Add runc features command

Fix issue 3274

See `types/features/features.go`.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Author: AkihiroSuda

features.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/opencontainers/runc/libcontainer/capabilities"
+	"github.com/opencontainers/runc/libcontainer/configs"
+	"github.com/opencontainers/runc/libcontainer/seccomp"
+	"github.com/opencontainers/runc/libcontainer/specconv"
+	"github.com/opencontainers/runc/types/features"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/urfave/cli"
+)
+
+var featuresCommand = cli.Command{
+	Name:      "features",
+	Usage:     "show the enabled features",
+	ArgsUsage: "",
+	Description: `Show the enabled features.
+   The result is parsable as a JSON.
+   See https://pkg.go.dev/github.com/opencontainers/runc/types/features for the type definition.
+`,
+	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 0, exactArgs); err != nil {
+			return err
+		}
+
+		tru := true
+
+		feat := features.Features{
+			OCIVersionMin: "1.0.0",
+			OCIVersionMax: specs.Version,
+			Annotations: map[string]string{
+				features.AnnotationRuncVersion:           version,
+				features.AnnotationRuncCommit:            gitCommit,
+				features.AnnotationRuncCheckpointEnabled: "true",
+			},
+			Hooks:        configs.KnownHookNames(),
+			MountOptions: specconv.KnownMountOptions(),
+			Linux: &features.Linux{
+				Namespaces:   specconv.KnownNamespaces(),
+				Capabilities: capabilities.KnownCapabilities(),
+				Cgroup: &features.Cgroup{
+					V1:          &tru,
+					V2:          &tru,
+					Systemd:     &tru,
+					SystemdUser: &tru,
+				},
+				Apparmor: &features.Apparmor{
+					Enabled: &tru,
+				},
+				Selinux: &features.Selinux{
+					Enabled: &tru,
+				},
+			},
+		}
+
+		if seccomp.Enabled {
+			feat.Linux.Seccomp = &features.Seccomp{
+				Enabled:   &tru,
+				Actions:   seccomp.KnownActions(),
+				Operators: seccomp.KnownOperators(),
+				Archs:     seccomp.KnownArchs(),
+			}
+			major, minor, patch := seccomp.Version()
+			feat.Annotations[features.AnnotationLibseccompVersion] = fmt.Sprintf("%d.%d.%d", major, minor, patch)
+		}
+
+		enc := json.NewEncoder(context.App.Writer)
+		enc.SetIndent("", "    ")
+		return enc.Encode(feat)
+	},
+}

libcontainer/capabilities/capabilities.go

@@ -35,6 +35,17 @@ func init() {
 	}
 }
 
+// KnownCapabilities returns the list of the known capabilities.
+// Used by `runc features`.
+func KnownCapabilities() []string {
+	list := capability.List()
+	res := make([]string, len(list))
+	for i, c := range list {
+		res[i] = "CAP_" + strings.ToUpper(c.String())
+	}
+	return res
+}
+
 // New creates a new Caps from the given Capabilities config. Unknown Capabilities
 // or Capabilities that are unavailable in the current environment are ignored,
 // printing a warning instead.

libcontainer/configs/config.go

@@ -251,6 +251,19 @@ const (
 	Poststop HookName = "poststop"
 )
 
+// KnownHookNames returns the known hook names.
+// Used by `runc features`.
+func KnownHookNames() []string {
+	return []string{
+		string(Prestart), // deprecated
+		string(CreateRuntime),
+		string(CreateContainer),
+		string(StartContainer),
+		string(Poststart),
+		string(Poststop),
+	}
+}
+
 type Capabilities struct {
 	// Bounding is the set of capabilities checked by the kernel.
 	Bounding []string

libcontainer/seccomp/config.go

@@ -2,6 +2,7 @@ package seccomp
 
 import (
 	"fmt"
+	"sort"
 
 	"github.com/opencontainers/runc/libcontainer/configs"
 )
@@ -16,6 +17,17 @@ var operators = map[string]configs.Operator{
 	"SCMP_CMP_MASKED_EQ": configs.MaskEqualTo,
 }
 
+// KnownOperators returns the list of the known operations.
+// Used by `runc features`.
+func KnownOperators() []string {
+	var res []string
+	for k := range operators {
+		res = append(res, k)
+	}
+	sort.Strings(res)
+	return res
+}
+
 var actions = map[string]configs.Action{
 	"SCMP_ACT_KILL":   configs.Kill,
 	"SCMP_ACT_ERRNO":  configs.Errno,
@@ -26,6 +38,17 @@ var actions = map[string]configs.Action{
 	"SCMP_ACT_NOTIFY": configs.Notify,
 }
 
