Support --pid=container:xxx for nerdctl run cmd

- Add context and client to `setPlatformOptions()`
- Add branch for platform-specific container opts
- Add PIDContainer label into container's labels. It only works on linux
platform.
- Add reconfigPIDContainer() into container's start process. It recovers
the pid namespace from its PIDContainer label.

Signed-off-by: Min Uk Lee <minuk.dev@gmail.com>

README.md

@@ -372,7 +372,7 @@ Basic flags:
 - :whale: `--rm`: Automatically remove the container when it exits
 - :whale: `--pull=(always|missing|never)`: Pull image before running
   - Default: "missing"
-- :whale: `--pid=(host)`: PID namespace to use
+- :whale: `--pid=(host|container:<container>)`: PID namespace to use
 - :whale: `--stop-signal`: Signal to stop a container (default "SIGTERM")
 - :whale: `--stop-timeout`: Timeout (in seconds) to stop a container
 

cmd/nerdctl/restart_linux_test.go

@@ -17,6 +17,8 @@
 package main
 
 import (
+	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/containerd/nerdctl/pkg/testutil"
@@ -42,3 +44,28 @@ func TestRestart(t *testing.T) {
 	newPid := newInspect.State.Pid
 	assert.Assert(t, pid != newPid)
 }
+
+func TestRestartPIDContainer(t *testing.T) {
+	t.Parallel()
+	base := testutil.NewBase(t)
+
+	baseContainerName := testutil.Identifier(t)
+	base.Cmd("run", "-d", "--name", baseContainerName, testutil.AlpineImage, "sleep", "infinity").Run()
+	defer base.Cmd("rm", "-f", baseContainerName).Run()
+
+	sharedContainerName := testutil.Identifier(t)
+	base.Cmd("run", "-d", "--name", sharedContainerName, fmt.Sprintf("--pid=container:%s", baseContainerName), testutil.AlpineImage, "sleep", "infinity").Run()
+	defer base.Cmd("rm", "-f", sharedContainerName).Run()
+
+	base.Cmd("restart", baseContainerName).AssertOK()
+	base.Cmd("restart", sharedContainerName).AssertOK()
+
+	// output format : <inode number> /proc/1/ns/pid
+	// example output: 4026532581 /proc/1/ns/pid
+	basePSResult := base.Cmd("exec", baseContainerName, "ls", "-Li", "/proc/1/ns/pid").Run()
+	baseOutput := strings.TrimSpace(basePSResult.Stdout())
+	sharedPSResult := base.Cmd("exec", sharedContainerName, "ls", "-Li", "/proc/1/ns/pid").Run()
+	sharedOutput := strings.TrimSpace(sharedPSResult.Stdout())
+
+	assert.Equal(t, baseOutput, sharedOutput)
+}

cmd/nerdctl/run.go

@@ -50,6 +50,7 @@ import (
 	"github.com/containerd/nerdctl/pkg/netutil"
 	"github.com/containerd/nerdctl/pkg/platformutil"
 	"github.com/containerd/nerdctl/pkg/referenceutil"
+	"github.com/containerd/nerdctl/pkg/rootlessutil"
 	"github.com/containerd/nerdctl/pkg/strutil"
 	"github.com/containerd/nerdctl/pkg/taskutil"
 	dopts "github.com/docker/cli/opts"
@@ -431,7 +432,7 @@ func createContainer(cmd *cobra.Command, ctx context.Context, client *containerd
 		oci.WithDefaultSpec(),
 	)
 
-	opts, err = setPlatformOptions(opts, cmd, id)
+	opts, err = setPlatformOptions(ctx, opts, cmd, client, id)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -669,6 +670,11 @@ func createContainer(cmd *cobra.Command, ctx context.Context, client *containerd
 	spec := containerd.WithSpec(&s, opts...)
 	cOpts = append(cOpts, spec)
 
+	cOpts, err = setPlatformContainerOptions(ctx, cOpts, cmd, client, id)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	container, err := client.NewContainer(ctx, id, cOpts...)
 	if err != nil {
 		gcContainer := func() {
@@ -1141,3 +1147,46 @@ func parseEnvVars(paths []string) ([]string, error) {
 	}
 	return vars, nil
 }
+
+func generateSharingPIDOpts(ctx context.Context, targetCon containerd.Container) ([]oci.SpecOpts, error) {
+	opts := make([]oci.SpecOpts, 0)
+
+	task, err := targetCon.Task(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+	status, err := task.Status(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if status.Status != containerd.Running {
+		return nil, fmt.Errorf("shared container is not running")
+	}
+
+	spec, err := targetCon.Spec(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	isHost := true
+	for _, n := range spec.Linux.Namespaces {
+		if n.Type == specs.PIDNamespace {
+			isHost = false
+		}
+	}
+	if isHost {
+		opts = append(opts, oci.WithHostNamespace(specs.PIDNamespace))
+		if rootlessutil.IsRootless() {
+			opts = append(opts, withBindMountHostProcfs)
+		}
+	} else {
+		ns := specs.LinuxNamespace{
+			Type: specs.PIDNamespace,
+			Path: fmt.Sprintf("/proc/%d/ns/pid", task.Pid()),
+		}
+		opts = append(opts, oci.WithLinuxNamespace(ns))
+	}
+
+	return opts, nil
+}

