k3s/vendor/k8s.io/kubernetes/pkg/volume/csi/csi_plugin.go

/*
Copyright 2017 The Kubernetes 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 csi

import (
	"errors"
	"fmt"
	"os"
	"path"
	"sort"
	"strings"
	"sync"
	"time"

	"context"

	"k8s.io/klog"

	api "k8s.io/api/core/v1"
	apierrs "k8s.io/apimachinery/pkg/api/errors"
	meta "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	utilversion "k8s.io/apimachinery/pkg/util/version"
	"k8s.io/apimachinery/pkg/util/wait"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	csiapiinformer "k8s.io/client-go/informers"
	csiinformer "k8s.io/client-go/informers/storage/v1beta1"
	clientset "k8s.io/client-go/kubernetes"
	csilister "k8s.io/client-go/listers/storage/v1beta1"
	"k8s.io/kubernetes/pkg/features"
	"k8s.io/kubernetes/pkg/volume"
	"k8s.io/kubernetes/pkg/volume/csi/nodeinfomanager"
)

const (
	// CSIPluginName is the name of the in-tree CSI Plugin
	CSIPluginName = "kubernetes.io/csi"

	// TODO (vladimirvivien) implement a more dynamic way to discover
	// the unix domain socket path for each installed csi driver.
	// TODO (vladimirvivien) would be nice to name socket with a .sock extension
	// for consistency.
	csiAddrTemplate = "/var/lib/kubelet/plugins/%v/csi.sock"
	csiTimeout      = 15 * time.Second
	volNameSep      = "^"
	volDataFileName = "vol_data.json"
	fsTypeBlockName = "block"

	// TODO: increase to something useful
	csiResyncPeriod = time.Minute
)

var (
	WaitForValidHostName bool
	csiPluginInstance *csiPlugin
	csiPluginLock sync.Mutex
)

var deprecatedSocketDirVersions = []string{"0.1.0", "0.2.0", "0.3.0", "0.4.0"}

type csiPlugin struct {
	host              volume.VolumeHost
	blockEnabled      bool
	csiDriverLister   csilister.CSIDriverLister
	csiDriverInformer csiinformer.CSIDriverInformer
}

//TODO (vladimirvivien) add this type to storage api
type driverMode string

const persistentDriverMode driverMode = "persistent"
const ephemeralDriverMode driverMode = "ephemeral"

// ProbeVolumePlugins returns implemented plugins
func ProbeVolumePlugins() []volume.VolumePlugin {
	csiPluginLock.Lock()
	defer csiPluginLock.Unlock()

	if csiPluginInstance != nil {
		return []volume.VolumePlugin{csiPluginInstance}
	}

	csiPluginInstance = &csiPlugin{
		host:         nil,
		blockEnabled: utilfeature.DefaultFeatureGate.Enabled(features.CSIBlockVolume),
	}
	return []volume.VolumePlugin{csiPluginInstance}
}

// volume.VolumePlugin methods
var _ volume.VolumePlugin = &csiPlugin{}

// RegistrationHandler is the handler which is fed to the pluginwatcher API.
type RegistrationHandler struct {
}

// TODO (verult) consider using a struct instead of global variables
// csiDrivers map keep track of all registered CSI drivers on the node and their
// corresponding sockets
var csiDrivers = &DriversStore{}

var nim nodeinfomanager.Interface

// PluginHandler is the plugin registration handler interface passed to the
// pluginwatcher module in kubelet
var PluginHandler = &RegistrationHandler{}