+// KnownActions returns the list of the known actions.
+// Used by `runc features`.
+func KnownActions() []string {
+	var res []string
+	for k := range actions {
+		res = append(res, k)
+	}
+	sort.Strings(res)
+	return res
+}
+
 var archs = map[string]string{
 	"SCMP_ARCH_X86":         "x86",
 	"SCMP_ARCH_X86_64":      "amd64",
@@ -45,6 +68,17 @@ var archs = map[string]string{
 	"SCMP_ARCH_S390X":       "s390x",
 }
 
+// KnownArchs returns the list of the known archs.
+// Used by `runc features`.
+func KnownArchs() []string {
+	var res []string
+	for k := range archs {
+		res = append(res, k)
+	}
+	sort.Strings(res)
+	return res
+}
+
 // ConvertStringToOperator converts a string into a Seccomp comparison operator.
 // Comparison operators use the names they are assigned by Libseccomp's header.
 // Attempting to convert a string that is not a valid operator results in an

libcontainer/seccomp/seccomp_linux.go

@@ -265,3 +265,6 @@ func matchCall(filter *libseccomp.ScmpFilter, call *configs.Syscall, defAct libs
 func Version() (uint, uint, uint) {
 	return libseccomp.GetLibraryVersion()
 }
+
+// Enabled is true if seccomp support is compiled in.
+const Enabled = true

libcontainer/seccomp/seccomp_unsupported.go

@@ -23,3 +23,6 @@ func InitSeccomp(config *configs.Seccomp) (int, error) {
 func Version() (uint, uint, uint) {
 	return 0, 0, 0
 }
+
+// Enabled is true if seccomp support is compiled in.
+const Enabled = false

libcontainer/specconv/spec_linux.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -105,6 +106,38 @@ func initMaps() {
 	})
 }
 
+// KnownNamespaces returns the list of the known namespaces.
+// Used by `runc features`.
+func KnownNamespaces() []string {
+	initMaps()
+	var res []string
+	for k := range namespaceMapping {
+		res = append(res, string(k))
+	}
+	sort.Strings(res)
+	return res
+}
+
+// KnownMountOptions returns the list of the known mount options.
+// Used by `runc features`.
+func KnownMountOptions() []string {
+	initMaps()
+	var res []string
+	for k := range mountFlags {
+		res = append(res, k)
+	}
+	for k := range mountPropagationMapping {
+		if k != "" {
+			res = append(res, k)
+		}
+	}
+	for k := range extensionFlags {
+		res = append(res, k)
+	}
+	sort.Strings(res)
+	return res
+}
+
 // AllowedDevices is the set of devices which are automatically included for
 // all containers.
 //

main.go

@@ -132,6 +132,7 @@ func main() {
 		startCommand,
 		stateCommand,
 		updateCommand,
+		featuresCommand,
 	}
 	app.Before = func(context *cli.Context) error {
 		if !context.IsSet("root") && xdgRuntimeDir != "" {

