Add support for drop-in config files in a container

This change adds support for drop-in files in a container. Here
the user needs to set RUNTIME_DROP_IN_CONFIG_HOST_PATH in addition
to RUNTIME_DROP_IN_CONFIG. In this case when updating the top-level
containerd config, the imports will use the host path instead of the
container path.

Signed-off-by: Evan Lezar <[email protected]>

Author: elezar

cmd/nvidia-ctk-installer/container/container.go

@@ -35,7 +35,8 @@ const (
 
 // Options defines the shared options for the CLIs to configure containers runtimes.
 type Options struct {
-	DropInConfig string
+	DropInConfig         string
+	DropInConfigHostPath string
 	// TODO: Rename to TopLevelConfig
 	Config string
 	Socket string

cmd/nvidia-ctk-installer/container/runtime/containerd/containerd.go

@@ -19,6 +19,7 @@ package containerd
 import (
 	"encoding/json"
 	"fmt"
+	"path/filepath"
 
 	log "github.com/sirupsen/logrus"
 	cli "github.com/urfave/cli/v3"
@@ -173,6 +174,7 @@ func GetLowlevelRuntimePaths(o *container.Options, co *Options) ([]string, error
 func getRuntimeConfig(o *container.Options, co *Options) (engine.Interface, error) {
 	return containerd.New(
 		containerd.WithTopLevelConfigPath(o.Config),
+		containerd.WithContainerPathAsHostPath(filepath.Dir(o.DropInConfig), filepath.Dir(o.DropInConfigHostPath)),
 		containerd.WithConfigSource(
 			toml.LoadFirst(
 				containerd.CommandLineSource(o.HostRootMount, o.ExecutablePath),

cmd/nvidia-ctk-installer/container/runtime/runtime.go

@@ -61,6 +61,13 @@ func Flags(opts *Options) []cli.Flag {
 			Destination: &opts.DropInConfig,
 			Sources:     cli.EnvVars("RUNTIME_DROP_IN_CONFIG"),
 		},
+		&cli.StringFlag{
+			Name: "drop-in-config-host-path",
+			Usage: "When running in a container, this is the path to the drop-in config (--drop-in-config) on the host. " +
+				"This is required to correctly update the top-level config if required since paths there must be host-relative.",
+			Destination: &opts.DropInConfigHostPath,
+			Sources:     cli.EnvVars("RUNTIME_DROP_IN_CONFIG_HOST_PATH"),
+		},
 		&cli.StringFlag{
 			Name:        "executable-path",
 			Usage:       "The path to the runtime executable. This is used to extract the current config",

pkg/config/engine/containerd/config_drop_in.go

@@ -37,11 +37,12 @@ var _ engine.Interface = (*ConfigWithDropIn)(nil)
 // A topLevelConfig stores the original on-disk top-level config.
 // The path to the config is also stored to allow it to be modified if required.
 type topLevelConfig struct {
-	path   string
-	config *Config
+	path                   string
+	containerToHostPathMap map[string]string
+	config                 *Config
 }
 
-func NewConfigWithDropIn(topLevelConfigPath string, tlConfig *Config, dropInConfig engine.Interface) *ConfigWithDropIn {
+func NewConfigWithDropIn(topLevelConfigPath string, containerToHostPathMap map[string]string, tlConfig *Config, dropInConfig engine.Interface) *ConfigWithDropIn {
 	return &ConfigWithDropIn{
 		topLevelConfig: &topLevelConfig{
 			path:   topLevelConfigPath,
@@ -117,13 +118,27 @@ func (c *topLevelConfig) removeImports(dropInFilename string) {
 		return
 	}
 
-	requiredImport := filepath.Dir(dropInFilename) + "/*.toml"
+	requiredImport := c.importPattern(dropInFilename)
 	if currentImports[0] != requiredImport {
 		return
 	}
 	c.config.Delete("imports")
 }
 
+func (c *topLevelConfig) importPattern(dropInFilename string) string {
+	return c.asHostPath(filepath.Dir(dropInFilename)) + "/*.toml"
+}
+
+func (c *topLevelConfig) asHostPath(path string) string {
+	if c.containerToHostPathMap == nil {
+		return path
+	}
+	if hostPath, ok := c.containerToHostPathMap[path]; ok {
+		return hostPath
+	}
+	return path
+}
+
 // removeVersion removes the version if it is the ONLY field in the file.
 func (c *topLevelConfig) removeVersion() {
 	if len(c.config.Keys()) > 1 {
@@ -142,7 +157,7 @@ func (c *topLevelConfig) ensureImports(dropInFilename string) {
 		currentImports = ci
 	}
 
-	requiredImport := filepath.Dir(dropInFilename) + "/*.toml"
+	requiredImport := c.importPattern(dropInFilename)
 	for _, currentImport := range currentImports {
 		// If the requiredImport is already present, then we need not update the config.
 		if currentImport == requiredImport {

pkg/config/engine/containerd/containerd.go

@@ -141,7 +141,7 @@ func New(opts ...Option) (engine.Interface, error) {
 			},
 		}
 
-		cfg := NewConfigWithDropIn(b.topLevelConfigPath, topLevelConfig, dropInConfig)
+		cfg := NewConfigWithDropIn(b.topLevelConfigPath, b.containerToHostPathMap, topLevelConfig, dropInConfig)
 		return cfg, nil
 	}
 }

pkg/config/engine/containerd/option.go

@@ -29,11 +29,26 @@ type builder struct {
 	topLevelConfigPath   string
 	runtimeType          string
 	containerAnnotations []string
+
+	containerToHostPathMap map[string]string
 }
 
 // Option defines a function that can be used to configure the config builder
 type Option func(*builder)
 
+// WithContainerPathAsHostPath maps a given container path to a host path.
+func WithContainerPathAsHostPath(containerPath string, hostPath string) Option {
+	return func(b *builder) {
+		if containerPath == "" || hostPath == "" || containerPath == hostPath {
+			return
+		}
+		if b.containerToHostPathMap == nil {
+			b.containerToHostPathMap = make(map[string]string)
+		}
+		b.containerToHostPathMap[containerPath] = hostPath
+	}
+}
+
 // WithLogger sets the logger for the config builder
 func WithLogger(logger logger.Interface) Option {
 	return func(b *builder) {