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runtime: Files are not synced between host and guest VMs

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This PR resolves the default kubelet root dir symbolic link and
uses it as the absolute path for the fs watcher regexs

Fixes: https://github.com/kata-containers/kata-containers/issues/9986

Signed-off-by: Silenio Quarti <silenio_quarti@ca.ibm.com>
This commit is contained in:
Silenio Quarti 2024-08-15 09:29:13 -04:00
parent 74662a0721
commit 5d815ffde1
1 changed files with 27 additions and 8 deletions
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35
src/runtime/virtcontainers/fs_share_linux.go
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@ -32,35 +32,48 @@ import (
)
// Splitting Regex pattern:
// configVolRegex: Regex to match directory structure for k8's volume mounts.
// Use regex for strict matching instead of strings.Contains
// match for kubernetes.io~configmap, kubernetes.io~secret, kubernetes.io~projected, kubernetes.io~downward-api
// as recommended in review comments for PR #7211
// Default K8S root directory
var defaultKubernetesRootDir = "/var/lib/kubelet"
// Example directory structure for the volume mounts.
// /var/lib/kubelet/pods/f51ae853-557e-4ce1-b60b-a1101b555612/volumes/kubernetes.io~configmap
// /var/lib/kubelet/pods/f51ae853-557e-4ce1-b60b-a1101b555612/volumes/kubernetes.io~secret
// /var/lib/kubelet/pods/f51ae853-557e-4ce1-b60b-a1101b555612/volumes/kubernetes.io~projected
// /var/lib/kubelet/pods/f51ae853-557e-4ce1-b60b-a1101b555612/volumes/kubernetes.io~downward-api
var configVolRegexString = "^/var/lib/kubelet/pods/[a-fA-F0-9\\-]{36}/volumes/kubernetes\\.io~(configmap|secret|projected|downward-api)"
var configVolRegex = regexp.MustCompile(configVolRegexString)
var configVolRegexString = "/pods/[a-fA-F0-9\\-]{36}/volumes/kubernetes\\.io~(configmap|secret|projected|downward-api)"
// timestampDirRegex: Regex to match only the timestamped directory inside the above volume mount
// Regex for the temp directory with timestamp that is used to handle the updates by K8s
// Examples
// /var/lib/kubelet/pods/e33907eb-54c7-4113-a3dc-447f247084cc/volumes/kubernetes.io~secret/foosecret/..2023_07_27_07_13_00.1257228
// /var/lib/kubelet/pods/e33907eb-54c7-4113-a3dc-447f247084cc/volumes/kubernetes.io~downward-api/fooinfo/..2023_07_27_07_13_00.3704578339
// The timestamp is of the format 2023_07_27_07_13_00.3704578339 or 2023_07_27_07_13_00.1257228
var timestampDirRegexString = ".*[0-9]{4}_[0-9]{2}_[0-9]{2}_[0-9]{2}_[0-9]{2}_[0-9]{2}.[0-9]+$"
var timestampDirRegex = regexp.MustCompile(configVolRegexString + timestampDirRegexString)
func unmountNoFollow(path string) error {
return syscall.Unmount(path, syscall.MNT_DETACH|UmountNoFollow)
}
// Resolve the K8S root dir if it is a symbolic link
func resolveRootDir() string {
rootDir, err := os.Readlink(defaultKubernetesRootDir)
if err != nil {
// Use the default root dir in case of any errors resolving the root dir symlink
return defaultKubernetesRootDir
}
return rootDir
}
type FilesystemShare struct {
sandbox *Sandbox
watcher *fsnotify.Watcher
// Regex to match directory structure for k8's volume mounts.
configVolRegex *regexp.Regexp
// Regex to match only the timestamped directory inside the k8's volume mount
timestampDirRegex *regexp.Regexp
// The same volume mount can be shared by multiple containers in the same sandbox (pod)
srcDstMap map[string][]string
srcDstMapLock sync.Mutex
@ -77,12 +90,18 @@ func NewFilesystemShare(s *Sandbox) (FilesystemSharer, error) {
return nil, fmt.Errorf("Creating watcher returned error %w", err)
}
kubernetesRootDir := resolveRootDir()
configVolRegex := regexp.MustCompile("^" + kubernetesRootDir + configVolRegexString)
timestampDirRegex := regexp.MustCompile("^" + kubernetesRootDir + configVolRegexString + timestampDirRegexString)
return &FilesystemShare{
prepared: false,
sandbox: s,
watcherDoneChannel: make(chan bool),
srcDstMap: make(map[string][]string),
watcher: watcher,
configVolRegex: configVolRegex,
timestampDirRegex: timestampDirRegex,
}, nil
}
@ -318,14 +337,14 @@ func (f *FilesystemShare) ShareFile(ctx context.Context, c *Container, m *Mount)
return err
}
if configVolRegex.MatchString(srcPath) {
if f.configVolRegex.MatchString(srcPath) {
// fsNotify doesn't add watcher recursively.
// So we need to add the watcher for directories under kubernetes.io~configmap, kubernetes.io~secret,
// kubernetes.io~downward-api and kubernetes.io~projected
// Add watcher only to the timestamped directory containing secrets to prevent
// multiple events received from also watching the parent directory.
if info.Mode().IsDir() && timestampDirRegex.MatchString(srcPath) {
if info.Mode().IsDir() && f.timestampDirRegex.MatchString(srcPath) {
// The cm dir is of the form /var/lib/kubelet/pods/<uid>/volumes/kubernetes.io~configmap/foo/{..data, key1, key2,...}
// The secret dir is of the form /var/lib/kubelet/pods/<uid>/volumes/kubernetes.io~secret/foo/{..data, key1, key2,...}
// The projected dir is of the form /var/lib/kubelet/pods/<uid>/volumes/kubernetes.io~projected/foo/{..data, key1, key2,...}
@ -753,7 +772,7 @@ func (f *FilesystemShare) StartFileEventWatcher(ctx context.Context) error {
source := event.Name
f.Logger().Infof("StartFileEventWatcher: source for the event: %s", source)
if timestampDirRegex.FindString(source) != "" {
if f.timestampDirRegex.FindString(source) != "" {
// This block will be entered when the timestamped directory is removed.
// This also indicates that foo/..data contains the updated info