anchor.diff:        sha256 = "a5350777b191e910334d3a107b5e5219b72ffa393da4186da1e0a4552aeeded6";
       };
       "3" = {
  -      version = "3.1.3";
  -      multihash = "QmPLdT2JXCwsVPv6Fhr2ruSFfRPB5FBydjUWJ63EsabNBT";
  -      sha256 = "e34cf60cffc80aa1322d2c3a9b81e662c2576d2b03e53ddf1079615634e6f553";
  +      fetchzipVersion = 2;
  +      version = "3.1.5";
  +      sha256 = "58ab9d597ad5c2cac33b603770bd3e444beebc853034b0e5a00f7e612730b2cc";
       };
     };
   
     inherit (stdenv.lib)
       optionalString;
   
  -  inherit (sources."${channel}")
  +  source = sources."${channel}";
  +
  +  inherit (source)
       version
       multihash
       sha256;
  
positive.code: stdenv.mkDerivation rec {
    name = "iperf-${version}";
  
    src = fetchurl {
      name = "${name}.tar.gz";
      url = "https://iperf.fr/download/source/${name}-source.tar.gz";
      inherit multihash sha256;
    };
  
    postInstall = optionalString (channel == "3") ''
      ln -s iperf3 $out/bin/iperf
  
negative.code: { stdenv
  , fetchFromGitHub
  , fetchurl
  
  , channel
  