Add Transform interface and initial implemention for a root transform

Signed-off-by: Christopher Desiniotis <cdesiniotis@nvidia.com>

pkg/nvcdi/transform/api.go

@@ -0,0 +1,24 @@
+/**
+# 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 transform
+
+import "github.com/container-orchestrated-devices/container-device-interface/specs-go"
+
+// Transformer defines the API for applying arbitrary transforms to a spec in-place
+type Transformer interface {
+	Transform(*specs.Spec) error
+}

pkg/nvcdi/transform/root.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 transform
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
+)
+
+type rootTransformer struct {
+	root       string
+	targetRoot string
+}
+
+var _ Transformer = (*rootTransformer)(nil)
+
+// NewRootTransformer creates a new transformer for modifying
+// the root for paths in a CDI spec.
+func NewRootTransformer(root string, targetRoot string) Transformer {
+	t := rootTransformer{
+		root:       root,
+		targetRoot: targetRoot,
+	}
+	return t
+}
+
+// Transform replaces the root in a spec with a new root.
+// It walks the spec and replaces all host paths that start with root with the target root.
+func (t rootTransformer) Transform(spec *specs.Spec) error {
+	if spec == nil {
+		return nil
+	}
+
+	for _, d := range spec.Devices {
+		if err := t.applyToEdits(&d.ContainerEdits); err != nil {
+			return fmt.Errorf("failed to apply root transform to device %s: %w", d.Name, err)
+		}
+	}
+
+	if err := t.applyToEdits(&spec.ContainerEdits); err != nil {
+		return fmt.Errorf("failed to apply root transform to spec: %w", err)
+	}
+	return nil
+}
+
+func (t rootTransformer) applyToEdits(edits *specs.ContainerEdits) error {
+	for i, dn := range edits.DeviceNodes {
+		dn.HostPath = t.transformPath(dn.HostPath)
+		edits.DeviceNodes[i] = dn
+	}
+
+	for i, hook := range edits.Hooks {
+		hook.Path = t.transformPath(hook.Path)
+
+		// TODO: The args need more attention. For the hooks that create symlinks we would have to transform these too.
+		var args []string
+		for _, arg := range hook.Args {
+			args = append(args, t.transformPath(arg))
+		}
+		hook.Args = args
+		edits.Hooks[i] = hook
+	}
+
+	for i, mount := range edits.Mounts {
+		mount.HostPath = t.transformPath(mount.HostPath)
+		edits.Mounts[i] = mount
+	}
+
+	return nil
+}
+
+func (t rootTransformer) transformPath(path string) string {
+	if !strings.HasPrefix(path, t.root) {
+		return path
+	}
+
+	return filepath.Join(t.targetRoot, strings.TrimPrefix(path, t.root))
+}

pkg/nvcdi/transform/root_test.go

@@ -0,0 +1,126 @@
+/**
+# 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 transform
+
+import (
+	"testing"
+
+	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRootTransformer(t *testing.T) {
+	testCases := []struct {
+		description  string
+		root         string
+		targetRoot   string
+		spec         *specs.Spec
+		expectedSpec *specs.Spec
+	}{
+		{
+			description:  "nil spec",
+			root:         "/root",
+			targetRoot:   "/target-root",
+			spec:         nil,
+			expectedSpec: nil,
+		},
+		{
+			description:  "empty spec",
+			root:         "/root",
+			targetRoot:   "/target-root",
+			spec:         &specs.Spec{},
+			expectedSpec: &specs.Spec{},
+		},
+		{
+			description: "device nodes",
+			root:        "/root",
+			targetRoot:  "/target-root",
+			spec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					DeviceNodes: []*specs.DeviceNode{
+						{HostPath: "/root/dev/nvidia0"},
+						{HostPath: "/target-root/dev/nvidia1"},
+						{HostPath: "/different-root/dev/nvidia2"},
+					},
+				},
+			},
+			expectedSpec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					DeviceNodes: []*specs.DeviceNode{
+						{HostPath: "/target-root/dev/nvidia0"},
+						{HostPath: "/target-root/dev/nvidia1"},
+						{HostPath: "/different-root/dev/nvidia2"},
+					},
+				},
+			},
+		},
+		{
+			description: "mounts",
+			root:        "/root",
+			targetRoot:  "/target-root",
+			spec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					Mounts: []*specs.Mount{
+						{HostPath: "/root/lib/lib1.so"},
+						{HostPath: "/target-root/lib/lib2.so"},
+						{HostPath: "/different-root/lib/lib3.so"},
+					},
+				},
+			},
+			expectedSpec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					Mounts: []*specs.Mount{
+						{HostPath: "/target-root/lib/lib1.so"},
+						{HostPath: "/target-root/lib/lib2.so"},
+						{HostPath: "/different-root/lib/lib3.so"},
+					},
+				},
+			},
+		},
+		{
+			description: "hooks",
+			root:        "/root",
+			targetRoot:  "/target-root",
+			spec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					Hooks: []*specs.Hook{
+						{Path: "/root/usr/bin/nvidia-ctk"},
+						{Path: "/target-root/usr/bin/nvidia-ctk"},
+						{Path: "/different-root/usr/bin/nvidia-ctk"},
+					},
+				},
+			},
+			expectedSpec: &specs.Spec{
+				ContainerEdits: specs.ContainerEdits{
+					Hooks: []*specs.Hook{
+						{Path: "/target-root/usr/bin/nvidia-ctk"},
+						{Path: "/target-root/usr/bin/nvidia-ctk"},
+						{Path: "/different-root/usr/bin/nvidia-ctk"},
+					},
+				},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			err := NewRootTransformer(tc.root, tc.targetRoot).Transform(tc.spec)
+			require.NoError(t, err)
+			require.Equal(t, tc.spec, tc.expectedSpec)
+		})
+	}
+}