if_run in hostap mode: issue with stations in the power save mode

[Alexander Zagrebin]

Hi!

On 07.02.2011 09:11:02 +0100, Bernhard Schmidt wrote:

> For example, if you call 'ifconfig wlan0 ssid <newssid>' the new ssid is 
> passed over using a IOCTL. It would be interesting to know what function 
> in net80211 are called regarding beacon updates and which of those call 
> into the run driver. Ultimately it's about figuring out if special 
> handling for such cases are required and if so, how to do it.

I've added a debug output on allocation, changing and deallocation of a
beacon into if_run.c and tried to change SSID while the net.wlan.0.debug is -1.
Here is the log contents:

kernel: wlan0: ieee80211_init
kernel: wlan0: start running, 1 vaps running
kernel: wlan0: ieee80211_new_state_locked: RUN -> SCAN (nrunning 0 nscanning 0)
kernel: wlan0: ieee80211_newstate_cb: RUN -> INIT arg 0
kernel: wlan0: hostap_newstate: RUN -> INIT (0)
kernel: wlan0: node_reclaim: remove 0xffffff8003bd7000<00:14:d1:a8:66:1d> from station table, refcnt 1
kernel: wlan0: ieee80211_alloc_node 0xffffff8004eae000<00:14:d1:a8:66:1d> in station table
kernel: wlan0: [00:14:d1:a8:66:1d] ieee80211_alloc_node: inact_reload 2
kernel: wlan0: ieee80211_newstate_cb: INIT -> SCAN arg 0
kernel: wlan0: hostap_newstate: INIT -> SCAN (0)
kernel: wlan0: ieee80211_create_ibss: creating HOSTAP on channel 6
kernel: wlan0: ieee80211_alloc_node 0xffffff8003bd7000<00:14:d1:a8:66:1d> in station table
kernel: 
kernel: wlan0: [00:14:d1:a8:66:1d] ieee80211_alloc_node: inact_reload 2
kernel: wlan0: set WME_AC_BE (chan) [acm 0 aifsn 3 logcwmin 4 logcwmax 6 txop 0]
kernel: wlan0: set WME_AC_BE (bss ) [acm 0 aifsn 3 logcwmin 4 logcwmax 10 txop 0]
kernel: wlan0: set WME_AC_BK (chan) [acm 0 aifsn 7 logcwmin 4 logcwmax 10 txop 0]
kernel: wlan0: set WME_AC_BK (bss ) [acm 0 aifsn 7 logcwmin 4 logcwmax 10 txop 0]
kernel: wlan0: set WME_AC_VI (chan) [acm 0 aifsn 1 logcwmin 3 logcwmax 4 txop 94]
kernel: wlan0: set WME_AC_VI (bss ) [acm 0 aifsn 2 logcwmin 3 logcwmax 4 txop 94]
kernel: wlan0: set WME_AC_VO (chan) [acm 0 aifsn 1 logcwmin 2 logcwmax 3 txop 47]
kernel: wlan0: set WME_AC_VO (bss ) [acm 0 aifsn 2 logcwmin 2 logcwmax 3 txop 47]
kernel: wlan0: ieee80211_wme_updateparams_locked: WME params updated, cap_info 0x6
kernel: wlan0: ieee80211_new_state_locked: SCAN -> RUN (nrunning 0 nscanning 0)
kernel: wlan0: ieee80211_newstate_cb: SCAN -> RUN arg -1
kernel: run0: run_update_beacon_cb: updating beacon
kernel: wlan0: ieee80211_beacon_update: traffic 0, enable aggressive mode
kernel: wlan0: update WME_AC_BE (chan+bss) [acm 0 aifsn 2 logcwmin 4 logcwmax 10 txop 0]
kernel: wlan0: update WME_AC_BE (chan+bss) logcwmin 3
kernel: wlan0: ieee80211_wme_updateparams_locked: WME params updated, cap_info 0x7
kernel: wlan0: hostap_newstate: SCAN -> RUN (-1)
kernel: wlan0: synchronized with 00:14:d1:a8:66:1d ssid "test" channel 6 start 0Mb
kernel: wlan0: [00:14:d1:a8:66:1d] ieee80211_node_authorize: inact_reload 20

As you can see, run_update_beacon_cb() is invoked, but at this time the
beacon is already allocated. As the beacon is allocated, run_update_beacon_cb()
invokes ieee80211_beacon_update(). As we know, the ieee80211_beacon_update()
doesn't update the SSID, so the SSID remains untouched.
Nevertheless the changing or hiding/unhiding a SSID seems to be working.
It is possible to explain: the station uses an active scan.
The ieee80211_send_proberesp()/ieee80211_alloc_proberesp() returns the frame,
containing an updated SSID, but AP continues to broadcast beacon with the
outdated data.
The possible solution is to deallocate a beacon on a state change.
I've decided to deallocate a beacon on 'to RUN' state transition.
The additional patch is attached.
I'll do an additional tests later today...

-- 
Alexander Zagrebin
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