autotest: Change DHCP Field and Option to namedtuple
This lets us use these objects as fields in a dictionary without
implementing a lot of very tedious operation methods. This in turn
fixes this nonsense where we use the names of Options in some places and
the Option numbers in others.
BUG=chromium-os:34417
TEST=unittests pass, autotest tests pass
Change-Id: I971b98505d0a1e95fd40e6ea3557a7dee63dfa62
Reviewed-on: https://gerrit.chromium.org/gerrit/33151
Commit-Ready: Christopher Wiley <[email protected]>
Reviewed-by: Christopher Wiley <[email protected]>
Tested-by: Christopher Wiley <[email protected]>
diff --git a/client/cros/dhcp_packet.py b/client/cros/dhcp_packet.py
index 87f54d3..3d55389 100644
--- a/client/cros/dhcp_packet.py
+++ b/client/cros/dhcp_packet.py
@@ -29,94 +29,66 @@
file still pass.
"""
+import collections
import logging
import random
import socket
import struct
-class Option(object):
- """
- Represents an option in a DHCP packet. Options may or may not be present
- and are not parsed into any particular format. This means that the value of
- options is always in the form of a byte string.
- """
- def __init__(self, name, number, size):
- super(Option, self).__init__()
- self._name = name
- self._number = number
- self._size = size
+"""
+Represents an option in a DHCP packet. Options may or may not be present
+and are not parsed into any particular format. This means that the value of
+options is always in the form of a byte string.
- @property
- def name(self):
- return self._name
+|name|
+A human readable name for this option.
- @property
- def number(self):
- """
- Every DHCP option has a number that goes into the packet to indicate
- which particular option is being encoded in the next few bytes. This
- property returns that number for each option.
- """
- return self._number
+|number|
+Every DHCP option has a number that goes into the packet to indicate
+which particular option is being encoded in the next few bytes. This
+property returns that number for each option.
- @property
- def size(self):
- """
- The size property is a hint for what kind of size we might expect the
- option to be. For instance, options with a size of 1 are expected to
- always be 1 byte long. Negative sizes are variable length fields that
- are expected to be at least abs(size) bytes long.
+|size|
+The size property is a hint for what kind of size we might expect the
+option to be. For instance, options with a size of 1 are expected to
+always be 1 byte long. Negative sizes are variable length fields that
+are expected to be at least abs(size) bytes long.
- However, the size property is just a hint, and is not enforced or
- checked in any way.
- """
- return self._size
+However, the size property is just a hint, and is not enforced or
+checked in any way.
+"""
+Option = collections.namedtuple("Option", ["name", "number", "size"])
+"""
+Represents a required field in a DHCP packet. Unlike options, we sometimes
+parse fields into more meaningful data types. For instance, the hardware
+type field in an IPv4 packet is parsed into an int rather than being left as
+a raw byte string of length 1.
-class Field(object):
- """
- Represents a required field in a DHCP packet. Unlike options, we sometimes
- parse fields into more meaningful data types. For instance, the hardware
- type field in an IPv4 packet is parsed into an int rather than being left as
- a raw byte string of length 1.
- """
- def __init__(self, name, wire_format, offset, size):
- super(Field, self).__init__()
- self._name = name
- self._wire_format = wire_format
- self._offset = offset
- self._size = size
+|name|
+A human readable name for this option.
- @property
- def name(self):
- return self._name
+|wire_format|
+The wire format for a field defines how it will be parsed out of a DHCP
+packet. For instance, the value for |FIELD_OP| is an integer in Python land,
+but goes on the wire as "!B", a single (network order) byte. Fields that
+contain IP addresses like FIELD_SERVER_IP are strings of octets (like
+"\x0A\x0A\x01\x01" as returned by socket.inet_aton("10.10.1.1")) in Python land,
+and "!4s" on the wire, which is just a network order byte string, exactly like
+the Python format.
- @property
- def wire_format(self):
- """
- The wire format for a field defines how it will be parsed out of a DHCP
- packet.
- """
- return self._wire_format
+|offset|
+The |offset| for a field defines the starting byte of the field in the
+binary packet string. |offset| is used during parsing, along with
+|size| to extract the byte string of a field.
