container_linux.go

// +build linux

package libcontainer

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"strings"
	"sync"
	"syscall"

	"github.com/Sirupsen/logrus"
	"github.com/golang/protobuf/proto"
	"github.com/opencontainers/runc/libcontainer/cgroups"
	"github.com/opencontainers/runc/libcontainer/configs"
	"github.com/opencontainers/runc/libcontainer/criurpc"
	"github.com/vishvananda/netlink/nl"
)

const stdioFdCount = 3

type linuxContainer struct {
	id            string
	root          string
	config        *configs.Config
	cgroupManager cgroups.Manager
	initPath      string
	initArgs      []string
	initProcess   parentProcess
	criuPath      string
	m             sync.Mutex
	criuVersion   int
}

// State represents a running container's state
type State struct {
	BaseState

	// Platform specific fields below here

	// Path to all the cgroups setup for a container. Key is cgroup subsystem name
	// with the value as the path.
	CgroupPaths map[string]string `json:"cgroup_paths"`

	// NamespacePaths are filepaths to the container's namespaces. Key is the namespace type
	// with the value as the path.
	NamespacePaths map[configs.NamespaceType]string `json:"namespace_paths"`

	// Container's standard descriptors (std{in,out,err}), needed for checkpoint and restore
	ExternalDescriptors []string `json:"external_descriptors,omitempty"`
}

// A libcontainer container object.
//
// Each container is thread-safe within the same process. Since a container can
// be destroyed by a separate process, any function may return that the container
// was not found.
type Container interface {
	BaseContainer

	// Methods below here are platform specific

	// Checkpoint checkpoints the running container's state to disk using the criu(8) utility.
	//
	// errors:
	// Systemerror - System error.
	Checkpoint(criuOpts *CriuOpts) error

	// Restore restores the checkpointed container to a running state using the criu(8) utiity.
	//
	// errors:
	// Systemerror - System error.
	Restore(process *Process, criuOpts *CriuOpts) error

	// If the Container state is RUNNING or PAUSING, sets the Container state to PAUSING and pauses
	// the execution of any user processes. Asynchronously, when the container finished being paused the
	// state is changed to PAUSED.
	// If the Container state is PAUSED, do nothing.
	//
	// errors:
	// ContainerDestroyed - Container no longer exists,
	// Systemerror - System error.
	Pause() error

	// If the Container state is PAUSED, resumes the execution of any user processes in the
	// Container before setting the Container state to RUNNING.
	// If the Container state is RUNNING, do nothing.
	//
	// errors:
	// ContainerDestroyed - Container no longer exists,
	// Systemerror - System error.
	Resume() error

	// NotifyOOM returns a read-only channel signaling when the container receives an OOM notification.
	//
	// errors:
	// Systemerror - System error.
	NotifyOOM() (<-chan struct{}, error)
}

// ID returns the container's unique ID
func (c *linuxContainer) ID() string {
	return c.id
}

// Config returns the container's configuration
func (c *linuxContainer) Config() configs.Config {
	return *c.config
}

func (c *linuxContainer) Status() (Status, error) {
	c.m.Lock()
	defer c.m.Unlock()
	return c.currentStatus()
}

func (c *linuxContainer) State() (*State, error) {
	c.m.Lock()
	defer c.m.Unlock()
	return c.currentState()
}

func (c *linuxContainer) Processes() ([]int, error) {
	pids, err := c.cgroupManager.GetPids()
	if err != nil {
		return nil, newSystemError(err)
	}
	return pids, nil
}

func (c *linuxContainer) Stats() (*Stats, error) {
	var (
		err   error
		stats = &Stats{}
	)
	if stats.CgroupStats, err = c.cgroupManager.GetStats(); err != nil {
		return stats, newSystemError(err)
	}
	for _, iface := range c.config.Networks {
		switch iface.Type {
		case "veth":
			istats, err := getNetworkInterfaceStats(iface.HostInterfaceName)
			if err != nil {
				return stats, newSystemError(err)
			}
			stats.Interfaces = append(stats.Interfaces, istats)
		}
	}
	return stats, nil
}

