ackhandler: remove the packet list element from the correct list

internal/ackhandler/sent_packet_history.go

@@ -108,8 +108,7 @@ func (h *sentPacketHistory) Remove(p protocol.PacketNumber) error {
 	if !ok {
 		return fmt.Errorf("packet %d not found in sent packet history", p)
 	}
-	h.outstandingPacketList.Remove(el)
-	h.etcPacketList.Remove(el)
+	el.List().Remove(el)
 	delete(h.packetMap, p)
 	return nil
 }
@@ -139,10 +138,7 @@ func (h *sentPacketHistory) DeclareLost(p *Packet) *Packet {
 	if !ok {
 		return nil
 	}
-	// try to remove it from both lists, as we don't know which one it currently belongs to.
-	// Remove is a no-op for elements that are not in the list.
-	h.outstandingPacketList.Remove(el)
-	h.etcPacketList.Remove(el)
+	el.List().Remove(el)
 	p.declaredLost = true
 	// move it to the correct position in the etc list (based on the packet number)
 	for el = h.etcPacketList.Back(); el != nil; el = el.Prev() {

internal/utils/linkedlist/linkedlist.go

@@ -43,6 +43,10 @@ func (e *Element[T]) Prev() *Element[T] {
 	return nil
 }
 
+func (e *Element[T]) List() *List[T] {
+	return e.list
+}
+
 // List represents a doubly linked list.
 // The zero value for List is an empty list ready to use.
 type List[T any] struct {