// ValidatePlugin is called by kubelet's plugin watcher upon detection
// of a new registration socket opened by CSI Driver registrar side car.
func (h *RegistrationHandler) ValidatePlugin(pluginName string, endpoint string, versions []string, foundInDeprecatedDir bool) error {
	klog.Infof(log("Trying to validate a new CSI Driver with name: %s endpoint: %s versions: %s, foundInDeprecatedDir: %v",
		pluginName, endpoint, strings.Join(versions, ","), foundInDeprecatedDir))

	if foundInDeprecatedDir {
		// CSI 0.x drivers used /var/lib/kubelet/plugins as the socket dir.
		// This was deprecated as the socket dir for kubelet drivers, in lieu of a dedicated dir /var/lib/kubelet/plugins_registry
		// The deprecated dir will only be allowed for a whitelisted set of old versions.
		// CSI 1.x drivers should use the /var/lib/kubelet/plugins_registry
		if !isDeprecatedSocketDirAllowed(versions) {
			err := fmt.Errorf("socket for CSI driver %q versions %v was found in a deprecated dir. Drivers implementing CSI 1.x+ must use the new dir", pluginName, versions)
			klog.Error(err)
			return err
		}
	}

	_, err := h.validateVersions("ValidatePlugin", pluginName, endpoint, versions)
	return err
}

// RegisterPlugin is called when a plugin can be registered
func (h *RegistrationHandler) RegisterPlugin(pluginName string, endpoint string, versions []string) error {
	klog.Infof(log("Register new plugin with name: %s at endpoint: %s", pluginName, endpoint))

	highestSupportedVersion, err := h.validateVersions("RegisterPlugin", pluginName, endpoint, versions)
	if err != nil {
		return err
	}

	// Storing endpoint of newly registered CSI driver into the map, where CSI driver name will be the key
	// all other CSI components will be able to get the actual socket of CSI drivers by its name.
	csiDrivers.Set(pluginName, Driver{
		endpoint:                endpoint,
		highestSupportedVersion: highestSupportedVersion,
	})

	// Get node info from the driver.
	csi, err := newCsiDriverClient(csiDriverName(pluginName))
	if err != nil {
		return err
	}

	ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
	defer cancel()

	driverNodeID, maxVolumePerNode, accessibleTopology, err := csi.NodeGetInfo(ctx)
	if err != nil {
		if unregErr := unregisterDriver(pluginName); unregErr != nil {
			klog.Error(log("registrationHandler.RegisterPlugin failed to unregister plugin due to previous error: %v", unregErr))
		}
		return err
	}

	err = nim.InstallCSIDriver(pluginName, driverNodeID, maxVolumePerNode, accessibleTopology)
	if err != nil {
		if unregErr := unregisterDriver(pluginName); unregErr != nil {
			klog.Error(log("registrationHandler.RegisterPlugin failed to unregister plugin due to previous error: %v", unregErr))
		}
		return err
	}

	return nil
}

func (h *RegistrationHandler) validateVersions(callerName, pluginName string, endpoint string, versions []string) (*utilversion.Version, error) {
	if len(versions) == 0 {
		err := fmt.Errorf("%s for CSI driver %q failed. Plugin returned an empty list for supported versions", callerName, pluginName)
		klog.Error(err)
		return nil, err
	}

	// Validate version
	newDriverHighestVersion, err := highestSupportedVersion(versions)
	if err != nil {
		err := fmt.Errorf("%s for CSI driver %q failed. None of the versions specified %q are supported. err=%v", callerName, pluginName, versions, err)
		klog.Error(err)
		return nil, err
	}

	existingDriver, driverExists := csiDrivers.Get(pluginName)
	if driverExists {
		if !existingDriver.highestSupportedVersion.LessThan(newDriverHighestVersion) {
			err := fmt.Errorf("%s for CSI driver %q failed. Another driver with the same name is already registered with a higher supported version: %q", callerName, pluginName, existingDriver.highestSupportedVersion)
			klog.Error(err)
			return nil, err
		}
	}

	return newDriverHighestVersion, nil
}

// DeRegisterPlugin is called when a plugin removed its socket, signaling
// it is no longer available
func (h *RegistrationHandler) DeRegisterPlugin(pluginName string) {
	klog.V(4).Info(log("registrationHandler.DeRegisterPlugin request for plugin %s", pluginName))
	if err := unregisterDriver(pluginName); err != nil {
		klog.Error(log("registrationHandler.DeRegisterPlugin failed: %v", err))
	}
}

