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import logging
import socket
import select
from typing import Tuple, List, Optional
from timeit import default_timer
from time import sleep
import json
import collections
from . import packet, options, utils
from .exceptions import DHCPClientError
COL_LEN = 80
Lease = collections.namedtuple(
"Lease", ["discover", "offer", "request", "ack", "time", "server"]
)
def format_dhcp_packet(pkt: packet.DHCPPacket) -> str:
line_divider = ";-" + "".ljust(COL_LEN, "-") + ";\n"
options_list = options.OptionList(pkt.options)
msg_type_option = options_list.by_code(53)
padding = " "
if msg_type_option:
msg_type = list(msg_type_option.value.values())[0]
else:
msg_type = "UNKNOWN MSG TYPE"
broadcast = "BROADCAST" if pkt.flags else "UNICAST"
client_info_padding = 18
client_info = f"{pkt.htype} - {pkt.chaddr} ({utils.mac2vendor(pkt.chaddr)})"
if (
visual_diff := (
utils.visual_length(client_info) - (COL_LEN - client_info_padding)
)
) > 0:
client_info = client_info[:-visual_diff]
output = (
f"{pkt.op} / {msg_type} / {broadcast}\n"
+ f"{len(pkt.asbytes)} bytes / TX ID {hex(pkt.xid).upper()} / {pkt.secs} seconds elapsed\n"
+ "Client info:".ljust(client_info_padding)
+ client_info
+ "\n"
+ "Client address:".ljust(client_info_padding)
+ f"{pkt.ciaddr}\n"
+ "Your address:".ljust(client_info_padding)
+ f"{pkt.yiaddr}\n"
+ "Next server:".ljust(client_info_padding)
+ f"{pkt.siaddr}\n"
+ "Relay:".ljust(client_info_padding)
+ f"{pkt.giaddr}"
)
output = (
"\n".join(
[
f"; {line.ljust(COL_LEN if utils.visual_length(line) < COL_LEN else 0, padding)};"
for line in output.split("\n")
]
)
+ "\n"
)
output = line_divider + output + line_divider
output += "; " + "OPTIONS:".ljust(COL_LEN, padding) + ";\n"
output += (
"\n".join(
[
f"; {line.ljust(COL_LEN, padding)};"
for line in options_list.json.split("\n")
]
)
+ "\n"
)
output += line_divider
return output
class DHCPClient(object):
def __init__(
self,
interface: str = None,
send_from_port: int = 68,
send_to_port: int = 67,
max_retries: int = 10,
socket_poll_interval: int = 10,
retry_interval: int = 100,
):
self.listening_ports = [67]
self.send_from_port = send_from_port
self.send_to_port = send_to_port
self.max_pkt_size = 4096
self.interface = interface
self.listening_sockets = self.get_listening_sockets()
self.writing_sockets = self.get_writing_sockets()
self.listening_sockets += self.writing_sockets
# self.listening_sockets += self.writing_sockets
logging.debug(f"listening sockets: {self.listening_sockets}")
logging.debug(f"write sockets: {self.writing_sockets}")
self.except_sockets: List[socket.socket] = []
self.max_tries = max_retries
self.socket_poll_interval = socket_poll_interval
self.retry_interval = retry_interval
self.select_timout = 0
self.offer_servers: List[str] = []
self.ack_server: str = ""
def send_discover(
self, server: str, discover_packet: packet.DHCPPacket, verbosity: int
):
self.send(server, self.send_to_port, discover_packet.asbytes, verbosity)
def receive_offer(self, tx_id: int, verbosity: int) -> Optional[packet.DHCPPacket]:
logging.debug("Listening for offer packet...")
