Hang w/2.2 SDK and WiFi.scanNetworks in AP mode with TCP in-flight

[earlephilhower]

Basic Infos

WiFi.scanNetworks in SDK 2.2 never returns to the main app under certain conditions when in AP mode.

No WDT or stack dump is produced, the ESP simply never returns from the call, no data is sent over WiFi, and a reset is required to regain operation.

Hardware

Hardware: WeMos D1 mini
Core Version: Failing: GIT head ; passing: GIT (f9ac524).

Description

Discovered this while rebuilding my app PsychoPlug (https://github.com/earlephilhower/psychoplug) with latest GIT head. Sample code below reproduces the failure using the HTTPSServer example code + a bit of my own stuff that produced the web page.

ESP initializes and goes into AP mode and has a SSL (443) server to allow a cell phone or laptop to connect and set the configuration of the app. The setup.html page is generated and sent line-by-line using client.print()s to a WiFiClientSecure object.

Headers are sent, the HTML prefixes, and some intro form fields.

Then WiFi.scanNetworks() is called to generate a popup menu on the page to allow the user to select which AP to connect to in operational mode.

Under SDK 2.2, this call to wifi.scannetworks() never returns. Under the commit right before SDK2.2 it operates as expected.

Replacing the call in the sample script with

int cnt = 0; // int cnt = WiFi.scanNetworks();

also works properly.

Adding a Serial.printf before it makes it work, too:

Serial.printf("1234\n");
int cnt = WiFi.scanNetworks();

Putting in a yield() prior to the call, or changing to 80MHz operation, doesn't fix it and it still crashes.

Erasing the flash settings area (and the entire chip) has no effect.

To Reproduce

Run script, connect to "testap" (no password) and go to https://192.168.1.4/ . On 2.1 you'll get a header and a popup menu of detected APs, as well as serial output showing

....
new client
+SentSetupHTML   (started the page xmission)
done
-SendSetupHTML   (ended page xmission)

When it hangs the "-SendSetupHTML" line never comes and no WDT fires, the ESP just hangs forever.

Settings in IDE

Module: Wemos D1 Mini
Flash Size: 4MB
CPU Frequency: 160Mhz
LWIP: v2 (lo mem & hi BW show same behavior)

Sketch

#include <ESP8266WiFi.h>

// The certificate is stored in PMEM 
static const uint8_t x509[] PROGMEM = {
  0x30, 0x82, 0x01, 0x3d, 0x30, 0x81, 0xe8, 0x02, 0x09, 0x00, 0xfe, 0x56,
  0x46, 0xf2, 0x78, 0xc6, 0x51, 0x17, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86,
  0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x0b, 0x05, 0x00, 0x30, 0x26, 0x31,
  0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x0c, 0x07, 0x45, 0x53,
  0x50, 0x38, 0x32, 0x36, 0x36, 0x31, 0x12, 0x30, 0x10, 0x06, 0x03, 0x55,
  0x04, 0x03, 0x0c, 0x09, 0x31, 0x32, 0x37, 0x2e, 0x30, 0x2e, 0x30, 0x2e,
  0x31, 0x30, 0x1e, 0x17, 0x0d, 0x31, 0x37, 0x30, 0x33, 0x31, 0x38, 0x31,
  0x34, 0x34, 0x39, 0x31, 0x38, 0x5a, 0x17, 0x0d, 0x33, 0x30, 0x31, 0x31,
  0x32, 0x35, 0x31, 0x34, 0x34, 0x39, 0x31, 0x38, 0x5a, 0x30, 0x26, 0x31,
  0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x0c, 0x07, 0x45, 0x53,
  0x50, 0x38, 0x32, 0x36, 0x36, 0x31, 0x12, 0x30, 0x10, 0x06, 0x03, 0x55,
  0x04, 0x03, 0x0c, 0x09, 0x31, 0x32, 0x37, 0x2e, 0x30, 0x2e, 0x30, 0x2e,
  0x31, 0x30, 0x5c, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7,
  0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x4b, 0x00, 0x30, 0x48, 0x02,
  0x41, 0x00, 0xc6, 0x72, 0x6c, 0x12, 0xe1, 0x20, 0x4d, 0x10, 0x0c, 0xf7,
  0x3a, 0x2a, 0x5a, 0x49, 0xe2, 0x2d, 0xc9, 0x7a, 0x63, 0x1d, 0xef, 0xc6,
  0xbb, 0xa3, 0xd6, 0x6f, 0x59, 0xcb, 0xd5, 0xf6, 0xbe, 0x34, 0x83, 0x33,
  0x50, 0x80, 0xec, 0x49, 0x63, 0xbf, 0xee, 0x59, 0x94, 0x67, 0x8b, 0x8d,
  0x81, 0x85, 0x23, 0x24, 0x06, 0x52, 0x76, 0x55, 0x9d, 0x18, 0x09, 0xb3,
  0x3c, 0x10, 0x40, 0x05, 0x01, 0xf3, 0x02, 0x03, 0x01, 0x00, 0x01, 0x30,
  0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x0b,
  0x05, 0x00, 0x03, 0x41, 0x00, 0x69, 0xdc, 0x6c, 0x9b, 0xa7, 0x62, 0x57,
  0x7e, 0x03, 0x01, 0x45, 0xad, 0x9a, 0x83, 0x90, 0x3a, 0xe7, 0xdf, 0xe8,
  0x8f, 0x46, 0x00, 0xd3, 0x5f, 0x2b, 0x0a, 0xde, 0x92, 0x1b, 0xc5, 0x04,
  0xc5, 0xc0, 0x76, 0xf4, 0xf6, 0x08, 0x36, 0x97, 0x27, 0x82, 0xf1, 0x60,
  0x76, 0xc2, 0xcd, 0x67, 0x6c, 0x4b, 0x6c, 0xca, 0xfd, 0x97, 0xfd, 0x33,
  0x9e, 0x12, 0x67, 0x6b, 0x98, 0x7e, 0xd5, 0x80, 0x8f
};

