Hi Peter,

you have to create a Layer 2 interface somehow on top of your serial link - L2TP on PPP may be one way to do it, but you stack quite a bit of headers and can't really use the broadcast nature of the medium as you say. I'm not an expert on those serial drone radios, there may be some better readily available solutions. You could send the Ethernet frame as is with some checksumming I guess. Channel access is probably not ideal either (there is no CSMA/CA or arbitration).

How fast is your drone radio? I hope its more than 9600 baud ... :)

Cheers, Simon

On Wednesday, July 12, 2023 2:14:48 PM CEST Peter Milani wrote:

Thanks Simon,

So to clarify, PPP relies on a higher level layer than what BATMAN uses? So you have to create an ethernet layer 2 interface using l2tp. But are more or less restricted to point to point routing in that case which l2tp will be travelling across. So there's no alternate method you're aware of that can make use of the general broadcast nature of the underlying radio... e.g.. from an application perspective, I can transmit a serial message from one radio and pick that message with multiple receivers?

cheers Peter

On Wed, 12 Jul 2023 at 21:55, Simon Wunderlich sw@simonwunderlich.de

wrote:

...

On Wednesday, July 12, 2023 6:29:50 AM CEST petermilani80@gmail.com wrote:

...

Hi All,

I've just started using batman and was trying to see if I could get it to work over a serial radio link such as the simple serial devices commonly used in cheap drone telemetry. The goal here is to enable low bandwidth

but

...

adhoc ip networking.

I had set up a pair of radios to connect using pppd and I was wondering

if I

...

could utilise batman to try and create a mesh. An example of setting up

the

...

serial ports as ppp interfaces:

$ sudo pppd /dev/ttyUSB0 57600 noauth nodetach 10.42.5.5:

That works fine but applying batman to that interface was unsuccessful. I think that was due to limitations in the ppp and interfaces created by pppd: e.g.

$ sudo batctl if add ppp0 Error - failed to add interface ppp0: Invalid argument

The interface ppp0 was specified as POINTTOPOINT e.g.

$ ip link $ ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc

fq_codel

...

state UNKNOWN mode DEFAULT group default qlen 3

I'm not an expert in this so don't have full visibility of all the tools available. I was wondering if there were better ways to set this up, possibly not using pppd? Any guidance would be appreciated.

cheers Peter

Hi Peter,

batman-adv requires an Ethernet compatible interface (Layer 2) to operate. PPP interfaces are Layer 3 interfaces (IP Layer), so that will not work. You could make a L2 tunnel over your PPP interface such as l2tp or vxlan and use that. Or perhaps there is a different/better way to enable an Ethernet Link over your drone radio directly ....

Cheers,

    Simon