Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/scapy/layers/l2tp.py: 74%

1# SPDX-License-Identifier: GPL-2.0-only 

2# This file is part of Scapy 

3# See https://scapy.net/ for more information 

4# Copyright (C) Philippe Biondi <phil@secdev.org> 

5 

6""" 

7L2TP (Layer 2 Tunneling Protocol) for VPNs. 

8 

9[RFC 2661] 

10""" 

11 

12import struct 

13 

14from scapy.packet import Packet, bind_layers, bind_bottom_up 

15from scapy.fields import BitEnumField, ConditionalField, FlagsField, \ 

16 PadField, ShortField 

17from scapy.layers.inet import UDP 

18from scapy.layers.ppp import PPP 

19 

20 

21class L2TP(Packet): 

22 name = "L2TP" 

23 fields_desc = [ 

24 FlagsField("hdr", 0, 12, ['res00', 'res01', 'res02', 'res03', 'priority', 'offset', # noqa: E501 

25 'res06', 'sequence', 'res08', 'res09', 'length', 'control']), # noqa: E501 

26 BitEnumField("version", 2, 4, {2: 'L2TPv2'}), 

27 

28 ConditionalField(ShortField("len", None), 

29 lambda pkt: pkt.hdr & 'control+length'), 

30 ShortField("tunnel_id", 0), 

31 ShortField("session_id", 0), 

32 ConditionalField(ShortField("ns", 0), 

33 lambda pkt: pkt.hdr & 'sequence+control'), 

34 ConditionalField(ShortField("nr", 0), 

35 lambda pkt: pkt.hdr & 'sequence+control'), 

36 ConditionalField( 

37 PadField(ShortField("offset", 0), 4, b"\x00"), 

38 lambda pkt: not (pkt.hdr & 'control') and pkt.hdr & 'offset' 

39 ) 

40 ] 

41 

42 def post_build(self, pkt, pay): 

43 if self.len is None and self.hdr & 'control+length': 

44 tmp_len = len(pkt) + len(pay) 

45 pkt = pkt[:2] + struct.pack("!H", tmp_len) + pkt[4:] 

46 return pkt + pay 

47 

48 

49bind_bottom_up(UDP, L2TP, dport=1701) 

50bind_bottom_up(UDP, L2TP, sport=1701) 

51bind_layers(UDP, L2TP, dport=1701, sport=1701) 

52bind_layers(L2TP, PPP,)