Merge pull request #6270 from mheon/detached_exec

Implement detached exec

1 files changed, 599 insertions, 0 deletions

diff --git a/libpod/oci_conmon_exec_linux.go b/libpod/oci_conmon_exec_linux.go
new file mode 100644
index 000000000..51819f90a
--- /dev/null
+++ b/libpod/oci_conmon_exec_linux.go
@@ -0,0 +1,599 @@
+package libpod
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"syscall"
+	"time"
+
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/libpod/libpod/define"
+	"github.com/containers/libpod/pkg/errorhandling"
+	"github.com/containers/libpod/pkg/util"
+	"github.com/containers/libpod/utils"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+	"k8s.io/client-go/tools/remotecommand"
+)
+
+// ExecContainer executes a command in a running container
+func (r *ConmonOCIRuntime) ExecContainer(c *Container, sessionID string, options *ExecOptions, streams *define.AttachStreams) (int, chan error, error) {
+	if options == nil {
+		return -1, nil, errors.Wrapf(define.ErrInvalidArg, "must provide an ExecOptions struct to ExecContainer")
+	}
+	if len(options.Cmd) == 0 {
+		return -1, nil, errors.Wrapf(define.ErrInvalidArg, "must provide a command to execute")
+	}
+
+	if sessionID == "" {
+		return -1, nil, errors.Wrapf(define.ErrEmptyID, "must provide a session ID for exec")
+	}
+
+	// TODO: Should we default this to false?
+	// Or maybe make streams mandatory?
+	attachStdin := true
+	if streams != nil {
+		attachStdin = streams.AttachInput
+	}
+
+	var ociLog string
+	if logrus.GetLevel() != logrus.DebugLevel && r.supportsJSON {
+		ociLog = c.execOCILog(sessionID)
+	}
+
+	execCmd, pipes, err := r.startExec(c, sessionID, options, attachStdin, ociLog)
+	if err != nil {
+		return -1, nil, err
+	}
+
+	// Only close sync pipe. Start and attach are consumed in the attach
+	// goroutine.
+	defer func() {
+		if pipes.syncPipe != nil && !pipes.syncClosed {
+			errorhandling.CloseQuiet(pipes.syncPipe)
+			pipes.syncClosed = true
+		}
+	}()
+
+	// TODO Only create if !detach
+	// Attach to the container before starting it
+	attachChan := make(chan error)
+	go func() {
+		// attachToExec is responsible for closing pipes
+		attachChan <- c.attachToExec(streams, options.DetachKeys, sessionID, pipes.startPipe, pipes.attachPipe)
+		close(attachChan)
+	}()
+
+	if err := execCmd.Wait(); err != nil {
+		return -1, nil, errors.Wrapf(err, "cannot run conmon")
+	}
+
+	pid, err := readConmonPipeData(pipes.syncPipe, ociLog)
+
+	return pid, attachChan, err
+}
+
+// ExecContainerHTTP executes a new command in an existing container and
+// forwards its standard streams over an attach
+func (r *ConmonOCIRuntime) ExecContainerHTTP(ctr *Container, sessionID string, options *ExecOptions, httpConn net.Conn, httpBuf *bufio.ReadWriter, streams *HTTPAttachStreams, cancel <-chan bool) (int, chan error, error) {
+	if streams != nil {
+		if !streams.Stdin && !streams.Stdout && !streams.Stderr {
+			return -1, nil, errors.Wrapf(define.ErrInvalidArg, "must provide at least one stream to attach to")
+		}
+	}
+
+	if options == nil {
+		return -1, nil, errors.Wrapf(define.ErrInvalidArg, "must provide exec options to ExecContainerHTTP")
+	}
+
+	detachString := config.DefaultDetachKeys
+	if options.DetachKeys != nil {
+		detachString = *options.DetachKeys
+	}
+	detachKeys, err := processDetachKeys(detachString)
+	if err != nil {
+		return -1, nil, err
+	}
+
+	// TODO: Should we default this to false?
+	// Or maybe make streams mandatory?
+	attachStdin := true
+	if streams != nil {
+		attachStdin = streams.Stdin
+	}
+
+	var ociLog string
+	if logrus.GetLevel() != logrus.DebugLevel && r.supportsJSON {
+		ociLog = ctr.execOCILog(sessionID)
+	}
+
+	execCmd, pipes, err := r.startExec(ctr, sessionID, options, attachStdin, ociLog)
+	if err != nil {
+		return -1, nil, err
+	}
+
+	// Only close sync pipe. Start and attach are consumed in the attach
+	// goroutine.