cmd/nerdctl/run_freebsd.go

@@ -19,6 +19,7 @@ package main
 import (
 	"context"
 
+	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/oci"
 	"github.com/spf13/cobra"
@@ -38,6 +39,10 @@ func runShellComplete(cmd *cobra.Command, args []string, toComplete string) ([]s
 	return nil, cobra.ShellCompDirectiveNoFileComp
 }
 
-func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]oci.SpecOpts, error) {
+func setPlatformOptions(ctx context.Context, opts []oci.SpecOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]oci.SpecOpts, error) {
 	return opts, nil
 }
+
+func setPlatformContainerOptions(ctx context.Context, cOpts []containerd.NewContainerOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]containerd.NewContainerOpts, error) {
+	return cOpts, nil
+}

cmd/nerdctl/run_linux.go

@@ -21,7 +21,10 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/containerd/containerd"
 	"github.com/containerd/nerdctl/pkg/bypass4netnsutil"
+	"github.com/containerd/nerdctl/pkg/idutil/containerwalker"
+	"github.com/containerd/nerdctl/pkg/labels"
 	"github.com/containerd/nerdctl/pkg/rootlessutil"
 	"github.com/containerd/nerdctl/pkg/strutil"
 	"github.com/docker/go-units"
@@ -55,7 +58,7 @@ func runShellComplete(cmd *cobra.Command, args []string, toComplete string) ([]s
 	}
 }
 
-func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]oci.SpecOpts, error) {
+func setPlatformOptions(ctx context.Context, opts []oci.SpecOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]oci.SpecOpts, error) {
 	opts = append(opts,
 		oci.WithDefaultUnixDevices,
 		WithoutRunMount(), // unmount default tmpfs on "/run": https://github.com/containerd/nerdctl/issues/157)
@@ -128,21 +131,15 @@ func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]o
 		opts = append(opts, oci.WithDevShmSize(shmBytes/1024))
 	}
 
-	pidNs, err := cmd.Flags().GetString("pid")
+	pid, err := cmd.Flags().GetString("pid")
 	if err != nil {
 		return nil, err
 	}
-	pidNs = strings.ToLower(pidNs)
-	if pidNs != "" {
-		if pidNs != "host" {
-			return nil, fmt.Errorf("invalid pid namespace. Set --pid=host to enable host pid namespace")
-		} else {
-			opts = append(opts, oci.WithHostNamespace(specs.PIDNamespace))
-			if rootlessutil.IsRootless() {
-				opts = append(opts, withBindMountHostProcfs)
-			}
-		}
+	pidOpts, err := generatePIDOpts(ctx, client, pid)
+	if err != nil {
+		return nil, err
 	}
+	opts = append(opts, pidOpts...)
 
 	ulimitOpts, err := generateUlimitsOpts(cmd)
 	if err != nil {
@@ -192,6 +189,21 @@ func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]o
 	return opts, nil
 }
 
