DNS gets corrupted after a short time

[gskjold]

Board

Custom board with ESP32-S2 mini

Device Description

Custom board (https://amsleser.no) for reading smart meters

Hardware Configuration

GPIO10 = Voltage divider
GPIO13 = LED
GPIO14 = LED
GPIO16 = Serial RX

The following GPIO have been grounded to improve GND routing:
11, 12, 21, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 45, 46

Version

v2.0.9

IDE Name

PlatformIO

Operating System

Linux (Ubuntu)

Flash frequency

40MHz

PSRAM enabled

yes

Upload speed

460800

Description

It connects to the WiFi and has the correct IP for a little while. In my case it changes from 192.168.28.1 to 32.1.70.66 within 10 minutes of starting the code, but from what I hear from users of the project where this was brought to my attention, it seems like the time varies (https://github.com/UtilitechAS/amsreader-firmware)

This could be related to network configuration, but I am out of ideas on how to debug this.

Sketch

https://github.com/gskjold/esp32-wifi-problem


#include <WiFi.h>
#define SSID "SSID"
#define PSK "PSK"
unsigned long lastSysout = 0;

void setup() {
	Serial.begin(115200);
	Serial.setDebugOutput(true);
	WiFi.mode(WIFI_STA);
	WiFi.begin(SSID, PSK);
}
void loop() {
	unsigned long now = millis();
	if(now-lastSysout > 30000) {
		IPAddress dns1 = WiFi.dnsIP(0);
		Serial.printf("DNS: %s\n", dns1.toString().c_str());
		lastSysout = now;
	}
	yield();
}

### Debug Message

```plain
ESP-ROM:esp32s2-rc4-20191025
Build:Oct 25 2019
rst:0x1 (POWERON),boot:0x8 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3ffe6100,len:0x11c
load:0x4004c000,len:0xa28
load:0x40050000,len:0x2740
entry 0x4004c174
[   519][D][WiFiGeneric.cpp:1035] _eventCallback(): Arduino Event: 0 - WIFI_READY
[   558][V][WiFiGeneric.cpp:340] _arduino_event_cb(): STA Started
[   559][D][WiFiGeneric.cpp:1035] _eventCallback(): Arduino Event: 2 - STA_START
[   561][V][WiFiGeneric.cpp:97] set_esp_interface_ip(): Configuring Station static IP: 0.0.0.0, MASK: 0.0.0.0, GW: 0.0.0.0
[   634][V][WiFiGeneric.cpp:355] _arduino_event_cb(): STA Connected: SSID: no23-mob, BSSID: 82:ac:b9:61:3f:7c, Channel: 1, Auth: WPA2_PSK
[   635][D][WiFiGeneric.cpp:1035] _eventCallback(): Arduino Event: 4 - STA_CONNECTED
[   658][V][WiFiGeneric.cpp:369] _arduino_event_cb(): STA Got New IP:192.168.28.100
[   659][D][WiFiGeneric.cpp:1035] _eventCallback(): Arduino Event: 7 - STA_GOT_IP
[   662][D][WiFiGeneric.cpp:1098] _eventCallback(): STA IP: 192.168.28.100, MASK: 255.255.255.0, GW: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 192.168.28.1
DNS: 32.1.70.66
DNS: 32.1.70.66
DNS: 32.1.70.66
DNS: 32.1.70.66
DNS: 32.1.70.66
DNS: 32.1.70.66
DNS: 32.1.70.66

Other Steps to Reproduce

Insert your SSID and PSK in the code, boot and wait at least 10min (maybe more)

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[bertmelis]

dnsIP != localIP != gatewayIP

[gskjold]

Could you elaborate on this? The dns returned from dhcp is the same as gw, but ip is .100

[SuGlider]

I think it has to do with the DHCP server in the WiFi Router.
Maybe the DHCP Lease Renewal Process for a very short Lease period causes the issue...

Would it be possible that the DHCP lease time expires and some other AP/Router responds to the ESP32-S2 STA with a new DNS information?

[gskjold]

No other dhcpv4 exists on this network, but it does have v6. Could that be it? The lease is 1hr though. I have three customers reporting the same issue, so it is not a problem spesific for my network.

[SuGlider]

No other dhcpv4 exists on this network, but it does have v6. Could that be it?

Not sure... you can try it by turning off the v6... just to make sure it is not the cause.

---

I only have a dhcpv4 here.
I have tested it for about 30 minutes and DNS IP has not changed.
I'll leave it working here for a couple hours and check if it changes.

I'll let you know.

[gskjold]

I have two VLAN from my router, one for IoT and one for everything else. The IoT network has its own subnet and WiFi. If I switch to IoT WiFi the problem does not appear actually (just double checked). But if I put in on the "normal" WiFi, it happens within 10mins. The only difference as far as i can tell is the v6 provided by radvd on my pfsense router. There are also some difference in DTIM on WiFi, but I don't think that is the problem.

I just changed the router config to turn off v6, and the DNS on the ESP instantly changed to 0.0.0.0. I reset the device and left it running for 15 minutes. Still no change in DNS, so it could look like we are on the right track. I have to leave for work, but can leave the device running through the day.

I know that at least one of my customers have the same ISP as me, which means he also have native ipv6 on his network. He uses the ISPs standard router, which means we have different brand router and AP.

If there is anything I can do to increase debug logging from the ESP to see what it receives, please let me know.

[SuGlider]

I only have a dhcpv4 here. I have tested it for about 30 minutes and DNS IP has not changed. I'll leave it working here for a couple hours and check if it changes.

I'll let you know.

I have tested it for almost 8 hrs. It keeps the ESP32 DNS IP always the same.
I've a single AP WiFi IPv4 router here.
ESP32 DNS IP address is assigned by the DHCP Server in the AP (WiFi Router).

If I change it in the WiFi router, it changes in the ESP32 after DHCP leasing period expiration (renewed in the re-leasing).

[SuGlider]

If there is anything I can do to increase debug logging from the ESP to see what it receives, please let me know.

One way to increase the debug logging is to set verbose logging in the IDF level.
ESP32 Arduino has all IDF libraries already precompiled only with ERROR logging.
In order to change it, it is necessary to rebuild all IDF libraries or to use Arduino as IDF component and rebuild the whole project (including the IDF and Arduino source code) into a new final binary.

I think that using Arduino as IDF component may be the easiest way to go.
IDF lets you change anything using make menuconfig option.

[gskjold]

I think that using Arduino as IDF component may be the easiest way to go.
IDF lets you change anything using make menuconfig option.

Thanks, I'll try this when I get home. I haven't used IDF that much, but I think I'll find my way around. I'll report back what I find