per-BSS driver data

Johannes Berg johannes
Sat Feb 23 11:02:11 PST 2008

On Sat, 2008-02-23 at 10:23 -0800, Jouni Malinen wrote:
> On Sat, Feb 23, 2008 at 10:54:46AM +0100, Johannes Berg wrote:
> > I've been thinking for a while that driver_nl80211.c will need per-BSS
> > driver data, in fact, it will have to use that for a number of variables
> > that I pushed out of the kernel.
> Could you please give some examples of what variables would be
> configured in this way?

For example, I have a requirement that you can't set the beacon interval
before setting the beacon, they are set at the same time in the kernel.
Hence, I need to store the beacon interval somewhere. It seems this
could theoretically non-constant across BSSes.

More importantly, I have removed the 802.1X setting from the kernel,
hence hostapd needs to keep track of that variable. It is per-BSS and
needs to be known when a new STA is added so that when 802.1X is
disabled I can set the AUTHORIZED flag right away.

> So far, I've been adding ifname argument to driver wrapper functions
> when they have needed multi-BSS support. See, e.g., set_ieee8021x() or
> set_encryption(). This works both for multi-BSS and multi-SSID (VLANs
> within same BSS). Would the interface name be enough to handle the cases
> you've been thinking of or would something additional information be
> needed here?

Well the interface name could be done but for the 802.1X variable I
still need more variables so I'd need to do some BSS list or so in the

> We could add private data structure for bss_add() and if_add() and use
> that instead or well, more likely a shared structure since number of
> functions can be used both for BSSes and VLANs, but that would be larger
> change for the driver wrapper interface.

A private structure would be best, but it is indeed quite a large

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