DNS requests from Android11 cause disconnects

[tofublock]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am using the latest version of esp32-wifi-manager
• I have searched open and closed issues to ensure it has not already been reported

Description

Building this project out of the box and trying to connect to the captive portal from Android11 I get "Header fields are too long for server to interpret", which is fixed by adjusting CONFIG_HTTPD_MAX_REQ_HDR_LEN=1024 in menuconfig (a lower value might work.)
Connecting to the device after adjusting this I see the captive portal, but am kicked off the connection within about 5 seconds almost every time. After a few tries it sometimes stays on.
I suspect that the problem is most likely with the DNS server. It seems that a lot of DNS requests from the connecting device bring the unwanted behaviour out more.
All this happens with no log output - just a WIFI_EVENT_AP_STADISCONNECTED.

Similar behaviour is seen from a Win10 device with Firefox, where a browser full of AJAX tabs will prevent the captive portal from loading, but without a browser open it comes up fine. In this case at least the connection is not interrupted and navigating to 10.10.0.1 works.

Has anybody else seen this behaviour and found a way around it? My next guess would be to start poking around in the DNS server response, but I'm a bit out of my depth here...

Regardless of that issue, thanks a lot for this project, @tonyp7!

Steps to Reproduce

1. Build and flash master branch as is and try to connect from Android11 => "Header fields are too long for server to interpret"
2. Change CONFIG_HTTPD_MAX_REQ_HDR_LEN=1024 => Captive portal comes up for a few seconds, then WiFi disconnects

System Configuration

ESP-IDF 4.3
ESP32 chip revision 1

[Vxs14]

Hy, i have got the same issue with ESP-IDF 4.2, did you find a solution ?

[tofublock]

Turning off the DNS server helps, at the cost of losing captive portal functionality.

[Vxs14]

Thank you, indeed it helps for the connection but I should like to use some portal functionalities, i will try to rewrite the DNS code

[tofublock]

I found that only replying to a specific domain request helps a lot: Encapsulate lines 159 to 171 of dns_server.c in an if(strcmp(domain, "portal.info") == 0) block.

I'd be curious to know if you figure out more about it!