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cmd/run: Optimize 'enter' and 'run' in the non-fallback case #813

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merged 2 commits into from
Jun 25, 2021
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cmd/run: Optimize 'enter' and 'run' in the non-fallback case #813

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323afb9
cmd/run: Split out the code to construct the arguments to 'podman exec'
debarshiray Jun 25, 2021
4536e2c
cmd/run: Optimize 'enter' and 'run' in the non-fallback case
debarshiray Jun 25, 2021
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212 changes: 116 additions & 96 deletions src/cmd/run.go
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,9 @@ var (
distro string
release string
}

runFallbackCommands = [][]string{{"/bin/bash", "-l"}}
runFallbackWorkDirs = []string{"" /* $HOME */}
)

var runCmd = &cobra.Command{
Expand Down Expand Up @@ -265,104 +268,101 @@ func runCommand(container string,

logrus.Debugf("Container %s is initialized", container)

if _, err := isCommandPresent(container, command[0]); err != nil {
if fallbackToBash {
fmt.Fprintf(os.Stderr,
"Error: command %s not found in container %s\n",
command[0],
container)
fmt.Fprintf(os.Stderr, "Using /bin/bash instead.\n")

command = []string{"/bin/bash", "-l"}
} else {
return fmt.Errorf("command %s not found in container %s", command[0], container)
}
if err := runCommandWithFallbacks(container, command, emitEscapeSequence, fallbackToBash); err != nil {
return err
}

if pathPresent, _ := isPathPresent(container, workingDirectory); !pathPresent {
fmt.Fprintf(os.Stderr, "Error: path %s not found in container %s\n",
workingDirectory, container)
fmt.Fprintf(os.Stderr, "Using %s instead.\n",
currentUser.HomeDir)

workingDirectory = currentUser.HomeDir
}
return nil
}

func runCommandWithFallbacks(container string, command []string, emitEscapeSequence, fallbackToBash bool) error {
logrus.Debug("Checking if 'podman exec' supports disabling the detach keys")

var detachKeys []string
var detachKeysSupported bool

if podman.CheckVersion("1.8.1") {
logrus.Debug("'podman exec' supports disabling the detach keys")
detachKeys = []string{"--detach-keys", ""}
detachKeysSupported = true
}

envOptions := utils.GetEnvOptionsForPreservedVariables()
logLevelString := podman.LogLevel.String()

execArgs := []string{
"--log-level", logLevelString,
"exec",
}

execArgs = append(execArgs, detachKeys...)

execArgs = append(execArgs, []string{
"--interactive",
"--tty",
"--user", currentUser.Username,
"--workdir", workingDirectory,
}...)

execArgs = append(execArgs, envOptions...)
runFallbackCommandsIndex := 0
runFallbackWorkDirsIndex := 0
workDir := workingDirectory

execArgs = append(execArgs, []string{
container,
"capsh", "--caps=", "--", "-c", "exec \"$@\"", "/bin/sh",
}...)

execArgs = append(execArgs, command...)
for {
execArgs := constructExecArgs(container, command, detachKeysSupported, envOptions, workDir)

if emitEscapeSequence {
fmt.Printf("\033]777;container;push;%s;toolbox;%s\033\\", container, currentUser.Uid)
}

logrus.Debugf("Running in container %s:", container)
logrus.Debug("podman")
for _, arg := range execArgs {
logrus.Debugf("%s", arg)
}
if emitEscapeSequence {
fmt.Printf("\033]777;container;push;%s;toolbox;%s\033\\", container, currentUser.Uid)
}

exitCode, err := shell.RunWithExitCode("podman", os.Stdin, os.Stdout, nil, execArgs...)
logrus.Debugf("Running in container %s:", container)
logrus.Debug("podman")
for _, arg := range execArgs {
logrus.Debugf("%s", arg)
}

if emitEscapeSequence {
fmt.Printf("\033]777;container;pop;;;%s\033\\", currentUser.Uid)
}
exitCode, err := shell.RunWithExitCode("podman", os.Stdin, os.Stdout, nil, execArgs...)