func (p *csiPlugin) Init(host volume.VolumeHost) error {
	csiPluginLock.Lock()
	defer csiPluginLock.Unlock()

	if WaitForValidHostName && host.GetHostName() == "" {
		for {
			if p.host != nil {
				return nil
			}
			csiPluginLock.Unlock()
			time.Sleep(time.Second)
			klog.Infof("Waiting for CSI volume hostname")
			csiPluginLock.Lock()
		}
	}

	p.host = host

	if utilfeature.DefaultFeatureGate.Enabled(features.CSIDriverRegistry) {
		csiClient := host.GetKubeClient()
		if csiClient == nil {
			klog.Warning(log("kubeclient not set, assuming standalone kubelet"))
		} else {
			// Start informer for CSIDrivers.
			factory := csiapiinformer.NewSharedInformerFactory(csiClient, csiResyncPeriod)
			p.csiDriverInformer = factory.Storage().V1beta1().CSIDrivers()
			p.csiDriverLister = p.csiDriverInformer.Lister()
			go factory.Start(wait.NeverStop)
		}
	}

	// Initializing the label management channels
	nim = nodeinfomanager.NewNodeInfoManager(host.GetNodeName(), host, nil)

	return nil
}

func (p *csiPlugin) GetPluginName() string {
	return CSIPluginName
}

// GetvolumeName returns a concatenated string of CSIVolumeSource.Driver<volNameSe>CSIVolumeSource.VolumeHandle
// That string value is used in Detach() to extract driver name and volumeName.
func (p *csiPlugin) GetVolumeName(spec *volume.Spec) (string, error) {
	csi, err := getPVSourceFromSpec(spec)
	if err != nil {
		klog.Error(log("plugin.GetVolumeName failed to extract volume source from spec: %v", err))
		return "", err
	}

	// return driverName<separator>volumeHandle
	return fmt.Sprintf("%s%s%s", csi.Driver, volNameSep, csi.VolumeHandle), nil
}

func (p *csiPlugin) CanSupport(spec *volume.Spec) bool {
	// TODO (vladimirvivien) CanSupport should also take into account
	// the availability/registration of specified Driver in the volume source
	if spec == nil {
		return false
	}

	return spec.PersistentVolume != nil && spec.PersistentVolume.Spec.CSI != nil
}

func (p *csiPlugin) IsMigratedToCSI() bool {
	return false
}

func (p *csiPlugin) RequiresRemount() bool {
	return false
}

func (p *csiPlugin) NewMounter(
	spec *volume.Spec,
	pod *api.Pod,
	_ volume.VolumeOptions) (volume.Mounter, error) {

	_, pvSrc, err := getSourceFromSpec(spec)
	if err != nil {
		return nil, err
	}

	var (
		driverName   string
		volumeHandle string
		readOnly     bool
	)

	switch {
	case pvSrc != nil:
		driverName = pvSrc.Driver
		volumeHandle = pvSrc.VolumeHandle
		readOnly = spec.ReadOnly
	default:
		return nil, fmt.Errorf("volume source not found in volume.Spec")
	}

	driverMode, err := p.getDriverMode(spec)
	if err != nil {
		return nil, err
	}

	k8s := p.host.GetKubeClient()
	if k8s == nil {
		klog.Error(log("failed to get a kubernetes client"))
		return nil, errors.New("failed to get a Kubernetes client")
	}

	mounter := &csiMountMgr{
		plugin:       p,
		k8s:          k8s,
		spec:         spec,
		pod:          pod,
		podUID:       pod.UID,
		driverName:   csiDriverName(driverName),
		driverMode:   driverMode,
		volumeID:     volumeHandle,
		specVolumeID: spec.Name(),
		readOnly:     readOnly,
	}
	mounter.csiClientGetter.driverName = csiDriverName(driverName)

	// Save volume info in pod dir
	dir := mounter.GetPath()
	dataDir := path.Dir(dir) // dropoff /mount at end

	if err := os.MkdirAll(dataDir, 0750); err != nil {
		klog.Error(log("failed to create dir %#v:  %v", dataDir, err))
		return nil, err
	}
	klog.V(4).Info(log("created path successfully [%s]", dataDir))