types/features/features.go

@@ -0,0 +1,129 @@
+// Package features provides the JSON structure that is printed by `runc features` (since runc v1.1.0).
+package features
+
+// Features represents the supported features of the runtime.
+type Features struct {
+	// OCIVersionMin is the minimum OCI Runtime Spec version recognized by the runtime, e.g., "1.0.0".
+	OCIVersionMin string `json:"ociVersionMin,omitempty"`
+
+	// OCIVersionMax is the maximum OCI Runtime Spec version recognized by the runtime, e.g., "1.0.2-dev".
+	OCIVersionMax string `json:"ociVersionMax,omitempty"`
+
+	// Hooks is the list of the recognized hook names, e.g., "createRuntime".
+	// Nil value means "unknown", not "no support for any hook".
+	Hooks []string `json:"hooks,omitempty"`
+
+	// MountOptions is the list of the recognized mount options, e.g., "ro".
+	// Nil value means "unknown", not "no support for any mount option".
+	MountOptions []string `json:"mountOptions,omitempty"`
+
+	// Linux is specific to Linux.
+	Linux *Linux `json:"linux,omitempty"`
+
+	// Annotations contains implementation-specific annotation strings,
+	// such as the implementation version, and third-party extensions.
+	Annotations map[string]string `json:"annotations,omitempty"`
+}
+
+// Linux is specific to Linux.
+type Linux struct {
+	// Namespaces is the list of the recognized namespaces, e.g., "mount".
+	// Nil value means "unknown", not "no support for any namespace".
+	Namespaces []string `json:"namespaces,omitempty"`
+
+	// Capabilities is the list of the recognized capabilities , e.g., "CAP_SYS_ADMIN".
+	// Nil value means "unknown", not "no support for any capability".
+	Capabilities []string `json:"capabilities,omitempty"`
+
+	Cgroup   *Cgroup   `json:"cgroup,omitempty"`
+	Seccomp  *Seccomp  `json:"seccomp,omitempty"`
+	Apparmor *Apparmor `json:"apparmor,omitempty"`
+	Selinux  *Selinux  `json:"selinux,omitempty"`
+}
+
+// Seccomp represents the "seccomp" field.
+type Seccomp struct {
+	// Enabled is true if seccomp support is compiled in.
+	// Nil value means "unknown", not "false".
+	Enabled *bool `json:"enabled,omitempty"`
+
+	// Actions is the list of the recognized actions, e.g., "SCMP_ACT_NOTIFY".
+	// Nil value means "unknown", not "no support for any action".
+	Actions []string `json:"actions,omitempty"`
+
+	// Operators is the list of the recognized actions, e.g., "SCMP_CMP_NE".
+	// Nil value means "unknown", not "no support for any operator".
+	Operators []string `json:"operators,omitempty"`
+
+	// Operators is the list of the recognized archs, e.g., "SCMP_ARCH_X86_64".
+	// Nil value means "unknown", not "no support for any arch".
+	Archs []string `json:"archs,omitempty"`
+}
+
+// Apparmor represents the "apparmor" field.
+type Apparmor struct {
+	// Enabled is true if AppArmor support is compiled in.
+	// Unrelated to whether the host supports AppArmor or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	Enabled *bool `json:"enabled,omitempty"`
+}
+
+// Selinux represents the "selinux" field.
+type Selinux struct {
+	// Enabled is true if SELinux support is compiled in.
+	// Unrelated to whether the host supports SELinux or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	Enabled *bool `json:"enabled,omitempty"`
+}
+
+// Cgroup represents the "cgroup" field.
+type Cgroup struct {
+	// V1 represents whether Cgroup v1 support is compiled in.
+	// Unrelated to whether the host uses cgroup v1 or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	V1 *bool `json:"v1,omitempty"`
+
+	// V2 represents whether Cgroup v2 support is compiled in.
+	// Unrelated to whether the host uses cgroup v2 or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	V2 *bool `json:"v2,omitempty"`
+
+	// Systemd represents whether systemd-cgroup support is compiled in.
+	// Unrelated to whether the host uses systemd or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	Systemd *bool `json:"systemd,omitempty"`
+
+	// SystemdUser represents whether user-scoped systemd-cgroup support is compiled in.
+	// Unrelated to whether the host uses systemd or not.
+	// Nil value means "unknown", not "false".
+	// Always true in the current version of runc.
+	SystemdUser *bool `json:"systemdUser,omitempty"`
+}
+
+const (
+	// AnnotationRuncVersion represents the version of runc, e.g., "1.2.3", "1.2.3+dev", "1.2.3-rc.4.", "1.2.3-rc.4+dev".
+	// Third party implementations such as crun and runsc MAY use this annotation to report the most compatible runc version,
+	// however, parsing this annotation value is discouraged.
+	AnnotationRuncVersion = "org.opencontainers.runc.version"
+
+	// AnnotationRuncCommit corresponds to the output of `git describe --dirty --long --always` in the runc repo.
+	// Third party implementations such as crun and runsc SHOULD NOT use this annotation, as their repo is different from the runc repo.
+	// Parsing this annotation value is discouraged.
+	AnnotationRuncCommit = "org.opencontainers.runc.commit"
+
+	// AnnotationRuncCheckpointEnabled is set to "true" if CRIU-based checkpointing is supported.
+	// Unrelated to whether the host supports CRIU or not.
+	// Always set to "true" in the current version of runc.
+	// This is defined as an annotation because checkpointing is a runc-specific feature that is not defined in the OCI Runtime Spec.
+	// Third party implementations such as crun and runsc MAY use this annotation.
+	AnnotationRuncCheckpointEnabled = "org.opencontainers.runc.checkpoint.enabled"
+
+	// AnnotationLibseccompVersion is the version of libseccomp, e.g., "2.5.1".
+	// Note that the runtime MAY support seccomp even when this annotation is not present.
+	AnnotationLibseccompVersion = "io.github.seccomp.libseccomp.version"
+)