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Message-ID: <20091117144239.47930866@nehalam>
Date: Tue, 17 Nov 2009 14:42:39 -0800
From: Stephen Hemminger <shemminger@...tta.com>
To: Johannes Berg <johannes@...solutions.net>
Cc: netdev <netdev@...r.kernel.org>,
linux-wireless <linux-wireless@...r.kernel.org>,
Felix Fietkau <nbd@...nwrt.org>
Subject: Re: [RFC v2] mac80211: disallow bridging managed/adhoc interfaces
On Tue, 17 Nov 2009 21:48:18 +0100
Johannes Berg <johannes@...solutions.net> wrote:
> A number of people have tried to add a wireless interface
> (in managed mode) to a bridge and then complained that it
> doesn't work. It cannot work, however, because in 802.11
> networks all packets need to be acknowledged and as such
> need to be sent to the right address. Promiscuous doesn't
> help here. The wireless address format used for these
> links has only space for three addresses, the
> * transmitter, which must be equal to the sender (origin)
> * receiver (on the wireless medium), which is the AP in
> the case of managed mode
> * the recipient (destination), which is on the APs local
> network segment
>
> In an IBSS, it is similar, but the receiver and recipient
> must match and the third address is used as the BSSID.
>
> To avoid such mistakes in the future, disallow adding a
> wireless interface to a bridge.
>
> Felix has recently added a four-address mode to the AP
> and client side that can be used (after negotiating that
> it is possible, which must happen out-of-band by setting
> up both sides) for bridging, so allow that case.
>
> Signed-off-by: Johannes Berg <johannes@...solutions.net>
Looks good, maybe true four-address mode support will be available
more widely, and this will no longer be an issue.
Acked-by: Stephen Hemminger <shemminger@...tta.com>
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