nixos-containers: add networkNamespace option

        extraFlags+=("--network-bridge=$HOST_BRIDGE")

      fi

      if [ -n "$NETWORK_NAMESPACE_PATH" ]; then

        extraFlags+=("--network-namespace-path=$NETWORK_NAMESPACE_PATH")

      fi

      extraFlags+=(${lib.escapeShellArgs (mapAttrsToList nspawnExtraVethArgs cfg.extraVeths)})

      for iface in $INTERFACES; do

              '';

            };

            networkNamespace = mkOption {

              type = types.nullOr types.path;

              default = null;

              description = ''

                Takes the path to a file representing a kernel network namespace that the container

                shall run in. The specified path should refer to a (possibly bind-mounted) network

                namespace file, as exposed by the kernel below /proc/<PID>/ns/net. This makes the

                container enter the given network namespace. One of the typical use cases is to give

                a network namespace under /run/netns created by ip-netns(8).

                Note that this option cannot be used together with other network-related options,

                such as --private-network or --network-interface=.

              '';

            };

            interfaces = mkOption {

              type = types.listOf types.str;

              default = [];

    {

      warnings = optional (!config.boot.enableContainers && config.containers != {})

        "containers.<name> is used, but boot.enableContainers is false. To use containers.<name>, set boot.enableContainers to true.";

      assertions = let

        mapper = name: cfg: optional (cfg.networkNamespace != null && (cfg.privateNetwork || cfg.interfaces != []))

          "containers.${name}.networkNamespace is mutally exclusive to containers.${name}.privateNetwork and containers.${name}.interfaces.";

      in mkMerge (mapAttrsToList mapper config.containers);

    }

    (mkIf (config.boot.enableContainers) (let

                  LOCAL_ADDRESS6=${cfg.localAddress6}

                ''}

              ''}

              ${optionalString (cfg.networkNamespace != null) ''

                NETWORK_NAMESPACE_PATH=${cfg.networkNamespace}

              ''}

              INTERFACES="${toString cfg.interfaces}"

              MACVLANS="${toString cfg.macvlans}"

              ${optionalString cfg.autoStart ''