Re: support for bridging ethernet and 802.11

Re: support for bridging ethernet and 802.11

[Johannes Berg]

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[adding linux-wireless]

On Thu, 2007-05-10 at 11:18 -0500, Kumar Gala wrote:
> I'm wondering how to tell if a given driver/device in the kernel  
> supports the ability to bridge between ethernet and 802.11.  From  
> searching the web it looks like only the prism driver/device supports  
> this.

Normally wireless drivers do 802.3 framing as the 802.11 standard more
or less requires, so it should "just work". Am I missing something?

johannes

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Re: support for bridging ethernet and 802.11

[Jouni Malinen]

On Thu, May 10, 2007 at 07:06:21PM +0200, Johannes Berg wrote:

> On Thu, 2007-05-10 at 11:18 -0500, Kumar Gala wrote:
> > I'm wondering how to tell if a given driver/device in the kernel  
> > supports the ability to bridge between ethernet and 802.11.  From  
> > searching the web it looks like only the prism driver/device supports  
> > this.

> Normally wireless drivers do 802.3 framing as the 802.11 standard more
> or less requires, so it should "just work". Am I missing something?

IEEE 802.11 allows only the own MAC address to be used as the source
address (addr2) when operating as a non-AP STA in BSS (client in Managed
mode). In other words, layer 2 bridging does not work properly. AP mode
and WDS links can be used for bridging without problems, but this will
of course require the driver to support these.

-- 
Jouni Malinen                                            PGP id EFC895FA

Re: support for bridging ethernet and 802.11

[Johannes Berg]

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On Thu, 2007-05-10 at 10:12 -0700, Jouni Malinen wrote:

> IEEE 802.11 allows only the own MAC address to be used as the source
> address (addr2) when operating as a non-AP STA in BSS (client in Managed
> mode). In other words, layer 2 bridging does not work properly. AP mode
> and WDS links can be used for bridging without problems, but this will
> of course require the driver to support these.

Ah forgot about that, I had only thought about AP/wired bridging. How
would the prism driver actually do bridging in STA mode though?

johannes

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Re: support for bridging ethernet and 802.11

[Jouni Malinen]

On Thu, May 10, 2007 at 07:19:35PM +0200, Johannes Berg wrote:

> Ah forgot about that, I had only thought about AP/wired bridging. How
> would the prism driver actually do bridging in STA mode though?

If that is referring to Host AP driver, there is support for using WDS
in client mode. If the AP understands this, the client could use
standard frames for its own packets (i.e., SA=own MAC addr) and WDS
frames for frames from all other addresses. There are some experimental
modes in Host AP driver that (if I remember correctly ;-) may allow this
to be used on a single netdev (i.e., no additional netdev needed for the
WDS link) and as such, this would look like working layer 2 bridging
between wlan0 and eth0 even in managed mode.

-- 
Jouni Malinen                                            PGP id EFC895FA

Re: support for bridging ethernet and 802.11

[Kumar Gala]

On May 10, 2007, at 12:25 PM, Jouni Malinen wrote:

> On Thu, May 10, 2007 at 07:19:35PM +0200, Johannes Berg wrote:
>
>> Ah forgot about that, I had only thought about AP/wired bridging. How
>> would the prism driver actually do bridging in STA mode though?
>
> If that is referring to Host AP driver, there is support for using WDS
> in client mode. If the AP understands this, the client could use
> standard frames for its own packets (i.e., SA=own MAC addr) and WDS
> frames for frames from all other addresses. There are some  
> experimental
> modes in Host AP driver that (if I remember correctly ;-) may allow  
> this
> to be used on a single netdev (i.e., no additional netdev needed  
> for the
> WDS link) and as such, this would look like working layer 2 bridging
> between wlan0 and eth0 even in managed mode.

I'm a little confused.  It seems from the thread that there are  
several forums of bridging.

What I'm trying to accomplish is to take all traffic from eth0 to  
wlan0 (and the other way around).  I'm happy to configure and  
associate wlan0 with an AP.

I believe the current USB adapter I've got is using the SOFTMAC code  
right now.

- k