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Fix random CaptivePortal.ino crashes (#6206)

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CaptivePortal.ino example did randomly crash for me ... so I start investigate ;-)

Decoding stack results
0x4016faea: WiFiUDP::write(unsigned char const*, unsigned int) at C:\Users\knoeb\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.5\libraries\WiFi\src\WiFiUdp.cpp line 201
0x400d4a4a: DNSServer::replyWithIP() at C:\Users\knoeb\AppData\Local\Temp\arduino_build_486825\sketch\src\DNSServer\DNSServer.cpp line 187
0x400d4d01: DNSServer::processNextRequest() at C:\Users\knoeb\AppData\Local\Temp\arduino_build_486825\sketch\src\DNSServer\DNSServer.cpp line 117
0x400d3e81: loop() at D:\Drive\Dokumente\HTL_Lehrer\2021_22\Projekte\Stromzaehler_Patrick\arduino/arduino.ino line 1078
0x400dd545: loopTask(void*) at C:\Users\knoeb\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.5\cores\esp32\main.cpp line 37
0x4008a0de: vPortTaskWrapper at /home/runner/work/esp32-arduino-lib-builder/esp32-arduino-lib-builder/esp-idf/components/freertos/port.c line 143

I found with wireshark a possibility to trigger the crash on demand is:
nslookup 3.1o1osr0092ons87rp375p1pq8q066o8p56or1sqsps6rs17r4384q9748qr1r52.699p1r741q737393648s29917o45p16q50rn517rnsp73pp68p1q259s92693qp.s607408539s0p06p7559os0899866344r7qq7rpns960o9576q65.r5n94r5so9784pq1.i.03.s.sophosxl.net

The problem was that QNameLength is a signed byte and therefore its not possible to count up to 255. Additionally we need 256 bytes for the QName string to accommodate for the zero termination.
This commit is contained in:
Patrick Behal
2022-01-31 12:25:43 +01:00
committed by GitHub
parent 7a6dae02aa
commit ef35baffb0
1 changed files with 3 additions and 3 deletions
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4
libraries/DNSServer/src/DNSServer.h
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@ -66,8 +66,8 @@ struct DNSHeader
struct DNSQuestion struct DNSQuestion
{ {
uint8_t QName[255] ; uint8_t QName[256] ; //need 1 Byte for zero termination!
int8_t QNameLength ; uint8_t QNameLength ;
uint16_t QType ; uint16_t QType ;
uint16_t QClass ; uint16_t QClass ;
} ; } ;