func (c *linuxContainer) Set(config configs.Config) error {
	c.m.Lock()
	defer c.m.Unlock()
	c.config = &config
	return c.cgroupManager.Set(c.config)
}

func (c *linuxContainer) Start(process *Process) error {
	c.m.Lock()
	defer c.m.Unlock()
	status, err := c.currentStatus()
	if err != nil {
		return err
	}
	doInit := status == Destroyed
	parent, err := c.newParentProcess(process, doInit)
	if err != nil {
		return newSystemError(err)
	}
	if err := parent.start(); err != nil {
		// terminate the process to ensure that it properly is reaped.
		if err := parent.terminate(); err != nil {
			logrus.Warn(err)
		}
		return newSystemError(err)
	}
	if doInit {
		c.updateState(parent)
	}
	if c.config.Hooks != nil {
		s := configs.HookState{
			Version: c.config.Version,
			ID:      c.id,
			Pid:     parent.pid(),
			Root:    c.config.Rootfs,
		}
		for _, hook := range c.config.Hooks.Poststart {
			if err := hook.Run(s); err != nil {
				if err := parent.terminate(); err != nil {
					logrus.Warn(err)
				}
				return newSystemError(err)
			}
		}
	}
	return nil
}

func (c *linuxContainer) Signal(s os.Signal) error {
	if err := c.initProcess.signal(s); err != nil {
		return newSystemError(err)
	}
	return nil
}

func (c *linuxContainer) newParentProcess(p *Process, doInit bool) (parentProcess, error) {
	parentPipe, childPipe, err := newPipe()
	if err != nil {
		return nil, newSystemError(err)
	}
	cmd, err := c.commandTemplate(p, childPipe)
	if err != nil {
		return nil, newSystemError(err)
	}
	if !doInit {
		return c.newSetnsProcess(p, cmd, parentPipe, childPipe)
	}
	return c.newInitProcess(p, cmd, parentPipe, childPipe)
}

func (c *linuxContainer) commandTemplate(p *Process, childPipe *os.File) (*exec.Cmd, error) {
	cmd := &exec.Cmd{
		Path: c.initPath,
		Args: c.initArgs,
	}
	cmd.Stdin = p.Stdin
	cmd.Stdout = p.Stdout
	cmd.Stderr = p.Stderr
	cmd.Dir = c.config.Rootfs
	if cmd.SysProcAttr == nil {
		cmd.SysProcAttr = &syscall.SysProcAttr{}
	}
	cmd.ExtraFiles = append(p.ExtraFiles, childPipe)
	cmd.Env = append(cmd.Env, fmt.Sprintf("_LIBCONTAINER_INITPIPE=%d", stdioFdCount+len(cmd.ExtraFiles)-1))
	// NOTE: when running a container with no PID namespace and the parent process spawning the container is
	// PID1 the pdeathsig is being delivered to the container's init process by the kernel for some reason
	// even with the parent still running.
	if c.config.ParentDeathSignal > 0 {
		cmd.SysProcAttr.Pdeathsig = syscall.Signal(c.config.ParentDeathSignal)
	}
	return cmd, nil
}

func (c *linuxContainer) newInitProcess(p *Process, cmd *exec.Cmd, parentPipe, childPipe *os.File) (*initProcess, error) {
	t := "_LIBCONTAINER_INITTYPE=standard"
	cloneFlags := c.config.Namespaces.CloneFlags()
	if cloneFlags&syscall.CLONE_NEWUSER != 0 {
		if err := c.addUidGidMappings(cmd.SysProcAttr); err != nil {
			// user mappings are not supported
			return nil, err
		}
		enableSetgroups(cmd.SysProcAttr)
		// Default to root user when user namespaces are enabled.
		if cmd.SysProcAttr.Credential == nil {
			cmd.SysProcAttr.Credential = &syscall.Credential{}
		}
	}
	cmd.Env = append(cmd.Env, t)
	cmd.SysProcAttr.Cloneflags = cloneFlags
	return &initProcess{
		cmd:        cmd,
		childPipe:  childPipe,
		parentPipe: parentPipe,
		manager:    c.cgroupManager,
		config:     c.newInitConfig(p),
		container:  c,
		process:    p,
	}, nil
}

