mininet: init at 2.3.0d4 (#41261)

Mininet (https://github.com/mininet/mininet) is a popular network emulator that
glues several components such as network namespaces, traffic control
commands into a set of python bindings. It is then "easy" to describe a
topology and run experiments on it.

nixos/modules/programs/mininet.nix

@@ -0,0 +1,39 @@
+# Global configuration for mininet
+# kernel must have NETNS/VETH/SCHED
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg  = config.programs.mininet;
+
+  generatedPath = with pkgs; makeSearchPath "bin"  [
+    iperf ethtool iproute socat
+  ];
+
+  pyEnv = pkgs.python.withPackages(ps: [ ps.mininet-python ]);
+
+  mnexecWrapped = pkgs.runCommand "mnexec-wrapper"
+    { buildInputs = [ pkgs.makeWrapper pkgs.pythonPackages.wrapPython ]; }
+    ''
+      makeWrapper ${pkgs.mininet}/bin/mnexec \
+        $out/bin/mnexec \
+        --prefix PATH : "${generatedPath}"
+
+      ln -s ${pyEnv}/bin/mn $out/bin/mn
+
+      # mn errors out without a telnet binary
+      # pkgs.telnet brings an undesired ifconfig into PATH see #43105
+      ln -s ${pkgs.telnet}/bin/telnet $out/bin/telnet
+    '';
+in
+{
+  options.programs.mininet.enable = mkEnableOption "Mininet";
+
+  config = mkIf cfg.enable {
+
+    virtualisation.vswitch.enable = true;
+
+    environment.systemPackages = [ mnexecWrapped ];
+  };
+}