adafruit_wiznet5k_dhcp.py

# SPDX-FileCopyrightText: 2009 Jordan Terell (blog.jordanterrell.com)
# SPDX-FileCopyrightText: 2020 Brent Rubell for Adafruit Industries
# SPDX-FileCopyrightText: 2021 Patrick Van Oosterwijck @ Silicognition LLC
#
# SPDX-License-Identifier: MIT

"""
`adafruit_wiznet5k_dhcp`
================================================================================

Pure-Python implementation of Jordan Terrell's DHCP library v0.3

* Author(s): Jordan Terrell, Brent Rubell

"""
import gc
import time
from random import randint
from micropython import const
import adafruit_wiznet5k.adafruit_wiznet5k_socket as socket
from adafruit_wiznet5k.adafruit_wiznet5k_socket import htonl, htons


# DHCP State Machine
STATE_DHCP_START = const(0x00)
STATE_DHCP_DISCOVER = const(0x01)
STATE_DHCP_REQUEST = const(0x02)
STATE_DHCP_LEASED = const(0x03)
STATE_DHCP_REREQUEST = const(0x04)
STATE_DHCP_RELEASE = const(0x05)
STATE_DHCP_WAIT = const(0x06)
STATE_DHCP_DISCONN = const(0x07)

# DHCP wait time between attempts
DHCP_WAIT_TIME = const(60)

# DHCP Message Types
DHCP_DISCOVER = const(1)
DHCP_OFFER = const(2)
DHCP_REQUEST = const(3)
DHCP_DECLINE = const(4)
DHCP_ACK = const(5)
DHCP_NAK = const(6)
DHCP_RELEASE = const(7)
DHCP_INFORM = const(8)

# DHCP Message OP Codes
DHCP_BOOT_REQUEST = const(0x01)
DHCP_BOOT_REPLY = const(0x02)

DHCP_HTYPE10MB = const(0x01)
DHCP_HTYPE100MB = const(0x02)

DHCP_HLENETHERNET = const(0x06)
DHCP_HOPS = const(0x00)

MAGIC_COOKIE = const(0x63825363)
MAX_DHCP_OPT = const(0x10)

# Default DHCP Server port
DHCP_SERVER_PORT = const(67)
# DHCP Lease Time, in seconds
DEFAULT_LEASE_TIME = const(900)
BROADCAST_SERVER_ADDR = (255, 255, 255, 255)

# DHCP Response Options
MSG_TYPE = 53
SUBNET_MASK = 1
ROUTERS_ON_SUBNET = 3
DNS_SERVERS = 6
DHCP_SERVER_ID = 54
T1_VAL = 58
T2_VAL = 59
LEASE_TIME = 51
OPT_END = 255

# Packet buffer
_BUFF = bytearray(318)


class DHCP:
    """W5k DHCP Client implementation.

    :param eth: Wiznet 5k object
    :param list mac_address: Hardware MAC.
    :param str hostname: The desired hostname, with optional {} to fill in MAC.
    :param int response_timeout: DHCP Response timeout.
    :param bool debug: Enable debugging output.

    """

    # pylint: disable=too-many-arguments, too-many-instance-attributes, invalid-name
    def __init__(
        self, eth, mac_address, hostname=None, response_timeout=30, debug=False
    ):
        self._debug = debug
        self._response_timeout = response_timeout

        # Prevent buffer overrun in send_dhcp_message()
        if len(mac_address) != 6:
            raise ValueError("The MAC address must be 6 bytes.")
        self._mac_address = mac_address

        # Set socket interface
        socket.set_interface(eth)
        self._eth = eth
        self._sock = None

        # DHCP state machine
        self._dhcp_state = STATE_DHCP_START
        self._initial_xid = 0
        self._transaction_id = 0
        self._start_time = 0

        # DHCP server configuration
        self.dhcp_server_ip = BROADCAST_SERVER_ADDR
        self.local_ip = 0
        self.gateway_ip = 0
        self.subnet_mask = 0
        self.dns_server_ip = 0

        # Lease configuration
        self._lease_time = 0
        self._last_lease_time = 0
        self._renew_in_sec = 0
        self._rebind_in_sec = 0
        self._t1 = 0
        self._t2 = 0

        # Select an initial transaction id
        self._transaction_id = randint(1, 0x7FFFFFFF)

        # Host name
        mac_string = "".join("{:02X}".format(o) for o in mac_address)
        self._hostname = bytes(
            (hostname or "WIZnet{}").split(".")[0].format(mac_string)[:42], "utf-8"
        )

    # pylint: disable=too-many-statements
    def send_dhcp_message(self, state, time_elapsed, renew=False):
        """Assemble and send a DHCP message packet to a socket.