func (c *linuxContainer) newSetnsProcess(p *Process, cmd *exec.Cmd, parentPipe, childPipe *os.File) (*setnsProcess, error) {
	cmd.Env = append(cmd.Env, "_LIBCONTAINER_INITTYPE=setns")
	// for setns process, we dont have to set cloneflags as the process namespaces
	// will only be set via setns syscall
	data, err := c.bootstrapData(0, c.initProcess.pid(), p.consolePath)
	if err != nil {
		return nil, err
	}
	// TODO: set on container for process management
	return &setnsProcess{
		cmd:           cmd,
		cgroupPaths:   c.cgroupManager.GetPaths(),
		childPipe:     childPipe,
		parentPipe:    parentPipe,
		config:        c.newInitConfig(p),
		process:       p,
		bootstrapData: data,
	}, nil
}

func (c *linuxContainer) newInitConfig(process *Process) *initConfig {
	return &initConfig{
		Config:           c.config,
		Args:             process.Args,
		Env:              process.Env,
		User:             process.User,
		Cwd:              process.Cwd,
		Console:          process.consolePath,
		Capabilities:     process.Capabilities,
		PassedFilesCount: len(process.ExtraFiles),
	}
}

func newPipe() (parent *os.File, child *os.File, err error) {
	fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM|syscall.SOCK_CLOEXEC, 0)
	if err != nil {
		return nil, nil, err
	}
	return os.NewFile(uintptr(fds[1]), "parent"), os.NewFile(uintptr(fds[0]), "child"), nil
}

func (c *linuxContainer) Destroy() error {
	c.m.Lock()
	defer c.m.Unlock()
	status, err := c.currentStatus()
	if err != nil {
		return err
	}
	if status != Destroyed {
		return newGenericError(fmt.Errorf("container is not destroyed"), ContainerNotStopped)
	}
	if !c.config.Namespaces.Contains(configs.NEWPID) {
		if err := killCgroupProcesses(c.cgroupManager); err != nil {
			logrus.Warn(err)
		}
	}
	err = c.cgroupManager.Destroy()
	if rerr := os.RemoveAll(c.root); err == nil {
		err = rerr
	}
	c.initProcess = nil
	if c.config.Hooks != nil {
		s := configs.HookState{
			Version: c.config.Version,
			ID:      c.id,
			Root:    c.config.Rootfs,
		}
		for _, hook := range c.config.Hooks.Poststop {
			if err := hook.Run(s); err != nil {
				return err
			}
		}
	}
	return err
}

func (c *linuxContainer) Pause() error {
	c.m.Lock()
	defer c.m.Unlock()
	return c.cgroupManager.Freeze(configs.Frozen)
}

func (c *linuxContainer) Resume() error {
	c.m.Lock()
	defer c.m.Unlock()
	return c.cgroupManager.Freeze(configs.Thawed)
}

func (c *linuxContainer) NotifyOOM() (<-chan struct{}, error) {
	return notifyOnOOM(c.cgroupManager.GetPaths())
}

// XXX debug support, remove when debugging done.
func addArgsFromEnv(evar string, args *[]string) {
	if e := os.Getenv(evar); e != "" {
		for _, f := range strings.Fields(e) {
			*args = append(*args, f)
		}
	}
	fmt.Printf(">>> criu %v\n", *args)
}

// check Criu version greater than or equal to min_version
func (c *linuxContainer) checkCriuVersion(min_version string) error {
	var x, y, z, versionReq int

