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# $Id: ppp.py 65 2010-03-26 02:53:51Z dugsong $
"""Point-to-Point Protocol."""
import struct
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):
__hdr__ = (
('p', 'B', PPP_IP),
)
_protosw = {}
def set_p(cls, p, pktclass):
cls._protosw[p] = pktclass
set_p = classmethod(set_p)
def get_p(cls, p):
return cls._protosw[p]
get_p = classmethod(get_p)
def unpack(self, buf):
dpkt.Packet.unpack(self, buf)
if self.p & PFC_BIT == 0:
self.p = struct.unpack('>H', buf[:2])[0]
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('>H', self.p)
return dpkt.Packet.pack_hdr(self)
except struct.error, e:
raise dpkt.PackError(str(e))
def __load_protos():
g = globals()
for k, v in g.iteritems():
if k.startswith('PPP_'):
name = k[4:]
modname = name.lower()
try:
mod = __import__(modname, g)
except ImportError:
continue
PPP.set_p(v, getattr(mod, name))
if not PPP._protosw:
__load_protos()
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