Re: About RTNet setup

From: Jan Kiszka <jan.kiszka@siemens.com>
To: Marco Tessore <marco.tessore@axelsw.it>,
	"Xenomai@xenomai.org" <Xenomai@xenomai.org>
Subject: Re: About RTNet setup
Date: Mon, 18 May 2020 10:56:52 +0200	[thread overview]
Message-ID: <cf47f625-f978-6f19-6512-d8af176cb6c7@siemens.com> (raw)
In-Reply-To: <97020454f0464394b9128a7620d8d631@axelsw.it>

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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