def encode_bit_str(self, obj):
if isinstance(obj._val, ASN1.ASN1Obj):
# obj._val: ASN1Obj, according to CONTAINING constraint
V = Layer('V')
V.append(Int('pad_len', Pt=0, Type='uint8'))
obj._val._encode()
V.extend(obj._val._msg)
obj._val._msg = None
#
else:
# obj._val: (BE uint value, BE uint bit length)
val_len = obj._val[1] // 8
val_ext = obj._val[1] % 8
if val_ext:
val_len += 1
V = Layer('V')
V.append(Int('pad_len', Pt=(8 - val_ext) % 8, Type='uint8'))
V.append(
Bit('val',
Pt=obj._val[0],
BitLen=obj._val[1],
Repr=self._REPR_BIT_STR))
if val_ext > 0:
V.append(
Bit('pad',
Pt=0,
BitLen=8 - val_ext,
Repr=self._REPR_BIT_STR))
#
obj._msg = BER_TLV(obj.get_name())
obj._msg.set(V)
self.handle_tag_enc(obj)
def __init__(self):
Layer.__init__(self)
self.insert(1, Layer('WR', ReprName='Withdrawn Routes'))
self.insert(3, Layer('TPA', ReprName='Total Path Attribute'))
# handle "Withdrawn Routes"
self.WRLen > self.WR
self.WRLen.PtFunc = lambda wr: len(wr)
# handle "Path Attributes"
self.TPALen > self.TPA
self.TPALen.PtFunc = lambda tpa: len(tpa)
# finally handle net reachibility info
self.NLRI.Len = (self.get_header, self.WRLen, self.TPALen)
self.NLRI.LenFunc = lambda args: args[0]().len() - \
(23 + args[1]() + args[2]())
def parse(self, buf=''):
self.__init__(self.CallName)
self.map(buf)
L = len(self)
#
# parse nested BER_TLV structures within the Value
if self[0].PC():
# indefinite form
indef = self[1]() == -1
# parsing further internal Value
buf = str(self[2])
inner = []
marker = None
while buf:
tlv = BER_TLV()
tlv.parse(buf)
buf = buf[len(tlv):]
if indef and (tlv[0]() == 0 and tlv[1]() == 0):
marker = tlv
marker.CallName = '_end_'
break
else:
inner.append(tlv)
if inner:
self.remove(self[2])
V = Layer('V')
V.extend(inner)
self.append(V)
if marker:
self.append(marker)
# returns the length parsed
return L
def encode_set_of(self, obj):
V = Layer('V')
for val in obj._val:
obj._cont._val = val
obj._cont._encode()
V.append(obj._cont._msg)
#
obj._cont._msg = None
obj._msg = BER_TLV(obj.get_name())
obj._msg.set(V)
self.handle_tag_enc(obj)
def encode_set(self, obj):
V = Layer('V')
for name in obj._cont:
if name in obj._val:
comp = obj._cont[name]
comp._val = obj._val[name]
comp._encode()
V.append(comp._msg)
comp._msg = None
#
obj._msg = BER_TLV(obj.get_name())
obj._msg.set(V)
self.handle_tag_enc(obj)
def decode_bit_str_val(self, obj):
tlv = self.handle_tag_dec(obj)
# obj._val: (BE uint value, BE uint bit length)
# map to a Layer including the pad_len initial octet
v_str = str(tlv[2])
if len(v_str) > 1:
pad_len = ord(v_str[0])
bit_len = 8 * (len(v_str) - 1) - pad_len
V = Layer('V')
V.append(Int('pad_len'), Type='uint8')
V.append(Bit('val', BitLen=bit_len, Repr=self._REPR_BIT_STR))
if pad_len > 0:
V.append(Bit('pad', BitLen=pad_len, Repr=self._REPR_BIT_STR))
V.map(v_str)
tlv.set(V)
#
obj._val = (V[1](), bit_len)
else:
obj._val = (0, 0)
def __init__(self):
Layer.__init__(self)
self.append(Layer('Options'))
self.OptLen > self.Options
self.OptLen.PtFunc = lambda opt: len(opt)
