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## This file is part of Scapy
## See http://www.secdev.org/projects/scapy for more informations
## Copyright (C) Philippe Biondi <phil@secdev.org>
## This program is published under a GPLv2 license
"""
L2TP (Layer 2 Tunneling Protocol) for VPNs.
[RFC 2661]
"""
import struct
from scapy.packet import *
from scapy.fields import *
from scapy.layers.inet import UDP
from scapy.layers.ppp import PPP
class L2TP(Packet):
fields_desc = [ ShortEnumField("pkt_type",2,{2:"data"}),
ShortField("len", None),
ShortField("tunnel_id", 0),
ShortField("session_id", 0),
ShortField("ns", 0),
ShortField("nr", 0),
ShortField("offset", 0) ]
def post_build(self, pkt, pay):
if self.len is None:
l = len(pkt)+len(pay)
pkt = pkt[:2]+struct.pack("!H", l)+pkt[4:]
return pkt+pay
bind_layers( UDP, L2TP, sport=1701, dport=1701)
bind_layers( L2TP, PPP, )
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