{ stdenv, fetchurl, makeWrapper
, openssl, python27, iproute, perl, kernel ? null }:

with stdenv.lib;

let
  _kernel = kernel;
in stdenv.mkDerivation rec {
  version = "2.3.1";
  name = "openvswitch-${version}";

  src = fetchurl {
    url = "http://openvswitch.org/releases/${name}.tar.gz";
    sha256 = "1lmwyhm5wmdv1l4v1v5xd36d5ra21jz9ix57nh1lgm8iqc0lj5r1";
  };

  kernel = optional (_kernel != null) _kernel.dev;

  buildInputs = [ makeWrapper openssl python27 perl ];

  configureFlags = [
    "--localstatedir=/var"
    "--sharedstatedir=/var"
    "--sbindir=$(out)/bin"
  ] ++ (optionals (_kernel != null) ["--with-linux"]);

  # Leave /var out of this!
  installFlags = [
    "LOGDIR=$(TMPDIR)/dummy"
    "RUNDIR=$(TMPDIR)/dummy"
    "PKIDIR=$(TMPDIR)/dummy"
  ];

  postInstall = ''
    cp debian/ovs-monitor-ipsec $out/share/openvswitch/scripts
    makeWrapper \
      $out/share/openvswitch/scripts/ovs-monitor-ipsec \
      $out/bin/ovs-monitor-ipsec \
      --prefix PYTHONPATH : "$out/share/openvswitch/python"
    substituteInPlace $out/share/openvswitch/scripts/ovs-monitor-ipsec \
      --replace "UnixctlServer.create(None)" "UnixctlServer.create(os.environ['UNIXCTLPATH'])"
    substituteInPlace $out/share/openvswitch/scripts/ovs-monitor-ipsec \
      --replace "self.psk_file" "root_prefix + self.psk_file"
    substituteInPlace $out/share/openvswitch/scripts/ovs-monitor-ipsec \
      --replace "self.cert_dir" "root_prefix + self.cert_dir"
  '';

  meta = {
    platforms = platforms.linux;
    description = "A multilayer virtual switch";
    longDescription =
      ''
      Open vSwitch is a production quality, multilayer virtual switch
      licensed under the open source Apache 2.0 license. It is
      designed to enable massive network automation through
      programmatic extension, while still supporting standard
      management interfaces and protocols (e.g. NetFlow, sFlow, SPAN,
      RSPAN, CLI, LACP, 802.1ag). In addition, it is designed to
      support distribution across multiple physical servers similar
      to VMware's vNetwork distributed vswitch or Cisco's Nexus 1000V.
      '';
    homepage = "http://openvswitch.org/";
    licence = "Apache 2.0";
  };
}