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container.go
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package lxcri
import (
"context"
"fmt"
"os"
"path/filepath"
"strings"
"time"
"github.com/lxc/lxcri/pkg/specki"
"github.com/opencontainers/runtime-spec/specs-go"
"github.com/rs/zerolog"
"golang.org/x/sys/unix"
"gopkg.in/lxc/go-lxc.v2"
)
// ContainerConfig is the configuration for a single Container instance.
type ContainerConfig struct {
// The Spec used to generate the liblxc config file.
// Any changes to the spec after creating the liblxc config file have no effect
// and should be avoided.
// NOTE The Spec must be serialized with the runtime config (lxcri.json)
// This is required because Spec.Annotations are required for Container.State()
// and spec.Namespaces are required for attach.
Spec *specs.Spec
// ContainerID is the identifier of the container.
// The ContainerID is used as name for the containers runtime directory.
// The ContainerID must be unique at least through all containers of a runtime.
// The ContainerID should match the following pattern `[a-z][a-z0-9-_]+`
ContainerID string
// BundlePath is the OCI bundle path.
BundlePath string
ConsoleSocket string `json:",omitempty"`
// MonitorCgroupDir is the cgroup directory path
// for the liblxc monitor process `lxcri-start`
// relative to the cgroup root.
MonitorCgroupDir string
CgroupDir string
// Use systemd encoded cgroup path (from crio-o/conmon)
// is true if /etc/crio/crio.conf#cgroup_manager = "systemd"
SystemdCgroup bool
// LogFile is the liblxc log file path
LogFile string
// LogLevel is the liblxc log level
LogLevel string
// Log is the container Logger
Log zerolog.Logger `json:"-"`
}
// ConfigFilePath returns the path to the liblxc config file.
func (c Container) ConfigFilePath() string {
return c.RuntimePath("config")
}
func (c Container) syncFifoPath() string {
return c.RuntimePath("syncfifo")
}
// RuntimePath returns the absolute path to the given sub path
// within the container runtime directory.
func (c Container) RuntimePath(subPath ...string) string {
return filepath.Join(c.runtimeDir, filepath.Join(subPath...))
}
// Container is the runtime state of a container instance.
type Container struct {
LinuxContainer *lxc.Container `json:"-"`
*ContainerConfig
CreatedAt time.Time
// Pid is the process ID of the liblxc monitor process ( see ExecStart )
Pid int
runtimeDir string
}
func (c *Container) create() error {
if err := os.MkdirAll(c.runtimeDir, 0777); err != nil {
return fmt.Errorf("failed to create container dir: %w", err)
}
if err := os.Chmod(c.runtimeDir, 0777); err != nil {
return errorf("failed to chmod %s: %w", err)
}
f, err := os.OpenFile(c.RuntimePath("config"), os.O_EXCL|os.O_CREATE|os.O_RDWR, 0640)
if err != nil {
return err
}
if err := f.Close(); err != nil {
return fmt.Errorf("failed to close empty config tmpfile: %w", err)
}
c.LinuxContainer, err = lxc.NewContainer(c.ContainerID, filepath.Dir(c.runtimeDir))
if err != nil {
return err
}
return nil
}
func (c *Container) load() error {
err := specki.DecodeJSONFile(c.RuntimePath("lxcri.json"), c)
if err != nil {
return fmt.Errorf("failed to load container config: %w", err)
}
_, err = os.Stat(c.ConfigFilePath())
if err != nil {
return fmt.Errorf("failed to load lxc config file: %w", err)
}
c.LinuxContainer, err = lxc.NewContainer(c.ContainerID, filepath.Dir(c.runtimeDir))
if err != nil {
return fmt.Errorf("failed to create lxc container: %w", err)
}
err = c.LinuxContainer.LoadConfigFile(c.ConfigFilePath())
if err != nil {
return fmt.Errorf("failed to load config file: %w", err)
}
return nil
}
func (c *Container) waitMonitorStopped(ctx context.Context) error {
for {
select {
case <-ctx.Done():
return ctx.Err()
default:
if !c.isMonitorRunning() {
return nil
}
time.Sleep(time.Millisecond * 100)
}
}
}
func (c *Container) isMonitorRunning() bool {
if c.Pid < 2 {
return false
}
var ws unix.WaitStatus
pid, err := unix.Wait4(c.Pid, &ws, unix.WNOHANG, nil)
if pid == c.Pid {
c.Log.Info().Msgf("monitor %d died: exited:%t exit_status:%d signaled:%t signal:%s",
c.Pid, ws.Exited(), ws.ExitStatus(), ws.Signaled(), ws.Signal())
return false
}
// if WNOHANG was specified and one or more child(ren) specified by pid exist,
// but have not yet exited, then 0 is returned
if pid == 0 {
return true
}
// This runtime process may not be the parent of the monitor process
if err == unix.ECHILD {
// check if the process is still runnning
err := unix.Kill(c.Pid, 0)
if err == nil {
return true
}
// it's not running
if err == unix.ESRCH {
return false
}
}
return false
}
func (c *Container) waitCreated(ctx context.Context) error {
for {
select {
case <-ctx.Done():
return ctx.Err()
default:
if !c.isMonitorRunning() {
return fmt.Errorf("monitor already died")
}
state := c.LinuxContainer.State()
if !(state == lxc.RUNNING) {
c.Log.Debug().Stringer("state", state).Msg("wait for state lxc.RUNNING")
time.Sleep(time.Millisecond * 100)
continue
}
initState, err := c.getContainerInitState()
if err != nil {
return err
}
if initState == specs.StateCreated {
return nil
}
return fmt.Errorf("unexpected init state %q", initState)
}
}
}
func (c *Container) waitStarted(ctx context.Context) error {
for {
select {
case <-ctx.Done():
return ctx.Err()
default:
if !c.isMonitorRunning() {
return nil
}
initState, _ := c.getContainerInitState()
if initState != specs.StateCreated {
return nil
}
time.Sleep(time.Millisecond * 10)
}
}
}
// State wraps specs.State and adds runtime specific state.
