Inject symlinks hook for creating symlinks in a container

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

cmd/nvidia-container-runtime/modifier/experimental.go

@@ -89,12 +89,17 @@ func NewExperimentalModifier(logger *logrus.Logger, cfg *config.Config, ociSpec
 			return nil, fmt.Errorf("failed to create CSV discoverer: %v", err)
 		}
 
-		hooks, err := discover.NewLDCacheUpdateHook(logger, csvDiscoverer, config)
+		ldcacheUpdateHook, err := discover.NewLDCacheUpdateHook(logger, csvDiscoverer, config)
 		if err != nil {
-			return nil, fmt.Errorf("failed to create hook discoverer: %v", err)
+			return nil, fmt.Errorf("failed to create ldcach update hook discoverer: %v", err)
 		}
 
-		d = discover.NewList(csvDiscoverer, hooks)
+		createSymlinksHook, err := discover.NewCreateSymlinksHook(logger, csvFiles, config)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create symlink hook discoverer: %v", err)
+		}
+
+		d = discover.NewList(csvDiscoverer, ldcacheUpdateHook, createSymlinksHook)
 	default:
 		return nil, fmt.Errorf("invalid discover mode: %v", cfg.NVIDIAContainerRuntimeConfig.DiscoverMode)
 	}

internal/discover/symlinks.go

@@ -0,0 +1,71 @@
+/**
+# 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 discover
+
+import (
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/lookup"
+	"github.com/container-orchestrated-devices/container-device-interface/pkg/cdi"
+	"github.com/sirupsen/logrus"
+)
+
+type symlinks struct {
+	None
+	logger                  *logrus.Logger
+	lookup                  lookup.Locator
+	nvidiaCTKExecutablePath string
+	csvFiles                []string
+}
+
+// NewCreateSymlinksHook creates a discoverer for a hook that creates required symlinks in the container
+func NewCreateSymlinksHook(logger *logrus.Logger, csvFiles []string, cfg *Config) (Discover, error) {
+	d := symlinks{
+		logger:                  logger,
+		lookup:                  lookup.NewExecutableLocator(logger, cfg.Root),
+		nvidiaCTKExecutablePath: cfg.NVIDIAContainerToolkitCLIExecutablePath,
+		csvFiles:                csvFiles,
+	}
+
+	return &d, nil
+}
+
+// Hooks returns a hook to create the symlinks from the required CSV files
+func (d symlinks) Hooks() ([]Hook, error) {
+	hookPath := nvidiaCTKDefaultFilePath
+	targets, err := d.lookup.Locate(d.nvidiaCTKExecutablePath)
+	if err != nil {
+		d.logger.Warnf("Failed to locate %v: %v", d.nvidiaCTKExecutablePath, err)
+	} else if len(targets) == 0 {
+		d.logger.Warnf("%v not found", d.nvidiaCTKExecutablePath)
+	} else {
+		d.logger.Debugf("Found %v candidates: %v", d.nvidiaCTKExecutablePath, targets)
+		hookPath = targets[0]
+	}
+	d.logger.Debugf("Using NVIDIA Container Toolkit CLI path %v", hookPath)
+
+	args := []string{hookPath, "hook", "create-symlinks"}
+	for _, f := range d.csvFiles {
+		args = append(args, "--csv-filenames", f)
+	}
+
+	h := Hook{
+		Lifecycle: cdi.CreateContainerHook,
+		Path:      hookPath,
+		Args:      args,
+	}
+
+	return []Hook{h}, nil
+}