Re: vcan multithreaded problem testing

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 02/16/2014 11:04 AM, John Whitmore wrote:
> Hello all, I'll try keep this short. I'm using vcan to test code I'm porting
> from my embedded hardware. My embedded code has a simple dispatcher which
> process all messages received from the Network. Higher layers of the
> Application register an interest in certain CAN ids or ranges.
> 
> I don't need this dispatcher as Socket CAN filters already so in porting my
> application the higher layers now simply create a new linux thread and socket
> to listen for CAN Frames that they have an interest in.
> 
> My problem is that in testing with vcan if my core process thead sends a CAN
> id which a child thread is filtering on then the child thread receives the
> message. I've looked at vcan code and it simply consumes the sent frames back
> into the linux networking stack.
> 
> At present a single process will not receive a CAN Frame which is sends but
> it's child threads will recive the frame. Is there a way to restrict this? I
> might have to wait until I get back to Hardware and test there but it would be
> very handy to be able to use vcan.

The CAN stack doesn't care about thread or processes, it's all about
sockets.

By default a socket doesn't receive the CAN frame it sends. When a CAN
frame is successfully send, by default all other sockets receive the
locally created CAN frames, too. You can change both defaults. Have a
look at the can.txt documentation in the Linux kernel:

http://lxr.free-electrons.com/source/Documentation/networking/can.txt#L184
http://lxr.free-electrons.com/source/Documentation/networking/can.txt#L502
http://lxr.free-electrons.com/source/Documentation/networking/can.txt#L513

Feel free to ask, if you need more information.

cheers,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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