        :param int state: DHCP Message state.
        :param float time_elapsed: Number of seconds elapsed since DHCP process started
        :param bool renew: Set True for renew and rebind
        """
        _BUFF[:] = b"\x00" * len(_BUFF)
        # OP
        _BUFF[0] = DHCP_BOOT_REQUEST
        # HTYPE
        _BUFF[1] = DHCP_HTYPE10MB
        # HLEN
        _BUFF[2] = DHCP_HLENETHERNET
        # HOPS
        _BUFF[3] = DHCP_HOPS

        # Transaction ID (xid)
        self._initial_xid = htonl(self._transaction_id)
        self._initial_xid = self._initial_xid.to_bytes(4, "big")
        _BUFF[4:7] = self._initial_xid

        # seconds elapsed
        _BUFF[8] = (int(time_elapsed) & 0xFF00) >> 8
        _BUFF[9] = int(time_elapsed) & 0x00FF

        # flags
        flags = htons(0x8000)
        flags = flags.to_bytes(2, "big")
        _BUFF[10] = flags[1]
        _BUFF[11] = flags[0]

        # NOTE: Skipping ciaddr/yiaddr/siaddr/giaddr
        # as they're already set to 0.0.0.0
        # Except when renewing, then fill in ciaddr
        if renew:
            _BUFF[12:15] = bytes(self.local_ip)

        # chaddr
        _BUFF[28:34] = self._mac_address

        # NOTE:  192 octets of 0's, BOOTP legacy

        # Magic Cookie
        _BUFF[236] = (MAGIC_COOKIE >> 24) & 0xFF
        _BUFF[237] = (MAGIC_COOKIE >> 16) & 0xFF
        _BUFF[238] = (MAGIC_COOKIE >> 8) & 0xFF
        _BUFF[239] = MAGIC_COOKIE & 0xFF

        # Option - DHCP Message Type
        _BUFF[240] = 53
        _BUFF[241] = 0x01
        _BUFF[242] = state

        # Option - Client Identifier
        _BUFF[243] = 61
        # Length
        _BUFF[244] = 0x07
        # HW Type - ETH
        _BUFF[245] = 0x01
        # Client MAC Address
        for mac, val in enumerate(self._mac_address):
            _BUFF[246 + mac] = val

        # Option - Host Name
        _BUFF[252] = 12
        hostname_len = len(self._hostname)
        after_hostname = 254 + hostname_len
        _BUFF[253] = hostname_len
        _BUFF[254:after_hostname] = self._hostname

        if state == DHCP_REQUEST and not renew:
            # Set the parsed local IP addr
            _BUFF[after_hostname] = 50
            _BUFF[after_hostname + 1] = 0x04
            _BUFF[after_hostname + 2 : after_hostname + 6] = bytes(self.local_ip)
            # Set the parsed dhcp server ip addr
            _BUFF[after_hostname + 6] = 54
            _BUFF[after_hostname + 7] = 0x04
            _BUFF[after_hostname + 8 : after_hostname + 12] = bytes(self.dhcp_server_ip)

        _BUFF[after_hostname + 12] = 55
        _BUFF[after_hostname + 13] = 0x06
        # subnet mask
        _BUFF[after_hostname + 14] = 1
        # routers on subnet
        _BUFF[after_hostname + 15] = 3
        # DNS
        _BUFF[after_hostname + 16] = 6
        # domain name
        _BUFF[after_hostname + 17] = 15
        # renewal (T1) value
        _BUFF[after_hostname + 18] = 58
        # rebinding (T2) value
        _BUFF[after_hostname + 19] = 59
        _BUFF[after_hostname + 20] = 255

        # Send DHCP packet
        self._sock.send(_BUFF)

    # pylint: disable=too-many-branches, too-many-statements
    def parse_dhcp_response(self):
        """Parse DHCP response from DHCP server.
        Returns DHCP packet type.
        """
        # store packet in buffer
        _BUFF = self._sock.recv()
        if self._debug:
            print("DHCP Response: ", _BUFF)

        # -- Parse Packet, FIXED -- #
        # Validate OP
        assert (
            _BUFF[0] == DHCP_BOOT_REPLY
        ), "Malformed Packet - \
            DHCP message OP is not expected BOOT Reply."

