nri: add experimental NRI plugin.

Add a common NRI 'service' plugin. It takes care of relaying
requests and respones to and from NRI (external NRI plugins)
and the high-level containerd namespace-independent logic of
applying NRI container adjustments and updates to actual CRI
and other containers.

The namespace-dependent details of the necessary container
manipulation operations are to be implemented by namespace-
specific adaptations. This NRI plugin defines the API which
such adaptations need to implement.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

pkg/nri/container.go

@@ -0,0 +1,72 @@
+/*
+   Copyright The containerd Authors.
+
+   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 nri
+
+import (
+	nri "github.com/containerd/nri/pkg/adaptation"
+)
+
+// Container interface for interacting with NRI.
+type Container interface {
+	GetDomain() string
+
+	GetPodSandboxID() string
+	GetID() string
+	GetName() string
+	GetState() nri.ContainerState
+	GetLabels() map[string]string
+	GetAnnotations() map[string]string
+	GetArgs() []string
+	GetEnv() []string
+	GetMounts() []*nri.Mount
+	GetHooks() *nri.Hooks
+	GetLinuxContainer() LinuxContainer
+
+	GetPid() uint32
+}
+
+type LinuxContainer interface {
+	GetLinuxNamespaces() []*nri.LinuxNamespace
+	GetLinuxDevices() []*nri.LinuxDevice
+	GetLinuxResources() *nri.LinuxResources
+	GetOOMScoreAdj() *int
+	GetCgroupsPath() string
+}
+
+func commonContainerToNRI(ctr Container) *nri.Container {
+	return &nri.Container{
+		Id:           ctr.GetID(),
+		PodSandboxId: ctr.GetPodSandboxID(),
+		Name:         ctr.GetName(),
+		State:        ctr.GetState(),
+		Labels:       ctr.GetLabels(),
+		Annotations:  ctr.GetAnnotations(),
+		Args:         ctr.GetArgs(),
+		Env:          ctr.GetEnv(),
+		Mounts:       ctr.GetMounts(),
+		Hooks:        ctr.GetHooks(),
+		Pid:          ctr.GetPid(),
+	}
+}
+
+func containersToNRI(ctrList []Container) []*nri.Container {
+	ctrs := []*nri.Container{}
+	for _, ctr := range ctrList {
+		ctrs = append(ctrs, containerToNRI(ctr))
+	}
+	return ctrs
+}