+	defer func() {
+		if pipes.syncPipe != nil && !pipes.syncClosed {
+			errorhandling.CloseQuiet(pipes.syncPipe)
+			pipes.syncClosed = true
+		}
+	}()
+
+	attachChan := make(chan error)
+	go func() {
+		// attachToExec is responsible for closing pipes
+		attachChan <- attachExecHTTP(ctr, sessionID, httpBuf, streams, pipes, detachKeys, options.Terminal, cancel)
+		close(attachChan)
+	}()
+
+	// Wait for conmon to succeed, when return.
+	if err := execCmd.Wait(); err != nil {
+		return -1, nil, errors.Wrapf(err, "cannot run conmon")
+	}
+
+	pid, err := readConmonPipeData(pipes.syncPipe, ociLog)
+
+	return pid, attachChan, err
+}
+
+// ExecContainerDetached executes a command in a running container, but does
+// not attach to it.
+func (r *ConmonOCIRuntime) ExecContainerDetached(ctr *Container, sessionID string, options *ExecOptions, stdin bool) (int, error) {
+	if options == nil {
+		return -1, errors.Wrapf(define.ErrInvalidArg, "must provide exec options to ExecContainerHTTP")
+	}
+
+	var ociLog string
+	if logrus.GetLevel() != logrus.DebugLevel && r.supportsJSON {
+		ociLog = ctr.execOCILog(sessionID)
+	}
+
+	execCmd, pipes, err := r.startExec(ctr, sessionID, options, stdin, ociLog)
+	if err != nil {
+		return -1, err
+	}
+
+	defer func() {
+		pipes.cleanup()
+	}()
+
+	// Wait for Conmon to tell us we're ready to attach.
+	// We aren't actually *going* to attach, but this means that we're good
+	// to proceed.
+	if _, err := readConmonPipeData(pipes.attachPipe, ""); err != nil {
+		return -1, err
+	}
+
+	// Start the exec session
+	if err := writeConmonPipeData(pipes.startPipe); err != nil {
+		return -1, err
+	}
+
+	// Wait for conmon to succeed, when return.
+	if err := execCmd.Wait(); err != nil {
+		return -1, errors.Wrapf(err, "cannot run conmon")
+	}
+
+	pid, err := readConmonPipeData(pipes.syncPipe, ociLog)
+
+	return pid, err
+}
+
+// ExecAttachResize resizes the TTY of the given exec session.
+func (r *ConmonOCIRuntime) ExecAttachResize(ctr *Container, sessionID string, newSize remotecommand.TerminalSize) error {
+	controlFile, err := openControlFile(ctr, ctr.execBundlePath(sessionID))
+	if err != nil {
+		return err
+	}
+	defer controlFile.Close()
+
+	if _, err = fmt.Fprintf(controlFile, "%d %d %d\n", 1, newSize.Height, newSize.Width); err != nil {
+		return errors.Wrapf(err, "failed to write to ctl file to resize terminal")
+	}
+
+	return nil
+}
+
+// ExecStopContainer stops a given exec session in a running container.
+func (r *ConmonOCIRuntime) ExecStopContainer(ctr *Container, sessionID string, timeout uint) error {
+	pid, err := ctr.getExecSessionPID(sessionID)
+	if err != nil {
+		return err
+	}
+
+	logrus.Debugf("Going to stop container %s exec session %s", ctr.ID(), sessionID)
+
+	// Is the session dead?
+	// Ping the PID with signal 0 to see if it still exists.
+	if err := unix.Kill(pid, 0); err != nil {
+		if err == unix.ESRCH {
+			return nil
+		}
+		return errors.Wrapf(err, "error pinging container %s exec session %s PID %d with signal 0", ctr.ID(), sessionID, pid)
+	}
+
+	if timeout > 0 {
+		// Use SIGTERM by default, then SIGSTOP after timeout.
+		logrus.Debugf("Killing exec session %s (PID %d) of container %s with SIGTERM", sessionID, pid, ctr.ID())
+		if err := unix.Kill(pid, unix.SIGTERM); err != nil {
+			if err == unix.ESRCH {
+				return nil
+			}
+			return errors.Wrapf(err, "error killing container %s exec session %s PID %d with SIGTERM", ctr.ID(), sessionID, pid)
+		}
+
+		// Wait for the PID to stop
+		if err := waitPidStop(pid, time.Duration(timeout)*time.Second); err != nil {
+			logrus.Warnf("Timed out waiting for container %s exec session %s to stop, resorting to SIGKILL", ctr.ID(), sessionID)
+		} else {
+			// No error, container is dead
+			return nil
+		}
+	}
+
+	// SIGTERM did not work. On to SIGKILL.
