Uplink with FPort 255 and invalid MIC!

[mohsenmoqadam]

Uplink with FPort 255 and invalid MIC!

[terrillmoore]

The LMIC sends an ACK to the confirmed downlink message without a port number because there's no application payload. I guess that the Network service is not tested yet for this situation. Check https://github.com/mcci-catena/arduino-lmic/blob/master/doc/LoRaWAN-at-a-glance.pdf which correctly says: "FPort is present if any payload bytes are present" but forgets to say "if and only if". My guess is that the NS code is not anticipating this case, and is instead reading off the end of the buffer (and assuming the MIC starts one byte late).

Best regards,
--Terry

[mohsenmoqadam]

Thanks, Terry.
Based on your guidance if FramePayload is empty, then we must calculate MIC with: MHDR|DevAddr|FCtrl|FCnt|FOpts.

Now my problem is solved and all things are okay, again I would like to admire your subtlety and quick response