Virtual wireless network card for mac80211

Virtual wireless network card for mac80211

[Henning Rogge]

Hello,

I'm looking for a way to simulate a ieee802.11 card on a linux system. Is 
there an equivalent for tun/tap for the mac80211 layer, so I can just send 
the communication with a wireless device back to userspace (and data from 
userspace into the wireless stack) ?

Henning Rogge

Re: Virtual wireless network card for mac80211

[John W. Linville]

On Wed, Nov 14, 2007 at 01:16:50PM +0100, Henning Rogge wrote:

> I'm looking for a way to simulate a ieee802.11 card on a linux system. Is 
> there an equivalent for tun/tap for the mac80211 layer, so I can just send 
> the communication with a wireless device back to userspace (and data from 
> userspace into the wireless stack) ?

No, but I have been thinking about this as well.  It might be a nice
capability to have, so long as the regulatory spectre continues to
discourage some vendors from disclosing information about their
hardware.  At least such a scenario seems less grey w.r.t. GPL
compliance.

Still, I would not want to put much effort into a project that
distracts from development of fully open source drivers.  But I think
the performance of such a solution would be sub-optimal enough to
discourage full reliance upon it.  And the plus of having a userland
binary driver versus no driver at all might make it worthwhile.

What is the situation that makes this interesting to you?

Thanks,

John
-- 
John W. Linville
linville@tuxdriver.com

Re: Virtual wireless network card for mac80211

[Henning Rogge]

Am Mittwoch 14 November 2007 16:08:39 schrieben Sie:
> On Wed, Nov 14, 2007 at 01:16:50PM +0100, Henning Rogge wrote:
> No, but I have been thinking about this as well.  It might be a nice
> capability to have, so long as the regulatory spectre continues to
> discourage some vendors from disclosing information about their
> hardware.  At least such a scenario seems less grey w.r.t. GPL
> compliance.
>
> Still, I would not want to put much effort into a project that
> distracts from development of fully open source drivers.  But I think
> the performance of such a solution would be sub-optimal enough to
> discourage full reliance upon it.  And the plus of having a userland
> binary driver versus no driver at all might make it worthwhile.
>
> What is the situation that makes this interesting to you?
I'm not interested in having a binary driver but in simulation of mobile 
networks with virtual machines. By placing a virtual driver into the mac80211 
layer the sollution would be totally transparent for the clients, even for 
applications with Radiotap headers and Libpcap.
A central server would be connected to the userspace parts of the virtual 
driver and simulate connections between the VMs.

Henning Rogge

Re: Virtual wireless network card for mac80211

[Johannes Berg]

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> I'm looking for a way to simulate a ieee802.11 card on a linux system. Is 
> there an equivalent for tun/tap for the mac80211 layer, so I can just send 
> the communication with a wireless device back to userspace (and data from 
> userspace into the wireless stack) ?

No. I've described this task on
http://kernelnewbies.org/KernelProjects/Mac80211TestDriver and somebody
was interested in writing one, but I never heard back from him.

johannes

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Re: Virtual wireless network card for mac80211

[Johannes Berg]

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> No, but I have been thinking about this as well.  It might be a nice
> capability to have, so long as the regulatory spectre continues to
> discourage some vendors from disclosing information about their
> hardware.  At least such a scenario seems less grey w.r.t. GPL
> compliance.

This could be doable with a shim driver and uio, but you'd need at least
some DMA engine programming etc. in the kernel. But you want that
anyway.

johannes

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Re: Virtual wireless network card for mac80211

[John W. Linville]

On Wed, Nov 14, 2007 at 04:20:15PM +0100, Henning Rogge wrote:
> Am Mittwoch 14 November 2007 16:08:39 schrieben Sie:

> > What is the situation that makes this interesting to you?

> I'm not interested in having a binary driver but in simulation of mobile 
> networks with virtual machines. By placing a virtual driver into the mac80211 
> layer the sollution would be totally transparent for the clients, even for 
> applications with Radiotap headers and Libpcap.
> A central server would be connected to the userspace parts of the virtual 
> driver and simulate connections between the VMs.

Even better -- a completely legitimate use for such a feature. :-)

Such a driver might also serve as a development tool for the mac80211
stack developers, and as a model for how drivers should behave when
interacting with mac80211.

In fact, I think Johannes Berg submitted this to the Kernel Newbies
project suggestions already:

	http://kernelnewbies.org/KernelProjects/Mac80211TestDriver

So, any aspiring wireless/kernel hackers out there?

John
-- 
John W. Linville
linville@tuxdriver.com

Re: Virtual wireless network card for mac80211

[Mike Kershaw]

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On Wed, Nov 14, 2007 at 01:16:50PM +0100, Henning Rogge wrote:
> Hello,
> 
> I'm looking for a way to simulate a ieee802.11 card on a linux system. Is 
> there an equivalent for tun/tap for the mac80211 layer, so I can just send 
> the communication with a wireless device back to userspace (and data from 
> userspace into the wireless stack) ?

Depending what you're trying to do, I did patches for tuntap that went
in a year or two ago that allow you to set the link type and write
radiotap/80211 frames.  Kismet-newcore (it's in branches in svn if you
care) uses this to replicate mangled frames back out to other userspace
programs.

http://svn.kismetwireless.net/code/branch/kismet-newcore/dumpfile_tuntap.cc

If you want something that actually responds to iw* ioctls, etc, then
this probably isn't what you want however.

-m

-- 
Mike Kershaw/Dragorn <dragorn@kismetwireless.net>
GPG Fingerprint: 3546 89DF 3C9D ED80 3381  A661 D7B2 8822 738B BDB1

"A baby seal walks into a club..."

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Re: Virtual wireless network card for mac80211

[Henning Rogge]

Am Mittwoch 14 November 2007 16:59:58 schrieb Mike Kershaw:
> Depending what you're trying to do, I did patches for tuntap that went
> in a year or two ago that allow you to set the link type and write
> radiotap/80211 frames.  Kismet-newcore (it's in branches in svn if you
> care) uses this to replicate mangled frames back out to other userspace
> programs.

> http://svn.kismetwireless.net/code/branch/kismet-newcore/dumpfile_tuntap.cc
Okay, that seems to be what I was looking for. It's not as flexible as a full 
virtual network card, but it has all features I need, thank you.

(it seems that none of the online documentation I found for tuntap contains 
this capability)

Henning