+	logrus.Debugf("Killing exec session %s (PID %d) of container %s with SIGKILL", sessionID, pid, ctr.ID())
+	if err := unix.Kill(pid, unix.SIGTERM); err != nil {
+		if err == unix.ESRCH {
+			return nil
+		}
+		return errors.Wrapf(err, "error killing container %s exec session %s PID %d with SIGKILL", ctr.ID(), sessionID, pid)
+	}
+
+	// Wait for the PID to stop
+	if err := waitPidStop(pid, killContainerTimeout*time.Second); err != nil {
+		return errors.Wrapf(err, "timed out waiting for container %s exec session %s PID %d to stop after SIGKILL", ctr.ID(), sessionID, pid)
+	}
+
+	return nil
+}
+
+// ExecUpdateStatus checks if the given exec session is still running.
+func (r *ConmonOCIRuntime) ExecUpdateStatus(ctr *Container, sessionID string) (bool, error) {
+	pid, err := ctr.getExecSessionPID(sessionID)
+	if err != nil {
+		return false, err
+	}
+
+	logrus.Debugf("Checking status of container %s exec session %s", ctr.ID(), sessionID)
+
+	// Is the session dead?
+	// Ping the PID with signal 0 to see if it still exists.
+	if err := unix.Kill(pid, 0); err != nil {
+		if err == unix.ESRCH {
+			return false, nil
+		}
+		return false, errors.Wrapf(err, "error pinging container %s exec session %s PID %d with signal 0", ctr.ID(), sessionID, pid)
+	}
+
+	return true, nil
+}
+
+// ExecContainerCleanup cleans up files created when a command is run via
+// ExecContainer. This includes the attach socket for the exec session.
+func (r *ConmonOCIRuntime) ExecContainerCleanup(ctr *Container, sessionID string) error {
+	// Clean up the sockets dir. Issue #3962
+	// Also ignore if it doesn't exist for some reason; hence the conditional return below
+	if err := os.RemoveAll(filepath.Join(r.socketsDir, sessionID)); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+// ExecAttachSocketPath is the path to a container's exec session attach socket.
+func (r *ConmonOCIRuntime) ExecAttachSocketPath(ctr *Container, sessionID string) (string, error) {
+	// We don't even use container, so don't validity check it
+	if sessionID == "" {
+		return "", errors.Wrapf(define.ErrInvalidArg, "must provide a valid session ID to get attach socket path")
+	}
+
+	return filepath.Join(r.socketsDir, sessionID, "attach"), nil
+}
+
+// This contains pipes used by the exec API.
+type execPipes struct {
+	syncPipe     *os.File
+	syncClosed   bool
+	startPipe    *os.File
+	startClosed  bool
+	attachPipe   *os.File
+	attachClosed bool
+}
+
+func (p *execPipes) cleanup() {
+	if p.syncPipe != nil && !p.syncClosed {
+		errorhandling.CloseQuiet(p.syncPipe)
+		p.syncClosed = true
+	}
+	if p.startPipe != nil && !p.startClosed {
+		errorhandling.CloseQuiet(p.startPipe)
+		p.startClosed = true
+	}
+	if p.attachPipe != nil && !p.attachClosed {
+		errorhandling.CloseQuiet(p.attachPipe)
+		p.attachClosed = true
+	}
+}
+
+// Start an exec session's conmon parent from the given options.
