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Watch sysctl changes to ensure expected values
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,90 @@ | ||
| package control | ||
|
|
||
| import ( | ||
| "os" | ||
| "strings" | ||
| "sync" | ||
|
|
||
| "github.com/fsnotify/fsnotify" | ||
| "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| const SysctlPrefixPath = "/proc/sys/" | ||
|
|
||
| var sysctl *SysctlManager | ||
|
|
||
| type SysctlManager struct { | ||
| mux sync.Mutex | ||
| watcher *fsnotify.Watcher | ||
| expectations map[string]string | ||
| } | ||
|
|
||
| func init() { | ||
| var err error | ||
| if sysctl, err = NewSysctlManager(); err != nil { | ||
| logrus.Fatalf("failed to create sysctl manager: %v", err) | ||
| } | ||
| } | ||
|
|
||
| func NewSysctlManager() (*SysctlManager, error) { | ||
| watcher, err := fsnotify.NewWatcher() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| manager := &SysctlManager{ | ||
| mux: sync.Mutex{}, | ||
| watcher: watcher, | ||
| expectations: map[string]string{}, | ||
| } | ||
| go manager.StartWatch() | ||
| return manager, nil | ||
| } | ||
|
|
||
| func (s *SysctlManager) StartWatch() { | ||
| for { | ||
| select { | ||
| case event, ok := <-s.watcher.Events: | ||
| if !ok { | ||
| return | ||
| } | ||
| if event.Has(fsnotify.Write) { | ||
| logrus.Tracef("sysctl write event: %+v", event) | ||
| s.mux.Lock() | ||
| expected, ok := s.expectations[event.Name] | ||
| s.mux.Unlock() | ||
| if ok { | ||
| raw, err := os.ReadFile(event.Name) | ||
| if err != nil { | ||
| logrus.Errorf("failed to read sysctl file %s: %v", event.Name, err) | ||
| } | ||
| value := strings.TrimSpace(string(raw)) | ||
| if value != expected { | ||
| logrus.Infof("sysctl %s has unexpected value %s, expected %s", event.Name, value, expected) | ||
| if err := os.WriteFile(event.Name, []byte(expected), 0644); err != nil { | ||
| logrus.Errorf("failed to write sysctl file %s: %v", event.Name, err) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| case err, ok := <-s.watcher.Errors: | ||
| if !ok { | ||
| return | ||
| } | ||
| logrus.Errorf("sysctl watcher error: %v", err) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func (s *SysctlManager) Set(key string, value string, watch bool) (err error) { | ||
| path := SysctlPrefixPath + strings.Replace(key, ".", "/", -1) | ||
| if watch { | ||
| s.mux.Lock() | ||
| s.expectations[path] = value | ||
| s.mux.Unlock() | ||
| if err = s.watcher.Add(path); err != nil { | ||
| return | ||
| } | ||
| } | ||
| return os.WriteFile(path, []byte(value), 0644) | ||
| } |
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