	_, err := fmt.Sscanf(min_version, "%d.%d.%d\n", &x, &y, &z) // 1.5.2
	if err != nil {
		_, err = fmt.Sscanf(min_version, "Version: %d.%d\n", &x, &y) // 1.6
	}
	versionReq = x*10000 + y*100 + z

	out, err := exec.Command(c.criuPath, "-V").Output()
	if err != nil {
		return fmt.Errorf("Unable to execute CRIU command: %s", c.criuPath)
	}

	x = 0
	y = 0
	z = 0
	if ep := strings.Index(string(out), "-"); ep >= 0 {
		// criu Git version format
		var version string
		if sp := strings.Index(string(out), "GitID"); sp > 0 {
			version = string(out)[sp:ep]
		} else {
			return fmt.Errorf("Unable to parse the CRIU version: %s", c.criuPath)
		}

		n, err := fmt.Sscanf(string(version), "GitID: v%d.%d.%d", &x, &y, &z) // 1.5.2
		if err != nil {
			n, err = fmt.Sscanf(string(version), "GitID: v%d.%d", &x, &y) // 1.6
			y++
		} else {
			z++
		}
		if n < 2 || err != nil {
			return fmt.Errorf("Unable to parse the CRIU version: %s %d %s", version, n, err)
		}
	} else {
		// criu release version format
		n, err := fmt.Sscanf(string(out), "Version: %d.%d.%d\n", &x, &y, &z) // 1.5.2
		if err != nil {
			n, err = fmt.Sscanf(string(out), "Version: %d.%d\n", &x, &y) // 1.6
		}
		if n < 2 || err != nil {
			return fmt.Errorf("Unable to parse the CRIU version: %s %d %s", out, n, err)
		}
	}

	c.criuVersion = x*10000 + y*100 + z

	if c.criuVersion < versionReq {
		return fmt.Errorf("CRIU version must be %s or higher", min_version)
	}

	return nil
}

const descriptorsFilename = "descriptors.json"

func (c *linuxContainer) addCriuDumpMount(req *criurpc.CriuReq, m *configs.Mount) {
	mountDest := m.Destination
	if strings.HasPrefix(mountDest, c.config.Rootfs) {
		mountDest = mountDest[len(c.config.Rootfs):]
	}

	extMnt := &criurpc.ExtMountMap{
		Key: proto.String(mountDest),
		Val: proto.String(mountDest),
	}
	req.Opts.ExtMnt = append(req.Opts.ExtMnt, extMnt)
}

func (c *linuxContainer) Checkpoint(criuOpts *CriuOpts) error {
	c.m.Lock()
	defer c.m.Unlock()

	if err := c.checkCriuVersion("1.5.2"); err != nil {
		return err
	}

	if criuOpts.ImagesDirectory == "" {
		criuOpts.ImagesDirectory = filepath.Join(c.root, "criu.image")
	}

	// Since a container can be C/R'ed multiple times,
	// the checkpoint directory may already exist.
	if err := os.Mkdir(criuOpts.ImagesDirectory, 0755); err != nil && !os.IsExist(err) {
		return err
	}

	if criuOpts.WorkDirectory == "" {
		criuOpts.WorkDirectory = filepath.Join(c.root, "criu.work")
	}

	if err := os.Mkdir(criuOpts.WorkDirectory, 0755); err != nil && !os.IsExist(err) {
		return err
	}

	workDir, err := os.Open(criuOpts.WorkDirectory)
	if err != nil {
		return err
	}
	defer workDir.Close()

	imageDir, err := os.Open(criuOpts.ImagesDirectory)
	if err != nil {
		return err
	}
	defer imageDir.Close()

	rpcOpts := criurpc.CriuOpts{
		ImagesDirFd:    proto.Int32(int32(imageDir.Fd())),
		WorkDirFd:      proto.Int32(int32(workDir.Fd())),
		LogLevel:       proto.Int32(4),
		LogFile:        proto.String("dump.log"),
		Root:           proto.String(c.config.Rootfs),
		ManageCgroups:  proto.Bool(true),
		NotifyScripts:  proto.Bool(true),
		Pid:            proto.Int32(int32(c.initProcess.pid())),
		ShellJob:       proto.Bool(criuOpts.ShellJob),
		LeaveRunning:   proto.Bool(criuOpts.LeaveRunning),
		TcpEstablished: proto.Bool(criuOpts.TcpEstablished),
		ExtUnixSk:      proto.Bool(criuOpts.ExternalUnixConnections),
		FileLocks:      proto.Bool(criuOpts.FileLocks),
	}