// And so is the key.  These could also be in DRAM
static const uint8_t rsakey[] PROGMEM = {
  0x30, 0x82, 0x01, 0x3a, 0x02, 0x01, 0x00, 0x02, 0x41, 0x00, 0xc6, 0x72,
  0x6c, 0x12, 0xe1, 0x20, 0x4d, 0x10, 0x0c, 0xf7, 0x3a, 0x2a, 0x5a, 0x49,
  0xe2, 0x2d, 0xc9, 0x7a, 0x63, 0x1d, 0xef, 0xc6, 0xbb, 0xa3, 0xd6, 0x6f,
  0x59, 0xcb, 0xd5, 0xf6, 0xbe, 0x34, 0x83, 0x33, 0x50, 0x80, 0xec, 0x49,
  0x63, 0xbf, 0xee, 0x59, 0x94, 0x67, 0x8b, 0x8d, 0x81, 0x85, 0x23, 0x24,
  0x06, 0x52, 0x76, 0x55, 0x9d, 0x18, 0x09, 0xb3, 0x3c, 0x10, 0x40, 0x05,
  0x01, 0xf3, 0x02, 0x03, 0x01, 0x00, 0x01, 0x02, 0x40, 0x35, 0x0b, 0x74,
  0xd3, 0xff, 0x15, 0x51, 0x44, 0x0f, 0x13, 0x2e, 0x9b, 0x0f, 0x93, 0x5c,
  0x3f, 0xfc, 0xf1, 0x17, 0xf9, 0x72, 0x94, 0x5e, 0xa7, 0xc6, 0xb3, 0xf0,
  0xfe, 0xc9, 0x6c, 0xb1, 0x1e, 0x83, 0xb3, 0xc6, 0x45, 0x3a, 0x25, 0x60,
  0x7c, 0x3d, 0x92, 0x7d, 0x53, 0xec, 0x49, 0x8d, 0xb5, 0x45, 0x10, 0x99,
  0x9b, 0xc6, 0x22, 0x3a, 0x68, 0xc7, 0x13, 0x4e, 0xb6, 0x04, 0x61, 0x21,
  0x01, 0x02, 0x21, 0x00, 0xea, 0x8c, 0x21, 0xd4, 0x7f, 0x3f, 0xb6, 0x91,
  0xfa, 0xf8, 0xb9, 0x2d, 0xcb, 0x36, 0x36, 0x02, 0x5f, 0xf0, 0x0c, 0x6e,
  0x87, 0xaa, 0x5c, 0x14, 0xf6, 0x56, 0x8e, 0x12, 0x92, 0x25, 0xde, 0xb3,
  0x02, 0x21, 0x00, 0xd8, 0x99, 0x01, 0xf1, 0x04, 0x0b, 0x98, 0xa3, 0x71,
  0x56, 0x1d, 0xea, 0x6f, 0x45, 0xd1, 0x36, 0x70, 0x76, 0x8b, 0xab, 0x69,
  0x30, 0x58, 0x9c, 0xe0, 0x45, 0x97, 0xe7, 0xb6, 0xb5, 0xef, 0xc1, 0x02,
  0x21, 0x00, 0xa2, 0x01, 0x06, 0xc0, 0xf2, 0xdf, 0xbc, 0x28, 0x1a, 0xb4,
  0xbf, 0x9b, 0x5c, 0xd8, 0x65, 0xf7, 0xbf, 0xf2, 0x5b, 0x73, 0xe0, 0xeb,
  0x0f, 0xcd, 0x3e, 0xd5, 0x4c, 0x2e, 0x91, 0x99, 0xec, 0xb7, 0x02, 0x20,
  0x4b, 0x9d, 0x46, 0xd7, 0x3c, 0x01, 0x4c, 0x5d, 0x2a, 0xb0, 0xd4, 0xaa,
  0xc6, 0x03, 0xca, 0xa0, 0xc5, 0xac, 0x2c, 0xe0, 0x3f, 0x4d, 0x98, 0x71,
  0xd3, 0xbd, 0x97, 0xe5, 0x55, 0x9c, 0xb8, 0x41, 0x02, 0x20, 0x02, 0x42,
  0x9f, 0xd1, 0x06, 0x35, 0x3b, 0x42, 0xf5, 0x64, 0xaf, 0x6d, 0xbf, 0xcd,
  0x2c, 0x3a, 0xcd, 0x0a, 0x9a, 0x4d, 0x7c, 0xad, 0x29, 0xd6, 0x36, 0x57,
  0xd5, 0xdf, 0x34, 0xeb, 0x26, 0x03
};
 

