diff --git a/common/buf/copy.go b/common/buf/copy.go
index 87a9518e..c1721eb5 100644
--- a/common/buf/copy.go
+++ b/common/buf/copy.go
@@ -8,6 +8,11 @@ import (
 	"v2ray.com/core/common/signal"
 )
 
+// ActivityNotifiable is a object that accepts activity notification outside the object
+type ActivityNotifiable interface {
+	NotifyActivity() error
+}
+
 type dataHandler func(MultiBuffer)
 
 type copyHandler struct {
@@ -31,6 +36,15 @@ func UpdateActivity(timer signal.ActivityUpdater) CopyOption {
 	}
 }
 
+// NotifyActivity is a CopyOption to notify activity on each data copy operation.
+func NotifyActivity(notifier ActivityNotifiable) CopyOption {
+	return func(handler *copyHandler) {
+		handler.onData = append(handler.onData, func(MultiBuffer) {
+			notifier.NotifyActivity()
+		})
+	}
+}
+
 // CountSize is a CopyOption that sums the total size of data copied into the given SizeCounter.
 func CountSize(sc *SizeCounter) CopyOption {
 	return func(handler *copyHandler) {