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|
//go:build freebsd
package unshare
import (
"bytes"
"errors"
"fmt"
"io"
"os"
"os/exec"
"runtime"
"strconv"
"syscall"
"github.com/containers/storage/pkg/reexec"
"github.com/sirupsen/logrus"
)
// Cmd wraps an exec.Cmd created by the reexec package in unshare(),
// and one day might handle setting ID maps and other related setting*s
// by triggering initialization code in the child.
type Cmd struct {
*exec.Cmd
Setsid bool
Setpgrp bool
Ctty *os.File
Hook func(pid int) error
}
// Command creates a new Cmd which can be customized.
func Command(args ...string) *Cmd {
cmd := reexec.Command(args...)
return &Cmd{
Cmd: cmd,
}
}
func (c *Cmd) Start() error {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
// Set environment variables to tell the child to synchronize its startup.
if c.Env == nil {
c.Env = os.Environ()
}
// Create the pipe for reading the child's PID.
pidRead, pidWrite, err := os.Pipe()
if err != nil {
return fmt.Errorf("creating pid pipe: %w", err)
}
c.Env = append(c.Env, fmt.Sprintf("_Containers-pid-pipe=%d", len(c.ExtraFiles)+3))
c.ExtraFiles = append(c.ExtraFiles, pidWrite)
// Create the pipe for letting the child know to proceed.
continueRead, continueWrite, err := os.Pipe()
if err != nil {
pidRead.Close()
pidWrite.Close()
return fmt.Errorf("creating continue read/write pipe: %w", err)
}
c.Env = append(c.Env, fmt.Sprintf("_Containers-continue-pipe=%d", len(c.ExtraFiles)+3))
c.ExtraFiles = append(c.ExtraFiles, continueRead)
// Pass along other instructions.
if c.Setsid {
c.Env = append(c.Env, "_Containers-setsid=1")
}
if c.Setpgrp {
c.Env = append(c.Env, "_Containers-setpgrp=1")
}
if c.Ctty != nil {
c.Env = append(c.Env, fmt.Sprintf("_Containers-ctty=%d", len(c.ExtraFiles)+3))
c.ExtraFiles = append(c.ExtraFiles, c.Ctty)
}
// Make sure we clean up our pipes.
defer func() {
if pidRead != nil {
pidRead.Close()
}
if pidWrite != nil {
pidWrite.Close()
}
if continueRead != nil {
continueRead.Close()
}
if continueWrite != nil {
continueWrite.Close()
}
}()
// Start the new process.
err = c.Cmd.Start()
if err != nil {
return err
}
// Close the ends of the pipes that the parent doesn't need.
continueRead.Close()
continueRead = nil
pidWrite.Close()
pidWrite = nil
// Read the child's PID from the pipe.
pidString := ""
b := new(bytes.Buffer)
if _, err := io.Copy(b, pidRead); err != nil {
return fmt.Errorf("reading child PID: %w", err)
}
pidString = b.String()
pid, err := strconv.Atoi(pidString)
if err != nil {
fmt.Fprintf(continueWrite, "error parsing PID %q: %v", pidString, err)
return fmt.Errorf("parsing PID %q: %w", pidString, err)
}
// Run any additional setup that we want to do before the child starts running proper.
if c.Hook != nil {
if err = c.Hook(pid); err != nil {
fmt.Fprintf(continueWrite, "hook error: %v", err)
return err
}
}
return nil
}
func (c *Cmd) Run() error {
if err := c.Start(); err != nil {
return err
}
return c.Wait()
}
func (c *Cmd) CombinedOutput() ([]byte, error) {
return nil, errors.New("unshare: CombinedOutput() not implemented")
}
func (c *Cmd) Output() ([]byte, error) {
return nil, errors.New("unshare: Output() not implemented")
}
type Runnable interface {
Run() error
}
// ExecRunnable runs the specified unshare command, captures its exit status,
// and exits with the same status.
func ExecRunnable(cmd Runnable, cleanup func()) {
exit := func(status int) {
if cleanup != nil {
cleanup()
}
os.Exit(status)
}
if err := cmd.Run(); err != nil {
if exitError, ok := err.(*exec.ExitError); ok {
if exitError.ProcessState.Exited() {
if waitStatus, ok := exitError.ProcessState.Sys().(syscall.WaitStatus); ok {
if waitStatus.Exited() {
logrus.Debugf("%v", exitError)
exit(waitStatus.ExitStatus())
}
if waitStatus.Signaled() {
logrus.Debugf("%v", exitError)
exit(int(waitStatus.Signal()) + 128)
}
}
}
}
logrus.Errorf("%v", err)
logrus.Errorf("(Unable to determine exit status)")
exit(1)
}
exit(0)
}
|
