Re: SJA1000 loopback feature

[Alexander GQ Gerasiov <gq@cs.msu.su>]

Thu, 19 Jun 2014 16:55:40 +0200
Oliver Hartkopp <socketcan@hartkopp.net> wrote:

> >> Just to give an example how I dealed with such situation:
> >>
> >> 1. Let all applications run on a virtual CAN interface (e.g.
> >> vcan0). 2. make a cross routing with can-gw netlink routes
> > 
> > Yes, I was thinking about it. We strictly need the same order of
> > events on both buses (local/virtual and remote/hardware), but in
> > case of bridging (userspace, or even in-kernel one) race is
> > possible. So we'd better use one bus (to rule them all =)) 
> > 
> 
> You have a strict order on vcan0. And this order is then transfered
> to the real can0. OTOH the order on can0 is forwarded to vcan0. Where
> do you see a problem here?
Correct me if I'm wrong, but if I'm quite sure, there will be the
following problem:

Application works on vcan and initiate transmit A on time T.
Another (hardware) node initiate transmit B on physical bus on the same
T.

On vcan you will see A (on T+dt1), B (on T+dt1+dt2).
On bus you will see B (on T+dt3), A (on T+dt3+dt4).

As we develop testbench environment, the order of events our software
see (and logs) should be the same as hardware nodes see.

-- 
Alexander.