Re: SEGFAULT when using multiple

[Geoffrey Bugniot <g.bugniot () gmail com>]

Guy Harris <guy <at> alum.mit.edu> writes:

> Somebody who works on the PF_PACKET socket code in the Linux kernel?
> My *guess* is that there's something wrong with the code that handles 
> memory-mapped access to the socket (if it weren't using the
> memory-mapped code, it might not be any less likely to panic, but it might
> be less likely to get a segmentation fault in user-mode code) when more than
> one process is using it.
>
> netsniff-ng:
>
>       http://netsniff-ng.org/
>
> apparently also uses memory-mapped access to PF_PACKET sockets, and
> doesn't use libpcap; see what happens if you compile it for your embedded
> board and try to run two instances of it.  If you have 
> problems with that, then libpcap isn't involved at all, and you'd need to get
> some of the Linux networking code developers involved.  (If that works, then
> it is probably still at least in part a Linux kernel issue, given that you're
> getting kernel panics, but there *might* also be an issue with how libpcap is
> using the memory-mapped mechanism.)

OK,

I'v just cross-compiled netsniff-ng, and run it on my board. With only one
instance of netsniff-ng, my board reboot. If I disable all my network 
interfaces (ifdown -a), no reboot, netsniff-ng just don't find an interface.

With gdb, I notice that my board reboots after the last instruction
of __init_stage_fallback_dev function (from netsniff-ng's code). This function
is use to initialize the listening interface (i.e: eth0).

So, I think the problem is not libpcap. The problem might be the hardware
or the kernel configuration...

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