cri: annotations for controlling RDT class

Use goresctrl for parsing container and pod annotations related to RDT.

In practice, from the users' point of view, this patchs adds support for
a container annotation and two separate pod annotations for controlling
the RDT class of containers.

Container annotation can be used by a CRI client:
  "io.kubernetes.cri.rdt-class"

Pod annotations for specifying the RDT class in the K8s pod spec level:
  "rdt.resources.beta.kubernetes.io/pod"
  (pod-wide default for all containers within)

  "rdt.resources.beta.kubernetes.io/container.<container_name>"
  (container-specific overrides)

Annotations are intended as an intermediate step before the CRI API
supports RDT.

Signed-off-by: Markus Lehtonen <markus.lehtonen@intel.com>

pkg/cri/server/rdt_linux.go

@@ -0,0 +1,39 @@
+//go:build !no_rdt
+
+/*
+   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 server
+
+import (
+	"fmt"
+
+	"github.com/containerd/containerd/services/tasks"
+	"github.com/intel/goresctrl/pkg/rdt"
+)
+
+// rdtClassFromAnnotations examines container and pod annotations of a
+// container and returns its effective RDT class.
+func rdtClassFromAnnotations(containerName string, containerAnnotations, podAnnotations map[string]string) (string, error) {
+	cls, err := rdt.ContainerClassFromAnnotations(containerName, containerAnnotations, podAnnotations)
+	if err != nil {
+		return "", err
+	}
+	if cls != "" && !tasks.RdtEnabled() {
+		return "", fmt.Errorf("RDT disabled, refusing to set RDT class of container %q to %q", containerName, cls)
+	}
+	return cls, nil
+}