anchor.diff:  
   let
     optional = stdenv.lib.optional;
  -  version = "3.30";
  +  version = "3.31";
     name = "libreswan-${version}";
     binPath = stdenv.lib.makeBinPath [
       bash iproute iptables procps coreutils gnused gawk nss.tools which python
  
positive.code:   enableParallelBuilding = true;
  
    meta = with stdenv.lib; {
      homepage = https://libreswan.org;
      description = "A free software implementation of the VPN protocol based on IPSec and the Internet Key Exchange";
      platforms = platforms.linux ++ platforms.darwin ++ platforms.freebsd;
      license = licenses.gpl2;
  
negative.code: 
    src = fetchurl {
      url = "https://download.libreswan.org/${name}.tar.gz";
      sha256 = "1wxqsv11nqgfj5and5xzfgh6ayqvl47midcghd5ryynh60mp7naa";
    };
  
    # These flags were added to compile v3.18. Try to lift them when updating.
  