dhcp.py returns 0 value in parse_dhcp_response(), causes dhcp_state_machine() to raise exception

[schaefer01]

hi,
I've got a firewall issue, parse_dhcp_response() fails and returns 0, but dhcp_state_machine() does not
test for error response, assumes a value uses the value in a conditional statement, and raises this exception:

object with buffer protocol required

the code is here:
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"): <------- exception raised here

[schaefer01]

as a side note, there are mutiple different error paths in parse_dhcp_response() that all return 0's
it would be nice to have a diagnostic to indicate which failure path is taken when a failure occurs

[anecdata]

@schaefer01 Can you re-test the code from PR 80 and confirm it solves your issue?

[schaefer01]

hi,
yes, thank you.
bob s.