Add support for updating crio configs

This adds support for updating crio configs (instead of installing hooks)
and adds crio support to the nvidia-ctk runtime configure command.

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

internal/config/crio/crio.go

@@ -0,0 +1,125 @@
+/**
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+#
+# 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 crio
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/pelletier/go-toml"
+	log "github.com/sirupsen/logrus"
+)
+
+// LoadConfig loads the cri-o config from disk
+func LoadConfig(config string) (*toml.Tree, error) {
+	log.Infof("Loading config: %v", config)
+
+	info, err := os.Stat(config)
+	if os.IsExist(err) && info.IsDir() {
+		return nil, fmt.Errorf("config file is a directory")
+	}
+
+	configFile := config
+	if os.IsNotExist(err) {
+		configFile = "/dev/null"
+		log.Infof("Config file does not exist, creating new one")
+	}
+
+	cfg, err := toml.LoadFile(configFile)
+	if err != nil {
+		return nil, err
+	}
+
+	log.Infof("Successfully loaded config")
+
+	return cfg, nil
+}
+
+// UpdateConfig updates the cri-o config to include the NVIDIA Container Runtime
+func UpdateConfig(config *toml.Tree, runtimeClass string, runtimePath string, setAsDefault bool) error {
+	switch runc := config.Get("crio.runtime.runtimes.runc").(type) {
+	case *toml.Tree:
+		runc, _ = toml.Load(runc.String())
+		config.SetPath([]string{"crio", "runtime", "runtimes", runtimeClass}, runc)
+	}
+
+	config.SetPath([]string{"crio", "runtime", "runtimes", runtimeClass, "runtime_path"}, runtimePath)
+	config.SetPath([]string{"crio", "runtime", "runtimes", runtimeClass, "runtime_type"}, "oci")
+
+	if setAsDefault {
+		config.SetPath([]string{"crio", "runtime", "default_runtime"}, runtimeClass)
+	}
+
+	return nil
+}
+
+// RevertConfig reverts the cri-o config to remove the NVIDIA Container Runtime
+func RevertConfig(config *toml.Tree, runtimeClass string) error {
+	if runtime, ok := config.GetPath([]string{"crio", "runtime", "default_runtime"}).(string); ok {
+		if runtimeClass == runtime {
+			config.DeletePath([]string{"crio", "runtime", "default_runtime"})
+		}
+	}
+
+	runtimeClassPath := []string{"crio", "runtime", "runtimes", runtimeClass}
+	config.DeletePath(runtimeClassPath)
+	for i := 0; i < len(runtimeClassPath); i++ {
+		remainingPath := runtimeClassPath[:len(runtimeClassPath)-i]
+		if entry, ok := config.GetPath(remainingPath).(*toml.Tree); ok {
+			if len(entry.Keys()) != 0 {
+				break
+			}
+			config.DeletePath(remainingPath)
+		}
+	}
+
+	return nil
+}
+
+// FlushConfig flushes the updated/reverted config out to disk
+func FlushConfig(config string, cfg *toml.Tree) error {
+	log.Infof("Flushing config")
+
+	output, err := cfg.ToTomlString()
+	if err != nil {
+		return fmt.Errorf("unable to convert to TOML: %v", err)
+	}
+
+	switch len(output) {
+	case 0:
+		err := os.Remove(config)
+		if err != nil {
+			return fmt.Errorf("unable to remove empty file: %v", err)
+		}
+		log.Infof("Config empty, removing file")
+	default:
+		f, err := os.Create(config)
+		if err != nil {
+			return fmt.Errorf("unable to open '%v' for writing: %v", config, err)
+		}
+		defer f.Close()
+
+		_, err = f.WriteString(output)
+		if err != nil {
+			return fmt.Errorf("unable to write output: %v", err)
+		}
+	}
+
+	log.Infof("Successfully flushed config")
+
+	return nil
+}