+func (r *ConmonOCIRuntime) startExec(c *Container, sessionID string, options *ExecOptions, attachStdin bool, ociLog string) (_ *exec.Cmd, _ *execPipes, deferredErr error) {
+	pipes := new(execPipes)
+
+	if options == nil {
+		return nil, nil, errors.Wrapf(define.ErrInvalidArg, "must provide an ExecOptions struct to ExecContainer")
+	}
+	if len(options.Cmd) == 0 {
+		return nil, nil, errors.Wrapf(define.ErrInvalidArg, "must provide a command to execute")
+	}
+
+	if sessionID == "" {
+		return nil, nil, errors.Wrapf(define.ErrEmptyID, "must provide a session ID for exec")
+	}
+
+	// create sync pipe to receive the pid
+	parentSyncPipe, childSyncPipe, err := newPipe()
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "error creating socket pair")
+	}
+	pipes.syncPipe = parentSyncPipe
+
+	defer func() {
+		if deferredErr != nil {
+			pipes.cleanup()
+		}
+	}()
+
+	// create start pipe to set the cgroup before running
+	// attachToExec is responsible for closing parentStartPipe
+	childStartPipe, parentStartPipe, err := newPipe()
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "error creating socket pair")
+	}
+	pipes.startPipe = parentStartPipe
+
+	// create the attach pipe to allow attach socket to be created before
+	// $RUNTIME exec starts running. This is to make sure we can capture all output
+	// from the process through that socket, rather than half reading the log, half attaching to the socket
+	// attachToExec is responsible for closing parentAttachPipe
+	parentAttachPipe, childAttachPipe, err := newPipe()
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "error creating socket pair")
+	}
+	pipes.attachPipe = parentAttachPipe
+
+	childrenClosed := false
+	defer func() {
+		if !childrenClosed {
+			errorhandling.CloseQuiet(childSyncPipe)
+			errorhandling.CloseQuiet(childAttachPipe)
+			errorhandling.CloseQuiet(childStartPipe)
+		}
+	}()
+
+	runtimeDir, err := util.GetRuntimeDir()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	finalEnv := make([]string, 0, len(options.Env))
+	for k, v := range options.Env {
+		finalEnv = append(finalEnv, fmt.Sprintf("%s=%s", k, v))
+	}
+
+	processFile, err := prepareProcessExec(c, options.Cmd, finalEnv, options.Terminal, options.Cwd, options.User, sessionID)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	args := r.sharedConmonArgs(c, sessionID, c.execBundlePath(sessionID), c.execPidPath(sessionID), c.execLogPath(sessionID), c.execExitFileDir(sessionID), ociLog, "")
+
+	if options.PreserveFDs > 0 {
+		args = append(args, formatRuntimeOpts("--preserve-fds", fmt.Sprintf("%d", options.PreserveFDs))...)
+	}
+
+	for _, capability := range options.CapAdd {
+		args = append(args, formatRuntimeOpts("--cap", capability)...)
+	}
+
+	if options.Terminal {
+		args = append(args, "-t")
+	}
+
+	if attachStdin {
+		args = append(args, "-i")
+	}
+
+	// Append container ID and command
+	args = append(args, "-e")
+	// TODO make this optional when we can detach
+	args = append(args, "--exec-attach")
+	args = append(args, "--exec-process-spec", processFile.Name())
+
+	if len(options.ExitCommand) > 0 {
+		args = append(args, "--exit-command", options.ExitCommand[0])
+		for _, arg := range options.ExitCommand[1:] {
+			args = append(args, []string{"--exit-command-arg", arg}...)
+		}
+	}
+
+	logrus.WithFields(logrus.Fields{
+		"args": args,
+	}).Debugf("running conmon: %s", r.conmonPath)
+	// TODO: Need to pass this back so we can wait on it.
+	execCmd := exec.Command(r.conmonPath, args...)
+
+	// TODO: This is commented because it doesn't make much sense in HTTP
+	// attach, and I'm not certain it does for non-HTTP attach as well.
+	// if streams != nil {
+	// 	// Don't add the InputStream to the execCmd. Instead, the data should be passed
+	// 	// through CopyDetachable
+	// 	if streams.AttachOutput {
+	// 		execCmd.Stdout = options.Streams.OutputStream
+	// 	}
+	// 	if streams.AttachError {
+	// 		execCmd.Stderr = options.Streams.ErrorStream
+	// 	}
+	// }
+
+	conmonEnv, extraFiles, err := r.configureConmonEnv(runtimeDir)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if options.PreserveFDs > 0 {
+		for fd := 3; fd < int(3+options.PreserveFDs); fd++ {
+			execCmd.ExtraFiles = append(execCmd.ExtraFiles, os.NewFile(uintptr(fd), fmt.Sprintf("fd-%d", fd)))
+		}
+	}
+
+	// we don't want to step on users fds they asked to preserve
+	// Since 0-2 are used for stdio, start the fds we pass in at preserveFDs+3
+	execCmd.Env = r.conmonEnv
+	execCmd.Env = append(execCmd.Env, fmt.Sprintf("_OCI_SYNCPIPE=%d", options.PreserveFDs+3), fmt.Sprintf("_OCI_STARTPIPE=%d", options.PreserveFDs+4), fmt.Sprintf("_OCI_ATTACHPIPE=%d", options.PreserveFDs+5))
+	execCmd.Env = append(execCmd.Env, conmonEnv...)
+
+	execCmd.ExtraFiles = append(execCmd.ExtraFiles, childSyncPipe, childStartPipe, childAttachPipe)
+	execCmd.ExtraFiles = append(execCmd.ExtraFiles, extraFiles...)
