Some ressources to be update on the go
ESP NOW protocol:
https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/wifi/esp_now.html
http://wiki.ai-thinker.com/_media/esp8266/docs/30c_esp-now_user_guide_en.pdf
Linux Wireless Networking:
https://www.linux.com/blog/linux-wireless-networking-short-walk
After swimming in a lot of information, I think I found the perfect starting point to send and receive raw 802.11 packet !
https://warmcat.com/git/packetspammer
Update 12/14/2018: Here is an other lib to send and receive raw wifi packet, It even has a python binding...To be tested soon..
https://github.com/kismetwireless/lorcon
Update 03/01/2019: The useful information was here
https://www.kernel.org/doc/Documentation/networking/mac80211-injection.txt
This is very good work, please keep it up!
The ESP-Now can be a good alternative for low cost home nodes. I am not ready to drop my RFM69 radios yet, but soon it might be possible.
I keep seeing this 20 devices limitation (or 10 with encryption). Do you know where it comes from? could a more powerful GW handle more ?