        xid = _BUFF[4:8]
        if bytes(xid) < self._initial_xid:
            print("f")
            return 0, 0

        self.local_ip = tuple(_BUFF[16:20])
        if _BUFF[28:34] == 0:
            return 0, 0

        if int.from_bytes(_BUFF[235:240], "big") != MAGIC_COOKIE:
            return 0, 0

        # -- Parse Packet, VARIABLE -- #
        ptr = 240
        while _BUFF[ptr] != OPT_END:
            if _BUFF[ptr] == MSG_TYPE:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += opt_len
                msg_type = _BUFF[ptr]
                ptr += 1
            elif _BUFF[ptr] == SUBNET_MASK:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self.subnet_mask = tuple(_BUFF[ptr : ptr + opt_len])
                ptr += opt_len
            elif _BUFF[ptr] == DHCP_SERVER_ID:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self.dhcp_server_ip = tuple(_BUFF[ptr : ptr + opt_len])
                ptr += opt_len
            elif _BUFF[ptr] == LEASE_TIME:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self._lease_time = int.from_bytes(_BUFF[ptr : ptr + opt_len], "big")
                ptr += opt_len
            elif _BUFF[ptr] == ROUTERS_ON_SUBNET:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self.gateway_ip = tuple(_BUFF[ptr : ptr + opt_len])
                ptr += opt_len
            elif _BUFF[ptr] == DNS_SERVERS:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self.dns_server_ip = tuple(_BUFF[ptr : ptr + 4])
                ptr += opt_len  # still increment even though we only read 1 addr.
            elif _BUFF[ptr] == T1_VAL:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self._t1 = int.from_bytes(_BUFF[ptr : ptr + opt_len], "big")
                ptr += opt_len
            elif _BUFF[ptr] == T2_VAL:
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                self._t2 = int.from_bytes(_BUFF[ptr : ptr + opt_len], "big")
                ptr += opt_len
            elif _BUFF[ptr] == 0:
                break
            else:
                # We're not interested in this option
                ptr += 1
                opt_len = _BUFF[ptr]
                ptr += 1
                # no-op
                ptr += opt_len

        if self._debug:
            print(
                "Msg Type: {}\nSubnet Mask: {}\nDHCP Server IP: {}\nDNS Server IP: {}\
                  \nGateway IP: {}\nLocal IP: {}\nT1: {}\nT2: {}\nLease Time: {}".format(
                    msg_type,
                    self.subnet_mask,
                    self.dhcp_server_ip,
                    self.dns_server_ip,
                    self.gateway_ip,
                    self.local_ip,
                    self._t1,
                    self._t2,
                    self._lease_time,
                )
            )

        gc.collect()
        return msg_type, xid

    # pylint: disable=too-many-branches, too-many-statements
    def _dhcp_state_machine(self):
        """DHCP state machine without wait loops to enable cooperative multi tasking
        This state machine is used both by the initial blocking lease request and
        the non-blocking DHCP maintenance function"""
        if self._eth.link_status:
            if self._dhcp_state == STATE_DHCP_DISCONN:
                self._dhcp_state = STATE_DHCP_START
        else:
            if self._dhcp_state != STATE_DHCP_DISCONN:
                self._dhcp_state = STATE_DHCP_DISCONN
                self.dhcp_server_ip = BROADCAST_SERVER_ADDR
                self._last_lease_time = 0
                reset_ip = (0, 0, 0, 0)
                self._eth.ifconfig = (reset_ip, reset_ip, reset_ip, reset_ip)
                if self._sock is not None:
                    self._sock.close()
                    self._sock = None

        if self._dhcp_state == STATE_DHCP_START:
            self._start_time = time.monotonic()
            self._transaction_id = (self._transaction_id + 1) & 0x7FFFFFFF
            try:
                self._sock = socket.socket(type=socket.SOCK_DGRAM)
            except RuntimeError:
                if self._debug:
                    print("* DHCP: Failed to allocate socket")
                self._dhcp_state = STATE_DHCP_WAIT
            else:
                self._sock.settimeout(self._response_timeout)
                self._sock.bind((None, 68))
                self._sock.connect((self.dhcp_server_ip, DHCP_SERVER_PORT))
                if self._last_lease_time == 0 or time.monotonic() > (
                    self._last_lease_time + self._lease_time
                ):
                    if self._debug:
                        print("* DHCP: Send discover to {}".format(self.dhcp_server_ip))
                    self.send_dhcp_message(
                        STATE_DHCP_DISCOVER, (time.monotonic() - self._start_time)
                    )
                    self._dhcp_state = STATE_DHCP_DISCOVER
                else:
                    if self._debug:
                        print("* DHCP: Send request to {}".format(self.dhcp_server_ip))
                    self.send_dhcp_message(
                        DHCP_REQUEST, (time.monotonic() - self._start_time), True
                    )
                    self._dhcp_state = STATE_DHCP_REQUEST

