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package libcontainer
import (
"encoding/json"
"errors"
"fmt"
"io"
"os"
"strconv"
"github.com/opencontainers/runc/libcontainer/utils"
"github.com/sirupsen/logrus"
)
type syncType string
// Constants that are used for synchronisation between the parent and child
// during container setup. They come in pairs (with procError being a generic
// response which is followed by an &initError).
//
// [ child ] <-> [ parent ]
//
// procMountPlease --> [open(2) or open_tree(2) and configure mount]
// Arg: configs.Mount
// <-- procMountFd
// file: mountfd
//
// procSeccomp --> [forward fd to listenerPath]
// file: seccomp fd
// --- no return synchronisation
//
// procHooks --> [run hooks]
// <-- procHooksDone
//
// procReady --> [final setup]
// <-- procRun
//
// procSeccomp --> [grab seccomp fd with pidfd_getfd()]
// <-- procSeccompDone
const (
procError syncType = "procError"
procReady syncType = "procReady"
procRun syncType = "procRun"
procHooks syncType = "procHooks"
procHooksDone syncType = "procHooksDone"
procMountPlease syncType = "procMountPlease"
procMountFd syncType = "procMountFd"
procSeccomp syncType = "procSeccomp"
procSeccompDone syncType = "procSeccompDone"
)
type syncFlags int
const (
syncFlagHasFd syncFlags = (1 << iota)
)
type syncT struct {
Type syncType `json:"type"`
Flags syncFlags `json:"flags"`
Arg *json.RawMessage `json:"arg,omitempty"`
File *os.File `json:"-"` // passed oob through SCM_RIGHTS
}
func (s syncT) String() string {
str := "type:" + string(s.Type)
if s.Flags != 0 {
str += " flags:0b" + strconv.FormatInt(int64(s.Flags), 2)
}
if s.Arg != nil {
str += " arg:" + string(*s.Arg)
}
if s.File != nil {
str += " file:" + s.File.Name() + " (fd:" + strconv.Itoa(int(s.File.Fd())) + ")"
}
return str
}
// initError is used to wrap errors for passing them via JSON,
// as encoding/json can't unmarshal into error type.
type initError struct {
Message string `json:"message,omitempty"`
}
func (i initError) Error() string {
return i.Message
}
func doWriteSync(pipe *syncSocket, sync syncT) error {
sync.Flags &= ^syncFlagHasFd
if sync.File != nil {
sync.Flags |= syncFlagHasFd
}
logrus.Debugf("writing sync %s", sync)
data, err := json.Marshal(sync)
if err != nil {
return fmt.Errorf("marshal sync %v: %w", sync.Type, err)
}
if _, err := pipe.WritePacket(data); err != nil {
return fmt.Errorf("writing sync %v: %w", sync.Type, err)
}
if sync.Flags&syncFlagHasFd != 0 {
logrus.Debugf("writing sync file %s", sync)
if err := utils.SendFile(pipe.File(), sync.File); err != nil {
return fmt.Errorf("sending file after sync %q: %w", sync.Type, err)
}
}
return nil
}
func writeSync(pipe *syncSocket, sync syncType) error {
return doWriteSync(pipe, syncT{Type: sync})
}
func writeSyncArg(pipe *syncSocket, sync syncType, arg interface{}) error {
argJSON, err := json.Marshal(arg)
if err != nil {
return fmt.Errorf("writing sync %v: marshal argument failed: %w", sync, err)
}
argJSONMsg := json.RawMessage(argJSON)
return doWriteSync(pipe, syncT{Type: sync, Arg: &argJSONMsg})
}
func doReadSync(pipe *syncSocket) (syncT, error) {
var sync syncT
logrus.Debugf("reading sync")
packet, err := pipe.ReadPacket()
if err != nil {
if errors.Is(err, io.EOF) {
logrus.Debugf("sync pipe closed")
return sync, err
}
return sync, fmt.Errorf("reading from parent failed: %w", err)
}
if err := json.Unmarshal(packet, &sync); err != nil {
return sync, fmt.Errorf("unmarshal sync from parent failed: %w", err)
}
logrus.Debugf("read sync %s", sync)
if sync.Type == procError {
var ierr initError
if sync.Arg == nil {
return sync, errors.New("procError missing error payload")
}
if err := json.Unmarshal(*sync.Arg, &ierr); err != nil {
return sync, fmt.Errorf("unmarshal procError failed: %w", err)
}
return sync, &ierr
}
if sync.Flags&syncFlagHasFd != 0 {
logrus.Debugf("reading sync file %s", sync)
file, err := utils.RecvFile(pipe.File())
if err != nil {
return sync, fmt.Errorf("receiving fd from sync %v failed: %w", sync.Type, err)
}
sync.File = file
}
return sync, nil
}
func readSyncFull(pipe *syncSocket, expected syncType) (syncT, error) {
sync, err := doReadSync(pipe)
if err != nil {
return sync, err
}
if sync.Type != expected {
return sync, fmt.Errorf("unexpected synchronisation flag: got %q, expected %q", sync.Type, expected)
}
return sync, nil
}
func readSync(pipe *syncSocket, expected syncType) error {
sync, err := readSyncFull(pipe, expected)
if err != nil {
return err
}
if sync.Arg != nil {
return fmt.Errorf("sync %v had unexpected argument passed: %q", expected, string(*sync.Arg))
}
if sync.File != nil {
_ = sync.File.Close()
return fmt.Errorf("sync %v had unexpected file passed", sync.Type)
}
return nil
}
// parseSync runs the given callback function on each syncT received from the
// child. It will return once io.EOF is returned from the given pipe.
func parseSync(pipe *syncSocket, fn func(*syncT) error) error {
for {
sync, err := doReadSync(pipe)
if err != nil {
if errors.Is(err, io.EOF) {
break
}
return err
}
if err := fn(&sync); err != nil {
return err
}
}
return nil
}
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