On Fri, Feb 18, 2011 at 04:37:25PM +0530, Johannes Berg wrote:
> On Fri, 2011-02-18 at 14:16 +0530, Vivek Natarajan wrote:
> > There is a race on sending a data frame before the tx completion
> > of nullfunc frame for enabling power save. As the data quickly
> > follows the nullfunc frame, the AP thinks that the station is out
> > of power save and continues to send the frames. Whereas in the
> > station, the nullfunc ack will be processed after the tx completion
> > of data frame and mac80211 goes to powersave. Thus the power
> > save state mismatch between the station and the AP causes some
> > data loss and some applications fail because of that. This patch
> > fixes this issue.
> >
> > Signed-off-by: Vivek Natarajan <vnatarajan@xxxxxxxxxxx>
> > ---
> > net/mac80211/mlme.c | 11 ++++++++++-
> > net/mac80211/status.c | 2 --
> > 2 files changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> > index d89e878..91006a2 100644
> > --- a/net/mac80211/mlme.c
> > +++ b/net/mac80211/mlme.c
> > @@ -738,8 +738,16 @@ void ieee80211_dynamic_ps_enable_work(struct work_struct *work)
> > return;
> >
> > if ((local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) &&
> > - (!(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)))
> > + (!(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED))) {
> > + netif_tx_stop_all_queues(sdata->dev);
> > + /* flush all the frames queued in the driver before
> > + * going to power save
> > + */
> > + drv_flush(local, false);
>
> Ok, I should've thought of this earlier -- but can we really do this?
>
> I know we currently don't allow powersave when there's more than one
> interface, but we still allow it while there are monitor interfaces and
> a monitor interface could be sending packets, which would violate the
> flush() contract with the driver -- the driver may expect not to get any
> packets during flush.
AFIK we also are not stopping tx queue of monitor iface on offchannel.
Doing so could help flush().
> I'm not sure. Maybe we should disable powersave when there are monitor
> interfaces after all, even though that would rob us of a way to debug
> things. Thoughts?
>
drivers like ath9k receives all frames from any bss on FIF_PROMISC_IN_BSS,
since there is no specific hw filter for that. So in that case it would be
better to disable power save.
--
Rajkumar
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