Troubles with beacon_settings

Jouni Malinen jkmaline
Tue Feb 13 19:16:07 PST 2007

On Mon, Feb 12, 2007 at 03:18:07PM +0200, Emmanuel Grumbach wrote:

> I am trying to develop a driver for a WLAN NIC using D80211, and to have it
> working as an AP with Hostapd on top of D80211. Logically, I need a new
> beacon every DTIM period since the TIM Information Element gets changed
> every DTIM period. In my hostapd.conf:

TIM can change in every Beacon, not only once every DTIM period..

> I thought that hostapd should send an ioctl to set the beacon, this ioctl
> would be translated to ieee80211_config_interface by D80211 with the beacon
> set by hostapd.

hostapd does indeed configure the beacon template for d80211. I haven't
tested the current net/d80211 code on a system that would need the
beacon template in the radio driver, so I'm not completely sure about
the exact behavior of this part.

> driver_devicescape.c, this is what should happen. My problem is that this
> ioctl comes very late in the init process. Here is a short description of
> the init flow of D80211 (when hostapd sends its instructions), this is a
> list of handlers that I implement, and that D80211 calls:
>   1. add_interface
>   2. open (here I should be already able to send beacons according to
>   d80211.h)
>   3. config_interface (several times with beacon NULL)
> And much later, config_interface is called again with a non-null beacon.

It looks like the driver would need to be prepared for this and only
start beacon transmission once the beacon template is available.

> All this when I register as a driver that needs a beacon template. When I
> register as a driver that needs a full beacon frame, I should be able to
> call ieee80211_beacon_get to get a beacon, but this does not work (beacon is
> NULL).

This worked fine the last time I tried it..

> 2) Why does Hostapd begins to open and start my device before being able to
> give me a valid beacon ?

Why wouldn't it? Configuration is done in parts and I don't see any
clear requirement of beacon template being the first thing that would
need to be configured even before opening the netdev.

Jouni Malinen                                            PGP id EFC895FA

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