Add support for drop-in config

Signed-off-by: Harshal Patil <harpatil@redhat.com>

types/options.go

@@ -49,6 +49,12 @@ var (
 	defaultConfigFile = SystemConfigFile
 	// DefaultStoreOptions is a reasonable default set of options.
 	defaultStoreOptions StoreOptions
+
+	// defaultOverrideConfigFile path to override the default system wide storage.conf file
+	defaultOverrideConfigFile = "/etc/containers/storage.conf"
+
+	// defaultDropInConfigDir path to the folder containing drop in config files
+	defaultDropInConfigDir = "/etc/containers/storage.conf.d"
 )
 
 func loadDefaultStoreOptions() {
@@ -114,11 +120,101 @@ func loadDefaultStoreOptions() {
 
 // loadStoreOptions returns the default storage ops for containers
 func loadStoreOptions() (StoreOptions, error) {
-	storageConf, err := DefaultConfigFile()
+	baseConf, err := DefaultConfigFile()
+	if err != nil {
+		return defaultStoreOptions, err
+	}
+
+	// Load the base config file
+	baseOptions, err := loadStoreOptionsFromConfFile(baseConf)
+	if err != nil {
+		return defaultStoreOptions, err
+	}
+
+	if _, err := os.Stat(defaultDropInConfigDir); err != nil && os.IsNotExist(err) {
+		return defaultStoreOptions, err
+	}
+
+	baseOptions, err = mergeConfigFromDirectory(baseOptions, defaultDropInConfigDir)
 	if err != nil {
 		return defaultStoreOptions, err
 	}
-	return loadStoreOptionsFromConfFile(storageConf)
+
+	return baseOptions, nil
+}
+
+func mergeConfigFromDirectory(baseOptions StoreOptions, configDir string) (StoreOptions, error) {
+	err := filepath.Walk(configDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+
+		// Load drop-in options from the current file
+		dropInOptions, err := loadStoreOptionsFromConfFile(path)
+		if err != nil {
+			return err
+		}
+
+		// Merge the drop-in options into the base options
+		baseOptions = mergeStoreOptions(baseOptions, dropInOptions)
+		return nil
+	})
+	if err != nil {
+		return baseOptions, err
+	}
+	return baseOptions, nil
+}
+
+func mergeStoreOptions(base, dropIn StoreOptions) StoreOptions {
+	if dropIn.RunRoot != "" {
+		base.RunRoot = dropIn.RunRoot
+	}
+	if dropIn.GraphRoot != "" {
+		base.GraphRoot = dropIn.GraphRoot
+	}
+	if dropIn.ImageStore != "" {
+		base.ImageStore = dropIn.ImageStore
+	}
+	if dropIn.RootlessStoragePath != "" {
+		base.RootlessStoragePath = dropIn.RootlessStoragePath
+	}
+	if dropIn.GraphDriverName != "" {
+		base.GraphDriverName = dropIn.GraphDriverName
+	}
+	if dropIn.RootAutoNsUser != "" {
+		base.RootAutoNsUser = dropIn.RootAutoNsUser
+	}
+
+	base.GraphDriverPriority = appendUniqueStrings(base.GraphDriverPriority, dropIn.GraphDriverPriority)
+	base.GraphDriverOptions = appendUniqueStrings(base.GraphDriverOptions, dropIn.GraphDriverOptions)
+	base.UIDMap = appendUniqueIDMaps(base.UIDMap, dropIn.UIDMap)
+	base.GIDMap = appendUniqueIDMaps(base.GIDMap, dropIn.GIDMap)
+
+	// For map fields, simply merge the key-value pairs.
+	for key, value := range dropIn.PullOptions {
+		base.PullOptions[key] = value
+	}
+
+	// For boolean fields, use the drop-in value if it changes the default (assumed false).
+	if dropIn.DisableVolatile {
+		base.DisableVolatile = dropIn.DisableVolatile
+	}
+	if dropIn.TransientStore {
+		base.TransientStore = dropIn.TransientStore
+	}
+
+	// For numeric fields, use non-zero values from drop-in.
+	if dropIn.AutoNsMinSize != 0 {
+		base.AutoNsMinSize = dropIn.AutoNsMinSize
+	}
+	if dropIn.AutoNsMaxSize != 0 {
+		base.AutoNsMaxSize = dropIn.AutoNsMaxSize
+	}
+
+	return base
 }
 
