def post_build(self, pkt, pay):
"""
need to set the length of the whole PDU manually
to avoid any bit fiddling use a dummy class to build the layer content
also add padding if frame is < 64 bytes
Note: padding only handles Ether/n*Dot1Q/EtherCat
(no special mumbo jumbo)
:param pkt: raw string containing the current layer
:param pay: raw string containing the payload
:return: <new current layer> + payload
"""
class _EtherCatLengthCalc(Packet):
"""
dummy class used to generate str representation easily
"""
fields_desc = [
LEBitField('length', None, 11),
LEBitField('_reserved', 0, 1),
LEBitField('type', 0, 4),
]
payload_len = len(pay)
# length field is 11 bit
if payload_len > 2047:
raise ValueError('payload size {} exceeds maximum length {} '
'of EtherCat message.'.format(payload_len, 2047))
self.length = payload_len
vlan_headers_total_size = 0
upper_layer = self.underlayer
# add size occupied by VLAN tags
while upper_layer and isinstance(upper_layer, Dot1Q):
vlan_headers_total_size += 4
upper_layer = upper_layer.underlayer
if not isinstance(upper_layer, Ether):
raise Exception('missing Ether layer')
pad_len = EtherCat.ETHER_FRAME_MIN_LEN - (
EtherCat.ETHER_HEADER_LEN + vlan_headers_total_size +
EtherCat.ETHERCAT_HEADER_LEN + payload_len +
EtherCat.ETHER_FSC_LEN)
if pad_len > 0:
pad = Padding()
pad.load = b'\x00' * pad_len
return raw(_EtherCatLengthCalc(length=self.length,
type=self.type)) + pay + raw(pad)
else:
return raw(_EtherCatLengthCalc(length=self.length,
type=self.type)) + pay
def post_build(self, pkt, pay):
last_layer = not len(pay)
if last_layer and conf.contribs['LLDP'].strict_mode() and \
type(self).__name__ != LLDPDUEndOfLLDPDU.__name__:
raise LLDPInvalidLastLayerException('Last layer must be instance '
'of LLDPDUEndOfLLDPDU - '
'got {}'.
format(type(self).__name__))
under_layer = self.underlayer
if under_layer is None:
if conf.contribs['LLDP'].strict_mode():
raise LLDPMissingLowerLayer('No lower layer (Ethernet '
'or Dot1Q) provided.')
else:
return pkt + pay
not_lowest_lldpdu = under_layer.__class__.__base__.__name__ is 'LLDPDU'
if not_lowest_lldpdu:
return pkt + pay
frame_size, under_layer = LLDPDU._dot1q_headers_size(under_layer)
if not under_layer or not isinstance(under_layer, Ether):
if conf.contribs['LLDP'].strict_mode():
raise LLDPMissingLowerLayer('No Ethernet layer provided.')
else:
return pkt + pay
frame_size += LLDPDU.ETHER_HEADER_LEN
frame_size += len(pkt) + len(pay) + LLDPDU.ETHER_FSC_LEN
if frame_size < LLDPDU.ETHER_FRAME_MIN_LEN:
pad = Padding()
pad.load = b'\x00' * (LLDPDU.ETHER_FRAME_MIN_LEN - frame_size)
return pkt + pay + raw(pad)
else:
return pkt + pay
def post_build(self, pkt, pay):
last_layer = not len(pay)
if last_layer and conf.contribs['LLDP'].strict_mode() and \
type(self).__name__ != LLDPDUEndOfLLDPDU.__name__:
raise LLDPInvalidLastLayerException('Last layer must be instance '
'of LLDPDUEndOfLLDPDU - '
'got {}'.
format(type(self).__name__))
under_layer = self.underlayer
if under_layer is None:
if conf.contribs['LLDP'].strict_mode():
raise LLDPMissingLowerLayer('No lower layer (Ethernet '
'or Dot1Q) provided.')
else:
return pkt + pay
not_lowest_lldpdu = under_layer.__class__.__base__.__name__ is 'LLDPDU'
if not_lowest_lldpdu:
return pkt + pay
frame_size, under_layer = LLDPDU._dot1q_headers_size(under_layer)
if not under_layer or not isinstance(under_layer, Ether):
if conf.contribs['LLDP'].strict_mode():
raise LLDPMissingLowerLayer('No Ethernet layer provided.')
else:
return pkt + pay
frame_size += LLDPDU.ETHER_HEADER_LEN
frame_size += len(pkt) + len(pay) + LLDPDU.ETHER_FSC_LEN
if frame_size < LLDPDU.ETHER_FRAME_MIN_LEN:
pad = Padding()
pad.load = b'\x00' * (LLDPDU.ETHER_FRAME_MIN_LEN - frame_size)
return pkt + pay + raw(pad)
else:
return pkt + pay