Although it should not be possible to reenter the function esp_now_recv_cb, this is avoided by an additional boolean variable. It can not be realized by mutex because it would reenter from same thread context. If macro NDEBUG is not defined, an assertion is used.
Avoids parsing IPv6 packets to determine destination address.
Allows using 6Lo over ESP-NOW, which is required due to the low MTU of
ESP-NOW.
Co-authored-by: Gunar Schorcht <gunar@schorcht.net>