Fix DHCP hostname, make it user configurable

- DHCP hostname was set wrong, by trying to add the binary version
of the MAC, it became corrupt and was rejected by the DHCP server.
Default is now fixed, "WIZnetXXXXXXXXXXXX" where X'es are MAC.
- DHCP hostname is now settable on WIZNET5K class using 'hostname'
keyword argument.  If the string contains '{}', the MAC will be
inserted in this position.

Author: xorbit

adafruit_wiznet5k/adafruit_wiznet5k.py

@@ -142,8 +142,10 @@ class WIZNET5K:  # pylint: disable=too-many-public-methods
     :param ~busio.SPI spi_bus: The SPI bus the Wiznet module is connected to.
     :param ~digitalio.DigitalInOut cs: Chip select pin.
     :param ~digitalio.DigitalInOut rst: Optional reset pin.
-    :param bool dhcp: Whether to start DHCP automatically or not.
-    :param str mac: The Wiznet's MAC Address.
+    :param bool is_dhcp: Whether to start DHCP automatically or not.
+    :param list mac: The Wiznet's MAC Address.
+    :param str hostname: The desired hostname, with optional {} to fill in MAC.
+    :param int dhcp_timeout: Timeout in seconds for DHCP response.
     :param bool debug: Enable debugging output.
 
     """
@@ -154,8 +156,8 @@ class WIZNET5K:  # pylint: disable=too-many-public-methods
 
     # pylint: disable=too-many-arguments
     def __init__(
-        self, spi_bus, cs, reset=None, is_dhcp=True, mac=DEFAULT_MAC, debug=False,
-        dhcp_timeout=3
+        self, spi_bus, cs, reset=None, is_dhcp=True, mac=DEFAULT_MAC,
+        hostname=None, dhcp_timeout=3, debug=False
     ):
         self._debug = debug
         self._chip_type = None
@@ -183,13 +185,14 @@ def __init__(
         self._dns = 0
         # Set DHCP
         if is_dhcp:
-            ret = self.set_dhcp(dhcp_timeout)
+            ret = self.set_dhcp(hostname, dhcp_timeout)
             assert ret == 0, "Failed to configure DHCP Server!"
 
-    def set_dhcp(self, response_timeout=3):
+    def set_dhcp(self, hostname=None, response_timeout=3):
         """Initializes the DHCP client and attempts to retrieve
         and set network configuration from the DHCP server.
         Returns True if DHCP configured, False otherwise.
+        :param str hostname: The desired hostname, with optional {} to fill in MAC.
         :param int response_timeout: Time to wait for server to return packet, in seconds.
 
         """
@@ -198,7 +201,7 @@ def set_dhcp(self, response_timeout=3):
         self._src_port = 68
         # Return IP assigned by DHCP
         _dhcp_client = dhcp.DHCP(
-            self, self.mac_address, response_timeout, debug=self._debug
+            self, self.mac_address, hostname, response_timeout, debug=self._debug
         )
         ret = _dhcp_client.request_dhcp_lease()
         if ret == 1:

adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py

@@ -95,14 +95,14 @@ class DHCP:
     """W5k DHCP Client implementation.
     :param eth: Wiznet 5k object
     :param list mac_address: Hardware MAC.
-    :param int timeout: Packet parsing timeout.
-    :param int timeout_response: DHCP Response timeout.
+    :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, response_timeout=3, debug=False):
+    def __init__(self, eth, mac_address, hostname=None, response_timeout=3, debug=False):
         self._debug = debug
         self._response_timeout = response_timeout
         self._mac_address = mac_address
@@ -123,6 +123,7 @@ def __init__(self, eth, mac_address, response_timeout=3, debug=False):
         self.gateway_ip = 0
         self.subnet_mask = 0
         self.dns_server_ip = 0
+
         # Lease configuration
         self._lease_time = 0
         self._last_check_lease_ms = 0
@@ -131,6 +132,11 @@ def __init__(self, eth, mac_address, response_timeout=3, debug=False):
         self._t1 = 0
         self._t2 = 0
 
+        # 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")
+
     def send_dhcp_message(self, state, time_elapsed):
         """Assemble and send a DHCP message packet to a socket.
         :param int state: DHCP Message state.
@@ -192,38 +198,37 @@ def send_dhcp_message(self, state, time_elapsed):
 
         # 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]
+        hostname_len = len(self._hostname)
+        after_hostname = 254 + hostname_len
+        _BUFF[253] = hostname_len
+        _BUFF[254:after_hostname] = self._hostname
 
         if state == DHCP_REQUEST:
             # Set the parsed local IP addr
-            _BUFF[266] = 50
-            _BUFF[267] = 0x04
+            _BUFF[after_hostname] = 50
+            _BUFF[after_hostname+1] = 0x04
 
-            _BUFF[268:272] = self.local_ip
+            _BUFF[after_hostname+2:after_hostname+6] = self.local_ip
             # Set the parsed dhcp server ip addr
-            _BUFF[272] = 54
-            _BUFF[273] = 0x04
-            _BUFF[274:278] = self.dhcp_server_ip
+            _BUFF[after_hostname+6] = 54
+            _BUFF[after_hostname+7] = 0x04
+            _BUFF[after_hostname+8:after_hostname+12] = self.dhcp_server_ip
 
-        _BUFF[278] = 55
-        _BUFF[279] = 0x06
+        _BUFF[after_hostname+12] = 55
+        _BUFF[after_hostname+13] = 0x06
         # subnet mask
-        _BUFF[280] = 1
+        _BUFF[after_hostname+14] = 1
         # routers on subnet
-        _BUFF[281] = 3
+        _BUFF[after_hostname+15] = 3
         # DNS
-        _BUFF[282] = 6
+        _BUFF[after_hostname+16] = 6
         # domain name
-        _BUFF[283] = 15
+        _BUFF[after_hostname+17] = 15
         # renewal (T1) value
-        _BUFF[284] = 58
+        _BUFF[after_hostname+18] = 58
         # rebinding (T2) value
-        _BUFF[285] = 59
-        _BUFF[286] = 255
+        _BUFF[after_hostname+19] = 59
+        _BUFF[after_hostname+20] = 255
 
         # Send DHCP packet
         self._sock.send(_BUFF)