}

func NetnsSet(n NetnsFd) error {
	if err := unix.Setns(int(n.Fd()), unix.CLONE_NEWNET); err != nil {
		return fmt.Errorf("Error switching to ns fd %v: %v", n.Fd(), err)
	}
	return nil
}

// inspired by netns.Do() but with an existing fd.
func NetnsDo(fdable NetnsFd, toRun func() error) error {
	containedCall := func() error {
		threadNS, err := netns.GetCurrentNS()
		if err != nil {

	return "/host/proc/" + strconv.Itoa(pid) + "/ns/net"
}

func runInHost[T any](f func() (T, error)) (T, error) {
	var res T
	ns, err := netns.GetNS(getPidNamespace(1))
	if err != nil {
		return res, fmt.Errorf("failed to get host network: %v", err)
	}
	err = ns.Do(func(ns netns.NetNS) error {
		var err error
		res, err = f()
		return err
	})
	if err != nil {
		return res, fmt.Errorf("in host network: %v", err)
	}

package nodeagent

import "errors"

func inodeForFd(n NetnsFd) (uint64, error) {
	return 0, errors.New("not implemented")
}

func NetnsSet(n NetnsFd) error {
	return errors.New("not implemented")
}

func OpenNetns(nspath string) (NetnsCloser, error) {
	return nil, errors.New("not implemented")
}

// inspired by netns.Do() but with an existing fd.
func NetnsDo(fdable NetnsFd, toRun func() error) error {

	netns, err := runInHost(func() (string, error) { return getPodNetNs(pod) })
	if err != nil {
		m.With(resultLabel.Value(resultFail)).Increment()
		return fmt.Errorf("get netns: %v", err)
	}
	log = log.WithLabels("netns", netns)

	if err := redirectRunningPod(pod, netns); err != nil {
		log.Errorf("failed to setup redirection: %v", err)

	// in that case, try finding the netns using procfs.
	filter := map[types.UID]*corev1.Pod{
		pod.UID: pod,
	}
	return s.scanProcForPodsAndCache(filter)
}

func (s *NetServer) getOrOpenNetns(pod *corev1.Pod, netNs string) (Netns, error) {
	if netNs == "" {
		return s.getNetns(pod)
	}
	return s.openNetns(pod, netNs)
}

func (s *NetServer) openNetns(pod *corev1.Pod, netNs string) (Netns, error) {

    - on pod add, determines whether pod should have netns setup to redirect to Istio proxy. See [cmdAdd](#cmdadd-workflow) for detailed logic.
        - it connects to K8S using the kubeconfig and JWT token copied from install-cni to get Pod and Namespace. Since this is a short-running command, each invocation creates a new connection.
        - If so, calls `istio-iptables` with params to setup pod netns
        - If ambient, sets up the ambient logic.

var ErrNotImplemented = errors.New("not implemented")

// Program defines a method which programs iptables based on the parameters
// provided in Redirect.
func (ipt *iptables) Program(podName, netns string, rdrct *Redirect) error {
	return ErrNotImplemented

	if existing := p.currentPodCache[uid]; existing.Netns != nil {
		if existing.Netns.Inode() == workload.Netns.Inode() {
			workload.Netns.Close()
			// Replace the workload, but keep the old Netns
			p.currentPodCache[uid] = WorkloadInfo{
				Workload: workload.Workload,
				Netns:    existing.Netns,
			}
			// already in cache
			return existing.Netns
		}
		log.Debug("netns inode mismatch, using the new one")
	}

	cfg.DualStack = rdrct.dualStack
	if err := cfg.FillConfigFromEnvironment(); err != nil {
		return err
	}

	netNs, err := getNs(netns)
	if err != nil {
		err = fmt.Errorf("failed to open netns %q: %s", netns, err)
		return err
	}
	defer netNs.Close()

	return netNs.Do(func(_ ns.NetNS) error {
		log.Infof("============= Start iptables configuration for %v =============", podName)

	ConstructInitialSnapshot(ambientPods []*corev1.Pod) error
	Start(ctx context.Context)

	//	IsPodInMesh(ctx context.Context, pod *metav1.ObjectMeta, netNs string) (bool, error)
	AddPodToMesh(ctx context.Context, pod *corev1.Pod, podIPs []netip.Addr, netNs string) error
	RemovePodFromMesh(ctx context.Context, pod *corev1.Pod) error
	DelPodFromMesh(ctx context.Context, pod *corev1.Pod) error

	Stop()
}