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, "l"):
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, "l"):
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 send_dhcp_message(self, state, time_elapsed):
"""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 renewal.
"""
# 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, 'l')
_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, 'b')
_BUFF[10] = flags[1]
_BUFF[11] = flags[0]
# NOTE: Skipping cidaddr/yiaddr/siaddr/giaddr
# as they're already set to 0.0.0.0
# 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 in range(0, len(self._mac_address)):
_BUFF[246+mac] = self._mac_address[mac]
# Option - Host Name
_BUFF[252] = 12
_BUFF[253] = len(b"Wiznet") + 6
_BUFF[254:260] = b"WIZnet"
for mac in range(0, 5):
_BUFF[260+mac] = self._mac_address[mac]
if state == DHCP_REQUEST:
# Set the parsed local IP addr
_BUFF[266] = 50
_BUFF[267] = 0x04
_BUFF[268:272] = self.local_ip
# Set the parsed dhcp server ip addr
_BUFF[272] = 54
_BUFF[273] = 0x04
_BUFF[274:278] = self.dhcp_server_ip
_BUFF[278] = 55
_BUFF[279] = 0x06
# subnet mask
_BUFF[280] = 1
# routers on subnet
_BUFF[281] = 3
# DNS
_BUFF[282] = 6
# domain name
_BUFF[283] = 15
# renewal (T1) value
_BUFF[284] = 58
# rebinding (T2) value
_BUFF[285] = 59
_BUFF[286] = 255
# Send DHCP packet
self._sock.send(_BUFF)
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, "l")
_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, "b")
_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)