	// persist volume info data for teardown
	node := string(p.host.GetNodeName())
	volData := map[string]string{
		volDataKey.specVolID:  spec.Name(),
		volDataKey.volHandle:  volumeHandle,
		volDataKey.driverName: driverName,
		volDataKey.nodeName:   node,
		volDataKey.driverMode: string(driverMode),
	}

	attachID := getAttachmentName(volumeHandle, driverName, node)
	volData[volDataKey.attachmentID] = attachID

	if err := saveVolumeData(dataDir, volDataFileName, volData); err != nil {
		klog.Error(log("failed to save volume info data: %v", err))
		if err := os.RemoveAll(dataDir); err != nil {
			klog.Error(log("failed to remove dir after error [%s]: %v", dataDir, err))
			return nil, err
		}
		return nil, err
	}

	klog.V(4).Info(log("mounter created successfully"))

	return mounter, nil
}

func (p *csiPlugin) NewUnmounter(specName string, podUID types.UID) (volume.Unmounter, error) {
	klog.V(4).Infof(log("setting up unmounter for [name=%v, podUID=%v]", specName, podUID))

	unmounter := &csiMountMgr{
		plugin:       p,
		podUID:       podUID,
		specVolumeID: specName,
	}

	// load volume info from file
	dir := unmounter.GetPath()
	dataDir := path.Dir(dir) // dropoff /mount at end
	data, err := loadVolumeData(dataDir, volDataFileName)
	if err != nil {
		klog.Error(log("unmounter failed to load volume data file [%s]: %v", dir, err))
		return nil, err
	}
	unmounter.driverName = csiDriverName(data[volDataKey.driverName])
	unmounter.volumeID = data[volDataKey.volHandle]
	unmounter.csiClientGetter.driverName = unmounter.driverName

	return unmounter, nil
}

func (p *csiPlugin) ConstructVolumeSpec(volumeName, mountPath string) (*volume.Spec, error) {
	klog.V(4).Info(log("plugin.ConstructVolumeSpec [pv.Name=%v, path=%v]", volumeName, mountPath))

	volData, err := loadVolumeData(mountPath, volDataFileName)
	if err != nil {
		klog.Error(log("plugin.ConstructVolumeSpec failed loading volume data using [%s]: %v", mountPath, err))
		return nil, err
	}

	klog.V(4).Info(log("plugin.ConstructVolumeSpec extracted [%#v]", volData))

	var spec *volume.Spec
	spec = p.constructPVSourceSpec(volData[volDataKey.specVolID], volData[volDataKey.driverName], volData[volDataKey.volHandle])

	return spec, nil
}

// constructVolSourceSpec constructs volume.Spec with CSIVolumeSource
func (p *csiPlugin) constructVolSourceSpec(volSpecName, driverName string) *volume.Spec {
	vol := &api.Volume{
		Name: volSpecName,
		VolumeSource: api.VolumeSource{
			CSI: &api.CSIVolumeSource{
				Driver: driverName,
			},
		},
	}
	return volume.NewSpecFromVolume(vol)
}

//constructPVSourceSpec constructs volume.Spec with CSIPersistentVolumeSource
func (p *csiPlugin) constructPVSourceSpec(volSpecName, driverName, volumeHandle string) *volume.Spec {
	fsMode := api.PersistentVolumeFilesystem
	pv := &api.PersistentVolume{
		ObjectMeta: meta.ObjectMeta{
			Name: volSpecName,
		},
		Spec: api.PersistentVolumeSpec{
			PersistentVolumeSource: api.PersistentVolumeSource{
				CSI: &api.CSIPersistentVolumeSource{
					Driver:       driverName,
					VolumeHandle: volumeHandle,
				},
			},
			VolumeMode: &fsMode,
		},
	}
	return volume.NewSpecFromPersistentVolume(pv, false)
}