 // usePerUserStorage returns whether the user private storage must be used.

types/options_darwin.go

@@ -8,8 +8,6 @@ const (
 	SystemConfigFile        = "/usr/share/containers/storage.conf"
 )
 
-var defaultOverrideConfigFile = "/etc/containers/storage.conf"
-
 // canUseRootlessOverlay returns true if the overlay driver can be used for rootless containers
 func canUseRootlessOverlay(home, runhome string) bool {
 	return false

types/options_freebsd.go

@@ -8,11 +8,6 @@ const (
 	SystemConfigFile        = "/usr/local/share/containers/storage.conf"
 )
 
-// defaultConfigFile path to the system wide storage.conf file
-var (
-	defaultOverrideConfigFile = "/usr/local/etc/containers/storage.conf"
-)
-
 // canUseRootlessOverlay returns true if the overlay driver can be used for rootless containers
 func canUseRootlessOverlay(home, runhome string) bool {
 	return false

types/options_linux.go

@@ -16,11 +16,6 @@ const (
 	SystemConfigFile        = "/usr/share/containers/storage.conf"
 )
 
-// defaultConfigFile path to the system wide storage.conf file
-var (
-	defaultOverrideConfigFile = "/etc/containers/storage.conf"
-)
-
 // canUseRootlessOverlay returns true if the overlay driver can be used for rootless containers
 func canUseRootlessOverlay(home, runhome string) bool {
 	// we check first for fuse-overlayfs since it is cheaper.

types/options_test.go

@@ -214,3 +214,77 @@ func TestReloadConfigurationFile(t *testing.T) {
 
 	assert.Equal(t, strings.Contains(content.String(), "Failed to decode the keys [\\\"foo\\\" \\\"storage.options.graphroot\\\"] from \\\"./storage_broken.conf\\\"\""), true)
 }
+
+func TestMergeStoreOptions(t *testing.T) {
+	base := StoreOptions{
+		RunRoot:             "base/run",
+		GraphDriverPriority: []string{"overlay", "aufs"},
+		PullOptions:         map[string]string{"rate": "low"},
+		DisableVolatile:     false,
+	}
+	dropIn := StoreOptions{
+		RunRoot:             "dropin/run",
+		GraphDriverPriority: []string{"btrfs"},
+		PullOptions:         map[string]string{"rate": "high", "secure": "yes"},
+		DisableVolatile:     true,
+	}
+
+	expected := StoreOptions{
+		RunRoot:             "dropin/run",
+		GraphDriverPriority: []string{"overlay", "aufs", "btrfs"},
+		PullOptions:         map[string]string{"rate": "high", "secure": "yes"},
+		DisableVolatile:     true,
+	}
+
+	result := mergeStoreOptions(base, dropIn)
+	if !reflect.DeepEqual(result, expected) {
+		t.Errorf("Expected %+v, got %+v", expected, result)
+	}
+}
+
+func TestMergeConfigFromDirectory(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "testConfigDir")
+	if err != nil {
+		t.Fatalf("Failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	fileNames := []string{"config1.toml", "config2.toml"}
+	contents := []string{
+		`[storage]
+runroot = 'temp/run1'
+graphroot = 'temp/graph1'`,
+		`[storage]
+runroot = 'temp/run2'
+graphroot = 'temp/graph2'`,
+	}
+	for i, fileName := range fileNames {
+		filePath := filepath.Join(tempDir, fileName)
+		if err := os.WriteFile(filePath, []byte(contents[i]), 0o666); err != nil {
+			t.Fatalf("Failed to write to temp file: %v", err)
+		}
+	}
+
+	// Set base options
+	baseOptions := StoreOptions{
+		RunRoot:   "initial/run",
+		GraphRoot: "initial/graph",
+	}
+
+	// Expected results after merging configurations
+	expectedOptions := StoreOptions{
+		RunRoot:   "temp/run2", // Assuming the last file read overrides earlier values
+		GraphRoot: "temp/graph2",
+	}
+
+	// Run the merging function
+	mergedOptions, err := mergeConfigFromDirectory(baseOptions, tempDir)
+	if err != nil {
+		t.Fatalf("Error merging config from directory: %v", err)
+	}
+
+	// Assert the expected result
+	if mergedOptions.RunRoot != expectedOptions.RunRoot || mergedOptions.GraphRoot != expectedOptions.GraphRoot {
+		t.Errorf("Expected RunRoot to be %q and GraphRoot to be %q, got RunRoot %q and GraphRoot %q", expectedOptions.RunRoot, expectedOptions.GraphRoot, mergedOptions.RunRoot, mergedOptions.GraphRoot)
+	}
+}

