Add create-dev-char-symlinks hook

This change adds an nvidia-ctk hook create-dev-char-symlinks
subcommand that creates symlinks to device nodes (as required by
systemd) under /dev/char.

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

cmd/nvidia-ctk/hook/create-dev-char-symlinks/create-dev-char-symlinks.go

@@ -0,0 +1,209 @@
+/**
+# Copyright (c) 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 devchar
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli/v2"
+)
+
+const (
+	defaultDevCharPath = "/dev/char"
+)
+
+type command struct {
+	logger *logrus.Logger
+}
+
+type config struct {
+	devCharPath string
+	driverRoot  string
+	dryRun      bool
+}
+
+// NewCommand constructs a hook sub-command with the specified logger
+func NewCommand(logger *logrus.Logger) *cli.Command {
+	c := command{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// build
+func (m command) build() *cli.Command {
+	cfg := config{}
+
+	// Create the 'create-dev-char-symlinks' command
+	c := cli.Command{
+		Name:  "create-dev-char-symlinks",
+		Usage: "A hook to create symlinks to possible /dev/nv* devices in /dev/char",
+		Action: func(c *cli.Context) error {
+			return m.run(c, &cfg)
+		},
+	}
+
+	c.Flags = []cli.Flag{
+		&cli.StringFlag{
+			Name:        "dev-char-path",
+			Usage:       "The path at which the symlinks will be created. Symlinks will be created as `DEV_CHAR`/MAJOR:MINOR where MAJOR and MINOR are the major and minor numbers of a corresponding device node.",
+			Value:       defaultDevCharPath,
+			Destination: &cfg.devCharPath,
+			EnvVars:     []string{"DEV_CHAR_PATH"},
+		},
+		&cli.StringFlag{
+			Name:        "driver-root",
+			Usage:       "The path to the driver root. `DRIVER_ROOT`/dev is searched for NVIDIA device nodes.",
+			Value:       "/",
+			Destination: &cfg.driverRoot,
+			EnvVars:     []string{"DRIVER_ROOT"},
+		},
+		&cli.BoolFlag{
+			Name:        "dry-run",
+			Usage:       "If set, the command will not create any symlinks.",
+			Value:       false,
+			Destination: &cfg.dryRun,
+			EnvVars:     []string{"DRY_RUN"},
+		},
+	}
+
+	return &c
+}
+
+func (m command) run(c *cli.Context, cfg *config) error {
+	l := NewSymlinkCreator(
+		WithLogger(m.logger),
+		WithDevCharPath(cfg.devCharPath),
+		WithDriverRoot(cfg.driverRoot),
+		WithDryRun(cfg.dryRun),
+	)
+	err := l.CreateLinks()
+	if err != nil {
+		return fmt.Errorf("failed to create links: %v", err)
+	}
+	return nil
+}
+
+type linkCreator struct {
+	logger      *logrus.Logger
+	lister      nodeLister
+	driverRoot  string
+	devCharPath string
+	dryRun      bool
+}
+
+// Creator is an interface for creating symlinks to /dev/nv* devices in /dev/char.
+type Creator interface {
+	CreateLinks() error
+}
+
+// Option is a functional option for configuring the linkCreator.
+type Option func(*linkCreator)
+
+// NewSymlinkCreator creates a new linkCreator.
+func NewSymlinkCreator(opts ...Option) Creator {
+	c := linkCreator{}
+	for _, opt := range opts {
+		opt(&c)
+	}
+	if c.logger == nil {
+		c.logger = logrus.StandardLogger()
+	}
+	if c.driverRoot == "" {
+		c.driverRoot = "/"
+	}
+	if c.devCharPath == "" {
+		c.devCharPath = defaultDevCharPath
+	}
+	if c.lister == nil {
+		c.lister = existing{c.logger, c.driverRoot}
+	}
+	return c
+}
+
+// WithDriverRoot sets the driver root path.
+func WithDriverRoot(root string) Option {
+	return func(c *linkCreator) {
+		c.driverRoot = root
+	}
+}
+
+// WithDevCharPath sets the path at which the symlinks will be created.
+func WithDevCharPath(path string) Option {
+	return func(c *linkCreator) {
+		c.devCharPath = path
+	}
+}
+
+// WithDryRun sets the dry run flag.
+func WithDryRun(dryRun bool) Option {
+	return func(c *linkCreator) {
+		c.dryRun = dryRun
+	}
+}
+
+// WithLogger sets the logger.
+func WithLogger(logger *logrus.Logger) Option {
+	return func(c *linkCreator) {
+		c.logger = logger
+	}
+}
+
+// CreateLinks creates symlinks for all device nodes returned by the configured lister.
+func (m linkCreator) CreateLinks() error {
+	deviceNodes, err := m.lister.DeviceNodes()
+	if err != nil {
+		return fmt.Errorf("failed to get device nodes: %v", err)
+	}
+
+	if len(deviceNodes) != 0 && !m.dryRun {
+		err := os.MkdirAll(m.devCharPath, 0755)
+		if err != nil {
+			return fmt.Errorf("failed to create directory %s: %v", m.devCharPath, err)
+		}
+	}
+
+	for _, deviceNode := range deviceNodes {
+		target := deviceNode.path
+		linkPath := filepath.Join(m.devCharPath, deviceNode.devCharName())
+
+		m.logger.Infof("Creating link %s => %s", linkPath, target)
+		if m.dryRun {
+			continue
+		}
+
+		err = os.Symlink(target, linkPath)
+		if err != nil {
+			m.logger.Warnf("Could not create symlink: %v", err)
+		}
+	}
+
+	return nil
+}
+
+type deviceNode struct {
+	path  string
+	major uint32
+	minor uint32
+}
+
+func (d deviceNode) devCharName() string {
+	return fmt.Sprintf("%d:%d", d.major, d.minor)
+}