	// append optional criu opts, e.g., page-server and port
	if criuOpts.PageServer.Address != "" && criuOpts.PageServer.Port != 0 {
		rpcOpts.Ps = &criurpc.CriuPageServerInfo{
			Address: proto.String(criuOpts.PageServer.Address),
			Port:    proto.Int32(criuOpts.PageServer.Port),
		}
	}

	// append optional manage cgroups mode
	if criuOpts.ManageCgroupsMode != 0 {
		if err := c.checkCriuVersion("1.7"); err != nil {
			return err
		}
		rpcOpts.ManageCgroupsMode = proto.Uint32(uint32(criuOpts.ManageCgroupsMode))
	}

	t := criurpc.CriuReqType_DUMP
	req := &criurpc.CriuReq{
		Type: &t,
		Opts: &rpcOpts,
	}

	for _, m := range c.config.Mounts {
		switch m.Device {
		case "bind":
			c.addCriuDumpMount(req, m)
			break
		case "cgroup":
			binds, err := getCgroupMounts(m)
			if err != nil {
				return err
			}
			for _, b := range binds {
				c.addCriuDumpMount(req, b)
			}
			break
		}
	}

	// Write the FD info to a file in the image directory

	fdsJSON, err := json.Marshal(c.initProcess.externalDescriptors())
	if err != nil {
		return err
	}

	err = ioutil.WriteFile(filepath.Join(criuOpts.ImagesDirectory, descriptorsFilename), fdsJSON, 0655)
	if err != nil {
		return err
	}

	err = c.criuSwrk(nil, req, criuOpts, false)
	if err != nil {
		return err
	}
	return nil
}

func (c *linuxContainer) addCriuRestoreMount(req *criurpc.CriuReq, m *configs.Mount) {
	mountDest := m.Destination
	if strings.HasPrefix(mountDest, c.config.Rootfs) {
		mountDest = mountDest[len(c.config.Rootfs):]
	}

	extMnt := &criurpc.ExtMountMap{
		Key: proto.String(mountDest),
		Val: proto.String(m.Source),
	}
	req.Opts.ExtMnt = append(req.Opts.ExtMnt, extMnt)
}

func (c *linuxContainer) Restore(process *Process, criuOpts *CriuOpts) error {
	c.m.Lock()
	defer c.m.Unlock()

	if err := c.checkCriuVersion("1.5.2"); err != nil {
		return err
	}

	if criuOpts.WorkDirectory == "" {
		criuOpts.WorkDirectory = filepath.Join(c.root, "criu.work")
	}
	// Since a container can be C/R'ed multiple times,
	// the work directory may already exist.
	if err := os.Mkdir(criuOpts.WorkDirectory, 0655); err != nil && !os.IsExist(err) {
		return err
	}

	workDir, err := os.Open(criuOpts.WorkDirectory)
	if err != nil {
		return err
	}
	defer workDir.Close()

	if criuOpts.ImagesDirectory == "" {
		criuOpts.ImagesDirectory = filepath.Join(c.root, "criu.image")
	}
	imageDir, err := os.Open(criuOpts.ImagesDirectory)
	if err != nil {
		return err
	}
	defer imageDir.Close()

	// CRIU has a few requirements for a root directory:
	// * it must be a mount point
	// * its parent must not be overmounted
	// c.config.Rootfs is bind-mounted to a temporary directory
	// to satisfy these requirements.
	root := filepath.Join(c.root, "criu-root")
	if err := os.Mkdir(root, 0755); err != nil {
		return err
	}
	defer os.Remove(root)

	root, err = filepath.EvalSymlinks(root)
	if err != nil {
		return err
	}

	err = syscall.Mount(c.config.Rootfs, root, "", syscall.MS_BIND|syscall.MS_REC, "")
	if err != nil {
		return err
	}
	defer syscall.Unmount(root, syscall.MNT_DETACH)