WiFiServerSecure server(443);
static IPAddress setupIP = {192, 168, 4, 1};
static IPAddress setupMask = {255, 255, 255, 0};
static const char *ssid = "testap";
#define DOCTYPE "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">"
#define ENCODING "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\"/>\n"
#define WebPrintf(c, fmt, ...) { char webBuff[192]; snprintf_P(webBuff, sizeof(webBuff), PSTR(fmt), ## __VA_ARGS__); (c).print(webBuff); delay(10);}
#define WebPrintfPSTR(c, fmt, ...) { char webBuff[192]; snprintf_P(webBuff, sizeof(webBuff), (fmt), ## __VA_ARGS__); (c).print(webBuff); delay(10);}


void WebHeaders(WiFiClientSecure &client, PGM_P /*const char **/headers)
{
  WebPrintf(client, "HTTP/1.1 200 OK\r\n");
  WebPrintf(client, "Server: PsychoPlug\r\n");
  WebPrintf(client, "Content-type: text/html\r\n");
  WebPrintf(client, "Cache-Control: no-cache, no-store, must-revalidate\r\n");
  WebPrintf(client, "Pragma: no-cache\r\n");
  WebPrintf(client, "Connection: close\r\n");
  WebPrintf(client, "Expires: 0\r\n");
  if (headers) {
    WebPrintfPSTR(client, headers);
  }
  WebPrintf(client, "\r\n");
}

void WebFormText(WiFiClientSecure &client, /*const char **/ PGM_P label, const char *name, const char *value, bool enabled)
{
  WebPrintfPSTR(client, label);
  WebPrintf(client, ": <input type=\"text\" name=\"%s\" id=\"%s\" value=\"%s\" %s><br>\n", name, name, value, !enabled?"disabled":"");
}

void setup() {
  Serial.begin(115200);
  delay(10);

  // prepare GPIO2
  pinMode(2, OUTPUT);
  digitalWrite(2, 0);
  
  // Connect to WiFi network
  Serial.println();
  Serial.println();
  Serial.print("Starting up SSID: ");
  Serial.println(ssid);

  WiFi.mode(WIFI_AP);
  WiFi.softAPConfig(setupIP, setupIP, setupMask);
  WiFi.softAP(ssid);

  // Set the certificates from PMEM (if using DRAM remove the _P from the call)  
  server.setServerKeyAndCert_P(rsakey, sizeof(rsakey), x509, sizeof(x509));

  // Start the server
  server.begin();
  Serial.println("Server started");
  Serial.println(setupIP);
}

void loop() {
  // Check if a client has connected
  WiFiClientSecure client = server.available();
  if (!client) {
    return;
  }
  
  // Wait until the client sends some data
  Serial.println("new client");
  unsigned long timeout = millis() + 3000;
  while(!client.available() && millis() < timeout){
    delay(1);
  }
  if (millis() > timeout) {
    Serial.println("timeout");
    client.flush();
    client.stop();
    return;
  }

  // Read the first line of the request
//  String req = client.readStringUntil('\r');
//  Serial.println(req);
//  client.flush();

  Serial.printf("+SendSetupHTML\n");
  WebHeaders(client, NULL);
  WebPrintf(client, DOCTYPE);
  WebPrintf(client, "<html><head><title>PsychoPlug Setup</title>" ENCODING "</head>\n");
  WebPrintf(client, "<body><h1>PsychoPlug Setup</h1>\n");
  WebPrintf(client, "<form action=\"config.html\" method=\"POST\">\n");

  WebPrintf(client, "<br><h1>WiFi Network</h1>\n");
  WebFormText(client, PSTR("SSID"), "ssid", ssid, true);
  int cnt = WiFi.scanNetworks();
  if (cnt==0) {
    WebPrintf(client, "Discovered networks: No WIFI networks detected.<br>\n");
  } else {
    WebPrintf(client, "Discovered networks: <select onchange=\"setval(this)\">");
    WebPrintf(client, "<option></option>");
    for (byte i=0; i<cnt; i++) {
      WebPrintf(client, "<option>%s</option>", WiFi.SSID(i).c_str());
    }
    WebPrintf(client, "</select><br>\n");
  }
  Serial.printf("done\n");
  WebPrintf(client, "</form></body></html>\n");
  Serial.printf("-SendSetupHTML\n");
}