Add support for feature flags

This change adds a features config that allows
individual features to be toggled at a global level. Each feature can (by default)
be controlled by an environment variable.

The GDS, MOFED, NVSWITCH, and GDRCOPY features are examples of such features.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-ctk/config/config.go

@@ -109,8 +109,12 @@ func run(c *cli.Context, opts *options) error {
 		if err != nil {
 			return fmt.Errorf("invalid --set option %v: %w", set, err)
 		}
+		if value == nil {
+			_ = cfgToml.Delete(key)
+		} else {
 			cfgToml.Set(key, value)
 		}
+	}
 
 	if err := opts.EnsureOutputFolder(); err != nil {
 		return fmt.Errorf("failed to create output directory: %v", err)
@@ -146,20 +150,25 @@ func setFlagToKeyValue(setFlag string) (string, interface{}, error) {
 
 	kind := field.Kind()
 	if len(setParts) != 2 {
-		if kind == reflect.Bool {
+		if kind == reflect.Bool || (kind == reflect.Pointer && field.Elem().Kind() == reflect.Bool) {
 			return key, true, nil
 		}
 		return key, nil, fmt.Errorf("%w: expected key=value; got %v", errInvalidFormat, setFlag)
 	}
 
 	value := setParts[1]
+	if kind == reflect.Pointer && value != "nil" {
+		kind = field.Elem().Kind()
+	}
 	switch kind {
+	case reflect.Pointer:
+		return key, nil, nil
 	case reflect.Bool:
 		b, err := strconv.ParseBool(value)
 		if err != nil {
 			return key, value, fmt.Errorf("%w: %w", errInvalidFormat, err)
 		}
-		return key, b, err
+		return key, b, nil
 	case reflect.String:
 		return key, value, nil
 	case reflect.Slice:
@@ -201,7 +210,7 @@ func getStruct(current reflect.Type, paths ...string) (reflect.StructField, erro
 		if !ok {
 			continue
 		}
-		if v != tomlField {
+		if strings.SplitN(v, ",", 2)[0] != tomlField {
 			continue
 		}
 		if len(paths) == 1 {

internal/config/config.go

@@ -63,6 +63,9 @@ type Config struct {
 	NVIDIACTKConfig                  CTKConfig          `toml:"nvidia-ctk"`
 	NVIDIAContainerRuntimeConfig     RuntimeConfig      `toml:"nvidia-container-runtime"`
 	NVIDIAContainerRuntimeHookConfig RuntimeHookConfig  `toml:"nvidia-container-runtime-hook"`
+
+	// Features allows for finer control over optional features.
+	Features features `toml:"features,omitempty"`
 }
 
 // GetConfigFilePath returns the path to the config file for the configured system

