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/sandbox.go

@@ -0,0 +1,67 @@
+/*
+   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"
+)
+
+// PodSandbox interface for interacting with NRI.
+type PodSandbox interface {
+	GetDomain() string
+
+	GetID() string
+	GetName() string
+	GetUID() string
+	GetNamespace() string
+	GetLabels() map[string]string
+	GetAnnotations() map[string]string
+	GetRuntimeHandler() string
+	GetLinuxPodSandbox() LinuxPodSandbox
+
+	GetPid() uint32
+}
+
+type LinuxPodSandbox interface {
+	GetLinuxNamespaces() []*nri.LinuxNamespace
+	GetPodLinuxOverhead() *nri.LinuxResources
+	GetPodLinuxResources() *nri.LinuxResources
+	GetCgroupParent() string
+	GetCgroupsPath() string
+	GetLinuxResources() *nri.LinuxResources
+}
+
+func commonPodSandboxToNRI(pod PodSandbox) *nri.PodSandbox {
+	return &nri.PodSandbox{
+		Id:             pod.GetID(),
+		Name:           pod.GetName(),
+		Uid:            pod.GetUID(),
+		Namespace:      pod.GetNamespace(),
+		Labels:         pod.GetLabels(),
+		Annotations:    pod.GetAnnotations(),
+		RuntimeHandler: pod.GetRuntimeHandler(),
+		Pid:            pod.GetPid(),
+	}
+}
+
+func podSandboxesToNRI(podList []PodSandbox) []*nri.PodSandbox {
+	pods := []*nri.PodSandbox{}
+	for _, pod := range podList {
+		pods = append(pods, podSandboxToNRI(pod))
+	}
+	return pods
+}