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# $Id: ppp.py 65 2010-03-26 02:53:51Z dugsong $
# -*- coding: utf-8 -*-
"""Point-to-Point Protocol."""
from __future__ import absolute_import
import struct
from . import dpkt
# XXX - finish later
# http://www.iana.org/assignments/ppp-numbers
PPP_IP = 0x21 # Internet Protocol
PPP_IP6 = 0x57 # Internet Protocol v6
# Protocol field compression
PFC_BIT = 0x01
class PPP(dpkt.Packet):
# Note: This class is subclassed in PPPoE
"""Point-to-Point Protocol.
TODO: Longer class information....
Attributes:
__hdr__: Header fields of PPP.
TODO.
"""
__hdr__ = (
('addr', 'B', 0xff),
('cntrl', 'B', 3),
('p', 'B', PPP_IP),
)
_protosw = {}
@classmethod
def set_p(cls, p, pktclass):
cls._protosw[p] = pktclass
@classmethod
def get_p(cls, p):
return cls._protosw[p]
def unpack(self, buf):
dpkt.Packet.unpack(self, buf)
if self.p & PFC_BIT == 0:
try:
self.p = struct.unpack('>H', buf[2:4])[0]
except struct.error:
raise dpkt.NeedData
self.data = self.data[1:]
try:
self.data = self._protosw[self.p](self.data)
setattr(self, self.data.__class__.__name__.lower(), self.data)
except (KeyError, struct.error, dpkt.UnpackError):
pass
def pack_hdr(self):
try:
if self.p > 0xff:
return struct.pack('>BBH', self.addr, self.cntrl, self.p)
return dpkt.Packet.pack_hdr(self)
except struct.error as e:
raise dpkt.PackError(str(e))
def __load_protos():
g = globals()
for k, v in g.items():
if k.startswith('PPP_'):
name = k[4:]
modname = name.lower()
try:
mod = __import__(modname, g, level=1)
PPP.set_p(v, getattr(mod, name))
except (ImportError, AttributeError):
continue
def _mod_init():
"""Post-initialization called when all dpkt modules are fully loaded"""
if not PPP._protosw:
__load_protos()
def test_ppp():
# Test protocol compression
s = b"\xff\x03\x21"
p = PPP(s)
assert p.p == 0x21
s = b"\xff\x03\x00\x21"
p = PPP(s)
assert p.p == 0x21
def test_ppp_short():
s = b"\xff\x03\x00"
import pytest
pytest.raises(dpkt.NeedData, PPP, s)
def test_packing():
p = PPP()
assert p.pack_hdr() == b"\xff\x03\x21"
p.p = 0xc021 # LCP
assert p.pack_hdr() == b"\xff\x03\xc0\x21"
if __name__ == '__main__':
# Runs all the test associated with this class/file
test_ppp()
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