Move cmd/nvidia-container-runtime/modifier package to internal/modifier

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

internal/modifier/stable.go

@@ -0,0 +1,77 @@
+/*
+# Copyright (c) 2021, 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 modifier
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/config"
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/sirupsen/logrus"
+)
+
+// NewStableRuntimeModifier creates an OCI spec modifier that inserts the NVIDIA Container Runtime Hook into an OCI
+// spec. The specified logger is used to capture log output.
+func NewStableRuntimeModifier(logger *logrus.Logger) oci.SpecModifier {
+	m := stableRuntimeModifier{logger: logger}
+
+	return &m
+}
+
+// stableRuntimeModifier modifies an OCI spec inplace, inserting the nvidia-container-runtime-hook as a
+// prestart hook. If the hook is already present, no modification is made.
+type stableRuntimeModifier struct {
+	logger *logrus.Logger
+}
+
+// Modify applies the required modification to the incoming OCI spec, inserting the nvidia-container-runtime-hook
+// as a prestart hook.
+func (m stableRuntimeModifier) Modify(spec *specs.Spec) error {
+	path, err := exec.LookPath(config.NVIDIAContainerRuntimeHookExecutable)
+	if err != nil {
+		path = filepath.Join(config.DefaultExecutableDir, config.NVIDIAContainerRuntimeHookExecutable)
+		_, err = os.Stat(path)
+		if err != nil {
+			return err
+		}
+	}
+
+	m.logger.Infof("Using prestart hook path: %s", path)
+
+	args := []string{path}
+	if spec.Hooks == nil {
+		spec.Hooks = &specs.Hooks{}
+	} else if len(spec.Hooks.Prestart) != 0 {
+		for _, hook := range spec.Hooks.Prestart {
+			if strings.Contains(hook.Path, config.NVIDIAContainerRuntimeHookExecutable) {
+				m.logger.Infof("existing nvidia prestart hook found in OCI spec")
+				return nil
+			}
+		}
+	}
+
+	spec.Hooks.Prestart = append(spec.Hooks.Prestart, specs.Hook{
+		Path: path,
+		Args: append(args, "prestart"),
+	})
+
+	return nil
+}