From d95249d019778719a59d0124a496c61e8b7830b0 Mon Sep 17 00:00:00 2001
From: Jan Sebechlebsky <sebechlebskyjan@gmail.com>
Date: Thu, 19 Jan 2017 18:40:16 +0100
Subject: [PATCH] Add support for RFC 2637 (PPTP) GRE
---
scapy/layers/l2.py | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/scapy/layers/l2.py b/scapy/layers/l2.py
index 40f44518..e81c4e7b 100644
--- a/scapy/layers/l2.py
+++ b/scapy/layers/l2.py
@@ -968,6 +968,13 @@ class GRE(Packet):
ConditionalField(XIntField("key",None), lambda pkt:pkt.key_present==1),
ConditionalField(XIntField("seqence_number",None), lambda pkt:pkt.seqnum_present==1),
]
+
+ @classmethod
+ def dispatch_hook(cls, _pkt=None, *args, **kargs):
+ if _pkt and struct.unpack("!H", _pkt[2:4])[0] == 0x880b:
+ return GRE_PPTP
+ return cls
+
def post_build(self, p, pay):
p += pay
if self.chksum_present and self.chksum is None:
@@ -976,6 +983,37 @@ class GRE(Packet):
return p
+class GRE_PPTP(GRE):
+
+ """
+ Enhanced GRE header used with PPTP
+ RFC 2637
+ """
+
+ name = "GRE PPTP"
+ fields_desc = [BitField("chksum_present", 0, 1),
+ BitField("routing_present", 0, 1),
+ BitField("key_present", 1, 1),
+ BitField("seqnum_present", 0, 1),
+ BitField("strict_route_source", 0, 1),
+ BitField("recursion_control", 0, 3),
+ BitField("acknum_present", 0, 1),
+ BitField("flags", 0, 4),
+ BitField("version", 1, 3),
+ XShortEnumField("proto", 0x880b, ETHER_TYPES),
+ ShortField("payload_len", None),
+ ShortField("call_id", None),
+ ConditionalField(XIntField("seqence_number", None), lambda pkt: pkt.seqnum_present == 1),
+ ConditionalField(XIntField("ack_number", None), lambda pkt: pkt.acknum_present == 1)]
+
+ def post_build(self, p, pay):
+ p += pay
+ if self.payload_len is None:
+ pay_len = len(pay)
+ p = p[:4] + chr((pay_len >> 8) & 0xff) + chr(pay_len & 0xff) + p[6:]
+ return p
+
+
### *BSD loopback layer
class LoIntEnumField(EnumField):
--
GitLab