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 + # noqa: E501
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)
return raw(_EtherCatLengthCalc(length=self.length,
type=self.type)) + pay
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 + # noqa: E501
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)
return raw(_EtherCatLengthCalc(length=self.length,
type=self.type)) + pay
def pad_udp(packet):
if UDP in packet:
# get layers after udp
layer_after = packet[UDP].payload.copy()
# build a padding layer
pad = Padding()
pad.load = '\x00' * 12
layer_before = packet.copy()
layer_before[UDP].remove_payload()
packet = layer_before / pad / layer_after
return packet
return packet
def pad_udp(packet):
if UDP in packet:
# get layers after udp
layer_after = packet[UDP].payload.copy()
print("packet: ", packet)
print("udp: ", packet[UDP])
print("payload: ", packet[UDP].payload)
# build a padding layer
pad = Padding()
pad.load = '\x00' * 12
print("pad:", pad.load)
layer_before = packet.copy()
layer_before[UDP].remove_payload()
print("remove udp payload:", layer_before)
packet = layer_before / pad / layer_after
return packet
return packet