cmd/nvidia-ctk/hook/create-dev-char-symlinks/existing.go

@@ -0,0 +1,95 @@
+/**
+# Copyright (c) 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 devchar
+
+import (
+	"path/filepath"
+	"strings"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/lookup"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+type nodeLister interface {
+	DeviceNodes() ([]deviceNode, error)
+}
+
+type existing struct {
+	logger     *logrus.Logger
+	driverRoot string
+}
+
+// DeviceNodes returns a list of NVIDIA device nodes in the specified root.
+// The nvidia-nvswitch* and nvidia-nvlink devices are excluded.
+func (m existing) DeviceNodes() ([]deviceNode, error) {
+	locator := lookup.NewCharDeviceLocator(
+		lookup.WithLogger(m.logger),
+		lookup.WithRoot(m.driverRoot),
+		lookup.WithOptional(true),
+	)
+
+	devices, err := locator.Locate("/dev/nvidia*")
+	if err != nil {
+		m.logger.Warnf("Error while locating device: %v", err)
+	}
+
+	capDevices, err := locator.Locate("/dev/nvidia-caps/nvidia-*")
+	if err != nil {
+		m.logger.Warnf("Error while locating caps device: %v", err)
+	}
+
+	if len(devices) == 0 && len(capDevices) == 0 {
+		m.logger.Infof("No NVIDIA devices found in %s", m.driverRoot)
+		return nil, nil
+	}
+
+	var deviceNodes []deviceNode
+	for _, d := range append(devices, capDevices...) {
+		if m.nodeIsBlocked(d) {
+			continue
+		}
+
+		var stat unix.Stat_t
+		err := unix.Stat(d, &stat)
+		if err != nil {
+			m.logger.Warnf("Could not stat device: %v", err)
+			continue
+		}
+		deviceNode := deviceNode{
+			path:  d,
+			major: unix.Major(uint64(stat.Rdev)),
+			minor: unix.Minor(uint64(stat.Rdev)),
+		}
+
+		deviceNodes = append(deviceNodes, deviceNode)
+	}
+
+	return deviceNodes, nil
+}
+
+// nodeIsBlocked returns true if the specified device node should be ignored.
+func (m existing) nodeIsBlocked(path string) bool {
+	blockedPrefixes := []string{"nvidia-fs", "nvidia-nvswitch", "nvidia-nvlink"}
+	nodeName := filepath.Base(path)
+	for _, prefix := range blockedPrefixes {
+		if strings.HasPrefix(nodeName, prefix) {
+			return true
+		}
+	}
+	return false
+}

cmd/nvidia-ctk/hook/hook.go

@@ -18,6 +18,7 @@ package hook
 
 import (
 	chmod "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook/chmod"
+	devchar "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook/create-dev-char-symlinks"
 	symlinks "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook/create-symlinks"
 	ldcache "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook/update-ldcache"
 	"github.com/sirupsen/logrus"
@@ -48,6 +49,7 @@ func (m hookCommand) build() *cli.Command {
 		ldcache.NewCommand(m.logger),
 		symlinks.NewCommand(m.logger),
 		chmod.NewCommand(m.logger),
+		devchar.NewCommand(m.logger),
 	}
 
 	return &hook