	t := criurpc.CriuReqType_RESTORE
	req := &criurpc.CriuReq{
		Type: &t,
		Opts: &criurpc.CriuOpts{
			ImagesDirFd:    proto.Int32(int32(imageDir.Fd())),
			WorkDirFd:      proto.Int32(int32(workDir.Fd())),
			EvasiveDevices: proto.Bool(true),
			LogLevel:       proto.Int32(4),
			LogFile:        proto.String("restore.log"),
			RstSibling:     proto.Bool(true),
			Root:           proto.String(root),
			ManageCgroups:  proto.Bool(true),
			NotifyScripts:  proto.Bool(true),
			ShellJob:       proto.Bool(criuOpts.ShellJob),
			ExtUnixSk:      proto.Bool(criuOpts.ExternalUnixConnections),
			TcpEstablished: proto.Bool(criuOpts.TcpEstablished),
			FileLocks:      proto.Bool(criuOpts.FileLocks),
		},
	}

	for _, m := range c.config.Mounts {
		switch m.Device {
		case "bind":
			c.addCriuRestoreMount(req, m)
			break
		case "cgroup":
			binds, err := getCgroupMounts(m)
			if err != nil {
				return err
			}
			for _, b := range binds {
				c.addCriuRestoreMount(req, b)
			}
			break
		}
	}
	for _, iface := range c.config.Networks {
		switch iface.Type {
		case "veth":
			veth := new(criurpc.CriuVethPair)
			veth.IfOut = proto.String(iface.HostInterfaceName)
			veth.IfIn = proto.String(iface.Name)
			req.Opts.Veths = append(req.Opts.Veths, veth)
			break
		case "loopback":
			break
		}
	}
	for _, i := range criuOpts.VethPairs {
		veth := new(criurpc.CriuVethPair)
		veth.IfOut = proto.String(i.HostInterfaceName)
		veth.IfIn = proto.String(i.ContainerInterfaceName)
		req.Opts.Veths = append(req.Opts.Veths, veth)
	}

	// append optional manage cgroups mode
	if criuOpts.ManageCgroupsMode != 0 {
		if err := c.checkCriuVersion("1.7"); err != nil {
			return err
		}
		req.Opts.ManageCgroupsMode = proto.Uint32(uint32(criuOpts.ManageCgroupsMode))
	}

	var (
		fds    []string
		fdJSON []byte
	)

	if fdJSON, err = ioutil.ReadFile(filepath.Join(criuOpts.ImagesDirectory, descriptorsFilename)); err != nil {
		return err
	}

	if err = json.Unmarshal(fdJSON, &fds); err != nil {
		return err
	}

	for i := range fds {
		if s := fds[i]; strings.Contains(s, "pipe:") {
			inheritFd := new(criurpc.InheritFd)
			inheritFd.Key = proto.String(s)
			inheritFd.Fd = proto.Int32(int32(i))
			req.Opts.InheritFd = append(req.Opts.InheritFd, inheritFd)
		}
	}

	err = c.criuSwrk(process, req, criuOpts, true)
	if err != nil {
		return err
	}
	return nil
}

func (c *linuxContainer) criuApplyCgroups(pid int, req *criurpc.CriuReq) error {
	if err := c.cgroupManager.Apply(pid); err != nil {
		return err
	}

	path := fmt.Sprintf("/proc/%d/cgroup", pid)
	cgroupsPaths, err := cgroups.ParseCgroupFile(path)
	if err != nil {
		return err
	}

	for c, p := range cgroupsPaths {
		cgroupRoot := &criurpc.CgroupRoot{
			Ctrl: proto.String(c),
			Path: proto.String(p),
		}
		req.Opts.CgRoot = append(req.Opts.CgRoot, cgroupRoot)
	}

	return nil
}

func (c *linuxContainer) criuSwrk(process *Process, req *criurpc.CriuReq, opts *CriuOpts, applyCgroups bool) error {
	fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_SEQPACKET|syscall.SOCK_CLOEXEC, 0)
	if err != nil {
		return err
	}

	logPath := filepath.Join(opts.WorkDirectory, req.GetOpts().GetLogFile())
	criuClient := os.NewFile(uintptr(fds[0]), "criu-transport-client")
	criuServer := os.NewFile(uintptr(fds[1]), "criu-transport-server")
	defer criuClient.Close()
	defer criuServer.Close()

