8000 KEP-127: user namespace support for stateless pods by giuseppe · Pull Request #116377 · kubernetes/kubernetes · GitHub
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KEP-127: user namespace support for stateless pods #116377

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Merged
merged 5 commits into from
Mar 14, 2023
Merged

KEP-127: user namespace support for stateless pods #116377

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79a34cf
cri-api: add mappings for volumes
giuseppe Feb 15, 2023
9075404
kubelet: use idmapped mounts for all volumes
giuseppe Feb 15, 2023
8af3cce
kubelet: remove GetHostIDsForPod()
rata Mar 7, 2023
16d76f6
kubelet: Don't reserve mapping for userns phase II
rata Mar 7, 2023
ec0410a
kubelet: Move userns manager to its own package
rata Mar 7, 2023
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4 changes: 0 additions & 4 deletions pkg/controller/volume/attachdetach/attach_detach_controller.go
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Expand Up @@ -819,10 +819,6 @@ func (adc *attachDetachController) GetPodVolumeDir(podUID types.UID, pluginName,
return ""
}

func (adc *attachDetachController) GetHostIDsForPod(pod *v1.Pod, containerUID, containerGID *int64) (hostUID, hostGID *int64, err error) {
return nil, nil, nil
}

func (adc *attachDetachController) GetPodPluginDir(podUID types.UID, pluginName string) string {
return ""
}
Expand Down
4 changes: 0 additions & 4 deletions pkg/controller/volume/expand/expand_controller.go
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Expand Up @@ -393,10 +393,6 @@ func (expc *expandController) GetPodsDir() string {
return ""
}

func (expc *expandController) GetHostIDsForPod(pod *v1.Pod, containerUID, containerGID *int64) (hostUID, hostGID *int64, err error) {
return nil, nil, nil
}

func (expc *expandController) GetPodVolumeDir(podUID types.UID, pluginName string, volumeName string) string {
return ""
}
Expand Down
4 changes: 0 additions & 4 deletions pkg/controller/volume/persistentvolume/volume_host.go
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Expand Up @@ -55,10 +55,6 @@ func (ctrl *PersistentVolumeController) GetPodVolumeDir(podUID types.UID, plugin
return ""
}

func (ctrl *PersistentVolumeController) GetHostIDsForPod(pod *v1.Pod, containerUID, containerGID *int64) (hostUID, hostGID *int64, err error) {
return nil, nil, nil
}

func (ctrl *PersistentVolumeController) GetPodPluginDir(podUID types.UID, pluginName string) string {
return ""
}
Expand Down
5 changes: 3 additions & 2 deletions pkg/kubelet/kubelet.go
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Expand Up @@ -109,6 +109,7 @@ import (
"k8s.io/kubernetes/pkg/kubelet/sysctl"
"k8s.io/kubernetes/pkg/kubelet/token"
kubetypes "k8s.io/kubernetes/pkg/kubelet/types"
"k8s.io/kubernetes/pkg/kubelet/userns"
"k8s.io/kubernetes/pkg/kubelet/util"
"k8s.io/kubernetes/pkg/kubelet/util/manager"
"k8s.io/kubernetes/pkg/kubelet/util/queue"
Expand Down Expand Up @@ -900,7 +901,7 @@ func NewMainKubelet(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
StateDirectory: rootDirectory,
})
klet.shutdownManager = shutdownManager
klet.usernsManager, err = MakeUserNsManager(klet)
klet.usernsManager, err = userns.MakeUserNsManager(klet)
if err != nil {
return nil, err
}
Expand Down Expand Up @@ -1248,7 +1249,7 @@ type Kubelet struct {
shutdownManager nodeshutdown.Manager

// Manage user namespaces
usernsManager *usernsManager
usernsManager *userns.UsernsManager

// Mutex to serialize new pod admission and existing pod resizing
podResizeMutex sync.Mutex
Expand Down
5 changes: 5 additions & 0 deletions pkg/kubelet/kubelet_getters.go
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Expand Up @@ -104,6 +104,11 @@ func (kl *Kubelet) GetPodDir(podUID types.UID) string {
return kl.getPodDir(podUID)
}

// ListPodsFromDisk gets a list of pods that have data directories.
func (kl *Kubelet) ListPodsFromDisk() ([]types.UID, error) {
return kl.listPodsFromDisk()
}

