R: About RTNet setup

[Marco Tessore <marco.tessore@axelsw.it>]

Thank you Jan


Marco Tessore

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-----Messaggio originale-----
Da: Jan Kiszka <jan.kiszka@siemens.com> 
Inviato: lunedì 18 maggio 2020 10:57
A: Marco Tessore <marco.tessore@axelsw.it>; Xenomai@xenomai.org
Oggetto: Re: About RTNet setup

On 15.05.20 15:15, Marco Tessore via Xenomai wrote:
> Good morning,
> I'm working in a project where I need send and receive RAW ethernet packet in realtime.
> I'm using a Xenomai 3.1 porting on an Ubuntu machine.
> RTNet is enabled in the kernel as modules.
> 
> The problem is that I don't really know how to setup the network in userspace.
> 
> If this mailing list is not appropriate for the issue please tell me where I can write.
> 
> The results of  rtifconfig is:
> rteth0    Medium: Ethernet  Hardware address: 6C:B3:11:52:4C:E9
>            IP address: 192.168.178.142  Broadcast address: 192.168.178.255
>            UP BROADCAST RUNNING  MTU: 1500
>            RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0
>            RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
> 
> rtlo      Medium: Local Loopback
>            IP address: 127.0.0.1
>            UP LOOPBACK RUNNING  MTU: 1500
> 
> So I tried rtping to ping another machine, in my network: that machine is not a realtime one, and rtping response is that there's no route to host.
> The first question is: does the other machine need to run rtnet as well to respond to the rtping protocol, or it's simply a realtime implementation of the standard ping?

No, but ARP resolution of RTnet nodes work only on explicit request. You need to run "rtroute solicit <ip>" for that, or the other side needs to ping you.

> 
> The second question is: to send and receive custom ethernet frames 
> from a userspace process, What is the best configuration of rtnet.conf ? I don't really need rt-tcpip and I don't know how TDMA works.
> 

You don't rtnet.conf and the setup tool then. Just load the rtnet, rt_packet, and rt-<driver> modules (provided you unbound the target interface from the Linux driver already), run rtifconfig on the rteth0 interface, and then you can use AF_PACKET sockets from your RT applications.

> Third question is about the API to use: I'm trying to see the examples, but I'have some troubles to actually implement this.

See demo/posix/cobalt/eth_p_all.c or
testsuite/smokey/net_packet_raw/packet_raw.c (not self-standing, though) for examples. Study "man 7 packet" for the raw interface (RTnet is widely compatible).

HTH,
Jan

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