Modify nsinit to register actions for argv 0

Signed-off-by: Michael Crosby <[email protected]>

nsinit/cli.go

@@ -7,7 +7,14 @@ import (
 	"github.com/codegangsta/cli"
 )
 
-var logPath = os.Getenv("log")
+var (
+	logPath = os.Getenv("log")
+	argvs   = make(map[string]func())
+)
+
+func init() {
+	argvs["nsenter"] = nsenter
+}
 
 func preload(context *cli.Context) error {
 	if logPath != "" {
@@ -20,7 +27,18 @@ func preload(context *cli.Context) error {
 }
 
 func NsInit() {
+	// we need to check our argv 0 for any registred functions to run instead of the
+	// normal cli code path
+
+	action, exists := argvs[os.Args[0]]
+	if exists {
+		action()
+
+		return
+	}
+
 	app := cli.NewApp()
+
 	app.Name = "nsinit"
 	app.Version = "0.1"
 	app.Author = "libcontainer maintainers"
@@ -36,7 +54,6 @@ func NsInit() {
 		initCommand,
 		statsCommand,
 		configCommand,
-		nsenterCommand,
 		pauseCommand,
 		unpauseCommand,
 	}

nsinit/nsenter.go

@@ -2,23 +2,30 @@ package nsinit
 
 import (
 	"log"
+	"os"
 
-	"github.com/codegangsta/cli"
 	"github.com/docker/libcontainer"
 	"github.com/docker/libcontainer/namespaces"
 	_ "github.com/docker/libcontainer/namespaces/nsenter"
 	"github.com/docker/libcontainer/syncpipe"
 )
 
-var nsenterCommand = cli.Command{
-	Name:   "nsenter",
-	Usage:  "init process for entering an existing namespace",
-	Action: nsenterAction,
+func findUserArgs() []string {
+	i := 0
+	for _, a := range os.Args {
+		i++
+
+		if a == "--" {
+			break
+		}
+	}
+
+	return os.Args[i:]
 }
 
 // this expects that we already have our namespaces setup by the C initializer
 // we are expected to finalize the namespace and exec the user's application
-func nsenterAction(context *cli.Context) {
+func nsenter() {
 	syncPipe, err := syncpipe.NewSyncPipeFromFd(0, 3)
 	if err != nil {
 		log.Fatalf("unable to create sync pipe: %s", err)
@@ -29,7 +36,7 @@ func nsenterAction(context *cli.Context) {
 		log.Fatalf("reading container config from parent: %s", err)
 	}
 
-	if err := namespaces.FinalizeSetns(config, context.Args()); err != nil {
+	if err := namespaces.FinalizeSetns(config, findUserArgs()); err != nil {
 		log.Fatalf("failed to nsenter: %s", err)
 	}
 }