docker-docs/vendor/src/github.com/docker/libcontainer/container_linux.go

// +build linux

package libcontainer

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sync"
	"syscall"

	log "github.com/Sirupsen/logrus"
	"github.com/docker/libcontainer/cgroups"
	"github.com/docker/libcontainer/configs"
)

const stdioFdCount = 3

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

// 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 {
			log.Warn(err)
		}
		return newSystemError(err)
	}
	process.ops = parent
	if doInit {

		c.updateState(parent)
	}
	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), nil
	}
	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
		}
		// 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),
	}, nil
}

func (c *linuxContainer) newSetnsProcess(p *Process, cmd *exec.Cmd, parentPipe, childPipe *os.File) *setnsProcess {
	cmd.Env = append(cmd.Env,
		fmt.Sprintf("_LIBCONTAINER_INITPID=%d", c.initProcess.pid()),
		"_LIBCONTAINER_INITTYPE=setns",
	)
	if p.consolePath != "" {
		cmd.Env = append(cmd.Env, "_LIBCONTAINER_CONSOLE_PATH="+p.consolePath)
	}
	// TODO: set on container for process management
	return &setnsProcess{
		cmd:         cmd,
		cgroupPaths: c.cgroupManager.GetPaths(),
		childPipe:   childPipe,
		parentPipe:  parentPipe,
		config:      c.newInitConfig(p),
	}
}

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 {
			log.Warn(err)
		}
	}
	err = c.cgroupManager.Destroy()
	if rerr := os.RemoveAll(c.root); err == nil {
		err = rerr
	}
	c.initProcess = nil
	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())
}

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()
	return json.NewEncoder(f).Encode(state)
}

func (c *linuxContainer) currentStatus() (Status, error) {
	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{
		ID:                   c.ID(),
		Config:               *c.config,
		InitProcessPid:       c.initProcess.pid(),
		InitProcessStartTime: startTime,
		CgroupPaths:          c.cgroupManager.GetPaths(),
		NamespacePaths:       make(map[configs.NamespaceType]string),
	}
	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
}