Re: outgoing interface field

[Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>]

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On Thu, 2008-06-19 at 16:09 -0400, Pavel Roskin wrote:
> On Thu, 2008-06-19 at 21:44 +0200, Johannes Berg wrote:
> > > Are you injecting by sending data to a socket?  I think the sockets are
> > > bound to VAPs, not to PHYs since VAPs are seen as network devices.
> > 
> > Yes. The socket is bound to a _cooked monitor_ interface.
> 
> Oh well, I should have guessed that.  Maybe we could introduce ioctl to
> put socket into "wireless injection mode", in which it would accept
> 802.11 packets with radiotap headers regardless of the interface mode.
> Then the sockets could be bound to the VAPs.

I don't want to see the kernel code for that.

> > > Besides, are you going to serve more than one VAP with one socket?  I
> > > would not do it without a good reason.  I think ioctl on the socket
> > > would be an easier solution, as it needs to be done once per VAP, not
> > > once per packet.
> > 
> > Well, yes, of course we're going to serve multiple BSSes with one socket
> > if they're all associated to one physical interface. Why not?
> 
> It's a cleaner approach to respect the virtual interface abstraction
> existing in the kernel rather than ignore it.  The kernel presents
> separate network interfaces to the userspace.

Well yeah, but what point is there in having many sockets? Anyway, Jouni
and I have pretty much decided on this, and you don't really get a say
unless you provide clean, working code :)

> Besides, radiotap headers are designed to be transferable between
> systems.  It should be possible to send frames with radiotap headers
> from another system, possibly with a different endianness and
> different
> wireless hardware.  Encoding local data (VAP number) makes radiotap
> headers system-specific.

This isn't designed to be ever saved to disk, it's for communication
between userspace and the kernel when running an AP. We just happen to
use radiotap for that to save inventing yet another interface.

> It's funny, we are creating the rules that exclude us, and then we are
> shopping around for sponsors.  We need exceptions for experimental use.

Actually, I just figured out that the OUIs have a 'locally assigned' bit
like MAC addresses (well I guess MAC addresses inherit it from OUIs), so
we can use that and assign "experimental" OUIs to ourselves as long as
they don't clash within radiotap.

johannes

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