        elif self._dhcp_state == STATE_DHCP_DISCOVER:
            if self._sock.available():
                if self._debug:
                    print("* DHCP: Parsing OFFER")
                msg_type, xid = self.parse_dhcp_response()
                if msg_type == DHCP_OFFER:
                    # Check if transaction ID matches, otherwise it may be an offer
                    # for another device
                    if htonl(self._transaction_id) == int.from_bytes(xid, "big"):
                        if self._debug:
                            print(
                                "* DHCP: Send request to {}".format(self.dhcp_server_ip)
                            )
                        self._transaction_id = (self._transaction_id + 1) & 0x7FFFFFFF
                        self.send_dhcp_message(
                            DHCP_REQUEST, (time.monotonic() - self._start_time)
                        )
                        self._dhcp_state = STATE_DHCP_REQUEST
                    else:
                        if self._debug:
                            print("* DHCP: Received OFFER with non-matching xid")
                else:
                    if self._debug:
                        print("* DHCP: Received DHCP Message is not OFFER")

        elif self._dhcp_state == STATE_DHCP_REQUEST:
            if self._sock.available():
                if self._debug:
                    print("* DHCP: Parsing ACK")
                msg_type, xid = self.parse_dhcp_response()
                # Check if transaction ID matches, otherwise it may be
                # for another device
                if htonl(self._transaction_id) == int.from_bytes(xid, "big"):
                    if msg_type == DHCP_ACK:
                        if self._debug:
                            print("* DHCP: Successful lease")
                        self._sock.close()
                        self._sock = None
                        self._dhcp_state = STATE_DHCP_LEASED
                        self._last_lease_time = self._start_time
                        if self._lease_time == 0:
                            self._lease_time = DEFAULT_LEASE_TIME
                        if self._t1 == 0:
                            # T1 is 50% of _lease_time
                            self._t1 = self._lease_time >> 1
                        if self._t2 == 0:
                            # T2 is 87.5% of _lease_time
                            self._t2 = self._lease_time - (self._lease_time >> 3)
                        self._renew_in_sec = self._t1
                        self._rebind_in_sec = self._t2
                        self._eth.ifconfig = (
                            self.local_ip,
                            self.subnet_mask,
                            self.gateway_ip,
                            self.dns_server_ip,
                        )
                        gc.collect()
                    else:
                        if self._debug:
                            print("* DHCP: Received DHCP Message is not ACK")
                else:
                    if self._debug:
                        print("* DHCP: Received non-matching xid")

        elif self._dhcp_state == STATE_DHCP_WAIT:
            if time.monotonic() > (self._start_time + DHCP_WAIT_TIME):
                if self._debug:
                    print("* DHCP: Begin retry")
                self._dhcp_state = STATE_DHCP_START
                if time.monotonic() > (self._last_lease_time + self._rebind_in_sec):
                    self.dhcp_server_ip = BROADCAST_SERVER_ADDR
                if time.monotonic() > (self._last_lease_time + self._lease_time):
                    reset_ip = (0, 0, 0, 0)
                    self._eth.ifconfig = (reset_ip, reset_ip, reset_ip, reset_ip)

        elif self._dhcp_state == STATE_DHCP_LEASED:
            if time.monotonic() > (self._last_lease_time + self._renew_in_sec):
                self._dhcp_state = STATE_DHCP_START
                if self._debug:
                    print("* DHCP: Time to renew lease")

        if self._dhcp_state in (
            STATE_DHCP_DISCOVER,
            STATE_DHCP_REQUEST,
        ) and time.monotonic() > (self._start_time + self._response_timeout):
            self._dhcp_state = STATE_DHCP_WAIT
            if self._sock is not None:
                self._sock.close()
                self._sock = None

    def request_dhcp_lease(self):
        """Request to renew or acquire a DHCP lease."""
        if self._dhcp_state in (STATE_DHCP_LEASED, STATE_DHCP_WAIT):
            self._dhcp_state = STATE_DHCP_START

        while self._dhcp_state not in (STATE_DHCP_LEASED, STATE_DHCP_WAIT):
            self._dhcp_state_machine()

        return self._dhcp_state == STATE_DHCP_LEASED

    def maintain_dhcp_lease(self):
        """Maintain DHCP lease"""
        self._dhcp_state_machine()