if verbosity > 1:
print("Listening for OFFER packet")
offer, addr = self.listen(tx_id, "DHCPOFFER", verbosity)
if offer:
logging.debug(f"Received offer packet from {addr} {offer}")
if verbosity > 1:
print(f"<< OFFER received from {addr[0]}:{addr[1]}")
print(format_dhcp_packet(offer))
self.offer_servers.append(addr)
else:
logging.debug("Did not receive offer, retrying")
if verbosity > 1:
print("Did not receive offer packet")
return offer
def send_request(
self, server: str, request_packet: packet.DHCPPacket, verbosity: int
):
self.send(server, self.send_to_port, request_packet.asbytes, verbosity)
def receive_ack(self, tx_id: int, verbosity: int) -> Optional[packet.DHCPPacket]:
logging.debug("Listening for ack packet...")
if verbosity > 1:
print("Listening for ACK packet")
ack, addr = self.listen(tx_id, "DHCPACK", verbosity)
if ack:
logging.debug(f"Received ack packet from {addr} {ack}")
if verbosity:
print(f"<< ACK received from {addr[0]}:{addr[1]}")
print(format_dhcp_packet(ack))
self.ack_server = addr
else:
logging.debug("Did not receive ack, retrying")
if verbosity > 1:
print("Did not receive ack packet")
return ack
def get_lease(
self,
mac_addr: Optional[str] = None,
broadcast: bool = True,
relay: Optional[str] = None,
server: str = "255.255.255.255",
ip_protocol: int = 4,
options_list: Optional[options.OptionList] = None,
verbose: int = 0,
) -> Lease:
mac_addr = mac_addr or utils.random_mac()
logging.debug("Synthetizing discover packet")
# D
discover = packet.DHCPPacket.Discover(
mac_addr, use_broadcast=broadcast, option_list=options_list, relay=relay
)
tx_id = discover.xid
logging.debug(f"Constructed discover packet: {discover}")
if verbose > 1:
print(format_dhcp_packet(discover))
start = default_timer()
logging.debug(f"Sending discover packet to {server} with {tx_id=}")
self.send_discover(server, discover, verbose)
# O
tries = 0
while not (offer := self.receive_offer(tx_id, verbose)):
logging.debug(f"Sleeping {self.retry_interval} ms then retrying discover")
sleep(self.retry_interval / 1000)
logging.debug(
f"Attempt {tries} - Sending discover packet to {server} with {tx_id=}"
)
if verbose > 1:
print("Resending DISCOVER packet")
self.send_discover(server, discover, verbose)
if tries > self.max_tries:
raise DHCPClientError(
"Unable to obtain offer run client with -d for debug info"
)
tries += 1
# R
request = packet.DHCPPacket.Request(
mac_addr,
int(default_timer() - start),
tx_id,
use_broadcast=broadcast,
option_list=options_list,
client_ip=offer.yiaddr,
relay=relay,
)
if verbose > 1:
print("REQUEST Packet")
print(format_dhcp_packet(request))
logging.debug(f"Constructed request packet: {request}")
logging.debug(f"Sending request packet to {server} with {tx_id=}")
self.send_request(server, request, verbose)
# A
tries = 0
while not (ack := self.receive_ack(tx_id, verbose)):
logging.debug(f"Sleeping {self.retry_interval} ms then retrying request")
sleep(self.retry_interval / 1000)
logging.debug(
f"Attempt {tries} - Sending request packet to {server} with {tx_id=}"
)
if verbose > 1:
print("Resending REQUEST packet")
self.send_request(server, request, verbose)
if tries > self.max_tries:
raise DHCPClientError(
"Unable to obtain ack run client with -d for debug info"
)
tries += 1
lease_time = default_timer() - start
lease = Lease(discover, offer, request, ack, lease_time, self.ack_server)
if verbose:
print(f"Client terminated after {lease_time * 1000:.0f} ms")
else:
print(
f"Lease succesful: {ack.yiaddr} -- {ack.chaddr} -- {lease_time * 1000:.0f} ms elapsed"
)
return lease
def get_valid_pkt(self, data: bytes) -> Optional[packet.DHCPPacket]:
pkt = None
try:
pkt = packet.DHCPPacket.from_bytes(data)
except Exception as e:
logging.debug(
f"Unable to parse received data as DHCP packet: {e} --- {data!r}"
)
return pkt
def listen(
self, tx_id: int, msg_type: str, verbosity: int
) -> Tuple[Optional[packet.DHCPPacket], Optional[str]]:
logging.debug(
f"Listening on {self.interface or 'all interfaces'}, UDP ports {self.listening_ports}"
)
tries = 0
dhcp_packet, addr = None, None
while tries < self.max_tries:
logging.debug(
f"Select: {select.select(self.listening_sockets, self.writing_sockets, self.except_sockets, 0)}"
)
if len(
socks := select.select(
self.listening_sockets,
self.writing_sockets,
self.except_sockets,
self.select_timout,
)[0]
):
for sock in socks:
data, addr = sock.recvfrom(self.max_pkt_size)
logging.debug(f"Received data from {addr}: {data}")
if (
(dhcp_packet := self.get_valid_pkt(data)) is not None
and dhcp_packet.xid == tx_id
and dhcp_packet.msg_type == msg_type
):
logging.debug(
f"Received valid DHCP packet of {dhcp_packet.msg_type} type"
)
return dhcp_packet, addr
else:
if dhcp_packet is None:
logging.debug("Invalid DHCP packet")
elif dhcp_packet.xid != tx_id:
logging.debug(
f"TX ID does not match expected ID {dhcp_packet.xid} != {tx_id}"
)
elif (msg_type_actual := dhcp_packet.msg_type) != msg_type:
logging.debug(
f"DHCP message type does not match expected: {msg_type_actual} != {msg_type}"
)
else:
logging.debug("Something is wrong with this packet")
logging.debug(dhcp_packet)
dhcp_packet = None
tries += 1
else:
logging.debug(
f"Attempt {tries} - No sockets available to read from... "
f"sleeping for {self.socket_poll_interval} ms"
)
if verbosity > 2:
print("Did not receive packet, sleeping...")
tries += 1
sleep(self.socket_poll_interval / 1000)
return dhcp_packet, addr
def get_socket(self, host: str, port: int) -> socket.socket:
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
sock.setblocking(False)
if self.interface:
try:
# Option 25 is SO_BINDTODEVICE, allows us to specify a device
# to bind to with this socket
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BINDTODEVICE, self.interface.encode())
logging.info(f"Binding to {self.interface}")
except:
# Less reliable method of binding to interface, required where
# socket option 25 does not exist (Windows)
sock.bind((utils.get_ip_by_iface(self.interface), port))
else:
sock.bind((host, port))
else:
sock.bind((host, port))
logging.info(f"Bound {socket}")
return sock
def get_writing_sockets(self) -> List[socket.socket]:
host = ""
port = self.send_from_port
logging.debug(f"Creating socket to send data, binding to {(host, port)}")
client_sock = self.get_socket(host, port)
return [client_sock]
def get_listening_sockets(self) -> List[socket.socket]:
socks = []
host = ""
for port in self.listening_ports:
logging.debug(f"Creating socket to receiving data, binding to {(host, port)}")
server_sock = self.get_socket(host, port)
socks.append(server_sock)
return socks
def send(self, remote_addr: str, remote_port: int, data: bytes, verbosity: int):
tries = 0
while tries < self.max_tries:
logging.debug(f"Select: {select.select(self.listening_sockets, self.writing_sockets, self.except_sockets, self.select_timout,)}")
if len(
socks := select.select(
self.listening_sockets,
self.writing_sockets,
self.except_sockets,
self.select_timout,
)[1]
):
sock = socks[0]
logging.debug(f"Connecting to {remote_addr}:{remote_port}")
logging.debug(f"Sending data {data!r}")
if verbosity > 1:
print(f">> Sending packet {remote_addr}:{remote_port}")
sock.sendto(data, (remote_addr, remote_port))
logging.debug(f"Packet Sent")
break
else:
logging.warning(
f"Attempt {tries} - No sockets available to write to... "
f"sleeping for {self.socket_poll_interval} ms"
)
tries += 1
sleep(self.socket_poll_interval / 1000)