	args := []string{"swrk", "3"}
	logrus.Debugf("Using CRIU %d at: %s", c.criuVersion, c.criuPath)
	logrus.Debugf("Using CRIU with following args: %s", args)
	cmd := exec.Command(c.criuPath, args...)
	if process != nil {
		cmd.Stdin = process.Stdin
		cmd.Stdout = process.Stdout
		cmd.Stderr = process.Stderr
	}
	cmd.ExtraFiles = append(cmd.ExtraFiles, criuServer)

	if err := cmd.Start(); err != nil {
		return err
	}
	criuServer.Close()

	defer func() {
		criuClient.Close()
		_, err := cmd.Process.Wait()
		if err != nil {
			return
		}
	}()

	if applyCgroups {
		err := c.criuApplyCgroups(cmd.Process.Pid, req)
		if err != nil {
			return err
		}
	}

	var extFds []string
	if process != nil {
		extFds, err = getPipeFds(cmd.Process.Pid)
		if err != nil {
			return err
		}
	}

	logrus.Debugf("Using CRIU in %s mode", req.GetType().String())
	val := reflect.ValueOf(req.GetOpts())
	v := reflect.Indirect(val)
	for i := 0; i < v.NumField(); i++ {
		st := v.Type()
		name := st.Field(i).Name
		if strings.HasPrefix(name, "XXX_") {
			continue
		}
		value := val.MethodByName("Get" + name).Call([]reflect.Value{})
		logrus.Debugf("CRIU option %s with value %v", name, value[0])
	}
	data, err := proto.Marshal(req)
	if err != nil {
		return err
	}
	_, err = criuClient.Write(data)
	if err != nil {
		return err
	}

	buf := make([]byte, 10*4096)
	for true {
		n, err := criuClient.Read(buf)
		if err != nil {
			return err
		}
		if n == 0 {
			return fmt.Errorf("unexpected EOF")
		}
		if n == len(buf) {
			return fmt.Errorf("buffer is too small")
		}

		resp := new(criurpc.CriuResp)
		err = proto.Unmarshal(buf[:n], resp)
		if err != nil {
			return err
		}
		if !resp.GetSuccess() {
			typeString := req.GetType().String()
			return fmt.Errorf("criu failed: type %s errno %d\nlog file: %s", typeString, resp.GetCrErrno(), logPath)
		}

		t := resp.GetType()
		switch {
		case t == criurpc.CriuReqType_NOTIFY:
			if err := c.criuNotifications(resp, process, opts, extFds); err != nil {
				return err
			}
			t = criurpc.CriuReqType_NOTIFY
			req = &criurpc.CriuReq{
				Type:          &t,
				NotifySuccess: proto.Bool(true),
			}
			data, err = proto.Marshal(req)
			if err != nil {
				return err
			}
			n, err = criuClient.Write(data)
			if err != nil {
				return err
			}
			continue
		case t == criurpc.CriuReqType_RESTORE:
		case t == criurpc.CriuReqType_DUMP:
			break
		default:
			return fmt.Errorf("unable to parse the response %s", resp.String())
		}

		break
	}

	// cmd.Wait() waits cmd.goroutines which are used for proxying file descriptors.
	// Here we want to wait only the CRIU process.
	st, err := cmd.Process.Wait()
	if err != nil {
		return err
	}
	if !st.Success() {
		return fmt.Errorf("criu failed: %s\nlog file: %s", st.String(), logPath)
	}
	return nil
}

// block any external network activity
func lockNetwork(config *configs.Config) error {
	for _, config := range config.Networks {
		strategy, err := getStrategy(config.Type)
		if err != nil {
			return err
		}

		if err := strategy.detach(config); err != nil {
			return err
		}
	}
	return nil
}

func unlockNetwork(config *configs.Config) error {
	for _, config := range config.Networks {
		strategy, err := getStrategy(config.Type)
		if err != nil {
			return err
		}
		if err = strategy.attach(config); err != nil {
			return err
		}
	}
	return nil
}

func (c *linuxContainer) criuNotifications(resp *criurpc.CriuResp, process *Process, opts *CriuOpts, fds []string) error {
	notify := resp.GetNotify()
	if notify == nil {
		return fmt.Errorf("invalid response: %s", resp.String())
	}

