Add stable discoverer for nvidia-container-runtime hook

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

internal/discover/discover.go

@@ -0,0 +1,30 @@
+/*
+# Copyright (c) 2021-2022, 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
+
+// Hook represents a discovered hook.
+type Hook struct {
+	Lifecycle string
+	Path      string
+	Args      []string
+}
+
+//go:generate moq -stub -out discover_mock.go . Discover
+// Discover defines an interface for discovering the devices, mounts, and hooks available on a system
+type Discover interface {
+	Hooks() ([]Hook, error)
+}

internal/discover/discover_mock.go

@@ -0,0 +1,70 @@
+// Code generated by moq; DO NOT EDIT.
+// github.com/matryer/moq
+
+package discover
+
+import (
+	"sync"
+)
+
+// Ensure, that DiscoverMock does implement Discover.
+// If this is not the case, regenerate this file with moq.
+var _ Discover = &DiscoverMock{}
+
+// DiscoverMock is a mock implementation of Discover.
+//
+// 	func TestSomethingThatUsesDiscover(t *testing.T) {
+//
+// 		// make and configure a mocked Discover
+// 		mockedDiscover := &DiscoverMock{
+// 			HooksFunc: func() ([]Hook, error) {
+// 				panic("mock out the Hooks method")
+// 			},
+// 		}
+//
+// 		// use mockedDiscover in code that requires Discover
+// 		// and then make assertions.
+//
+// 	}
+type DiscoverMock struct {
+	// HooksFunc mocks the Hooks method.
+	HooksFunc func() ([]Hook, error)
+
+	// calls tracks calls to the methods.
+	calls struct {
+		// Hooks holds details about calls to the Hooks method.
+		Hooks []struct {
+		}
+	}
+	lockHooks sync.RWMutex
+}
+
+// Hooks calls HooksFunc.
+func (mock *DiscoverMock) Hooks() ([]Hook, error) {
+	callInfo := struct {
+	}{}
+	mock.lockHooks.Lock()
+	mock.calls.Hooks = append(mock.calls.Hooks, callInfo)
+	mock.lockHooks.Unlock()
+	if mock.HooksFunc == nil {
+		var (
+			hooksOut []Hook
+			errOut   error
+		)
+		return hooksOut, errOut
+	}
+	return mock.HooksFunc()
+}
+
+// HooksCalls gets all the calls that were made to Hooks.
+// Check the length with:
+//     len(mockedDiscover.HooksCalls())
+func (mock *DiscoverMock) HooksCalls() []struct {
+} {
+	var calls []struct {
+	}
+	mock.lockHooks.RLock()
+	calls = mock.calls.Hooks
+	mock.lockHooks.RUnlock()
+	return calls
+}

internal/discover/stable.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 stable struct {
+	logger *logrus.Logger
+	lookup lookup.Locator
+}
+
+const (
+	nvidiaContainerRuntimeHookExecuable = "nvidia-container-runtime-hook"
+	hookDefaultFilePath                 = "/usr/bin/nvidia-container-runtime-hook"
+)
+
+var _ Discover = (*stable)(nil)
+
+// NewStableDiscoverer creates a discoverer for the stable runtime
+func NewStableDiscoverer(logger *logrus.Logger, root string) (Discover, error) {
+	d := stable{
+		logger: logger,
+		lookup: lookup.NewPathLocator(logger, root),
+	}
+
+	return &d, nil
+}
+
+// Hooks returns the "stable" NVIDIA Container Runtime hook
+func (d stable) Hooks() ([]Hook, error) {
+	var hooks []Hook
+
+	hookPath := hookDefaultFilePath
+	targets, err := d.lookup.Locate(nvidiaContainerRuntimeHookExecuable)
+	if err != nil {
+		d.logger.Warnf("Failed to locate %v: %v", nvidiaContainerRuntimeHookExecuable, err)
+	} else if len(targets) == 0 {
+		d.logger.Warnf("%v not found", nvidiaContainerRuntimeHookExecuable)
+	} else {
+		d.logger.Debugf("Found %v candidates: %v", nvidiaContainerRuntimeHookExecuable, targets)
+		hookPath = targets[0]
+	}
+	d.logger.Debugf("Using NVIDIA Container Runtime Hook path %v", hookPath)
+
+	args := []string{hookPath, "prestart"}
+	legacyHook := Hook{
+		Lifecycle: cdi.PrestartHook,
+		Path:      hookPath,
+		Args:      args,
+	}
+	hooks = append(hooks, legacyHook)
+	return hooks, nil
+}