NRI based Container ID Injection

nri-plugin.go

package main

import (
	"context"
	"flag"
	"fmt"
	"os"

	"github.com/sirupsen/logrus"
	"sigs.k8s.io/yaml"

	"github.com/containerd/nri/pkg/api"
	"github.com/containerd/nri/pkg/stub"
)

type config struct {
	CfgParam1 string `json:"cfgParam1"`
}

type plugin struct {
	stub stub.Stub
	mask stub.EventMask
}

var (
	cfg config
	log *logrus.Logger
)

func (p *plugin) Configure(config, runtime, version string) (stub.EventMask, error) {
	log.Infof("Connected to %s/%s...", runtime, version)

	if config == "" {
		return 0, nil
	}

	err := yaml.Unmarshal([]byte(config), &cfg)
	if err != nil {
		return 0, fmt.Errorf("failed to parse configuration: %w", err)
	}

	log.Info("Got configuration data %+v...", cfg)

	return 0, nil
}

func (p *plugin) Synchronize(pods []*api.PodSandbox, containers []*api.Container) ([]*api.ContainerUpdate, error) {
	log.Info("Synchronizing state with the runtime...")
	return nil, nil
}

func (p *plugin) Shutdown() {
	log.Info("Runtime shutting down...")
}

func (p *plugin) CreateContainer(pod *api.PodSandbox, ctr *api.Container) (*api.ContainerAdjustment, []*api.ContainerUpdate, error) {

	os.WriteFile("/tmp/container-id", []byte(ctr.GetId()), os.FileMode(0755))

	adjustment := &api.ContainerAdjustment{}
	updates := []*api.ContainerUpdate{}
	adjustment.Env = append(adjustment.Env, &api.KeyValue{
		Key:   "CONTAINER_ID",
		Value: ctr.GetId(),
	})
	adjustment.Mounts = append(adjustment.Mounts, &api.Mount{
		Source:      "/tmp/container-id",
		Destination: "/run/container-id",
		Type:        "bind",
		Options: []string{
			"rbind",
			"rprivate",
			"rw",
		},
	})
	return adjustment, updates, nil
}

func (p *plugin) onClose() {
	log.Infof("Connection to the runtime lost, exiting...")
	os.Exit(0)
}

func main() {
	var (
		pluginName string
		pluginIdx  string
		err        error
	)

	log = logrus.StandardLogger()
	log.SetFormatter(&logrus.TextFormatter{
		PadLevelText: true,
	})

	flag.StringVar(&pluginName, "name", "", "plugin name to register to NRI")
	flag.StringVar(&pluginIdx, "idx", "", "plugin index to register to NRI")
	flag.Parse()

	p := &plugin{}
	opts := []stub.Option{
		stub.WithOnClose(p.onClose),
	}
	if pluginName != "" {
		opts = append(opts, stub.WithPluginName(pluginName))
	}
	if pluginIdx != "" {
		opts = append(opts, stub.WithPluginIdx(pluginIdx))
	}

	if p.stub, err = stub.New(p, opts...); err != nil {
		log.Fatalf("failed to create plugin stub: %v", err)
	}

	if err = p.stub.Run(context.Background()); err != nil {
		log.Errorf("plugin exited (%v)", err)
		os.Exit(1)
	}
}

Add following to /etc/containerd/config.toml

  [plugins."io.containerd.nri.v1.nri"]
    config_file = "/etc/nri/nri.conf"
    disable = false
    plugin_path = "/opt/nri/plugins"
    socket_path = "/var/run/nri.sock"

And do the following

echo "disableConnections: false" > /etc/nri/nri.conf using containerd - v1.7.0-beta.2+