type State struct {
ContainerState string
RuntimePath string
SpecState specs.State
}
// State returns the runtime state of the containers process.
// The State.Pid value is the PID of the liblxc
// container monitor process (lxcri-start).
func (c *Container) State() (*State, error) {
status, err := c.ContainerState()
if err != nil {
return nil, errorf("failed go get container status: %w", err)
}
state := &State{
ContainerState: c.LinuxContainer.State().String(),
RuntimePath: c.RuntimePath(),
SpecState: specs.State{
Version: c.Spec.Version,
ID: c.ContainerID,
Bundle: c.RuntimePath(),
Pid: c.Pid,
Annotations: c.Spec.Annotations,
Status: status,
},
}
return state, nil
}
// ContainerState returns the current state of the container process,
// as defined by the OCI runtime spec.
func (c *Container) ContainerState() (specs.ContainerState, error) {
return c.state(c.LinuxContainer.State())
}
func (c *Container) state(s lxc.State) (specs.ContainerState, error) {
switch s {
case lxc.STOPPED:
return specs.StateStopped, nil
case lxc.STARTING:
return specs.StateCreating, nil
case lxc.RUNNING, lxc.STOPPING, lxc.ABORTING, lxc.FREEZING, lxc.FROZEN, lxc.THAWED:
return c.getContainerInitState()
default:
return specs.StateStopped, fmt.Errorf("unsupported lxc container state %q", s)
}
}
// getContainerInitState returns the detailed state of the container init process.
// This should be called if the container is in state lxc.RUNNING.
// On error the caller should call getContainerState() again
func (c *Container) getContainerInitState() (specs.ContainerState, error) {
initPid := c.LinuxContainer.InitPid()
if initPid < 1 {
return specs.StateStopped, nil
}
cmdlinePath := fmt.Sprintf("/proc/%d/cmdline", initPid)
cmdline, err := os.ReadFile(cmdlinePath)
// Ignore any error here. Most likely the error will be os.ErrNotExist.
// But I've seen race conditions where ESRCH is returned instead because
// the process has died while opening it's proc directory.
if err != nil {
if !(os.IsNotExist(err) || err == unix.ESRCH) {
c.Log.Warn().Str("file", cmdlinePath).Msgf("open failed: %s", err)
}
// init process died or returned
return specs.StateStopped, nil
}
if string(cmdline) == "/.lxcri/lxcri-init\000" {
return specs.StateCreated, nil
}
return specs.StateRunning, nil
}
func (c *Container) kill(ctx context.Context, signum unix.Signal) error {
c.Log.Info().Int("signum", int(signum)).Msg("killing container process")
// From `man pid_namespaces`: If the "init" process of a PID namespace terminates, the kernel
// terminates all of the processes in the namespace via a SIGKILL signal.
// NOTE: The liblxc monitor process `lxcri-start` doesn't propagate all signals to the init process,
// but handles some signals on its own. E.g SIGHUP tells the monitor process to hang up the terminal
// and terminate the init process with SIGTERM.
err := killCgroup(ctx, c, signum)
if err != nil && !os.IsNotExist(err) {
return fmt.Errorf("failed to kill group: %s", err)
}
return nil
}
// getConfigItem is a wrapper function and returns the
// first value returned by lxc.Container.ConfigItem
func (c *Container) getConfigItem(key string) string {
vals := c.LinuxContainer.ConfigItem(key)
if len(vals) > 0 {
first := vals[0]
// some lxc config values are set to '(null)' if unset eg. lxc.cgroup.dir
// TODO check if this is already fixed
if first != "(null)" {
return first
}
}
return ""
}
// setConfigItem is a wrapper for lxc.Container.setConfigItem.