- @property
- def offset(self):
- """
- The |offset| for a field defines the starting byte of the field in the
- binary packet string. |offset| is using during parsing, along with
- |size| to extract the byte string of a field.
- """
- return self._offset
-
- @property
- def size(self):
- """
- Fields in DHCP packets have a fixed size that must be respected. This
- size property is used in parsing to indicate that |self._size| number of
- bytes make up this field.
- """
- return self._size
-
+|size|
+Fields in DHCP packets have a fixed size that must be respected. This
+size property is used in parsing to indicate that |self._size| number of
+bytes make up this field.
+"""
+Field = collections.namedtuple("Field",
+ ["name", "wire_format", "offset", "size"])
# This is per RFC 2131. The wording doesn't seem to say that the packets must
# be this big, but that has been the historic assumption in implementations.
@@ -219,6 +191,7 @@
OPTION_VALUE_DHCP_MESSAGE_TYPE_NAK = "\x06"
OPTION_VALUE_DHCP_MESSAGE_TYPE_RELEASE = "\x07"
OPTION_VALUE_DHCP_MESSAGE_TYPE_INFORM = "\x08"
+OPTION_VALUE_DHCP_MESSAGE_TYPE_UNKNOWN = "\xFF"
OPTION_VALUE_PARAMETER_REQUEST_LIST_DEFAULT = \
chr(OPTION_SUBNET_MASK.number) + \
@@ -305,22 +278,22 @@
hwmac_addr += chr(OPTION_PAD)
packet = DhcpPacket()
- packet.set_field(FIELD_OP.name, FIELD_VALUE_OP_CLIENT_REQUEST)
- packet.set_field(FIELD_HWTYPE.name, FIELD_VALUE_HWTYPE_10MB_ETH)
- packet.set_field(FIELD_HWADDR_LEN.name, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
- packet.set_field(FIELD_RELAY_HOPS.name, 0)
- packet.set_field(FIELD_TRANSACTION_ID.name, random.getrandbits(32))
- packet.set_field(FIELD_TIME_SINCE_START.name, 0)
- packet.set_field(FIELD_FLAGS.name, 0)
- packet.set_field(FIELD_CLIENT_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_YOUR_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_SERVER_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_GATEWAY_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_CLIENT_HWADDR.name, hwmac_addr)
- packet.set_field(FIELD_MAGIC_COOKIE.name, FIELD_VALUE_MAGIC_COOKIE)
- packet.set_option(OPTION_DHCP_MESSAGE_TYPE.name,
+ packet.set_field(FIELD_OP, FIELD_VALUE_OP_CLIENT_REQUEST)
+ packet.set_field(FIELD_HWTYPE, FIELD_VALUE_HWTYPE_10MB_ETH)
+ packet.set_field(FIELD_HWADDR_LEN, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
+ packet.set_field(FIELD_RELAY_HOPS, 0)
+ packet.set_field(FIELD_TRANSACTION_ID, random.getrandbits(32))
+ packet.set_field(FIELD_TIME_SINCE_START, 0)
+ packet.set_field(FIELD_FLAGS, 0)
+ packet.set_field(FIELD_CLIENT_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_YOUR_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_SERVER_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_GATEWAY_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_CLIENT_HWADDR, hwmac_addr)
+ packet.set_field(FIELD_MAGIC_COOKIE, FIELD_VALUE_MAGIC_COOKIE)
+ packet.set_option(OPTION_DHCP_MESSAGE_TYPE,
OPTION_VALUE_DHCP_MESSAGE_TYPE_DISCOVERY)
- packet.set_option(OPTION_PARAMETER_REQUEST_LIST.name,
+ packet.set_option(OPTION_PARAMETER_REQUEST_LIST,
OPTION_VALUE_PARAMETER_REQUEST_LIST_DEFAULT)
return packet
@@ -337,26 +310,26 @@
particular offer.
