Add hook command to nvidia-ctk with update-ldcache subcommand

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

cmd/nvidia-ctk/hook/hook.go

@@ -0,0 +1,50 @@
+/**
+# 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 hook
+
+import (
+	ldcache "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook/update-ldcache"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli/v2"
+)
+
+type hookCommand struct {
+	logger *logrus.Logger
+}
+
+// NewCommand constructs a hook command with the specified logger
+func NewCommand(logger *logrus.Logger) *cli.Command {
+	c := hookCommand{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// build
+func (m hookCommand) build() *cli.Command {
+	// Create the 'hook' command
+	hook := cli.Command{
+		Name:  "hook",
+		Usage: "A collection of hooks that may be injected into an OCI spec",
+	}
+
+	hook.Subcommands = []*cli.Command{
+		ldcache.NewCommand(m.logger),
+	}
+
+	return &hook
+}

cmd/nvidia-ctk/hook/update-ldcache/update-ldcache.go

@@ -0,0 +1,155 @@
+/**
+# 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 ldcache
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli/v2"
+)
+
+type command struct {
+	logger *logrus.Logger
+}
+
+type config struct {
+	folders       cli.StringSlice
+	containerSpec string
+}
+
+// NewCommand constructs an update-ldcache command with the specified logger
+func NewCommand(logger *logrus.Logger) *cli.Command {
+	c := command{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// build the update-ldcache command
+func (m command) build() *cli.Command {
+	cfg := config{}
+
+	// Create the 'update-ldcache' command
+	c := cli.Command{
+		Name:  "update-ldcache",
+		Usage: "Update ldcache in a container by running ldconfig",
+		Action: func(c *cli.Context) error {
+			return m.run(c, &cfg)
+		},
+	}
+
+	c.Flags = []cli.Flag{
+		&cli.StringSliceFlag{
+			Name:        "folders",
+			Usage:       "Specifiy the additional folders to add to /etc/ld.so.conf before updating the ld cache",
+			Destination: &cfg.folders,
+		},
+		&cli.StringFlag{
+			Name:        "containerSpec",
+			Usage:       "Specify the path to the OCI container spec. If empty or '-' the spec will be read from STDIN",
+			Destination: &cfg.containerSpec,
+		},
+	}
+
+	return &c
+}
+
+func (m command) run(c *cli.Context, cfg *config) error {
+	var s specs.State
+
+	inputReader := os.Stdin
+	if cfg.containerSpec != "" && cfg.containerSpec != "-" {
+		inputFile, err := os.Open(cfg.containerSpec)
+		if err != nil {
+			return fmt.Errorf("failed to open intput: %v", err)
+		}
+		defer inputFile.Close()
+		inputReader = inputFile
+	}
+
+	d := json.NewDecoder(inputReader)
+	if err := d.Decode(&s); err != nil {
+		return fmt.Errorf("failed to decode container state: %v", err)
+	}
+
+	specFilePath := oci.GetSpecFilePath(s.Bundle)
+	specFile, err := os.Open(specFilePath)
+	if err != nil {
+		return fmt.Errorf("failed to open OCI spec file: %v", err)
+	}
+	defer specFile.Close()
+
+	spec, err := oci.LoadFrom(specFile)
+	if err != nil {
+		return fmt.Errorf("failed to load OCI spec: %v", err)
+	}
+
+	var containerRoot string
+	if spec.Root != nil {
+		containerRoot = spec.Root.Path
+	}
+
+	err = m.createConfig(containerRoot, cfg.folders.Value())
+	if err != nil {
+		return fmt.Errorf("failed to update ld.so.conf: %v", err)
+	}
+
+	args := []string{"/sbin/ldconfig"}
+	if containerRoot != "" {
+		args = append(args, "-r", containerRoot)
+	}
+
+	return syscall.Exec(args[0], args, nil)
+}
+
+// createConfig creates (or updates) /etc/ld.so.conf.d/nvcr-<RANDOM_STRING>.conf in the container
+// to include the required paths.
+func (m command) createConfig(root string, folders []string) error {
+	if len(folders) == 0 {
+		m.logger.Debugf("No folders to add to /etc/ld.so.conf")
+		return nil
+	}
+
+	configFile, err := os.CreateTemp(filepath.Join(root, "/etc/ld.so.conf.d"), "nvcr-*.conf")
+	if err != nil {
+		return fmt.Errorf("failed to create config file: %v", err)
+	}
+	defer configFile.Close()
+
+	m.logger.Debugf("Adding folders %v to %v", folders, configFile.Name())
+
+	configured := make(map[string]bool)
+	for _, folder := range folders {
+		if configured[folder] {
+			continue
+		}
+		_, err = configFile.WriteString(fmt.Sprintf("%s\n", folder))
+		if err != nil {
+			return fmt.Errorf("failed to update ld.so.conf.d: %v", err)
+		}
+		configured[folder] = true
+	}
+
+	return nil
+}

cmd/nvidia-ctk/main.go

@@ -19,6 +19,7 @@ package main
 import (
 	"os"
 
+	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook"
 	log "github.com/sirupsen/logrus"
 	cli "github.com/urfave/cli/v2"
 )
@@ -68,7 +69,9 @@ func main() {
 	}
 
 	// Define the subcommands
-	c.Commands = []*cli.Command{}
+	c.Commands = []*cli.Command{
+		hook.NewCommand(logger),
+	}
 
 	// Run the CLI
 	err := c.Run(os.Args)

internal/oci/spec_file.go

@@ -52,7 +52,7 @@ func (s *fileSpec) Load() error {
 	}
 	defer specFile.Close()
 
-	spec, err := loadFrom(specFile)
+	spec, err := LoadFrom(specFile)
 	if err != nil {
 		return fmt.Errorf("error loading OCI specification from file: %v", err)
 	}
@@ -60,8 +60,8 @@ func (s *fileSpec) Load() error {
 	return nil
 }
 
-// loadFrom reads the contents of the OCI spec from the specified io.Reader.
+// LoadFrom reads the contents of the OCI spec from the specified io.Reader.
-func loadFrom(reader io.Reader) (*specs.Spec, error) {
+func LoadFrom(reader io.Reader) (*specs.Spec, error) {
 	decoder := json.NewDecoder(reader)
 
 	var spec specs.Spec

internal/oci/spec_file_test.go

@@ -44,7 +44,7 @@ func TestLoadFrom(t *testing.T) {
 
 	for i, tc := range testCases {
 		var spec *specs.Spec
-		spec, err := loadFrom(bytes.NewReader(tc.contents))
+		spec, err := LoadFrom(bytes.NewReader(tc.contents))
 
 		if tc.isError {
 			require.Error(t, err, "%d: %v", i, tc)