Add creation of select driver symlinks to CDI spec

This change aligns the creation of symlinks under CDI with
the implementation in libnvidia-container. If the driver libraries
are present, the following symlinks are created:

* {{ .LibRoot }}/libcuda.so -> libcuda.so.1
* {{ .LibRoot }}/libnvidia-opticalflow.so -> libnvidia-opticalflow.so.1
* {{ .LibRoot }}/libGLX_indirect.so.0 -> libGLX_nvidia.so.{{ .Version }}

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

internal/discover/none.go

@@ -24,15 +24,15 @@ var _ Discover = (*None)(nil)
 
 // Devices returns an empty list of devices
 func (e None) Devices() ([]Device, error) {
-	return []Device{}, nil
+	return nil, nil
 }
 
 // Mounts returns an empty list of mounts
 func (e None) Mounts() ([]Mount, error) {
-	return []Mount{}, nil
+	return nil, nil
 }
 
 // Hooks returns an empty list of hooks
 func (e None) Hooks() ([]Hook, error) {
-	return []Hook{}, nil
+	return nil, nil
 }

internal/discover/symlinks.go

@@ -0,0 +1,108 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# 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 (
+	"fmt"
+	"path/filepath"
+)
+
+type additionalSymlinks struct {
+	Discover
+	version           string
+	nvidiaCDIHookPath string
+}
+
+// WithDriverDotSoSymlinks decorates the provided discoverer.
+// A hook is added that checks for specific driver symlinks that need to be created.
+func WithDriverDotSoSymlinks(mounts Discover, version string, nvidiaCDIHookPath string) Discover {
+	if version == "" {
+		version = "*.*"
+	}
+	return &additionalSymlinks{
+		Discover:          mounts,
+		nvidiaCDIHookPath: nvidiaCDIHookPath,
+		version:           version,
+	}
+}
+
+// Hooks returns a hook to create the additional symlinks based on the mounts.
+func (d *additionalSymlinks) Hooks() ([]Hook, error) {
+	mounts, err := d.Discover.Mounts()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get library mounts: %v", err)
+	}
+	hooks, err := d.Discover.Hooks()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get hooks: %v", err)
+	}
+
+	var links []string
+	processedPaths := make(map[string]bool)
+	processedLinks := make(map[string]bool)
+	for _, mount := range mounts {
+		if processedPaths[mount.Path] {
+			continue
+		}
+		processedPaths[mount.Path] = true
+
+		for _, link := range d.getLinksForMount(mount.Path) {
+			if processedLinks[link] {
+				continue
+			}
+			processedLinks[link] = true
+			links = append(links, link)
+		}
+	}
+
+	if len(links) == 0 {
+		return hooks, nil
+	}
+
+	hook := CreateCreateSymlinkHook(d.nvidiaCDIHookPath, links).(Hook)
+	return append(hooks, hook), nil
+}
+
+// getLinksForMount maps the path to created links if any.
+func (d additionalSymlinks) getLinksForMount(path string) []string {
+	dir, filename := filepath.Split(path)
+	switch {
+	case d.isDriverLibrary("libcuda.so", filename):
+		// XXX Many applications wrongly assume that libcuda.so exists (e.g. with dlopen).
+		// create libcuda.so -> libcuda.so.1 symlink
+		link := fmt.Sprintf("%s::%s", "libcuda.so.1", filepath.Join(dir, "libcuda.so"))
+		return []string{link}
+	case d.isDriverLibrary("libGLX_nvidia.so", filename):
+		// XXX GLVND requires this symlink for indirect GLX support.
+		// create libGLX_indirect.so.0 -> libGLX_nvidia.so.VERSION symlink
+		link := fmt.Sprintf("%s::%s", filename, filepath.Join(dir, "libGLX_indirect.so.0"))
+		return []string{link}
+	case d.isDriverLibrary("libnvidia-opticalflow.so", filename):
+		// XXX Fix missing symlink for libnvidia-opticalflow.so.
+		// create libnvidia-opticalflow.so -> libnvidia-opticalflow.so.1 symlink
+		link := fmt.Sprintf("%s::%s", "libnvidia-opticalflow.so.1", filepath.Join(dir, "libnvidia-opticalflow.so"))
+		return []string{link}
+	}
+	return nil
+}
+
+// isDriverLibrary checks whether the specified filename is a specific driver library.
+func (d additionalSymlinks) isDriverLibrary(libraryName string, filename string) bool {
+	pattern := libraryName + "." + d.version
+	match, _ := filepath.Match(pattern, filename)
+	return match
+}