func (p *csiPlugin) SupportsMountOption() bool {
	// TODO (vladimirvivien) use CSI VolumeCapability.MountVolume.mount_flags
	// to probe for the result for this method
	// (bswartz) Until the CSI spec supports probing, our only option is to
	// make plugins register their support for mount options or lack thereof
	// directly with kubernetes.
	return true
}

func (p *csiPlugin) SupportsBulkVolumeVerification() bool {
	return false
}

// volume.AttachableVolumePlugin methods
var _ volume.AttachableVolumePlugin = &csiPlugin{}

var _ volume.DeviceMountableVolumePlugin = &csiPlugin{}

func (p *csiPlugin) NewAttacher() (volume.Attacher, error) {
	k8s := p.host.GetKubeClient()
	if k8s == nil {
		klog.Error(log("unable to get kubernetes client from host"))
		return nil, errors.New("unable to get Kubernetes client")
	}

	return &csiAttacher{
		plugin:        p,
		k8s:           k8s,
		waitSleepTime: 1 * time.Second,
	}, nil
}

func (p *csiPlugin) NewDeviceMounter() (volume.DeviceMounter, error) {
	return p.NewAttacher()
}

func (p *csiPlugin) NewDetacher() (volume.Detacher, error) {
	k8s := p.host.GetKubeClient()
	if k8s == nil {
		klog.Error(log("unable to get kubernetes client from host"))
		return nil, errors.New("unable to get Kubernetes client")
	}

	return &csiAttacher{
		plugin:        p,
		k8s:           k8s,
		waitSleepTime: 1 * time.Second,
	}, nil
}

// TODO change CanAttach to return error to propagate ability
// to support Attachment or an error - see https://github.com/kubernetes/kubernetes/issues/74810
func (p *csiPlugin) CanAttach(spec *volume.Spec) bool {
	driverMode, err := p.getDriverMode(spec)
	if err != nil {
		return false
	}

	if driverMode == ephemeralDriverMode {
		klog.V(4).Info(log("driver ephemeral mode detected for spec %v", spec.Name))
		return false
	}

	pvSrc, err := getCSISourceFromSpec(spec)
	if err != nil {
		klog.Error(log("plugin.CanAttach failed to get info from spec: %s", err))
		return false
	}

	driverName := pvSrc.Driver

	skipAttach, err := p.skipAttach(driverName)
	if err != nil {
		klog.Error(log("plugin.CanAttach error when calling plugin.skipAttach for driver %s: %s", driverName, err))
		return false
	}

	return !skipAttach
}

func (p *csiPlugin) NewDeviceUnmounter() (volume.DeviceUnmounter, error) {
	return p.NewDetacher()
}

func (p *csiPlugin) GetDeviceMountRefs(deviceMountPath string) ([]string, error) {
	m := p.host.GetMounter(p.GetPluginName())
	return m.GetMountRefs(deviceMountPath)
}

// BlockVolumePlugin methods
var _ volume.BlockVolumePlugin = &csiPlugin{}

func (p *csiPlugin) NewBlockVolumeMapper(spec *volume.Spec, podRef *api.Pod, opts volume.VolumeOptions) (volume.BlockVolumeMapper, error) {
	if !p.blockEnabled {
		return nil, errors.New("CSIBlockVolume feature not enabled")
	}

	pvSource, err := getCSISourceFromSpec(spec)
	if err != nil {
		return nil, err
	}
	readOnly, err := getReadOnlyFromSpec(spec)
	if err != nil {
		return nil, err
	}

	klog.V(4).Info(log("setting up block mapper for [volume=%v,driver=%v]", pvSource.VolumeHandle, pvSource.Driver))

	k8s := p.host.GetKubeClient()
	if k8s == nil {
		klog.Error(log("failed to get a kubernetes client"))
		return nil, errors.New("failed to get a Kubernetes client")
	}

	mapper := &csiBlockMapper{
		k8s:        k8s,
		plugin:     p,
		volumeID:   pvSource.VolumeHandle,
		driverName: csiDriverName(pvSource.Driver),
		readOnly:   readOnly,
		spec:       spec,
		specName:   spec.Name(),
		podUID:     podRef.UID,
	}
	mapper.csiClientGetter.driverName = csiDriverName(pvSource.Driver)

