Merge pull request #80 from BiffoBear/dhcp_error_handling

DHCP state machine error handling

Author: FoamyGuy

adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py

@@ -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
@@ -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
@@ -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
@@ -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()
@@ -281,16 +278,16 @@ def parse_dhcp_response(
             )
 
         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
@@ -323,8 +320,8 @@ 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]
@@ -427,65 +424,79 @@ 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):

examples/wiznet5k_wsgiservertest.py

@@ -0,0 +1,138 @@
+# SPDX-FileCopyrightText: 2021 Patrick Van Oosterwijck @ Silicognition LLC
+#
+# SPDX-License-Identifier: MIT
+#
+# This demo was tested with the PoE-FeatherWing, which contains a 24AA02E48
+# chip to provide a globally unique MAC address, but can also work without
+# this chip for testing purposes by using a hard coded MAC.
+#
+# It also contains a `get_static_file` function that demonstrates how to
+# use a generator to serve large static files without using up too much
+# memory.  To avoid having to put extra files in the repo, it just serves
+# `code.py` which isn't very large, but to properly test it, adjust the code
+# to serve an image of several 100 kB to see how it works.
+#
+# There's also an endpoint that demonstrates that `requests` can be used to
+# get data from another socket and serve it.
+#
+
+import board
+import busio
+import digitalio
+import neopixel
+
+import adafruit_requests as requests
+from adafruit_wsgi.wsgi_app import WSGIApp
+from adafruit_wiznet5k.adafruit_wiznet5k import WIZNET5K
+import adafruit_wiznet5k.adafruit_wiznet5k_socket as socket
+import adafruit_wiznet5k.adafruit_wiznet5k_wsgiserver as server
+
+
+print("Wiznet5k Web Server Test")
+
+
+def get_mac(i2c_obj):
+    "Read MAC from 24AA02E48 chip and return it"
+    mac_addr = bytearray(6)
+    while not i2c_obj.try_lock():
+        pass
+    i2c_obj.writeto(0x50, bytearray((0xFA,)))
+    i2c_obj.readfrom_into(0x50, mac_addr, start=0, end=6)
+    i2c_obj.unlock()
+    return mac_addr
+
+
+def get_static_file(filename):
+    "Static file generator"
+    with open(filename, "rb") as f:
+        b = None
+        while b is None or len(b) == 2048:
+            b = f.read(2048)
+            yield b
+
+
+# Status LED
+led = neopixel.NeoPixel(board.NEOPIXEL, 1)
+led.brightness = 0.3
+led[0] = (255, 0, 0)
+
+# Chip Select for PoE-FeatherWing and Adafruit Ethernet FeatherWing
+cs = digitalio.DigitalInOut(board.D10)
+# Chip Select for Particle Ethernet FeatherWing
+# cs = digitalio.DigitalInOut(board.D5)
+
+# Initialize SPI bus
+spi_bus = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
+
+try:
+    # Initialize the I2C bus to read the MAC
+    i2c = busio.I2C(board.SCL, board.SDA)
+    # Read the MAC from the 24AA02E48 chip
+    mac = get_mac(i2c)
+except (RuntimeError, OSError):
+    # Hard coded MAC if there is no 24AA02E48
+    mac = b"\xFE\xED\xDE\xAD\xBE\xEF"
+
+# Initialize Ethernet interface with DHCP
+eth = WIZNET5K(spi_bus, cs, mac=mac)
+
+# Initialize a requests object with a socket and ethernet interface
+requests.set_socket(socket, eth)
+
+
+# Here we create our application, registering the
+# following functions to be called on specific HTTP GET requests routes
+
+web_app = WSGIApp()
+
+
+@web_app.route("/led/<r>/<g>/<b>")
+def led_on(request, r, g, b):  # pylint: disable=unused-argument
+    print("LED handler")
+    led.fill((int(r), int(g), int(b)))
+    return ("200 OK", [], ["LED set!"])
+
+
+@web_app.route("/")
+def root(request):  # pylint: disable=unused-argument
+    print("Root WSGI handler")
+    return ("200 OK", [], ["Root document"])
+
+
+@web_app.route("/large")
+def large(request):  # pylint: disable=unused-argument
+    print("Large pattern handler")
+    return ("200 OK", [], ["*-.-" * 2000])
+
+
+@web_app.route("/code")
+def code(request):  # pylint: disable=unused-argument
+    print("Static file code.py handler")
+    return ("200 OK", [], get_static_file("code.py"))
+
+
+@web_app.route("/btc")
+def btc(request):  # pylint: disable=unused-argument
+    print("BTC handler")
+    r = requests.get("http://api.coindesk.com/v1/bpi/currentprice/USD.json")
+    result = r.text
+    r.close()
+    return ("200 OK", [], [result])
+
+
+# Here we setup our server, passing in our web_app as the application
+server.set_interface(eth)
+wsgiServer = server.WSGIServer(80, application=web_app)
+
+print("Open this IP in your browser: ", eth.pretty_ip(eth.ip_address))
+
+# Start the server
+wsgiServer.start()
+led[0] = (0, 0, 255)
+
+while True:
+    # Our main loop where we have the server poll for incoming requests
+    wsgiServer.update_poll()
+    # Maintain DHCP lease
+    eth.maintain_dhcp_lease()
+    # Could do any other background tasks here, like reading sensors

optional_requirements.txt

@@ -1,3 +1,4 @@
 # SPDX-FileCopyrightText: 2022 Alec Delaney, for Adafruit Industries
 #
 # SPDX-License-Identifier: Unlicense
+pytest