"""
packet = DhcpPacket()
- packet.set_field(FIELD_OP.name, FIELD_VALUE_OP_SERVER_RESPONSE)
- packet.set_field(FIELD_HWTYPE.name, FIELD_VALUE_HWTYPE_10MB_ETH)
- packet.set_field(FIELD_HWADDR_LEN.name, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
+ packet.set_field(FIELD_OP, FIELD_VALUE_OP_SERVER_RESPONSE)
+ packet.set_field(FIELD_HWTYPE, FIELD_VALUE_HWTYPE_10MB_ETH)
+ packet.set_field(FIELD_HWADDR_LEN, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
# This has something to do with relay agents
- packet.set_field(FIELD_RELAY_HOPS.name, 0)
- packet.set_field(FIELD_TRANSACTION_ID.name, transaction_id)
- packet.set_field(FIELD_TIME_SINCE_START.name, 0)
- packet.set_field(FIELD_FLAGS.name, 0)
- packet.set_field(FIELD_CLIENT_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_YOUR_IP.name, socket.inet_aton(offer_ip))
- packet.set_field(FIELD_SERVER_IP.name, socket.inet_aton(server_ip))
- packet.set_field(FIELD_GATEWAY_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_CLIENT_HWADDR.name, hwmac_addr)
- packet.set_field(FIELD_MAGIC_COOKIE.name, FIELD_VALUE_MAGIC_COOKIE)
- packet.set_option(OPTION_DHCP_MESSAGE_TYPE.name,
+ packet.set_field(FIELD_RELAY_HOPS, 0)
+ packet.set_field(FIELD_TRANSACTION_ID, transaction_id)
+ packet.set_field(FIELD_TIME_SINCE_START, 0)
+ packet.set_field(FIELD_FLAGS, 0)
+ packet.set_field(FIELD_CLIENT_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_YOUR_IP, socket.inet_aton(offer_ip))
+ packet.set_field(FIELD_SERVER_IP, socket.inet_aton(server_ip))
+ packet.set_field(FIELD_GATEWAY_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_CLIENT_HWADDR, hwmac_addr)
+ packet.set_field(FIELD_MAGIC_COOKIE, FIELD_VALUE_MAGIC_COOKIE)
+ packet.set_option(OPTION_DHCP_MESSAGE_TYPE,
OPTION_VALUE_DHCP_MESSAGE_TYPE_OFFER)
- packet.set_option(OPTION_SUBNET_MASK.name,
+ packet.set_option(OPTION_SUBNET_MASK,
socket.inet_aton(offer_subnet_mask))
- packet.set_option(OPTION_SERVER_ID.name, socket.inet_aton(server_ip))
- packet.set_option(OPTION_IP_LEASE_TIME.name,
+ packet.set_option(OPTION_SERVER_ID, socket.inet_aton(server_ip))
+ packet.set_option(OPTION_IP_LEASE_TIME,
struct.pack("!I", int(lease_time_seconds)))
return packet
@@ -366,26 +339,26 @@
requested_ip,
server_ip):
packet = DhcpPacket()
- packet.set_field(FIELD_OP.name, FIELD_VALUE_OP_CLIENT_REQUEST)
- packet.set_field(FIELD_HWTYPE.name, FIELD_VALUE_HWTYPE_10MB_ETH)
- packet.set_field(FIELD_HWADDR_LEN.name, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
+ packet.set_field(FIELD_OP, FIELD_VALUE_OP_CLIENT_REQUEST)
+ packet.set_field(FIELD_HWTYPE, FIELD_VALUE_HWTYPE_10MB_ETH)
+ packet.set_field(FIELD_HWADDR_LEN, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
# This has something to do with relay agents
- packet.set_field(FIELD_RELAY_HOPS.name, 0)
- packet.set_field(FIELD_TRANSACTION_ID.name, transaction_id)
- packet.set_field(FIELD_TIME_SINCE_START.name, 0)
- packet.set_field(FIELD_FLAGS.name, 0)
- packet.set_field(FIELD_CLIENT_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_YOUR_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_SERVER_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_GATEWAY_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_CLIENT_HWADDR.name, hwmac_addr)
- packet.set_field(FIELD_MAGIC_COOKIE.name, FIELD_VALUE_MAGIC_COOKIE)
- packet.set_option(OPTION_REQUESTED_IP.name,
