forked from kubernetes/kubernetes
/
exec.go
208 lines (168 loc) · 4.4 KB
/
exec.go
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package main
import (
"fmt"
"io"
"log"
"os"
"os/exec"
"os/signal"
"syscall"
"text/tabwriter"
"github.com/codegangsta/cli"
"github.com/docker/docker/pkg/term"
"github.com/docker/libcontainer"
consolepkg "github.com/docker/libcontainer/console"
"github.com/docker/libcontainer/namespaces"
)
var execCommand = cli.Command{
Name: "exec",
Usage: "execute a new command inside a container",
Action: execAction,
Flags: []cli.Flag{
cli.BoolFlag{Name: "list", Usage: "list all registered exec functions"},
cli.StringFlag{Name: "func", Value: "exec", Usage: "function name to exec inside a container"},
},
}
func execAction(context *cli.Context) {
if context.Bool("list") {
w := tabwriter.NewWriter(os.Stdout, 10, 1, 3, ' ', 0)
fmt.Fprint(w, "NAME\tUSAGE\n")
for k, f := range argvs {
fmt.Fprintf(w, "%s\t%s\n", k, f.Usage)
}
w.Flush()
return
}
var exitCode int
container, err := loadConfig()
if err != nil {
log.Fatal(err)
}
state, err := libcontainer.GetState(dataPath)
if err != nil && !os.IsNotExist(err) {
log.Fatalf("unable to read state.json: %s", err)
}
if state != nil {
exitCode, err = startInExistingContainer(container, state, context.String("func"), context)
} else {
exitCode, err = startContainer(container, dataPath, []string(context.Args()))
}
if err != nil {
log.Fatalf("failed to exec: %s", err)
}
os.Exit(exitCode)
}
// the process for execing a new process inside an existing container is that we have to exec ourself
// with the nsenter argument so that the C code can setns an the namespaces that we require. Then that
// code path will drop us into the path that we can do the final setup of the namespace and exec the users
// application.
func startInExistingContainer(config *libcontainer.Config, state *libcontainer.State, action string, context *cli.Context) (int, error) {
var (
master *os.File
console string
err error
sigc = make(chan os.Signal, 10)
stdin = os.Stdin
stdout = os.Stdout
stderr = os.Stderr
)
signal.Notify(sigc)
if config.Tty {
stdin = nil
stdout = nil
stderr = nil
master, console, err = consolepkg.CreateMasterAndConsole()
if err != nil {
return -1, err
}
go io.Copy(master, os.Stdin)
go io.Copy(os.Stdout, master)
state, err := term.SetRawTerminal(os.Stdin.Fd())
if err != nil {
return -1, err
}
defer term.RestoreTerminal(os.Stdin.Fd(), state)
}
startCallback := func(cmd *exec.Cmd) {
go func() {
resizeTty(master)
for sig := range sigc {
switch sig {
case syscall.SIGWINCH:
resizeTty(master)
default:
cmd.Process.Signal(sig)
}
}
}()
}
return namespaces.ExecIn(config, state, context.Args(), os.Args[0], action, stdin, stdout, stderr, console, startCallback)
}
// startContainer starts the container. Returns the exit status or -1 and an
// error.
//
// Signals sent to the current process will be forwarded to container.
func startContainer(container *libcontainer.Config, dataPath string, args []string) (int, error) {
var (
cmd *exec.Cmd
sigc = make(chan os.Signal, 10)
)
signal.Notify(sigc)
createCommand := func(container *libcontainer.Config, console, dataPath, init string, pipe *os.File, args []string) *exec.Cmd {
cmd = namespaces.DefaultCreateCommand(container, console, dataPath, init, pipe, args)
if logPath != "" {
cmd.Env = append(cmd.Env, fmt.Sprintf("log=%s", logPath))
}
return cmd
}
var (
master *os.File
console string
err error
stdin = os.Stdin
stdout = os.Stdout
stderr = os.Stderr
)
if container.Tty {
stdin = nil
stdout = nil
stderr = nil
master, console, err = consolepkg.CreateMasterAndConsole()
if err != nil {
return -1, err
}
go io.Copy(master, os.Stdin)
go io.Copy(os.Stdout, master)
state, err := term.SetRawTerminal(os.Stdin.Fd())
if err != nil {
return -1, err
}
defer term.RestoreTerminal(os.Stdin.Fd(), state)
}
startCallback := func() {
go func() {
resizeTty(master)
for sig := range sigc {
switch sig {
case syscall.SIGWINCH:
resizeTty(master)
default:
cmd.Process.Signal(sig)
}
}
}()
}
return namespaces.Exec(container, stdin, stdout, stderr, console, dataPath, args, createCommand, startCallback)
}
func resizeTty(master *os.File) {
if master == nil {
return
}
ws, err := term.GetWinsize(os.Stdin.Fd())
if err != nil {
return
}
if err := term.SetWinsize(master.Fd(), ws); err != nil {
return
}
}