	// Save volume info in pod dir
	dataDir := getVolumeDeviceDataDir(spec.Name(), p.host)

	if err := os.MkdirAll(dataDir, 0750); err != nil {
		klog.Error(log("failed to create data dir %s:  %v", dataDir, err))
		return nil, err
	}
	klog.V(4).Info(log("created path successfully [%s]", dataDir))

	// persist volume info data for teardown
	node := string(p.host.GetNodeName())
	attachID := getAttachmentName(pvSource.VolumeHandle, pvSource.Driver, node)
	volData := map[string]string{
		volDataKey.specVolID:    spec.Name(),
		volDataKey.volHandle:    pvSource.VolumeHandle,
		volDataKey.driverName:   pvSource.Driver,
		volDataKey.nodeName:     node,
		volDataKey.attachmentID: attachID,
	}

	if err := saveVolumeData(dataDir, volDataFileName, volData); err != nil {
		klog.Error(log("failed to save volume info data: %v", err))
		if err := os.RemoveAll(dataDir); err != nil {
			klog.Error(log("failed to remove dir after error [%s]: %v", dataDir, err))
			return nil, err
		}
		return nil, err
	}

	return mapper, nil
}

func (p *csiPlugin) NewBlockVolumeUnmapper(volName string, podUID types.UID) (volume.BlockVolumeUnmapper, error) {
	if !p.blockEnabled {
		return nil, errors.New("CSIBlockVolume feature not enabled")
	}

	klog.V(4).Infof(log("setting up block unmapper for [Spec=%v, podUID=%v]", volName, podUID))
	unmapper := &csiBlockMapper{
		plugin:   p,
		podUID:   podUID,
		specName: volName,
	}

	// load volume info from file
	dataDir := getVolumeDeviceDataDir(unmapper.specName, p.host)
	data, err := loadVolumeData(dataDir, volDataFileName)
	if err != nil {
		klog.Error(log("unmapper failed to load volume data file [%s]: %v", dataDir, err))
		return nil, err
	}
	unmapper.driverName = csiDriverName(data[volDataKey.driverName])
	unmapper.volumeID = data[volDataKey.volHandle]
	unmapper.csiClientGetter.driverName = unmapper.driverName
	if err != nil {
		return nil, err
	}

	return unmapper, nil
}

func (p *csiPlugin) ConstructBlockVolumeSpec(podUID types.UID, specVolName, mapPath string) (*volume.Spec, error) {
	if !p.blockEnabled {
		return nil, errors.New("CSIBlockVolume feature not enabled")
	}

	klog.V(4).Infof("plugin.ConstructBlockVolumeSpec [podUID=%s, specVolName=%s, path=%s]", string(podUID), specVolName, mapPath)

	dataDir := getVolumeDeviceDataDir(specVolName, p.host)
	volData, err := loadVolumeData(dataDir, volDataFileName)
	if err != nil {
		klog.Error(log("plugin.ConstructBlockVolumeSpec failed loading volume data using [%s]: %v", mapPath, err))
		return nil, err
	}

	klog.V(4).Info(log("plugin.ConstructBlockVolumeSpec extracted [%#v]", volData))

	blockMode := api.PersistentVolumeBlock
	pv := &api.PersistentVolume{
		ObjectMeta: meta.ObjectMeta{
			Name: volData[volDataKey.specVolID],
		},
		Spec: api.PersistentVolumeSpec{
			PersistentVolumeSource: api.PersistentVolumeSource{
				CSI: &api.CSIPersistentVolumeSource{
					Driver:       volData[volDataKey.driverName],
					VolumeHandle: volData[volDataKey.volHandle],
				},
			},
			VolumeMode: &blockMode,
		},
	}