	switch {
	case notify.GetScript() == "post-dump":
		if !opts.LeaveRunning {
			f, err := os.Create(filepath.Join(c.root, "checkpoint"))
			if err != nil {
				return err
			}
			f.Close()
		}
		break

	case notify.GetScript() == "network-unlock":
		if err := unlockNetwork(c.config); err != nil {
			return err
		}
		break

	case notify.GetScript() == "network-lock":
		if err := lockNetwork(c.config); err != nil {
			return err
		}
		break

	case notify.GetScript() == "post-restore":
		pid := notify.GetPid()
		r, err := newRestoredProcess(int(pid), fds)
		if err != nil {
			return err
		}

		// TODO: crosbymichael restore previous process information by saving the init process information in
		// the container's state file or separate process state files.
		if err := c.updateState(r); err != nil {
			return err
		}
		process.ops = r
		break
	}

	return nil
}

func (c *linuxContainer) updateState(process parentProcess) error {
	c.initProcess = process
	state, err := c.currentState()
	if err != nil {
		return err
	}
	f, err := os.Create(filepath.Join(c.root, stateFilename))
	if err != nil {
		return err
	}
	defer f.Close()
	os.Remove(filepath.Join(c.root, "checkpoint"))
	return json.NewEncoder(f).Encode(state)
}

func (c *linuxContainer) currentStatus() (Status, error) {
	if _, err := os.Stat(filepath.Join(c.root, "checkpoint")); err == nil {
		return Checkpointed, nil
	}
	if c.initProcess == nil {
		return Destroyed, nil
	}
	// return Running if the init process is alive
	if err := syscall.Kill(c.initProcess.pid(), 0); err != nil {
		if err == syscall.ESRCH {
			return Destroyed, nil
		}
		return 0, newSystemError(err)
	}
	if c.config.Cgroups != nil && c.config.Cgroups.Freezer == configs.Frozen {
		return Paused, nil
	}
	return Running, nil
}

func (c *linuxContainer) currentState() (*State, error) {
	status, err := c.currentStatus()
	if err != nil {
		return nil, err
	}
	if status == Destroyed {
		return nil, newGenericError(fmt.Errorf("container destroyed"), ContainerNotExists)
	}
	startTime, err := c.initProcess.startTime()
	if err != nil {
		return nil, newSystemError(err)
	}
	state := &State{
		BaseState: BaseState{
			ID:                   c.ID(),
			Config:               *c.config,
			InitProcessPid:       c.initProcess.pid(),
			InitProcessStartTime: startTime,
		},
		CgroupPaths:         c.cgroupManager.GetPaths(),
		NamespacePaths:      make(map[configs.NamespaceType]string),
		ExternalDescriptors: c.initProcess.externalDescriptors(),
	}
	for _, ns := range c.config.Namespaces {
		state.NamespacePaths[ns.Type] = ns.GetPath(c.initProcess.pid())
	}
	for _, nsType := range configs.NamespaceTypes() {
		if _, ok := state.NamespacePaths[nsType]; !ok {
			ns := configs.Namespace{Type: nsType}
			state.NamespacePaths[ns.Type] = ns.GetPath(c.initProcess.pid())
		}
	}
	return state, nil
}

// bootstrapData encodes the necessary data in netlink binary format as a io.Reader.
// Consumer can write the data to a bootstrap program such as one that uses
// nsenter package to bootstrap the container's init process correctly, i.e. with
// correct namespaces, uid/gid mapping etc.
func (c *linuxContainer) bootstrapData(cloneFlags uintptr, pid int, consolePath string) (io.Reader, error) {
	// create the netlink message
	r := nl.NewNetlinkRequest(int(InitMsg), 0)
	// write pid
	r.AddData(&Int32msg{
		Type:  PidAttr,
		Value: uint32(pid),
	})
	// write console path
	if consolePath != "" {
		r.AddData(&Bytemsg{
			Type:  ConsolePathAttr,
			Value: []byte(consolePath),
		})
	}
	return bytes.NewReader(r.Serialize()), nil
}