libct/configs: add HookList.SetDefaultEnv

1. Make CommandHook.Command a pointer, which reduces the amount of data
   being copied when using hooks, and allows to modify command hooks.

2. Add SetDefaultEnv, which is to be used by the next commit.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### libcontainer API
+ * `configs.CommandHook` struct has changed, Command is now a pointer.
+   Also, `configs.NewCommandHook` now accepts a `*Command`. (#4325)
+
 ## [1.2.0] - 2024-10-22
 
 > できるときにできることをやるんだ。それが今だ。

libcontainer/configs/config.go

@@ -434,6 +434,16 @@ func (hooks Hooks) Run(name HookName, state *specs.State) error {
 	return nil
 }
 
+// SetDefaultEnv sets the environment for those CommandHook entries
+// that do not have one set.
+func (hooks HookList) SetDefaultEnv(env []string) {
+	for _, h := range hooks {
+		if ch, ok := h.(CommandHook); ok && len(ch.Env) == 0 {
+			ch.Env = env
+		}
+	}
+}
+
 type Hook interface {
 	// Run executes the hook with the provided state.
 	Run(*specs.State) error
@@ -463,17 +473,17 @@ type Command struct {
 }
 
 // NewCommandHook will execute the provided command when the hook is run.
-func NewCommandHook(cmd Command) CommandHook {
+func NewCommandHook(cmd *Command) CommandHook {
 	return CommandHook{
 		Command: cmd,
 	}
 }
 
 type CommandHook struct {
-	Command
+	*Command
 }
 
-func (c Command) Run(s *specs.State) error {
+func (c *Command) Run(s *specs.State) error {
 	b, err := json.Marshal(s)
 	if err != nil {
 		return err

libcontainer/configs/config_test.go

@@ -15,7 +15,7 @@ import (
 func TestUnmarshalHooks(t *testing.T) {
 	timeout := time.Second
 
-	hookCmd := configs.NewCommandHook(configs.Command{
+	hookCmd := configs.NewCommandHook(&configs.Command{
 		Path:    "/var/vcap/hooks/hook",
 		Args:    []string{"--pid=123"},
 		Env:     []string{"FOO=BAR"},
@@ -52,7 +52,7 @@ func TestUnmarshalHooksWithInvalidData(t *testing.T) {
 func TestMarshalHooks(t *testing.T) {
 	timeout := time.Second
 
-	hookCmd := configs.NewCommandHook(configs.Command{
+	hookCmd := configs.NewCommandHook(&configs.Command{
 		Path:    "/var/vcap/hooks/hook",
 		Args:    []string{"--pid=123"},
 		Env:     []string{"FOO=BAR"},
@@ -84,7 +84,7 @@ func TestMarshalHooks(t *testing.T) {
 func TestMarshalUnmarshalHooks(t *testing.T) {
 	timeout := time.Second
 
-	hookCmd := configs.NewCommandHook(configs.Command{
+	hookCmd := configs.NewCommandHook(&configs.Command{
 		Path:    "/var/vcap/hooks/hook",
 		Args:    []string{"--pid=123"},
 		Env:     []string{"FOO=BAR"},
@@ -194,7 +194,7 @@ exit 0
 	}
 	defer os.Remove(filename)
 
-	cmdHook := configs.NewCommandHook(configs.Command{
+	cmdHook := configs.NewCommandHook(&configs.Command{
 		Path: filename,
 		Args: []string{filename, "testarg"},
 		Env:  []string{"FOO=BAR"},
@@ -216,7 +216,7 @@ func TestCommandHookRunTimeout(t *testing.T) {
 	}
 	timeout := 100 * time.Millisecond
 
-	cmdHook := configs.NewCommandHook(configs.Command{
+	cmdHook := configs.NewCommandHook(&configs.Command{
 		Path:    "/bin/sleep",
 		Args:    []string{"/bin/sleep", "1"},
 		Timeout: &timeout,

libcontainer/factory_linux_test.go

@@ -31,14 +31,14 @@ func TestFactoryLoadContainer(t *testing.T) {
 		id            = "1"
 		expectedHooks = configs.Hooks{
 			configs.Prestart: configs.HookList{
-				configs.CommandHook{Command: configs.Command{Path: "prestart-hook"}},
+				configs.CommandHook{Command: &configs.Command{Path: "prestart-hook"}},
 			},
 			configs.Poststart: configs.HookList{
-				configs.CommandHook{Command: configs.Command{Path: "poststart-hook"}},
+				configs.CommandHook{Command: &configs.Command{Path: "poststart-hook"}},
 			},
 			configs.Poststop: configs.HookList{
 				unserializableHook{},
-				configs.CommandHook{Command: configs.Command{Path: "poststop-hook"}},
+				configs.CommandHook{Command: &configs.Command{Path: "poststop-hook"}},
 			},
 		}
 		expectedConfig = &configs.Config{

libcontainer/integration/exec_test.go

@@ -1022,13 +1022,13 @@ func TestHook(t *testing.T) {
 			}),
 		},
 		configs.CreateContainer: configs.HookList{
-			configs.NewCommandHook(configs.Command{
+			configs.NewCommandHook(&configs.Command{
 				Path: "/bin/bash",
 				Args: []string{"/bin/bash", "-c", fmt.Sprintf("touch ./%s", hookFiles[configs.CreateContainer])},
 			}),
 		},
 		configs.StartContainer: configs.HookList{
-			configs.NewCommandHook(configs.Command{
+			configs.NewCommandHook(&configs.Command{
 				Path: "/bin/sh",
 				Args: []string{"/bin/sh", "-c", fmt.Sprintf("touch /%s", hookFiles[configs.StartContainer])},
 			}),

libcontainer/specconv/spec_linux.go

@@ -1256,8 +1256,8 @@ func createHooks(rspec *specs.Spec, config *configs.Config) {
 	}
 }
 
-func createCommandHook(h specs.Hook) configs.Command {
-	cmd := configs.Command{
+func createCommandHook(h specs.Hook) *configs.Command {
+	cmd := &configs.Command{
 		Path: h.Path,
 		Args: h.Args,
 		Env:  h.Env,