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oci_conmon_linux.go
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oci_conmon_linux.go
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// Copyright (c) 2018-2022, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
// Includes code from https://github.com/containers/podman
// Released under the Apache License Version 2.0
package oci
import (
"bufio"
"context"
"encoding/json"
"fmt"
"os"
"os/exec"
"path"
"path/filepath"
"syscall"
"time"
"github.com/google/uuid"
"github.com/sylabs/singularity/v4/internal/pkg/buildcfg"
"github.com/sylabs/singularity/v4/internal/pkg/util/bin"
"github.com/sylabs/singularity/v4/pkg/sylog"
"golang.org/x/sys/unix"
)
type ociError struct {
Level string `json:"level,omitempty"`
Time string `json:"time,omitempty"`
Msg string `json:"msg,omitempty"`
}
// Create creates a container from an OCI bundle
func Create(containerID, bundlePath string, systemdCgroups bool) error {
conmon, err := bin.FindBin("conmon")
if err != nil {
return err
}
runtimeBin, err := Runtime()
if err != nil {
return err
}
// chdir to bundle and lock it, so another oci create cannot use the same bundle
absBundle, err := filepath.Abs(bundlePath)
if err != nil {
return fmt.Errorf("failed to determine bundle absolute path: %w", err)
}
if err := os.Chdir(absBundle); err != nil {
return fmt.Errorf("failed to change directory to %s: %w", absBundle, err)
}
if err := lockBundle(absBundle); err != nil {
return fmt.Errorf("while locking bundle: %w", err)
}
// Create our own state location for conmon and singularity related files
sd, err := stateDir(containerID)
if err != nil {
return fmt.Errorf("while computing state directory: %w", err)
}
err = os.MkdirAll(sd, 0o700)
if err != nil {
return fmt.Errorf("while creating state directory: %w", err)
}
containerUUID, err := uuid.NewRandom()
if err != nil {
return err
}
// Pipes for sync and start communication with conmon
syncFds, err := unix.Socketpair(unix.AF_LOCAL, unix.SOCK_SEQPACKET|unix.SOCK_CLOEXEC, 0)
if err != nil {
return fmt.Errorf("could not create sync socket pair: %w", err)
}
syncChild := os.NewFile(uintptr(syncFds[0]), "sync_child")
syncParent := os.NewFile(uintptr(syncFds[1]), "sync_parent")
defer syncParent.Close()
startFds, err := unix.Socketpair(unix.AF_LOCAL, unix.SOCK_SEQPACKET|unix.SOCK_CLOEXEC, 0)
if err != nil {
return fmt.Errorf("could not create sync socket pair: %w", err)
}
startChild := os.NewFile(uintptr(startFds[0]), "start_child")
startParent := os.NewFile(uintptr(startFds[1]), "start_parent")
defer startParent.Close()
singularityBin := filepath.Join(buildcfg.BINDIR, "singularity")
rsd, err := runtimeStateDir()
if err != nil {
return err
}
cmdArgs := []string{
"--api-version", "1",
"--cid", containerID,
"--name", containerID,
"--cuuid", containerUUID.String(),
"--runtime", runtimeBin,
"--conmon-pidfile", path.Join(sd, conmonPidFile),
"--container-pidfile", path.Join(sd, containerPidFile),
"--log-path", path.Join(sd, containerLogFile),
"--runtime-arg", "--root",
"--runtime-arg", rsd,
"--runtime-arg", "--log",
"--runtime-arg", path.Join(sd, runcLogFile),
"--full-attach",
"--terminal",
"--bundle", absBundle,
"--exit-command", singularityBin,
"--exit-command-arg", "--debug",
"--exit-command-arg", "oci",
"--exit-command-arg", "cleanup",
"--exit-command-arg", containerID,
}
if systemdCgroups {
cmdArgs = append(cmdArgs, "--systemd-cgroup")
}
cmd := exec.Command(conmon, cmdArgs...)