switch exitCode {
case 0:
if err != nil {
panic("unexpected error: 'podman exec' finished successfully")
}
case 125:
err = fmt.Errorf("failed to invoke 'podman exec' in container %s", container)
case 126:
err = fmt.Errorf("failed to invoke command %s in container %s", command[0], container)
case 127:
if pathPresent, _ := isPathPresent(container, workingDirectory); !pathPresent {
err = fmt.Errorf("directory %s not found in container %s", workingDirectory, container)
} else {
err = fmt.Errorf("command %s not found in container %s", command[0], container)
if emitEscapeSequence {
fmt.Printf("\033]777;container;pop;;;%s\033\\", currentUser.Uid)
}
default:
err = nil
}

if err != nil {
return err
switch exitCode {
case 0:
if err != nil {
panic("unexpected error: 'podman exec' finished successfully")
}
return nil
case 125:
err = fmt.Errorf("failed to invoke 'podman exec' in container %s", container)
return err
case 126:
err = fmt.Errorf("failed to invoke command %s in container %s", command[0], container)
return err
case 127:
if pathPresent, _ := isPathPresent(container, workDir); !pathPresent {
if runFallbackWorkDirsIndex < len(runFallbackWorkDirs) {
fmt.Fprintf(os.Stderr,
"Error: directory %s not found in container %s\n",
workDir,
container)

workDir = runFallbackWorkDirs[runFallbackWorkDirsIndex]
if workDir == "" {
workDir = currentUser.HomeDir
}

fmt.Fprintf(os.Stderr, "Using %s instead.\n", workDir)
runFallbackWorkDirsIndex++
} else {
err = fmt.Errorf("directory %s not found in container %s", workDir, container)
return err
}
} else {
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We can't assume that an exit code of 127 from podman exec means that either the working directory or the command was absent. The given shell might also return with 127, which will get forwarded by podman exec, if the last command that was attempted inside the shell was absent. In such cases this will create a loop.

See #872

if fallbackToBash && runFallbackCommandsIndex < len(runFallbackCommands) {
fmt.Fprintf(os.Stderr,
"Error: command %s not found in container %s\n",
command[0],
container)

command = runFallbackCommands[runFallbackCommandsIndex]
fmt.Fprintf(os.Stderr, "Using %s instead.\n", command[0])

runFallbackCommandsIndex++
} else {
err = fmt.Errorf("command %s not found in container %s", command[0], container)
return err
}
}
default:
return nil
}
}

return nil
panic("code should not be reached")
}

func runHelp(cmd *cobra.Command, args []string) {
Expand Down Expand Up @@ -417,6 +417,45 @@ func callFlatpakSessionHelper(container string) error {
return nil
}

func constructExecArgs(container string,
command []string,
detachKeysSupported bool,
envOptions []string,
workDir string) []string {
var detachKeys []string

if detachKeysSupported {
detachKeys = []string{"--detach-keys", ""}
}

logLevelString := podman.LogLevel.String()

execArgs := []string{
"--log-level", logLevelString,
"exec",
}

execArgs = append(execArgs, detachKeys...)

execArgs = append(execArgs, []string{
"--interactive",
"--tty",
"--user", currentUser.Username,
"--workdir", workDir,
}...)

execArgs = append(execArgs, envOptions...)

execArgs = append(execArgs, []string{
container,
"capsh", "--caps=", "--", "-c", "exec \"$@\"", "/bin/sh",
}...)

execArgs = append(execArgs, command...)

return execArgs
}

func getEntryPointAndPID(container string) (string, int, error) {
logrus.Debugf("Inspecting entry point of container %s", container)

Expand Down Expand Up @@ -449,25 +488,6 @@ func getEntryPointAndPID(container string) (string, int, error) {
return entryPoint, entryPointPIDInt, nil
}

func isCommandPresent(container, command string) (bool, error) {
logrus.Debugf("Looking for command %s in container %s", command, container)

logLevelString := podman.LogLevel.String()
args := []string{
"--log-level", logLevelString,
"exec",
"--user", currentUser.Username,
container,
"sh", "-c", "command -v \"$1\"", "sh", command,
}

if err := shell.Run("podman", nil, nil, nil, args...); err != nil {
return false, err
}

return true, nil
}

func isPathPresent(container, path string) (bool, error) {
logrus.Debugf("Looking for path %s in container %s", path, container)

Expand Down