"""
Implementation of the Client LinkLayer Address relay option as specified in :rfc:`6939`.
"""
from struct import pack, unpack_from
from typing import Union
from dhcpkit.display_strings import hardware_types
from dhcpkit.ipv6.messages import RelayServerMessage
from dhcpkit.ipv6.options import Option
from dhcpkit.protocol_element import ElementDataRepresentation
OPTION_CLIENT_LINKLAYER_ADDR = 79
[docs]class LinkLayerIdOption(Option):
"""
:rfc:`6939#section-4`
The format of the DHCPv6 Client Link-Layer Address option is shown
below.
.. code-block:: none
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CLIENT_LINKLAYER_ADDR | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| link-layer type (16 bits) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| link-layer address (variable length) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code
OPTION_CLIENT_LINKLAYER_ADDR (79)
option-length
2 + length of link-layer address
link-layer type
Client link-layer address type. The link-layer
type MUST be a valid hardware type assigned
by the IANA, as described in :rfc:`826`
link-layer address
Client link-layer address
"""
option_type = OPTION_CLIENT_LINKLAYER_ADDR
def __init__(self, link_layer_type: int = 0, link_layer_address: bytes = b''):
self.link_layer_type = link_layer_type
self.link_layer_address = link_layer_address
[docs] def display_link_layer_type(self) -> ElementDataRepresentation:
"""
Nicer representation of hardware types
:return: Representation of hardware type
"""
display = hardware_types.get(self.link_layer_type, 'Unknown')
return ElementDataRepresentation("{} ({})".format(display, self.link_layer_type))
[docs] def validate(self):
"""
Validate that the contents of this object conform to protocol specs.
"""
if not isinstance(self.link_layer_type, int) or not (0 <= self.link_layer_type < 2 ** 16):
raise ValueError("Link-layer type must be an unsigned 16 bit integer")
if not isinstance(self.link_layer_address, bytes):
raise ValueError("Link-layer address must be a sequence of bytes")
if len(self.link_layer_address) > (2 ** 16 - 3):
raise ValueError("link-layer address cannot be longer than {} bytes".format(2 ** 16 - 3))
[docs] def load_from(self, buffer: bytes, offset: int = 0, length: int = None) -> int:
"""
Load the internal state of this object from the given buffer. The buffer may contain more data after the
structured element is parsed. This data is ignored.
:param buffer: The buffer to read data from
:param offset: The offset in the buffer where to start reading
:param length: The amount of data we are allowed to read from the buffer
:return: The number of bytes used from the buffer
"""
my_offset, option_len = self.parse_option_header(buffer, offset, length, min_length=2)
# Parse the address type
self.link_layer_type = unpack_from('!H', buffer, offset=offset + my_offset)[0]
my_offset += 2
ll_len = option_len - 2
self.link_layer_address = buffer[offset + my_offset:offset + my_offset + ll_len]
my_offset += ll_len
return my_offset
[docs] def save(self) -> Union[bytes, bytearray]:
"""
Save the internal state of this object as a buffer.
:return: The buffer with the data from this element
"""
buffer = bytearray()
buffer.extend(pack('!HHH', self.option_type, len(self.link_layer_address) + 2, self.link_layer_type))
buffer.extend(self.link_layer_address)
return buffer
# Register where these options may occur
RelayServerMessage.add_may_contain(LinkLayerIdOption, 0, 1)