+ packet.set_field(FIELD_RELAY_HOPS, 0)
+ packet.set_field(FIELD_TRANSACTION_ID, transaction_id)
+ packet.set_field(FIELD_TIME_SINCE_START, 0)
+ packet.set_field(FIELD_FLAGS, 0)
+ packet.set_field(FIELD_CLIENT_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_YOUR_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_SERVER_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_GATEWAY_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_CLIENT_HWADDR, hwmac_addr)
+ packet.set_field(FIELD_MAGIC_COOKIE, FIELD_VALUE_MAGIC_COOKIE)
+ packet.set_option(OPTION_REQUESTED_IP,
socket.inet_aton(requested_ip))
- packet.set_option(OPTION_DHCP_MESSAGE_TYPE.name,
+ packet.set_option(OPTION_DHCP_MESSAGE_TYPE,
OPTION_VALUE_DHCP_MESSAGE_TYPE_REQUEST)
- packet.set_option(OPTION_SERVER_ID.name, socket.inet_aton(server_ip))
- packet.set_option(OPTION_PARAMETER_REQUEST_LIST.name,
+ packet.set_option(OPTION_SERVER_ID, socket.inet_aton(server_ip))
+ packet.set_option(OPTION_PARAMETER_REQUEST_LIST,
OPTION_VALUE_PARAMETER_REQUEST_LIST_DEFAULT)
return packet
@@ -397,26 +370,26 @@
server_ip,
lease_time_seconds):
packet = DhcpPacket()
- packet.set_field(FIELD_OP.name, FIELD_VALUE_OP_SERVER_RESPONSE)
- packet.set_field(FIELD_HWTYPE.name, FIELD_VALUE_HWTYPE_10MB_ETH)
- packet.set_field(FIELD_HWADDR_LEN.name, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
+ packet.set_field(FIELD_OP, FIELD_VALUE_OP_SERVER_RESPONSE)
+ packet.set_field(FIELD_HWTYPE, FIELD_VALUE_HWTYPE_10MB_ETH)
+ packet.set_field(FIELD_HWADDR_LEN, FIELD_VALUE_HWADDR_LEN_10MB_ETH)
# This has something to do with relay agents
- packet.set_field(FIELD_RELAY_HOPS.name, 0)
- packet.set_field(FIELD_TRANSACTION_ID.name, transaction_id)
- packet.set_field(FIELD_TIME_SINCE_START.name, 0)
- packet.set_field(FIELD_FLAGS.name, 0)
- packet.set_field(FIELD_CLIENT_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_YOUR_IP.name, socket.inet_aton(granted_ip))
- packet.set_field(FIELD_SERVER_IP.name, socket.inet_aton(server_ip))
- packet.set_field(FIELD_GATEWAY_IP.name, IPV4_NULL_ADDRESS)
- packet.set_field(FIELD_CLIENT_HWADDR.name, hwmac_addr)
- packet.set_field(FIELD_MAGIC_COOKIE.name, FIELD_VALUE_MAGIC_COOKIE)
- packet.set_option(OPTION_DHCP_MESSAGE_TYPE.name,
+ packet.set_field(FIELD_RELAY_HOPS, 0)
+ packet.set_field(FIELD_TRANSACTION_ID, transaction_id)
+ packet.set_field(FIELD_TIME_SINCE_START, 0)
+ packet.set_field(FIELD_FLAGS, 0)
+ packet.set_field(FIELD_CLIENT_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_YOUR_IP, socket.inet_aton(granted_ip))
+ packet.set_field(FIELD_SERVER_IP, socket.inet_aton(server_ip))
+ packet.set_field(FIELD_GATEWAY_IP, IPV4_NULL_ADDRESS)
+ packet.set_field(FIELD_CLIENT_HWADDR, hwmac_addr)
+ packet.set_field(FIELD_MAGIC_COOKIE, FIELD_VALUE_MAGIC_COOKIE)
+ packet.set_option(OPTION_DHCP_MESSAGE_TYPE,
OPTION_VALUE_DHCP_MESSAGE_TYPE_ACK)
- packet.set_option(OPTION_SUBNET_MASK.name,
+ packet.set_option(OPTION_SUBNET_MASK,
socket.inet_aton(granted_ip_subnet_mask))
- packet.set_option(OPTION_SERVER_ID.name, socket.inet_aton(server_ip))
- packet.set_option(OPTION_IP_LEASE_TIME.name,
+ packet.set_option(OPTION_SERVER_ID, socket.inet_aton(server_ip))
+ packet.set_option(OPTION_IP_LEASE_TIME,
struct.pack("!I", int(lease_time_seconds)))
return packet
@@ -448,10 +421,10 @@
self._logger.error("Invalid byte string for packet.")