cmd.Dir = absBundle
cmd.Env = append(cmd.Env, fmt.Sprintf("_OCI_SYNCPIPE=%d", 3), fmt.Sprintf("_OCI_STARTPIPE=%d", 4))
cmd.Stdin = os.Stdin
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.SysProcAttr = &syscall.SysProcAttr{
Setpgid: true,
}
cmd.ExtraFiles = append(cmd.ExtraFiles, syncChild, startChild)
// Run conmon and close it's end of the pipes in our parent process
sylog.Debugf("Starting conmon with args %v", cmdArgs)
if err := cmd.Start(); err != nil {
if err2 := releaseBundle(absBundle); err2 != nil {
sylog.Errorf("while releasing bundle: %v", err)
}
return fmt.Errorf("while starting conmon: %w", err)
}
syncChild.Close()
startChild.Close()
// No other setup at present... just signal conmon to start work
writeConmonPipeData(startParent)
// After conmon receives from start pipe it should start container and exit
// without error.
err = cmd.Wait()
if err != nil {
if err2 := releaseBundle(absBundle); err2 != nil {
sylog.Errorf("while releasing bundle: %v", err)
}
return fmt.Errorf("while starting conmon: %w", err)
}
// We check for errors from runc (which conmon invokes) via the sync pipe
pid, err := readConmonPipeData(syncParent, path.Join(sd, runcLogFile))
if err != nil {
if err2 := Delete(context.TODO(), containerID, systemdCgroups); err2 != nil {
sylog.Errorf("Removing container %s from runtime after creation failed", containerID)
}
return err
}
// Create a symlink from the state dir to the bundle, so it's easy to find later on.
bundleLink := path.Join(sd, "bundle")
if err := os.Symlink(absBundle, bundleLink); err != nil {
return fmt.Errorf("could not link attach socket: %w", err)
}
sylog.Infof("Container %s created with PID %d", containerID, pid)
return nil
}
// The following utility functions are taken from https://github.com/containers/podman
// Released under the Apache License Version 2.0
func readConmonPipeData(pipe *os.File, ociLog string) (int, error) {
// syncInfo is used to return data from monitor process to daemon
type syncInfo struct {
Data int `json:"data"`
Message string `json:"message,omitempty"`
}
// Wait to get container pid from conmon
type syncStruct struct {
si *syncInfo
err error
}
ch := make(chan syncStruct)
go func() {
var si *syncInfo
rdr := bufio.NewReader(pipe)
b, err := rdr.ReadBytes('\n')
if err != nil {
ch <- syncStruct{err: err}
}
if err := json.Unmarshal(b, &si); err != nil {
ch <- syncStruct{err: err}
return
}
ch <- syncStruct{si: si}
}()
data := -1
select {
case ss := <-ch:
if ss.err != nil {
if ociLog != "" {
ociLogData, err := os.ReadFile(ociLog)
if err == nil {
var ociErr ociError
if err := json.Unmarshal(ociLogData, &ociErr); err == nil {
return -1, fmt.Errorf("runc error: %s", ociErr.Msg)
}
}
}
return -1, fmt.Errorf("container create failed (no logs from conmon): %w", ss.err)
}
sylog.Debugf("Received: %d", ss.si.Data)
if ss.si.Data < 0 {
if ociLog != "" {
ociLogData, err := os.ReadFile(ociLog)
if err == nil {
var ociErr ociError
if err := json.Unmarshal(ociLogData, &ociErr); err == nil {
return ss.si.Data, fmt.Errorf("runc error: %s", ociErr.Msg)
}
}
}
// If we failed to parse the JSON errors, then print the output as it is
if ss.si.Message != "" {
return ss.si.Data, fmt.Errorf("runc error: %s", ss.si.Message)
}
return ss.si.Data, fmt.Errorf("container creation failed")
}
data = ss.si.Data
case <-time.After(createTimeout):
return -1, fmt.Errorf("container creation timeout")
}
return data, nil
}
// writeConmonPipeData writes nonce data to a pipe
func writeConmonPipeData(pipe *os.File) error {
someData := []byte{0}
_, err := pipe.Write(someData)
return err
}