types/options_windows.go

@@ -8,11 +8,6 @@ const (
 	SystemConfigFile        = "/usr/share/containers/storage.conf"
 )
 
-// defaultConfigFile path to the system wide storage.conf file
-var (
-	defaultOverrideConfigFile = "/etc/containers/storage.conf"
-)
-
 // canUseRootlessOverlay returns true if the overlay driver can be used for rootless containers
 func canUseRootlessOverlay(home, runhome string) bool {
 	return false

types/utils.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/containers/storage/pkg/fileutils"
 	"github.com/containers/storage/pkg/homedir"
+	"github.com/containers/storage/pkg/idtools"
 	"github.com/sirupsen/logrus"
 )
 
@@ -72,3 +73,31 @@ func reloadConfigurationFileIfNeeded(configFile string, storeOptions *StoreOptio
 	prevReloadConfig.mod = mtime
 	prevReloadConfig.configFile = configFile
 }
+
+// Helper function to append unique strings to a slice.
+func appendUniqueStrings(slice []string, elements []string) []string {
+	existing := make(map[string]bool)
+	for _, item := range slice {
+		existing[item] = true
+	}
+	for _, elem := range elements {
+		if !existing[elem] {
+			slice = append(slice, elem)
+		}
+	}
+	return slice
+}
+
+// Helper function to append unique IDMaps to a slice of IDMaps.
+func appendUniqueIDMaps(slice []idtools.IDMap, elements []idtools.IDMap) []idtools.IDMap {
+	seen := make(map[idtools.IDMap]bool)
+	for _, item := range slice {
+		seen[item] = true
+	}
+	for _, elem := range elements {
+		if !seen[elem] {
+			slice = append(slice, elem)
+		}
+	}
+	return slice
+}

types/utils_test.go

@@ -4,8 +4,10 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 
+	"github.com/containers/storage/pkg/idtools"
 	"github.com/containers/storage/pkg/unshare"
 	"gotest.tools/assert"
 )
@@ -42,3 +44,25 @@ func TestStorageConfOverrideEnvironmentDefaultConfigFileRoot(t *testing.T) {
 	assert.NilError(t, err)
 	assert.Equal(t, defaultFile, expectedPath)
 }
+
+func TestAppendUniqueStrings(t *testing.T) {
+	slice := []string{"one", "two"}
+	elements := []string{"two", "three"}
+	expected := []string{"one", "two", "three"}
+
+	result := appendUniqueStrings(slice, elements)
+	if !reflect.DeepEqual(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestAppendUniqueIDMaps(t *testing.T) {
+	slice := []idtools.IDMap{{ContainerID: 100, HostID: 1000, Size: 1}}
+	elements := []idtools.IDMap{{ContainerID: 100, HostID: 1000, Size: 1}, {ContainerID: 101, HostID: 1001, Size: 1}}
+	expected := []idtools.IDMap{{ContainerID: 100, HostID: 1000, Size: 1}, {ContainerID: 101, HostID: 1001, Size: 1}}
+
+	result := appendUniqueIDMaps(slice, elements)
+	if !reflect.DeepEqual(result, expected) {
+		t.Errorf("Expected %+v, got %+v", expected, result)
+	}
+}