return
for field in DHCP_PACKET_FIELDS:
- self._fields[field.name] = struct.unpack(field.wire_format,
- byte_str[field.offset :
- field.offset +
- field.size])[0]
+ self._fields[field] = struct.unpack(field.wire_format,
+ byte_str[field.offset :
+ field.offset +
+ field.size])[0]
offset = OPTIONS_START_OFFSET
while offset < len(byte_str) and ord(byte_str[offset]) != OPTION_END:
data_type = ord(byte_str[offset])
@@ -466,49 +439,49 @@
if option_bunch is None:
# Unsupported data type, of which we have many.
continue
- self._options[option_bunch.name] = data
+ if option_bunch == OPTION_PARAMETER_REQUEST_LIST:
+ options = [ord(c) for c in data]
+ logging.info("Requested options: %s" % str(options))
+ self._options[option_bunch] = data
@property
def client_hw_address(self):
- return self._fields["chaddr"]
+ return self._fields.get(FIELD_CLIENT_HWADDR)
@property
def is_valid(self):
+ """
+ Checks that we have (at a minimum) values for all the fields, and that
+ the magic cookie is set correctly.
+ """
for field in DHCP_PACKET_FIELDS:
- if (not field.name in self._fields or
- self._fields[field.name] is None):
- self._logger.info("Missing field %s in packet." % field.name)
+ if self._fields.get(field) is None:
+ self._logger.info("Missing field %s in packet." % field)
return False
- if (self._fields[FIELD_MAGIC_COOKIE.name] !=
- FIELD_VALUE_MAGIC_COOKIE):
+ if self._fields[FIELD_MAGIC_COOKIE] != FIELD_VALUE_MAGIC_COOKIE:
return False
return True
@property
def message_type(self):
- if not "dhcp_message_type" in self._options:
- return -1
- return self._options["dhcp_message_type"]
+ return self._options.get(OPTION_DHCP_MESSAGE_TYPE,
+ OPTION_VALUE_DHCP_MESSAGE_TYPE_UNKNOWN)
@property
def transaction_id(self):
- return self._fields["xid"]
+ return self._fields.get(FIELD_TRANSACTION_ID)
- def get_field(self, field_name):
- if field_name in self._fields:
- return self._fields[field_name]
- return None
+ def get_field(self, field):
+ return self._fields.get(field)
- def get_option(self, option_name):
- if option_name in self._options:
- return self._options[option_name]
- return None
+ def get_option(self, option):
+ return self._options.get(option)
- def set_field(self, field_name, field_value):
- self._fields[field_name] = field_value
+ def set_field(self, field, field_value):
+ self._fields[field] = field_value
- def set_option(self, option_name, option_value):
- self._options[option_name] = option_value
+ def set_option(self, option, option_value):
+ self._options[option] = option_value
def to_binary_string(self):
if not self.is_valid:
@@ -518,7 +491,7 @@
offset = 0
for field in DHCP_PACKET_FIELDS:
field_data = struct.pack(field.wire_format,
- self._fields[field.name])
+ self._fields[field])
while offset < field.offset:
# This should only happen when we're padding the fields because
# we're not filling in legacy BOOTP stuff.
@@ -529,17 +502,23 @@
# Last field processed is the magic cookie, so we're ready for options.
# Have to process options
for option in DHCP_PACKET_OPTIONS:
- if not option.name in self._options:
+ option_value = self._options.get(option)
+ if option_value is None:
continue
data.append(struct.pack("BB",
option.number,
- len(self._options[option.name])))
+ len(option_value)))
offset += 2
- data.append(self._options[option.name])
- offset += len(self._options[option.name])
+ data.append(option_value)
+ offset += len(option_value)
data.append(chr(OPTION_END))
offset += 1
while offset < DHCP_MIN_PACKET_SIZE:
data.append(chr(OPTION_PAD))
offset += 1
return "".join(data)
+
+ def __str__(self):
+ options = [k.name + "=" + str(v) for k, v in self._options.items()]
+ fields = [k.name + "=" + str(v) for k, v in self._fields.items()]
+ return "<DhcpPacket fields=%s, options=%s>" % (fields, options)