internal/config/features.go

@@ -0,0 +1,85 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package config
+
+type featureName string
+
+const (
+	FeatureGDS      = featureName("gds")
+	FeatureMOFED    = featureName("mofed")
+	FeatureNVSWITCH = featureName("nvswitch")
+	FeatureGDRCopy  = featureName("gdrcopy")
+)
+
+// features specifies a set of named features.
+type features struct {
+	GDS      *feature `toml:"gds,omitempty"`
+	MOFED    *feature `toml:"mofed,omitempty"`
+	NVSWITCH *feature `toml:"nvswitch,omitempty"`
+	GDRCopy  *feature `toml:"gdrcopy,omitempty"`
+}
+
+type feature bool
+
+// IsEnabled checks whether a specified named feature is enabled.
+// An optional list of environments to check for feature-specific environment
+// variables can also be supplied.
+func (fs features) IsEnabled(n featureName, in ...getenver) bool {
+	featureEnvvars := map[featureName]string{
+		FeatureGDS:      "NVIDIA_GDS",
+		FeatureMOFED:    "NVIDIA_MOFED",
+		FeatureNVSWITCH: "NVIDIA_NVSWITCH",
+		FeatureGDRCopy:  "NVIDIA_GDRCOPY",
+	}
+
+	envvar := featureEnvvars[n]
+	switch n {
+	case FeatureGDS:
+		return fs.GDS.isEnabled(envvar, in...)
+	case FeatureMOFED:
+		return fs.MOFED.isEnabled(envvar, in...)
+	case FeatureNVSWITCH:
+		return fs.NVSWITCH.isEnabled(envvar, in...)
+	case FeatureGDRCopy:
+		return fs.GDRCopy.isEnabled(envvar, in...)
+	default:
+		return false
+	}
+}
+
+// isEnabled checks whether a feature is enabled.
+// If the enabled value is explicitly set, this is returned, otherwise the
+// associated envvar is checked in the specified getenver for the string "enabled"
+// A CUDA container / image can be passed here.
+func (f *feature) isEnabled(envvar string, ins ...getenver) bool {
+	if f != nil {
+		return bool(*f)
+	}
+	if envvar == "" {
+		return false
+	}
+	for _, in := range ins {
+		if in.Getenv(envvar) == "enabled" {
+			return true
+		}
+	}
+	return false
+}
+
+type getenver interface {
+	Getenv(string) string
+}

internal/modifier/gated.go

@@ -26,13 +26,6 @@ import (
 	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
 )
 
-const (
-	nvidiaGDSEnvvar      = "NVIDIA_GDS"
-	nvidiaMOFEDEnvvar    = "NVIDIA_MOFED"
-	nvidiaNVSWITCHEnvvar = "NVIDIA_NVSWITCH"
-	nvidiaGDRCOPYEnvvar  = "NVIDIA_GDRCOPY"
-)
-
 // NewFeatureGatedModifier creates the modifiers for optional features.
 // These include:
 //
@@ -53,7 +46,7 @@ func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image
 	driverRoot := cfg.NVIDIAContainerCLIConfig.Root
 	devRoot := cfg.NVIDIAContainerCLIConfig.Root
 
-	if image.Getenv(nvidiaGDSEnvvar) == "enabled" {
+	if cfg.Features.IsEnabled(config.FeatureGDS, image) {
 		d, err := discover.NewGDSDiscoverer(logger, driverRoot, devRoot)
 		if err != nil {
 			return nil, fmt.Errorf("failed to construct discoverer for GDS devices: %w", err)
@@ -61,7 +54,7 @@ func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image
 		discoverers = append(discoverers, d)
 	}
 
-	if image.Getenv(nvidiaMOFEDEnvvar) == "enabled" {
+	if cfg.Features.IsEnabled(config.FeatureMOFED, image) {
 		d, err := discover.NewMOFEDDiscoverer(logger, devRoot)
 		if err != nil {
 			return nil, fmt.Errorf("failed to construct discoverer for MOFED devices: %w", err)
@@ -69,7 +62,7 @@ func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image
 		discoverers = append(discoverers, d)
 	}
 
-	if image.Getenv(nvidiaNVSWITCHEnvvar) == "enabled" {
+	if cfg.Features.IsEnabled(config.FeatureNVSWITCH, image) {
 		d, err := discover.NewNvSwitchDiscoverer(logger, devRoot)
 		if err != nil {
 			return nil, fmt.Errorf("failed to construct discoverer for NVSWITCH devices: %w", err)
@@ -77,7 +70,7 @@ func NewFeatureGatedModifier(logger logger.Interface, cfg *config.Config, image
 		discoverers = append(discoverers, d)
 	}
 
-	if image.Getenv(nvidiaGDRCOPYEnvvar) == "enabled" {
+	if cfg.Features.IsEnabled(config.FeatureGDRCopy, image) {
 		d, err := discover.NewGDRCopyDiscoverer(logger, devRoot)
 		if err != nil {
 			return nil, fmt.Errorf("failed to construct discoverer for GDRCopy devices: %w", err)