From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sebastian Smolorz <ssm@domain.hid>
Date: Fri, 30 Mar 2007 14:18:18 +0200
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Subject: [Xenomai-core] Re: iovec overwriting by CAN stack
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>

Jan Kiszka wrote:
> Wolfgang Grandegger wrote:
> > Jan Kiszka wrote:
> >> Hi Wolfgang,
> >>
> >> it's late, so I may have misread somecode, but don't you "update" the
> >> iovec descriptors a user passes on send/recvmsg on return (namely
> >> iovec_len)? I received some complaints about this /wrt to in-kernel CAN
> >> stack usage.
> >
> > It's done here:
> >
> > http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/drivers/can/rtcan_
> >raw.c?v=SVN-trunk#881
> >
> > http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/drivers/can/rtcan_
> >raw.c?v=SVN-trunk#734
> >
> >
> > I may have missed something. What are the real complaints? Is there a
> > test program?
>
> Not yet (will commit the related patch to our RACK likely later today).
> It's simply sending frames while re-using the msg+iovec structs in a loop.
>
> >> I always considered the same well-know behaviour of RTnet a bug, but now
> >> I found your code is doing this systematically, also for user space
> >> callers. Is this behaviour undefined or even required according POSIX or
> >> whatever?
> >
> > I don't know, it's Sebastian's Kode.
>
> Hmm, hope he will not say that he imitated RTnet...

Rather an imitation of the Linux kernel's behaviour. The memcpy_toiovec() and 
memcpy_fromiovec() functions [1] also modify the original iovec. 


[1] http://lxr.free-electrons.com/source/net/core/iovec.c

-- 
Sebastian