// and only adds additional logging.
func (c *Container) setConfigItem(key, value string) error {
err := c.LinuxContainer.SetConfigItem(key, value)
if err != nil {
return fmt.Errorf("failed to set config item '%s=%s': %w", key, value, err)
}
c.Log.Debug().Str(key, value).Msg("set config item")
return nil
}
// supportsConfigItem is a wrapper for lxc.Container.IsSupportedConfig item.
func (c *Container) supportsConfigItem(keys ...string) bool {
canCheck := lxc.VersionAtLeast(4, 0, 6)
if !canCheck {
c.Log.Warn().Msg("lxc.IsSupportedConfigItem is broken in liblxc < 4.0.6")
}
for _, key := range keys {
if canCheck && lxc.IsSupportedConfigItem(key) {
continue
}
c.Log.Info().Str("lxc.config", key).Msg("unsupported config item")
return false
}
return true
}
// Release releases resources allocated by the container.
func (c *Container) Release() error {
return c.LinuxContainer.Release()
}
func (c *Container) start(ctx context.Context) error {
// #nosec
fifo, err := os.OpenFile(c.syncFifoPath(), os.O_WRONLY, 0)
if err != nil {
return err
}
if err := fifo.Close(); err != nil {
return err
}
return c.waitStarted(ctx)
}
// ExecOptions contains options for Container.Exec and Container.ExecDetached
type ExecOptions struct {
// Namespaces is the list of container namespaces that the process is attached to.
// The process will is attached to all container namespaces if Namespaces is empty.
Namespaces []specs.LinuxNamespaceType
}
// ExecDetached executes the given process spec within the container.
// The given process is started and the process PID is returned.
// It's up to the caller to wait for the process to exit using the returned PID.
// The container state must be either specs.StateCreated or specs.StateRunning
// The given ExecOptions execOpts, control the execution environment of the the process.
func (c *Container) ExecDetached(proc *specs.Process, execOpts *ExecOptions) (pid int, err error) {
opts, err := c.attachOptions(proc, execOpts)
if err != nil {
return 0, errorf("failed to create attach options: %w", err)
}
pid, err = c.LinuxContainer.RunCommandNoWait(proc.Args, opts)
if err != nil {
return pid, errorf("failed to run exec cmd detached: %w", err)
}
return pid, nil
}
// Exec executes the given process spec within the container.
// It waits for the process to exit and returns its exit code.
// The container state must either be specs.StateCreated or specs.StateRunning
// The given ExecOptions execOpts control the execution environment of the the process.
func (c *Container) Exec(proc *specs.Process, execOpts *ExecOptions) (exitStatus int, err error) {
opts, err := c.attachOptions(proc, execOpts)
if err != nil {
return 0, errorf("failed to create attach options: %w", err)
}
exitStatus, err = c.LinuxContainer.RunCommandStatus(proc.Args, opts)
if err != nil {
return exitStatus, errorf("failed to run exec cmd: %w", err)
}
return exitStatus, nil
}
func (c *Container) attachOptions(procSpec *specs.Process, execOpts *ExecOptions) (lxc.AttachOptions, error) {
opts := lxc.AttachOptions{
StdinFd: 0,
StdoutFd: 1,
StderrFd: 2,
}
if procSpec == nil {
return opts, fmt.Errorf("process spec is nil")
}
opts.Cwd = procSpec.Cwd
// Use the environment defined by the process spec.
opts.ClearEnv = true
opts.Env = procSpec.Env
opts.UID = int(procSpec.User.UID)
opts.GID = int(procSpec.User.GID)
if n := len(procSpec.User.AdditionalGids); n > 0 {
opts.Groups = make([]int, n)
for i, g := range procSpec.User.AdditionalGids {
opts.Groups[i] = int(g)
}
}
if execOpts == nil {
execOpts = new(ExecOptions)
}
if len(execOpts.Namespaces) == 0 {
for t := range namespaceMap {
execOpts.Namespaces = append(execOpts.Namespaces, t)
}
}
c.Log.Debug().Msgf("attaching to namespaces %#v\n", execOpts.Namespaces)
for _, n := range c.Spec.Linux.Namespaces {
for _, t := range execOpts.Namespaces {
if n.Type == t {
if n, ok := namespaceMap[t]; ok {
opts.Namespaces |= n.CloneFlag
}
}
}
}
return opts, nil
}
// SetLog changes log file path and log level of the container (liblxc) instance.
// The settings are only valid until Release is called on this instance.
// The log settings applied at Runtime.Create are active until SetLog is called.
func (c *Container) SetLog(filename string, level string) error {
// Do not write to stdout by default.
// Stdout belongs to the container process.
// Explicitly disable it - allthough it is currently the default.
c.LinuxContainer.SetVerbosity(lxc.Quiet)
err := c.LinuxContainer.SetLogLevel(parseContainerLogLevel(level))
if err != nil {
return fmt.Errorf("failed to set container loglevel: %w", err)
}
if err := c.LinuxContainer.SetLogFile(filename); err != nil {
return fmt.Errorf("failed to set container log file: %w", err)
}
return nil
}
func parseContainerLogLevel(level string) lxc.LogLevel {
switch strings.ToLower(level) {
case "trace":
return lxc.TRACE
case "debug":
return lxc.DEBUG
case "info":
return lxc.INFO
case "notice":
return lxc.NOTICE
case "warn":
return lxc.WARN
case "error":
return lxc.ERROR
case "crit":
return lxc.CRIT
case "alert":
return lxc.ALERT
case "fatal":
return lxc.FATAL
default:
return lxc.WARN
}
}