// getPodDir returns the full path to the per-pod directory for the pod with
// the given UID.
func (kl *Kubelet) getPodDir(podUID types.UID) string {
Expand Down
4 changes: 0 additions & 4 deletions pkg/kubelet/kubelet_pods.go
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Expand Up @@ -426,10 +426,6 @@ func (kl *Kubelet) GetOrCreateUserNamespaceMappings(pod *v1.Pod) (*runtimeapi.Us
return kl.usernsManager.GetOrCreateUserNamespaceMappings(pod)
}

func (kl *Kubelet) getHostIDsForPod(pod *v1.Pod, containerUID, containerGID *int64) (hostUID, hostGID *int64, err error) {
return kl.usernsManager.getHostIDsForPod(pod, containerUID, containerGID)
}

// GeneratePodHostNameAndDomain creates a hostname and domain name for a pod,
// given that pod's spec and annotations or returns an error.
func (kl *Kubelet) GeneratePodHostNameAndDomain(pod *v1.Pod) (string, string, error) {
Expand Down
9 changes: 9 additions & 0 deletions pkg/kubelet/kuberuntime/kuberuntime_container_linux.go
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Expand Up @@ -54,6 +54,15 @@ func (m *kubeGenericRuntimeManager) applyPlatformSpecificContainerConfig(config
return err
}
config.Linux = cl

if utilfeature.DefaultFeatureGate.Enabled(kubefeatures.UserNamespacesStatelessPodsSupport) {
if cl.SecurityContext.NamespaceOptions.UsernsOptions != nil {
for _, mount := range config.Mounts {
mount.UidMappings = cl.SecurityContext.NamespaceOptions.UsernsOptions.Uids
mount.GidMappings = cl.SecurityContext.NamespaceOptions.UsernsOptions.Gids
}
}
}
return nil
}

Expand Down
116 changes: 23 additions & 93 deletions pkg/kubelet/userns_manager.go → pkg/kubelet/userns/userns_manager.go
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Expand Up @@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
limitations under the License.
*/

package kubelet
package userns

import (
"encoding/json"
Expand Down Expand Up @@ -49,11 +49,11 @@ const maxPods = 1024
const mapReInitializeThreshold = 1000

type userNsPodsManager interface {
getPodDir(podUID types.UID) string
listPodsFromDisk() ([]types.UID, error)
GetPodDir(podUID types.UID) string
ListPodsFromDisk() ([]types.UID, error)
}

type usernsManager struct {
type UsernsManager struct {
used *allocator.AllocationBitmap
usedBy map[types.UID]uint32 // Map pod.UID to range used
removed int
Expand Down Expand Up @@ -86,8 +86,8 @@ const mappingsFile = "userns"

// writeMappingsToFile writes the specified user namespace configuration to the pod
// directory.
func (m *usernsManager) writeMappingsToFile(pod types.UID, userNs userNamespace) error {
dir := m.kl.getPodDir(pod)
func (m *UsernsManager) writeMappingsToFile(pod types.UID, userNs userNamespace) error {
dir := m.kl.GetPodDir(pod)

data, err := json.Marshal(userNs)
if err != nil {
Expand Down Expand Up @@ -119,17 +119,17 @@ func (m *usernsManager) writeMappingsToFile(pod types.UID, userNs userNamespace)
}

// readMappingsFromFile reads the user namespace configuration from the pod directory.
func (m *usernsManager) readMappingsFromFile(pod types.UID) ([]byte, error) {
dir := m.kl.getPodDir(pod)
func (m *UsernsManager) readMappingsFromFile(pod types.UID) ([]byte, error) {
dir := m.kl.GetPodDir(pod)
fstore, err := utilstore.NewFileStore(dir, &utilfs.DefaultFs{})
if err != nil {
return nil, err
}
return fstore.Read(mappingsFile)
}

func MakeUserNsManager(kl userNsPodsManager) (*usernsManager, error) {
m := usernsManager{
func MakeUserNsManager(kl userNsPodsManager) (*UsernsManager, error) {
m := UsernsManager{
// Create a bitArray for all the UID space (2^32).
// As a by product of that, no index param to bitArray can be out of bounds (index is uint32).
used: allocator.NewAllocationMap((math.MaxUint32+1)/userNsLength, "user namespaces"),
Expand All @@ -141,17 +141,12 @@ func MakeUserNsManager(kl userNsPodsManager) (*usernsManager, error) {
return nil, err
}

