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 +120,48 @@ 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
 	}
-	return loadStoreOptionsFromConfFile(storageConf)
+
+	// Load the base config file
+	baseOptions, err := loadStoreOptionsFromConfFile(baseConf)
+	if err != nil {
+		return defaultStoreOptions, err
+	}
+
+	if _, err := os.Stat(defaultDropInConfigDir); err == nil {
+		// The directory exists, so merge the configuration from this directory
+		err = mergeConfigFromDirectory(&baseOptions, defaultDropInConfigDir)
+		if err != nil {
+			return defaultStoreOptions, err
+		}
+	} else if !os.IsNotExist(err) {
+		// There was an error other than the directory not existing
+		return defaultStoreOptions, err
+	}
+
+	return baseOptions, nil
+}
+
+func mergeConfigFromDirectory(baseOptions *StoreOptions, configDir string) error {
+	return 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
+		err = ReloadConfigurationFile(path, baseOptions)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	})
 }
 
 // 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 +214,50 @@ 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 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
+	err = mergeConfigFromDirectory(&baseOptions, tempDir)
+	if err != nil {
+		t.Fatalf("Error merging config from directory: %v", err)
+	}
+
+	// Assert the expected result
+	if baseOptions.RunRoot != expectedOptions.RunRoot || baseOptions.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, baseOptions.RunRoot, baseOptions.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