what does iwpriv do?

[Matt Price]

jamon, never said thanks for this -- so, as usual, thanks -- very much
appreciate your expertise.

matt

On Sat, Jul 3, 2010 at 1:45 PM, Jamon Camisso <jamon.camisso-H217xnMUJC0sA/PxXw9srA at public.gmane.org>wrote:

> On 07/03/2010 12:53 PM, Matt Price wrote:
> > hi folks,
> >
> > so, i have a faulty third-party wireless driver from realtek that causes
> > kernel panics on my ubuntu lucid machine.  The crash can be triggered
> > manually by running iwpriv -a as root; when running as a normal user, it
> > fails to trigger the crash. I include the output in my latest comment on
> the
> > bug report, here:
> > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/585938/comments/18;
> > it's pretty simple though really:
> >
> > lo no private ioctls.
> > eth0 no private ioctls.
> > wlan0 Available read-only private ioctl :
> > wlan0 firm_ver:63
> > Kernel Panic [etc...]
> >
> > here's my question:  how do i figure out what iwpriv is actually doing to
> > trigger this issue -- and is there anything i can do to stop this from
> > happening at othertimes?
>
> strace is a start, you can see various calls that a given binary makes
> and start to narrow down the cause of the panic. Here's an excerpt from
> "strace iwlist wlan0 scan":
>
> ioctl(3, SIOCGIWRANGE, 0x7fff60bb8230)  = 0
> ioctl(3, SIOCSIWSCAN, 0x7fff60bb8840)   = 0
> select(0, [], NULL, NULL, {0, 250000})  = 0 (Timeout)
> brk(0)                                  = 0x1c5f000
> brk(0x1c81000)                          = 0x1c81000
> <snip>
> select(0, [], NULL, NULL, {0, 100000})  = 0 (Timeout)
> ioctl(3, SIOCGIWSCAN, 0x7fff60bb8840)   = -1 E2BIG (Argument list too long)
> ioctl(3, SIOCGIWSCAN, 0x7fff60bb8840)   = 0
>
> Then there a bunch of write calls that spit out the list of wireless
> access points in my vicinity.
>
> So you can see that iwlist is calling ioctl, which, via the SIOCGIWSCAN
> event, asks the wireless driver to return its list of wireless signals.
> I believe that each driver has its own implementation of calls that are
> made for SIOCGIWSCAN events depending on the wireless firmware/hardware.
>
> Jamon
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