def _clone(packet: Packet, name: str) -> None:
"""Replaces the Scapy ``packet`` class by an exact copy.
This is a trick used when we need to modify a ``Packet`` class attribute
without affecting all instances of an object.
For instance, if we change ``fields_desc`` to add a field, all new
instances will be changed as this is a class attribute.
:param packet: the Scapy Packet to update.
:param name: the new class name for packet.
"""
# Checks if a binding exists between packet and its preceding layer
# (bindings are defined as a list of tuples `layer.payload_guess`)
in_payload_guess = False
if packet.underlayer is not None:
in_payload_guess = any(packet.__class__ in binding \
for binding in packet.underlayer.payload_guess)
# Duplicates our packet class and replaces it by the clone
# first checks that provided name is not already used, otherwise generates a new one
while name in [type(o).__name__ for o in gc.get_objects()]:
name = name + '_' + str(randint(1000000, 9999999))
class_copy = type(name, (packet.__class__, ), {})
packet.__class__ = class_copy
# Bindings with the preceding layer must be done again
if in_payload_guess:
packet.underlayer.payload_guess.insert(0, ({}, packet.__class__))