// Second block will be used for phase II. Don't assign that range for now.
if _, err := m.used.Allocate(1); err != nil {
return nil, err
}

// do not bother reading the list of pods if user namespaces are not enabled.
if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesStatelessPodsSupport) {
return &m, nil
}

found, err := kl.listPodsFromDisk()
found, err := kl.ListPodsFromDisk()
if err != nil {
if os.IsNotExist(err) {
return &m, nil
Expand All @@ -171,7 +166,7 @@ func MakeUserNsManager(kl userNsPodsManager) (*usernsManager, error) {

// recordPodMappings registers the range used for the user namespace if the
// usernsConfFile exists in the pod directory.
func (m *usernsManager) recordPodMappings(pod types.UID) error {
func (m *UsernsManager) recordPodMappings(pod types.UID) error {
content, err := m.readMappingsFromFile(pod)
if err != nil && err != utilstore.ErrKeyNotFound {
return err
Expand All @@ -187,15 +182,15 @@ func (m *usernsManager) recordPodMappings(pod types.UID) error {
}

// isSet checks if the specified index is already set.
func (m *usernsManager) isSet(v uint32) bool {
func (m *UsernsManager) isSet(v uint32) bool {
index := int(v / userNsLength)
return m.used.Has(index)
}

// allocateOne finds a free user namespace and allocate it to the specified pod.
// The first return value is the first ID in the user namespace, the second returns
// the length for the user namespace range.
func (m *usernsManager) allocateOne(pod types.UID) (firstID uint32, length uint32, err error) {
func (m *UsernsManager) allocateOne(pod types.UID) (firstID uint32, length uint32, err error) {
if m.numAllocated >= maxPods {
return 0, 0, fmt.Errorf("limit on count of pods with user namespaces exceeded (limit is %v, current pods with userns: %v)", maxPods, m.numAllocated)
}
Expand All @@ -222,7 +217,7 @@ func (m *usernsManager) allocateOne(pod types.UID) (firstID uint32, length uint3
}

// record stores the user namespace [from; from+length] to the specified pod.
func (m *usernsManager) record(pod types.UID, from, length uint32) (err error) {
func (m *UsernsManager) record(pod types.UID, from, length uint32) (err error) {
if length != userNsLength {
return fmt.Errorf("wrong user namespace length %v", length)
}
Expand Down Expand Up @@ -262,7 +257,7 @@ func (m *usernsManager) record(pod types.UID, from, length uint32) (err error) {
}

// Release releases the user namespace allocated to the specified pod.
func (m *usernsManager) Release(podUID types.UID) {
func (m *UsernsManager) Release(podUID types.UID) {
if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesStatelessPodsSupport) {
return
}
Expand All @@ -273,7 +268,7 @@ func (m *usernsManager) Release(podUID types.UID) {
m.releaseWithLock(podUID)
}

func (m *usernsManager) releaseWithLock(pod types.UID) {
func (m *UsernsManager) releaseWithLock(pod types.UID) {
v, ok := m.usedBy[pod]
if !ok {
klog.V(5).InfoS("pod user namespace allocation not present", "podUID", pod)
Expand All @@ -285,7 +280,7 @@ func (m *usernsManager) releaseWithLock(pod types.UID) {
m.numAllocated--
m.removed++

_ = os.Remove(filepath.Join(m.kl.getPodDir(pod), mappingsFile))
_ = os.Remove(filepath.Join(m.kl.GetPodDir(pod), mappingsFile))

if m.removed%mapReInitializeThreshold == 0 {
n := make(map[types.UID]uint32)
Expand All @@ -298,7 +293,7 @@ func (m *usernsManager) releaseWithLock(pod types.UID) {
m.used.Release(int(v / userNsLength))
}

func (m *usernsManager) parseUserNsFileAndRecord(pod types.UID, content []byte) (userNs userNamespace, err error) {
func (m *UsernsManager) parseUserNsFileAndRecord(pod types.UID, content []byte) (userNs userNamespace, err error) {
if err = json.Unmarshal([]byte(content), &userNs); err != nil {
err = fmt.Errorf("can't parse file: %w", err)
return
Expand Down Expand Up @@ -338,7 +333,7 @@ func (m *usernsManager) parseUserNsFileAndRecord(pod types.UID, content []byte)
return
}

func (m *usernsManager) createUserNs(pod *v1.Pod) (userNs userNamespace, err error) {
func (m *UsernsManager) createUserNs(pod *v1.Pod) (userNs userNamespace, err error) {
firstID, length, err := m.allocateOne(pod.UID)
if err != nil {
return
Expand Down Expand Up @@ -371,7 +366,7 @@ func (m *usernsManager) createUserNs(pod *v1.Pod) (userNs userNamespace, err err
}

