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DHCP state machine error handling #80

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Merged
merged 9 commits into from
Jan 9, 2023
Merged

DHCP state machine error handling #80

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d186cbe
Renamed wiznet5k_wsgiserver_test.py to wiznet5k_wsgiservertest.py to …
Dec 15, 2022
b55bdd2
Completed tests for __init__ and send_dhcp_message. Fixed two off-by-…
Dec 15, 2022
6469eac
Completed tests for parse_dhcp_message. Fixed an off-by-one error in …
Dec 15, 2022
2161e7f
Added tested for parse_dhcp_response failures. Fixed the logic for ch…
Dec 15, 2022
449010a
Refactored parse_dhcp_response to raise ValueError instead of returni…
Dec 15, 2022
caa5136
Altered the _dhcp_state_machine to handle exceptions raised by send_d…
Dec 16, 2022
26069ea
Added an else to the try statements.
Dec 16, 2022
3c2f2ac
Merge branch 'adafruit:main' into dhcp_error_handling
BiffoBear Dec 21, 2022
6bc9f63
Merge branch 'main' into dhcp_error_handling
FoamyGuy Jan 9, 2023
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151 changes: 80 additions & 71 deletions adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@
DHCP_HLENETHERNET = const(0x06)
DHCP_HOPS = const(0x00)

MAGIC_COOKIE = const(0x63825363)
MAGIC_COOKIE = b"c\x82Sc" # Four bytes 99.130.83.99
MAX_DHCP_OPT = const(0x10)

# Default DHCP Server port
Expand Down Expand Up @@ -179,7 +179,7 @@ def send_dhcp_message(
# 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
_BUFF[4:8] = self._initial_xid

# seconds elapsed
_BUFF[8] = (int(time_elapsed) & 0xFF00) >> 8
Expand All @@ -195,18 +195,15 @@ def send_dhcp_message(
# 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)
_BUFF[12:16] = 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
_BUFF[236:240] = MAGIC_COOKIE

# Option - DHCP Message Type
_BUFF[240] = 53
Expand Down Expand Up @@ -262,10 +259,10 @@ def send_dhcp_message(
# pylint: disable=too-many-branches, too-many-statements
def parse_dhcp_response(
self,
) -> Union[Tuple[int, bytes], Tuple[int, int]]:
) -> Tuple[int, bytearray]:
"""Parse DHCP response from DHCP server.

:return Union[Tuple[int, bytes], Tuple[int, int]]: DHCP packet type.
:return Tuple[int, bytearray]: DHCP packet type and ID.
"""
# store packet in buffer
_BUFF = self._sock.recv()
Expand All @@ -274,22 +271,20 @@ def parse_dhcp_response(

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

xid = _BUFF[4:8]
if bytes(xid) < self._initial_xid:
print("f")
return 0, 0
if bytes(xid) != self._initial_xid:
raise ValueError("DHCP response ID mismatch.")

self.local_ip = tuple(_BUFF[16:20])
if _BUFF[28:34] == 0:
return 0, 0
# Check that there is a server ID.
if _BUFF[28:34] == b"\x00\x00\x00\x00\x00\x00":
raise ValueError("No DHCP server ID in the response.")

if int.from_bytes(_BUFF[235:240], "big") != MAGIC_COOKIE:
return 0, 0
if _BUFF[236:240] != MAGIC_COOKIE:
raise ValueError("No DHCP Magic Cookie in the response.")

# -- Parse Packet, VARIABLE -- #
ptr = 240
Expand Down Expand Up @@ -322,8 +317,8 @@ def parse_dhcp_response(
ptr += 1
opt_len = _BUFF[ptr]
ptr += 1
self.gateway_ip = tuple(_BUFF[ptr : ptr + opt_len])
ptr += opt_len
self.gateway_ip = tuple(_BUFF[ptr : ptr + 4])
ptr += opt_len # still increment even though we only read 1 addr.
elif _BUFF[ptr] == DNS_SERVERS:
ptr += 1
opt_len = _BUFF[ptr]
Expand Down Expand Up @@ -426,65 +421,79 @@ def _dhcp_state_machine(self) -> None:
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)
try:
msg_type, xid = self.parse_dhcp_response()
except ValueError as error:
if self._debug:
print(error)
else:
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._transaction_id = (self._transaction_id + 1) & 0x7FFFFFFF
self.send_dhcp_message(
DHCP_REQUEST, (time.monotonic() - self._start_time)
)
self._dhcp_state = STATE_DHCP_REQUEST
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 OFFER with non-matching xid")
else:
if self._debug:
print("* DHCP: Received DHCP Message is not OFFER")
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()
try:
msg_type, xid = self.parse_dhcp_response()
except ValueError as error:
if self._debug:
print(error)
else:
# 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 DHCP Message is not ACK")
else:
if self._debug:
print("* DHCP: Received non-matching xid")
print("* DHCP: Received non-matching xid")

elif self._dhcp_state == STATE_DHCP_WAIT:
if time.monotonic() > (self._start_time + DHCP_WAIT_TIME):
Expand Down
0 examples/wiznet5k_wsgiserver_test.py → examples/wiznet5k_wsgiservertest.py
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File renamed without changes.
1 change: 1 addition & 0 deletions optional_requirements.txt
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
# SPDX-FileCopyrightText: 2022 Alec Delaney, for Adafruit Industries
#
# SPDX-License-Identifier: Unlicense
pytest
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