP`, not `PT_INTERP`; `${READELF:?}` keeps an unset variable from turning the grep into a pass.
          installCheckPhase = ''
            runHook preInstallCheck

            # Captured first: piping readelf straight into grep hides its exit
            # status, so a readelf that failed to read the file at all would
            # print nothing, match nothing, and pass as "static".
            if ! segments="$(''${READELF:?} -l "$out/bin/nxdns")"; then
              echo "readelf -l failed on $out/bin/nxdns" >&2
              exit 1
            fi
            if printf '%s' "$segments" | grep -q INTERP; then
              echo "nxdns has an INTERP segment: it is dynamically linked, not static" >&2
              exit 1
            fi

            if ! dynamic="$(''${READELF:?} -d "$out/bin/nxdns")"; then
              echo "readelf -d failed on $out/bin/nxdns" >&2
              exit 1
            fi
            if printf '%s' "$dynamic" | grep -q NEEDED; then
              echo "nxdns has DT_NEEDED entries: it links against shared libraries" >&2
              exit 1
            fi

            if ! reported="$($out/bin/nxdns version)"; then
              echo "nxdns version exited non-zero: the binary does not run here" >&2
              exit 1
            fi

            # Prefix match: releases before 0.0.17 print a commit sha after the version.
            case "$reported" in
              "nxdns ${version}"*) echo "nxdns version reports: $reported" ;;
              *)
                echo "nxdns version reports '$reported'; expected it to start with 'nxdns ${version}'" >&2
                exit 1
                ;;
            esac

            runHook postInstallCheck
          '';

          meta = {
            description = "DNS sinkhole with per-client policy groups";
            homepage = "https://git.mial.net/mokhtar/nxdns";
            license = lib.licenses.eupl12;
            mainProgram = "nxdns";
            platforms = systems;
            sourceProvenance = [ lib.sourceTypes.binaryNativeCode ];
          };
        };
    in
    {
      packages = nixpkgs.lib.genAttrs systems (system: {
        default = package system;
      });
    };
}