Updated RunIn API to match the new console handling behavior in HEAD.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)

namespaces/execin.go

@@ -4,39 +4,37 @@ package namespaces
 
 import (
 	"encoding/json"
+	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/label"
+	"github.com/docker/libcontainer/system"
+	"io"
 	"os"
 	"os/exec"
 	"strconv"
 	"syscall"
-
-	"github.com/docker/libcontainer"
-	"github.com/docker/libcontainer/label"
-	"github.com/docker/libcontainer/system"
 )
 
-// Runs the command under 'args' inside an existing container referred to by 'container'. This API currently does not support a Tty based 'term'.
+// Runs the command under 'args' inside an existing container referred to by 'container'.
 // Returns the exitcode of the command upon success and appropriate error on failure.
-func RunIn(container *libcontainer.Config, state *libcontainer.State, args []string, nsinitPath string, term Terminal, startCallback func()) (int, error) {
-	containerJson, err := getContainerJson(container)
+func RunIn(container *libcontainer.Config, state *libcontainer.State, args []string, nsinitPath string, stdin io.Reader, stdout, stderr io.Writer, console string, startCallback func(*exec.Cmd)) (int, error) {
+	initArgs, err := getNsEnterCommand(strconv.Itoa(state.InitPid), container, console, args)
 	if err != nil {
 		return -1, err
 	}
 
-	var cmd exec.Cmd
-
-	cmd.Path = nsinitPath
-	cmd.Args = getNsEnterCommand(nsinitPath, strconv.Itoa(state.InitPid), containerJson, args)
-
-	if err := term.Attach(&cmd); err != nil {
-		return -1, err
-	}
-	defer term.Close()
+	cmd := exec.Command(nsinitPath, initArgs...)
+	// Note: these are only used in non-tty mode
+	// if there is a tty for the container it will be opened within the namespace and the
+	// fds will be duped to stdin, stdiout, and stderr
+	cmd.Stdin = stdin
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
 
 	if err := cmd.Start(); err != nil {
 		return -1, err
 	}
 	if startCallback != nil {
-		startCallback()
+		startCallback(cmd)
 	}
 
 	if err := cmd.Wait(); err != nil {
@@ -50,16 +48,18 @@ func RunIn(container *libcontainer.Config, state *libcontainer.State, args []str
 
 // ExecIn uses an existing pid and joins the pid's namespaces with the new command.
 func ExecIn(container *libcontainer.Config, state *libcontainer.State, args []string) error {
-	containerJson, err := getContainerJson(container)
+	// Enter the namespace and then finish setup
+	args, err := getNsEnterCommand(strconv.Itoa(state.InitPid), container, "", args)
 	if err != nil {
 		return err
 	}
-	// Enter the namespace and then finish setup
-	finalArgs := getNsEnterCommand(os.Args[0], strconv.Itoa(state.InitPid), containerJson, args)
+
+	finalArgs := append([]string{os.Args[0]}, args...)
 
 	if err := system.Execv(finalArgs[0], finalArgs[0:], os.Environ()); err != nil {
 		return err
 	}
+
 	panic("unreachable")
 }
 
@@ -73,14 +73,25 @@ func getContainerJson(container *libcontainer.Config) (string, error) {
 	return string(containerJson), nil
 }
 
-func getNsEnterCommand(nsinitPath, initPid, containerJson string, args []string) []string {
-	return append([]string{
-		nsinitPath,
+func getNsEnterCommand(initPid string, container *libcontainer.Config, console string, args []string) ([]string, error) {
+	containerJson, err := getContainerJson(container)
+	if err != nil {
+		return nil, err
+	}
+
+	out := []string{
 		"nsenter",
 		"--nspid", initPid,
 		"--containerjson", containerJson,
-		"--",
-	}, args...)
+	}
+
+	if console != "" {
+		out = append(out, "--console", console)
+	}
+	out = append(out, "--")
+	out = append(out, args...)
+
+	return out, nil
 }
 
 // Run a command in a container after entering the namespace.

namespaces/nsenter.go

@@ -88,6 +88,7 @@ void nsenter() {
 	static const struct option longopts[] = {
 		{ "nspid",         required_argument, NULL, 'n' },
 		{ "containerjson", required_argument, NULL, 'c' },
+                { "console",       required_argument, NULL, 't' },
 		{ NULL,            0,                 NULL,  0  }
 	};
 
@@ -95,6 +96,7 @@ void nsenter() {
 	pid_t init_pid = -1;
 	char *init_pid_str = NULL;
 	char *container_json = NULL;
+        char *console = NULL;
 	while ((c = getopt_long_only(argc, argv, "n:s:c:", longopts, NULL)) != -1) {
 		switch (c) {
 		case 'n':
@@ -103,6 +105,9 @@ void nsenter() {
 		case 'c':
 			container_json = optarg;
 			break;
+		case 't':
+			console = optarg;
+			break;
 		}
 	}
 
@@ -121,6 +126,21 @@ void nsenter() {
 	argc -= 3;
 	argv += 3;
 
+        if (setsid() == -1) {
+               fprintf(stderr, "setsid failed. Error: %s\n", strerror(errno));
+               exit(1);
+        }
+
+        // before we setns we need to dup the console
+        int consolefd = -1;
+        if (console != NULL) {
+               consolefd = open(console, O_RDWR);
+               if (consolefd < 0) {
+                    fprintf(stderr, "nsenter: failed to open console %s\n", console, strerror(errno));
+                    exit(1);
+              }
+        }
+
 	// Setns on all supported namespaces.
 	char ns_dir[PATH_MAX];
 	memset(ns_dir, 0, PATH_MAX);
@@ -159,6 +179,21 @@ void nsenter() {
 	// We must fork to actually enter the PID namespace.
 	int child = fork();
 	if (child == 0) {
+       if (consolefd != -1) {
+        if (dup2(consolefd, STDIN_FILENO) != 0) {
+            fprintf(stderr, "nsenter: failed to dup 0 %s\n",  strerror(errno));
+            exit(1);
+        }
+        if (dup2(consolefd, STDOUT_FILENO) != STDOUT_FILENO) {
+            fprintf(stderr, "nsenter: failed to dup 1 %s\n",  strerror(errno));
+            exit(1);
+        }
+        if (dup2(consolefd, STDERR_FILENO) != STDERR_FILENO) {
+            fprintf(stderr, "nsenter: failed to dup 2 %s\n",  strerror(errno));
+            exit(1);
+        }
+}
+
 		// Finish executing, let the Go runtime take over.
 		return;
 	} else {

nsinit/nsenter.go

@@ -14,6 +14,7 @@ var nsenterCommand = cli.Command{
 	Flags: []cli.Flag{
 		cli.IntFlag{Name: "nspid"},
 		cli.StringFlag{Name: "containerjson"},
+		cli.StringFlag{Name: "console"},
 	},
 }