pkg/cdi: add K8s annotation handling functions.

Add functions for annotating containers for CDI device injection
and for extracting CDI device names from such annotations. These
functions can be used by CDI-aware devices plugins and runtimes,
to request the injection of CDI devices and to recover the names
of devices to inject correspondingly.

For example, the following call to AnnotateInjection
    annotations := map[string]string{}
    AnnotateInjection(annotations, "vendor.gpu", []string{
        "vendor.com/gpu=gpu0",
        "vendor.com/gpu=gpu1",
    })
produces the following annotations
    map[string]string{
        "cdi.k8s.io/vendor.gpu": "vendor.com/gpu=gpu0,vendor.com/gpu=gpu1",
    }

Subsequently parsing these annotations with
    devices, err := ParseAnnotations(annotations)
extracts and returns the original slice of devices to inject:
    []string{
        "vendor.com/gpu=gpu0",
        "vendor.com/gpu=gpu1",
    }

Notes:
  These functions provide a temporary solution for delivering
  CDI device injection requests from either a client or a K8s
  Device Plugin to the container runtime. They can be removed
  once dedicated fields to the same effect are added natively
  to the CRI protocol.

Signed-off-by: Krisztian Litkey <[email protected]>

Author: klihub

pkg/cdi/annotations.go

@@ -0,0 +1,139 @@
+/*
+   Copyright © 2021-2022 The CDI 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 cdi
+
+import (
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+const (
+	// AnnotationPrefix is the prefix for CDI container annotation keys.
+	AnnotationPrefix = "cdi.k8s.io/"
+)
+
+// UpdateAnnotations updates annotations with a plugin-specific CDI device
+// injection request for the given devices. Upon any error a non-nil error
+// is returned and annotations are left intact. By convention plugin should
+// be in the format of "vendor.device-type".
+func UpdateAnnotations(annotations map[string]string, plugin string, deviceID string, devices []string) (map[string]string, error) {
+	key, err := AnnotationKey(plugin, deviceID)
+	if err != nil {
+		return annotations, errors.Wrap(err, "CDI annotation failed")
+	}
+	if _, ok := annotations[key]; ok {
+		return annotations, errors.Errorf("CDI annotation failed, key %q used", key)
+	}
+	value, err := AnnotationValue(devices)
+	if err != nil {
+		return annotations, errors.Wrap(err, "CDI annotation failed")
+	}
+
+	if annotations == nil {
+		annotations = make(map[string]string)
+	}
+	annotations[key] = value
+
+	return annotations, nil
+}
+
+// ParseAnnotations parses annotations for CDI device injection requests.
+// The keys and devices from all such requests are collected into slices
+// which are returned as the result. All devices are expected to be fully
+// qualified CDI device names. If any device fails this check empty slices
+// are returned along with a non-nil error. The annotations are expected
+// to be formatted by, or in a compatible fashion to UpdateAnnotations().
+func ParseAnnotations(annotations map[string]string) ([]string, []string, error) {
+	var (
+		keys    []string
+		devices []string
+	)
+
+	for key, value := range annotations {
+		if !strings.HasPrefix(key, AnnotationPrefix) {
+			continue
+		}
+		for _, d := range strings.Split(value, ",") {
+			if !IsQualifiedName(d) {
+				return nil, nil, errors.Errorf("invalid CDI device name %q", d)
+			}
+			devices = append(devices, d)
+		}
+		keys = append(keys, key)
+	}
+
+	return keys, devices, nil
+}
+
+// AnnotationKey returns a unique annotation key for an device allocation
+// by a K8s device plugin. pluginName should be in the format of
+// "vendor.device-type". deviceID is the ID of the device the plugin is
+// allocating. It is used to make sure that the generated key is unique
+// even if multiple allocations by a single plugin needs to be annotated.
+func AnnotationKey(pluginName, deviceID string) (string, error) {
+	const maxNameLen = 63
+
+	if pluginName == "" {
+		return "", errors.New("invalid plugin name, empty")
+	}
+	if deviceID == "" {
+		return "", errors.New("invalid deviceID, empty")
+	}
+
+	name := pluginName + "_" + strings.ReplaceAll(deviceID, "/", "_")
+
+	if len(name) > maxNameLen {
+		return "", errors.Errorf("invalid plugin+deviceID %q, too long", name)
+	}
+
+	if c := rune(name[0]); !isAlphaNumeric(c) {
+		return "", errors.Errorf("invalid name %q, first '%c' should be alphanumeric",
+			name, c)
+	}
+	if len(name) > 2 {
+		for _, c := range name[1 : len(name)-1] {
+			switch {
+			case isAlphaNumeric(c):
+			case c == '_' || c == '-' || c == '.':
+			default:
+				return "", errors.Errorf("invalid name %q, invalid charcter '%c'",
+					name, c)
+			}
+		}
+	}
+	if c := rune(name[len(name)-1]); !isAlphaNumeric(c) {
+		return "", errors.Errorf("invalid name %q, last '%c' should be alphanumeric",
+			name, c)
+	}
+
+	return AnnotationPrefix + name, nil
+}
+
+// AnnotationValue returns an annotation value for the given devices.
+func AnnotationValue(devices []string) (string, error) {
+	value, sep := "", ""
+	for _, d := range devices {
+		if _, _, _, err := ParseQualifiedName(d); err != nil {
+			return "", err
+		}
+		value += sep + d
+		sep = ","
+	}
+
+	return value, nil
+}