Set Station MAC address & validate connect SSID len

[anecdata]

Allow Station MAC address to be set for MAC address randomization, private wifi address, etc., just like the big kids do.

For example, wifi.radio.mac_address = bytes((0x7E, 0xDF, 0xA1, 0xFF, 0xFF, 0xFF)) changes the MAC address of the Station and it connects to wifi, shows up on the router with the new address, and operates as expected.

Tested the following error scenarios successfully:

• ValueError: Invalid MAC address - too short, too long
• TypeError: object with buffer protocol required - None; MAC not of a buffer protocol type
• RuntimeError: Invalid multicast MAC address - any MAC address where bit 0 of the first octet is 1
• RuntimeError: Can't set MAC address while connected - wifi can be enabled / started, but station can't be connected to an AP
• RuntimeError: Station must be started - MAC address can't be set if wifi mode is not STA or STA+AP

Also added input validation for SSID length in the connect() function (max 32 bytes allowed):
wifi.radio.connect("*"*33, secrets["password"]) results in a ValueError
[thanks for finding that bug @jepler]

[anecdata]

uh-oh, now what, feather_m0_adalogger for de_DE failed... shorten my exception strings?

[dhalbert]

uh-oh, now what, feather_m0_adalogger for de_DE failed... shorten my exception strings?

This code is not included in feather_m0_adalogger, so the problem is something else. I build 7.1.0-beta.0 last night without difficulty, so this is surprising. I will take a look and try to replicate the overflow here.

[anecdata]

Old bug was in wifi init: station was started manually using ESP API rather than using common_hal_wifi_radio_start_station, leaving self->sta_mode = 0; This was OK on most typical runs, but caused problems when going into and out of station mode later. The manual start station was an artifact from when set_mode/common_hal_wifi_radio_start_station did more than just manage the wifi mode.

wifi.radio.mac_address behaves like wifi.radio.hostname, but not exactly. The Espressif docs are a little ambiguous. set_hostname is a NETIF API, set_mac_address is a WIFI API. You can change hostname any time after wifi init, but if there is a station connected to an AP, the hostname won't take effect until the next re-connection. You can change mac_address only while wifi mode is Station (or Station + AP), but similar to hostname with respect to active AP connection. Either can be changed when wifi is stopped/!enabled, but of course they won't take effect until the next re-connection.

So now things should be more robust with respect to wifi starts/enables and stops/disables, station mode starting and stopping, etc.:

Adafruit CircuitPython 7.0.0-rc.1-823-ge4f06f69c-dirty on 2021-11-12; Gravitech Cucumber R with ESP32S2
>>> import wifi
>>> from secrets import secrets
>>> 
>>> # after init, wifi is started/enabled, wifi mode is station, and there is no connection
>>> wifi.radio.hostname
'cucumber_r'
>>> f'{wifi.radio.mac_address[0]:02X}'
'7C'
>>> 
>>> # unlike hostname, wifi mode must be station to set mac_address
>>> wifi.radio.stop_station()
>>> wifi.radio.hostname = "hostname7A".encode()
>>> wifi.radio.hostname
'hostname7A'
>>> wifi.radio.mac_address = bytes((0x7A, 0xDF, 0xA1, 0xFF, 0xFF, 0xFF))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: Station must be started
>>> 
>>> # put wifi mode back to station
>>> wifi.radio.start_station()
>>> 
>>> wifi.radio.mac_address = bytes((0x7A, 0xDF, 0xA1, 0xFF, 0xFF, 0xFF))
>>> f'{wifi.radio.mac_address[0]:02X}'
'7A'
>>> 
>>> wifi.radio.connect(secrets["ssid"], secrets["password"])
>>> # ESP32-S2 now shows up in router with hostname "hostname7A" and MAC address 7A:DF:A1:FF:FF:FF
>>> 
>>> # now stop wifi and set new hostname and MAC address
>>> wifi.radio.enabled = False
>>> wifi.radio.hostname = "hostname78".encode()
>>> wifi.radio.hostname
'hostname78'
>>> wifi.radio.mac_address = bytes((0x78, 0xDF, 0xA1, 0xFF, 0xFF, 0xFF))
>>> f'{wifi.radio.mac_address[0]:02X}'
'78'
>>> 
>>> # now start wifi and connect
>>> wifi.radio.enabled = True
>>> wifi.radio.connect(secrets["ssid"], secrets["password"])
>>> # ESP32-S2 now shows up in router with hostname "hostname78" and MAC address 78:DF:A1:FF:FF:FF

[microdev1]

LGTM! Thanks @anecdata.