	return volume.NewSpecFromPersistentVolume(pv, false), nil
}

// skipAttach looks up CSIDriver object associated with driver name
// to determine if driver requies attachment volume operation
func (p *csiPlugin) skipAttach(driver string) (bool, error) {
	if !utilfeature.DefaultFeatureGate.Enabled(features.CSIDriverRegistry) {
		return false, nil
	}
	if p.csiDriverLister == nil {
		return false, errors.New("CSIDriver lister does not exist")
	}
	csiDriver, err := p.csiDriverLister.Get(driver)
	if err != nil {
		if apierrs.IsNotFound(err) {
			// Don't skip attach if CSIDriver does not exist
			return false, nil
		}
		return false, err
	}
	if csiDriver.Spec.AttachRequired != nil && *csiDriver.Spec.AttachRequired == false {
		return true, nil
	}
	return false, nil
}

// getDriverMode returns the driver mode for the specified spec: {persistent|ephemeral}.
// 1) If mode cannot be determined, it will default to "persistent".
// 2) If Mode cannot be resolved to either {persistent | ephemeral}, an error is returned
// See https://github.com/kubernetes/enhancements/blob/master/keps/sig-storage/20190122-csi-inline-volumes.md
func (p *csiPlugin) getDriverMode(spec *volume.Spec) (driverMode, error) {
	return persistentDriverMode, nil
}

func (p *csiPlugin) getPublishContext(client clientset.Interface, handle, driver, nodeName string) (map[string]string, error) {
	skip, err := p.skipAttach(driver)
	if err != nil {
		return nil, err
	}
	if skip {
		return nil, nil
	}

	attachID := getAttachmentName(handle, driver, nodeName)

	// search for attachment by VolumeAttachment.Spec.Source.PersistentVolumeName
	attachment, err := client.StorageV1().VolumeAttachments().Get(attachID, meta.GetOptions{})
	if err != nil {
		return nil, err // This err already has enough context ("VolumeAttachment xyz not found")
	}

	if attachment == nil {
		err = errors.New("no existing VolumeAttachment found")
		return nil, err
	}
	return attachment.Status.AttachmentMetadata, nil
}

func unregisterDriver(driverName string) error {
	csiDrivers.Delete(driverName)

	if err := nim.UninstallCSIDriver(driverName); err != nil {
		klog.Errorf("Error uninstalling CSI driver: %v", err)
		return err
	}

	return nil
}

// Return the highest supported version
func highestSupportedVersion(versions []string) (*utilversion.Version, error) {
	if len(versions) == 0 {
		return nil, fmt.Errorf("CSI driver reporting empty array for supported versions")
	}

	// Sort by lowest to highest version
	sort.Slice(versions, func(i, j int) bool {
		parsedVersionI, err := utilversion.ParseGeneric(versions[i])
		if err != nil {
			// Push bad values to the bottom
			return true
		}

		parsedVersionJ, err := utilversion.ParseGeneric(versions[j])
		if err != nil {
			// Push bad values to the bottom
			return false
		}

		return parsedVersionI.LessThan(parsedVersionJ)
	})

	for i := len(versions) - 1; i >= 0; i-- {
		highestSupportedVersion, err := utilversion.ParseGeneric(versions[i])
		if err != nil {
			return nil, err
		}

		if highestSupportedVersion.Major() <= 1 {
			return highestSupportedVersion, nil
		}
	}

	return nil, fmt.Errorf("None of the CSI versions reported by this driver are supported")
}

// Only drivers that implement CSI 0.x are allowed to use deprecated socket dir.
func isDeprecatedSocketDirAllowed(versions []string) bool {
	for _, version := range versions {
		if isV0Version(version) {
			return true
		}
	}

	return false
}

func isV0Version(version string) bool {
	parsedVersion, err := utilversion.ParseGeneric(version)
	if err != nil {
		return false
	}

	return parsedVersion.Major() == 0
}

func isV1Version(version string) bool {
	parsedVersion, err := utilversion.ParseGeneric(version)
	if err != nil {
		return false
	}

	return parsedVersion.Major() == 1
}