+func setPlatformContainerOptions(ctx context.Context, cOpts []containerd.NewContainerOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]containerd.NewContainerOpts, error) {
+	pid, err := cmd.Flags().GetString("pid")
+	if err != nil {
+		return nil, err
+	}
+
+	pidCOpts, err := generatePIDCOpts(ctx, client, pid)
+	if err != nil {
+		return nil, err
+	}
+	cOpts = append(cOpts, pidCOpts...)
+
+	return cOpts, nil
+}
+
 func setOOMScoreAdj(opts []oci.SpecOpts, cmd *cobra.Command) ([]oci.SpecOpts, error) {
 	if !cmd.Flags().Changed("oom-score-adj") {
 		return opts, nil
@@ -217,3 +229,83 @@ func withOOMScoreAdj(score int) oci.SpecOpts {
 		return nil
 	}
 }
+
+func generatePIDOpts(ctx context.Context, client *containerd.Client, pid string) ([]oci.SpecOpts, error) {
+	opts := make([]oci.SpecOpts, 0)
+	pid = strings.ToLower(pid)
+
+	switch pid {
+	case "":
+		// do nothing
+	case "host":
+		opts = append(opts, oci.WithHostNamespace(specs.PIDNamespace))
+		if rootlessutil.IsRootless() {
+			opts = append(opts, withBindMountHostProcfs)
+		}
+	default: // container:<id|name>
+		parsed := strings.Split(pid, ":")
+		if len(parsed) < 2 || parsed[0] != "container" {
+			return nil, fmt.Errorf("invalid pid namespace. Set --pid=[host|container:<name|id>")
+		}
+
+		containerName := parsed[1]
+		walker := &containerwalker.ContainerWalker{
+			Client: client,
+			OnFound: func(ctx context.Context, found containerwalker.Found) error {
+				if found.MatchCount > 1 {
+					return fmt.Errorf("multiple IDs found with provided prefix: %s", found.Req)
+				}
+
+				o, err := generateSharingPIDOpts(ctx, found.Container)
+				if err != nil {
+					return err
+				}
+				opts = append(opts, o...)
+
+				return nil
+			},
+		}
+		matchedCount, err := walker.Walk(ctx, containerName)
+		if err != nil {
+			return nil, err
+		}
+		if matchedCount < 1 {
+			return nil, fmt.Errorf("no such container: %s", containerName)
+		}
+	}
+
+	return opts, nil
+}
+
+func generatePIDCOpts(ctx context.Context, client *containerd.Client, pid string) ([]containerd.NewContainerOpts, error) {
+	pid = strings.ToLower(pid)
+
+	cOpts := make([]containerd.NewContainerOpts, 0)
+	parsed := strings.Split(pid, ":")
+	if len(parsed) < 2 || parsed[0] != "container" {
+		// no need to save pid options
+		return cOpts, nil
+	}
+
+	containerName := parsed[1]
+	walker := &containerwalker.ContainerWalker{
+		Client: client,
+		OnFound: func(ctx context.Context, found containerwalker.Found) error {
+			if found.MatchCount > 1 {
+				return fmt.Errorf("multiple IDs found with provided prefix: %s", found.Req)
+			}
+			cOpts = append(cOpts, containerd.WithAdditionalContainerLabels(map[string]string{
+				labels.PIDContainer: containerName,
+			}))
+			return nil
+		},
+	}
+	matchedCount, err := walker.Walk(ctx, containerName)
+	if err != nil {
+		return nil, err
+	}
+	if matchedCount < 1 {
+		return nil, fmt.Errorf("no such container: %s", containerName)
+	}
+	return cOpts, nil
+}

cmd/nerdctl/run_linux_test.go

@@ -75,6 +75,18 @@ func TestRunPidHost(t *testing.T) {
 	base.Cmd("run", "--rm", "--pid=host", testutil.AlpineImage, "ps", "auxw").AssertOutContains(strconv.Itoa(pid))
 }
 
+func TestRunPidContainer(t *testing.T) {
+	t.Parallel()
+	base := testutil.NewBase(t)
+
+	sharedContainerResult := base.Cmd("run", "-d", testutil.AlpineImage, "sleep", "infinity").Run()
+	baseContainerID := strings.TrimSpace(sharedContainerResult.Stdout())
+	defer base.Cmd("rm", "-f", baseContainerID).Run()
+
+	base.Cmd("run", "--rm", fmt.Sprintf("--pid=container:%s", baseContainerID),
+		testutil.AlpineImage, "ps", "ax").AssertOutContains("sleep infinity")
+}
+
 func TestRunIpcHost(t *testing.T) {
 	t.Parallel()
 	base := testutil.NewBase(t)

cmd/nerdctl/run_windows.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/oci"
 	"github.com/docker/go-units"
@@ -40,7 +41,7 @@ func runShellComplete(cmd *cobra.Command, args []string, toComplete string) ([]s
 	return nil, cobra.ShellCompDirectiveNoFileComp
 }
 
-func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]oci.SpecOpts, error) {
+func setPlatformOptions(ctx context.Context, opts []oci.SpecOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]oci.SpecOpts, error) {
 	cpus, err := cmd.Flags().GetFloat64("cpus")
 	if err != nil {
 		return nil, err
@@ -67,3 +68,7 @@ func setPlatformOptions(opts []oci.SpecOpts, cmd *cobra.Command, id string) ([]o
 
 	return opts, nil
 }
+
+func setPlatformContainerOptions(ctx context.Context, cOpts []containerd.NewContainerOpts, cmd *cobra.Command, client *containerd.Client, id string) ([]containerd.NewContainerOpts, error) {
+	return cOpts, nil
+}