+	execCmd.Dir = c.execBundlePath(sessionID)
+	execCmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+	}
+
+	err = startCommandGivenSelinux(execCmd)
+
+	// We don't need children pipes  on the parent side
+	errorhandling.CloseQuiet(childSyncPipe)
+	errorhandling.CloseQuiet(childAttachPipe)
+	errorhandling.CloseQuiet(childStartPipe)
+	childrenClosed = true
+
+	if err != nil {
+		return nil, nil, errors.Wrapf(err, "cannot start container %s", c.ID())
+	}
+	if err := r.moveConmonToCgroupAndSignal(c, execCmd, parentStartPipe); err != nil {
+		return nil, nil, err
+	}
+
+	if options.PreserveFDs > 0 {
+		for fd := 3; fd < int(3+options.PreserveFDs); fd++ {
+			// These fds were passed down to the runtime.  Close them
+			// and not interfere
+			if err := os.NewFile(uintptr(fd), fmt.Sprintf("fd-%d", fd)).Close(); err != nil {
+				logrus.Debugf("unable to close file fd-%d", fd)
+			}
+		}
+	}
+
+	return execCmd, pipes, nil
+}
+
+// Attach to a container over HTTP
+func attachExecHTTP(c *Container, sessionID string, httpBuf *bufio.ReadWriter, streams *HTTPAttachStreams, pipes *execPipes, detachKeys []byte, isTerminal bool, cancel <-chan bool) error {
+	if pipes == nil || pipes.startPipe == nil || pipes.attachPipe == nil {
+		return errors.Wrapf(define.ErrInvalidArg, "must provide a start and attach pipe to finish an exec attach")
+	}
+
+	defer func() {
+		if !pipes.startClosed {
+			errorhandling.CloseQuiet(pipes.startPipe)
+			pipes.startClosed = true
+		}
+		if !pipes.attachClosed {
+			errorhandling.CloseQuiet(pipes.attachPipe)
+			pipes.attachClosed = true
+		}
+	}()
+
+	logrus.Debugf("Attaching to container %s exec session %s", c.ID(), sessionID)
+
+	// set up the socket path, such that it is the correct length and location for exec
+	sockPath, err := c.execAttachSocketPath(sessionID)
+	if err != nil {
+		return err
+	}
+	socketPath := buildSocketPath(sockPath)
+
+	// 2: read from attachFd that the parent process has set up the console socket
+	if _, err := readConmonPipeData(pipes.attachPipe, ""); err != nil {
+		return err
+	}
+
+	// 2: then attach
+	conn, err := net.DialUnix("unixpacket", nil, &net.UnixAddr{Name: socketPath, Net: "unixpacket"})
+	if err != nil {
+		return errors.Wrapf(err, "failed to connect to container's attach socket: %v", socketPath)
+	}
+	defer func() {
+		if err := conn.Close(); err != nil {
+			logrus.Errorf("unable to close socket: %q", err)
+		}
+	}()
+
+	// Make a channel to pass errors back
+	errChan := make(chan error)
+
+	attachStdout := true
+	attachStderr := true
+	attachStdin := true
+	if streams != nil {
+		attachStdout = streams.Stdout
+		attachStderr = streams.Stderr
+		attachStdin = streams.Stdin
+	}
+
+	// Next, STDIN. Avoid entirely if attachStdin unset.
+	if attachStdin {
+		go func() {
+			logrus.Debugf("Beginning STDIN copy")
+			_, err := utils.CopyDetachable(conn, httpBuf, detachKeys)
+			logrus.Debugf("STDIN copy completed")
+			errChan <- err
+		}()
+	}
+
+	// 4: send start message to child
+	if err := writeConmonPipeData(pipes.startPipe); err != nil {
+		return err
+	}
+
+	// Handle STDOUT/STDERR *after* start message is sent
+	go func() {
+		var err error
+		if isTerminal {
+			// Hack: return immediately if attachStdout not set to
+			// emulate Docker.
+			// Basically, when terminal is set, STDERR goes nowhere.
+			// Everything does over STDOUT.
+			// Therefore, if not attaching STDOUT - we'll never copy
+			// anything from here.
+			logrus.Debugf("Performing terminal HTTP attach for container %s", c.ID())
+			if attachStdout {
+				err = httpAttachTerminalCopy(conn, httpBuf, c.ID())
+			}
+		} else {
+			logrus.Debugf("Performing non-terminal HTTP attach for container %s", c.ID())
+			err = httpAttachNonTerminalCopy(conn, httpBuf, c.ID(), attachStdin, attachStdout, attachStderr)
+		}
+		errChan <- err
+		logrus.Debugf("STDOUT/ERR copy completed")
+	}()
+
+	if cancel != nil {
+		select {
+		case err := <-errChan:
+			return err
+		case <-cancel:
+			return nil
+		}
+	} else {
+		var connErr error = <-errChan
+		return connErr
+	}
+}