networking module: vswitches: re-structure dependencies to systemd units

        createVswitchDevice = n: v: nameValuePair "${n}-netdev"

          (let

            managedInterfaces = filter (x: hasAttr x cfg.interfaces) v.interfaces;

            managedInterfaceServices = concatMap (i: [ "network-addresses-${i}.service" "network-link-${i}.service" ]) managedInterfaces;

            virtualInterfaces = filter (x: (hasAttr x cfg.interfaces) && cfg.interfaces.${x}.virtual) v.interfaces;

            virtualInterfaceServices = concatMap (i: [ "${i}-netdev.service" ]) virtualInterfaces;

            deps = map subsystemDevice v.interfaces;

            ofRules = pkgs.writeText "vswitch-${n}-openFlowRules" v.openFlowRules;

          in

          { description = "Open vSwitch Interface ${n}";

            wantedBy = [ "network.target" "vswitchd.service" (subsystemDevice n) ];

            requires = optionals v.bindInterfaces (deps ++ managedInterfaceServices ++ virtualInterfaceServices);

            requiredBy = optionals v.bindInterfaces (managedInterfaceServices ++ virtualInterfaceServices);

            bindsTo = deps ++ [ "vswitchd.service" ];

            wantedBy = [ "network.target" "vswitchd.service" ] ++ deps;

            bindsTo =  [ "vswitchd.service" (subsystemDevice n) ] ++ deps;

            partOf = [ "vswitchd.service" ];

            after = [ "network-pre.target" "vswitchd.service" ] ++ deps ++ managedInterfaceServices ++ virtualInterfaceServices;

            before = [ "network-interfaces.target" (subsystemDevice n) ];

            after = [ "network-pre.target" "vswitchd.service" ] ++ deps;

            before = [ "network-interfaces.target" ];

            serviceConfig.Type = "oneshot";

            serviceConfig.RemainAfterExit = true;

            path = [ pkgs.iproute config.virtualisation.vswitch.package ];

            "The physical network interfaces connected by the vSwitch.";

        };

        bindInterfaces = mkOption {

          type = types.bool;

          default = false;

          description = ''

            If true, then the interfaces of the vSwitch are brought 'up' and especially

            also 'down' together with the vSwitch. That requires that every interfaces

            is configured as a systemd network services.

          '';

        };

        controllers = mkOption {

          type = types.listOf types.str;

          default = [];