WiFi IP config issues, need WiFi::reset()

[giorgiogallina]

Dear developers,

I am having troubles in switching between WiFi's STA and AP mode on my Arduino GIGA R1 board.
In my scenario, I do the following:

1. I try to connect to some network (STA)
2. If connection fails, I open AP (with random IP address) to ask credentials from user
3. Once credentials are retrieved (or on timeout, or on error), repeat from point 1.

So far I found that:

• WiFiUDP::endPacket() often fails with error -3003 (NSAPI_ERROR_PARAMETER).
• For some unknown reasons, if I call IPAddress nullip = IPAddress(); WiFi.config(nullip, nullip, nullip, nullip); before WiFi.end() before STA connection, the latter is incredibly more likely to succeed.
• However, if I do so, WiFiUDP:endPacket() always fails as above.
• I found that if I do WiFi = WiFiClass(WiFiInterface::get_default_instance()) after WiFi.end() every time I switch between STA and AP, I have less troubles.

Before AP creation, a random IP address is set as follows:

_wifi_ap_ip = IPAddress((char)random(11, 172), (char)random(0, 255), (char)random(0, 255), 0x01);
WiFi.config(_wifi_ap_ip, _wifi_ap_ip, _wifi_ap_ip, IPAddress(255, 255, 255, 0));

I used to test my code on a protected network and I experienced fewer problems. Then I had to switch to an open network and a mess arose.

I guess a function like a total reset of the WiFi interface with sockets and everything, so to come back to a status as if the Arduino board was just switched on and no connection was attempted, would be advantageous in switching between STA and AP mode.

Thank you

[giorgiogallina]

So far, I have found that I need to call WiFi.disconnect() before WiFi.end(), since the latter does not automatically perform a disconnection. Since I used to invoke WiFi.config(nullip, ...) after explicit disconnection, probably it was not the config that enhanced subsequent probability of successful connection, but rather the explicit disconnection.
[Edit: this is true, but DHCP would not be restored]

In my code, I have also substituted the command

WiFi = WiFiClass(WiFiInterface::get_default_instance());

with the following

NetworkInterface* nif = WiFi.getNetwork();
if (nif != nullptr)
{ nif->set_default_parameters();
}

These modifications seem to improve my program, yet the WiFiUDP::endPacket() still fails with code -3003.
I'll keep debugging and update this issue with more details, if I discover anything interesting.

Meanwhile, I report that in WiFiClass::end(), the command _softAP = nullptr is invoked even if _sofAP was not stopped ("disconnected"), which may cause issues like some of the ones I was experiencing

[giorgiogallina]

On the side, I am wondering if in file ArduinoCore-mbed/libraries/WiFi/src/WiFi.cpp in function WiFiClass::beginAP(...), lines 131-134, a softAPInterface->stop() should be performed before returning.

Moreover, on line 136, the condition result == NSAPI_ERROR_OK seems redundant, isn't it?