// GetOrCreateUserNamespaceMappings returns the configuration for the sandbox user namespace
func (m *usernsManager) GetOrCreateUserNamespaceMappings(pod *v1.Pod) (*runtimeapi.UserNamespace, error) {
func (m *UsernsManager) GetOrCreateUserNamespaceMappings(pod *v1.Pod) (*runtimeapi.UserNamespace, error) {
if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesStatelessPodsSupport) {
return nil, nil
}
Expand Down Expand Up @@ -431,7 +426,7 @@ func (m *usernsManager) GetOrCreateUserNamespaceMappings(pod *v1.Pod) (*runtimea
// CleanupOrphanedPodUsernsAllocations reconciliates the state of user namespace
// allocations with the pods actually running. It frees any user namespace
// allocation for orphaned pods.
func (m *usernsManager) CleanupOrphanedPodUsernsAllocations(pods []*v1.Pod, runningPods []*kubecontainer.Pod) error {
func (m *UsernsManager) CleanupOrphanedPodUsernsAllocations(pods []*v1.Pod, runningPods []*kubecontainer.Pod) error {
if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesStatelessPodsSupport) {
return nil
}
Expand All @@ -448,7 +443,7 @@ func (m *usernsManager) CleanupOrphanedPodUsernsAllocations(pods []*v1.Pod, runn
}

allFound := sets.NewString()
found, err := m.kl.listPodsFromDisk()
found, err := m.kl.ListPodsFromDisk()
if err != nil {
return err
}
Expand Down Expand Up @@ -479,68 +474,3 @@ func (m *usernsManager) CleanupOrphanedPodUsernsAllocations(pods []*v1.Pod, runn

return nil
}

// getHostIDsForPod if the pod uses user namespaces, takes the uid and gid
// inside the container and returns the host UID and GID those are mapped to on
// the host. If containerUID/containerGID is nil, then it returns the host
// UID/GID for ID 0 inside the container.
// If the pod is not using user namespaces, as there is no mapping needed, the
// same containerUID and containerGID params are returned.
func (m *usernsManager) getHostIDsForPod(pod *v1.Pod, containerUID, containerGID *int64) (hostUID, hostGID *int64, err error) {
if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesStatelessPodsSupport) {
return containerUID, containerGID, nil
}

if pod == nil || pod.Spec.HostUsers == nil || *pod.Spec.HostUsers == true {
return containerUID, containerGID, nil
}

mapping, err := m.GetOrCreateUserNamespaceMappings(pod)
if err != nil {
err = fmt.Errorf("Error getting pod user namespace mapping: %w", err)
return
}

uid, err := hostIDFromMapping(mapping.Uids, containerUID)
if err != nil {
err = fmt.Errorf("Error getting host UID: %w", err)
return
}

gid, err := hostIDFromMapping(mapping.Gids, containerGID)
if err != nil {
err = fmt.Errorf("Error getting host GID: %w", err)
return
}

return &uid, &gid, nil
}

func hostIDFromMapping(mapping []*runtimeapi.IDMapping, containerId *int64) (int64, error) {
if len(mapping) == 0 {
return 0, fmt.Errorf("can't use empty user namespace mapping")
}

// If none is requested, root inside the container is used
id := int64(0)
if containerId != nil {
id = *containerId
}

for _, m := range mapping {
if m == nil {
continue
}

firstId := int64(m.ContainerId)
lastId := firstId + int64(m.Length) - 1

// The id we are looking for is in the range
if id >= firstId && id <= lastId {
// Return the host id for this container id
return int64(m.HostId) + id - firstId, nil
}
}

return 0, fmt.Errorf("ID: %v not present in pod user namespace", id)
}
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