Using reverse-engineered features for better meshing

[Juul]

This seems to be capable of both injecting arbitrary packets and a limited promiscuous mode that can capture packets addressed to the broadcast MAC address or the MAC address of the device.

I haven't tried it, but it looks like it is enough that you can do something like adhoc mode by having all devices in SOFTAP mode and either using the broadcast address or setting all nodes to have the same MAC.

[paidforby]

There is one problem, from previous experience, I know for a fact that the ESP truncates packets captured in promiscuous mode to ~128 bytes. Wonder how much this would constrain the data we need to send?

[paidforby]

Also, the nodeMCU firmware does not provide a function for enabling promiscuous mode, we could call it from Lua-wrapped C or modify the firmware to provide this functionality or just switch to writing the protocol in C. All of these are interesting possibilities, but I'm not sure if any are worth pursuing for what may just be a limited hack?

[paidforby]

After reading through this more I found a few interesting things:

• They apparently are not using promiscuous mode (which would allow the ESP to see all packets in the air, but truncate them), but rather just sniffing raw packets with wifi_raw_set_recv_cb(a feature of the esp iot sdk? having trouble finding this in the API reference, I think this is from an old SDK and may no longer be available in newer versions Espressif's closed source API)
• This sniffing only allows them to see only broadcast packets or ones directed to their MAC address. These would be all we need for meshing.
• I'm not sure what they mean by "reverse-engineering the wifi stack", but I suppose this person wants to expose full sniffing of raw wifi packets. This is not our concern, so there is no need for reverse engineering as I believe we can use the raw packet functions as they are.
• sending packets is done with the wifi_send_pkt_freedom function (this is in the API reference along with register/unregister callback functions)

All in all, this seems like a viable, if not the best solution (assuming I can find documentation on receiving raw packets). It isn't any less of a hack than what we are already doing in Lua.