def from_bytes(cls, bitstream):
packet = cls()
# Convert to ConstBitStream (if not already provided)
if not isinstance(bitstream, ConstBitStream):
if isinstance(bitstream, Bits):
bitstream = ConstBitStream(auto=bitstream)
else:
bitstream = ConstBitStream(bytes=bitstream)
# Read the next header type
packet.next_header = bitstream.read('uint:8')
# Read the header length, given in multiples of 8 octets
header_length = bitstream.read('uint:8') + 1
# Read the options
options_length = (header_length * 8) - 2
packet.options = bitstream.read('bytes:%d' % options_length)
# And the rest is payload
remaining = bitstream[bitstream.pos:]
packet.payload = remaining.bytes
payload_class = protocol_registry.get_type_class(packet.next_header)
if payload_class:
packet.payload = payload_class.from_bytes(packet.payload)
# Verify that the properties make sense
packet.sanitize()
return packet
def from_bytes(cls, bitstream, decode_payload=True):
"""
Parse the given packet and update properties accordingly
"""
packet = cls()
# Convert to ConstBitStream (if not already provided)
if not isinstance(bitstream, ConstBitStream):
if isinstance(bitstream, Bits):
bitstream = ConstBitStream(auto=bitstream)
else:
bitstream = ConstBitStream(bytes=bitstream)
# Read the version
version = bitstream.read("uint:4")
if version != packet.version:
raise ValueError("Provided bytes do not contain an IPv6 packet")
# Read the traffic class
packet.traffic_class = bitstream.read("uint:8")
# Read the flow label
packet.flow_label = bitstream.read("uint:20")
# Read the payload length
payload_length = bitstream.read("uint:16")
# Read the next header type
packet.next_header = bitstream.read("uint:8")
# Read the hop limit
packet.hop_limit = bitstream.read("uint:8")
# Read the source and destination addresses
packet.source = IPv6Address(bitstream.read("uint:128"))
packet.destination = IPv6Address(bitstream.read("uint:128"))
# And the rest is payload
packet.payload = bitstream.read("bytes:%d" % payload_length)
if decode_payload:
payload_class = protocol_registry.get_type_class(packet.next_header)
if payload_class:
packet.payload = payload_class.from_bytes(packet.payload)
# There should be no remaining bits
if bitstream.pos != bitstream.len:
raise ValueError("Bits remaining after processing packet")
# Verify that the properties make sense
packet.sanitize()
return packet
def from_bytes(cls, bitstream, decode_payload=True):
'''
Parse the given packet and update properties accordingly
'''
packet = cls()
# Convert to ConstBitStream (if not already provided)
if not isinstance(bitstream, ConstBitStream):
if isinstance(bitstream, Bits):
bitstream = ConstBitStream(auto=bitstream)
else:
bitstream = ConstBitStream(bytes=bitstream)
# Read the version
version = bitstream.read('uint:4')
if version != packet.version:
raise ValueError('Provided bytes do not contain an IPv4 packet')
# Read the header length
ihl = bitstream.read('uint:4')
if ihl < 5:
raise ValueError('Invalid IPv4 header length')
# Now that we know the length of the header we store it to be able
# to easily recalculate the header checksum later
remaining_header_bits = (ihl * 32) - 8
header = (BitStream('uint:4=4, uint:4=%d' % ihl) +
bitstream.peek(remaining_header_bits))
# Read the type of service
packet.tos = bitstream.read('uint:8')
# Read the total length
total_length = bitstream.read('uint:16')
if total_length < ihl * 4:
raise ValueError('Total length is shorter than the header')
# Read the identification
packet.identification = bitstream.read('uint:16')
# Read the flags
(reserved,
packet.dont_fragment,
packet.more_fragments) = bitstream.readlist('3*bool')
if reserved:
raise ValueError('Reserved flag must be 0')
# Read the fragment offset
packet.fragment_offset = bitstream.read('uint:13')
# Read the TTL
packet.ttl = bitstream.read('uint:8')
# Read the protocol number
packet.protocol = bitstream.read('uint:8')
# Read the header checksum
header_checksum = bitstream.read('uint:16')
# Set the checksum bits in the header to 0 and re-calculate
header[80:96] = BitStream(16)
my_checksum = checksum.ones_complement(header.bytes)
if my_checksum != header_checksum:
raise ValueError('Header checksum does not match')
# Read the source and destination addresses
packet.source = IPv4Address(bitstream.read('uint:32'))
packet.destination = IPv4Address(bitstream.read('uint:32'))
# Read the options
option_len = (ihl - 5) * 4
packet.options = bitstream.read('bytes:%d' % option_len)
# And the rest is payload
payload_bytes = (total_length) - (ihl * 4)
packet.payload = bitstream.read('bytes:%d' % payload_bytes)
if decode_payload:
payload_class = protocol_registry.get_type_class(packet.protocol)
if payload_class:
packet.payload = payload_class.from_bytes(packet.payload)
# There should be no remaining bits
if bitstream.pos != bitstream.len:
raise ValueError('Bits remaining after processing packet')
# Verify that the properties make sense
packet.sanitize()
return packet
