anchor.diff:  { stdenv, fetchurl, pkgconfig, gnutls, liburcu, lmdb, libcap_ng, libidn2, libunistring
  -, systemd, nettle, libedit, zlib, libiconv, libintl, libmaxminddb
  +, systemd, nettle, libedit, zlib, libiconv, libintl, libmaxminddb, libbpf, nghttp2
   , autoreconfHook
   }:
   
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "knot-dns";
    version = "2.9.6";
  
    src = fetchurl {
      url = "https://secure.nic.cz/files/knot-dns/knot-${version}.tar.xz";
      sha256 = "bf742883c6825b54f19f2dadca2c94fec1ff8bdcf0a52388e2e167937594b2e7";
    };
  
    outputs = [ "bin" "out" "dev" ];
  
negative.code:     gnutls liburcu libidn2 libunistring
      nettle libedit
      libiconv lmdb libintl
      libbpf # XDP support
      nghttp2 # DoH support in kdig
      libmaxminddb # optional for geoip module (it's tiny)
      # without sphinx &al. for developer documentation
      # TODO: add dnstap support?
    ]
      ++ optionals stdenv.isLinux [ libcap_ng systemd ]
      ++ optional stdenv.isDarwin zlib; # perhaps due to gnutls
  