> On 19/01/2023 15:02, Johannes Berg wrote:
> > On Mon, 2022-12-26 at 14:03 +0530, Rameshkumar Sundaram wrote:
> > > As per 802.11ax-2021, STAs shall process BSS Color Change Announcement
> > > (BCCA) from AP and switch to new color, but some STAs aren't processing
> > > BCCA from AP and not doing color switch, causing them to drop data
> > > frames from AP post color change.
> > >
> > > Provide an option to disable color collision detection and therefore
> > > not to do BCCA to mitigate the same from AP. If it's required in case
> > > where STA supports BCCA handling, then it can enabled in AP using this
> > > option.
> > >
> >
> > You should probably split this into cfg80211 and mac80211.
> >
> > Also, this doesn't really seem to make a lot of _sense_ since nothing in
> > the kernel actually acts on detection of a color collision - hostapd is
> > acting on that.
> >
> > So since you can easily make hostapd ignore the event, why do you even
> > need this?
>
> This may not be related, but the software color collision detection sends a
> netlink message for every colliding frame and it can hose up the system if
> the other network is very active.
>
> Also, cfg80211_bss_color_notify() complains that the wdev lock isn't held.
Hi Nicolas,
I agree, I think we can ratelimit netlink messages sent by the kernel to
userspace (e.g. to hostapd), I would say every 500ms is ok.
I guess we can move cfg80211_obss_color_collision_notify() in a dedicated
delayed_work so we can grab wdev mutex (cfg80211_obss_color_collision_notify is
currently running in interrupt context).
To give an idea, what do you think about patch below? (please note it is just
compiled tested so far).
Regards,
Lorenzo
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index f5d43f42f6d8..0aefaca989aa 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -4652,6 +4652,20 @@ void ieee80211_color_change_finalize_work(struct work_struct *work)
sdata_unlock(sdata);
}
+void ieee80211_color_collision_detection_work(struct work_struct *work)
+{
+ struct delayed_work *delayed_work = to_delayed_work(work);
+ struct ieee80211_link_data *link =
+ container_of(delayed_work, struct ieee80211_link_data,
+ dfs_cac_timer_work);
+ struct ieee80211_sub_if_data *sdata = link->sdata;
+
+ sdata_lock(sdata);
+ cfg80211_obss_color_collision_notify(sdata->dev, link->color_bitmap,
+ GFP_KERNEL);
+ sdata_unlock(sdata);
+}
+
void ieee80211_color_change_finish(struct ieee80211_vif *vif)
{
struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
@@ -4666,11 +4680,21 @@ ieee80211_obss_color_collision_notify(struct ieee80211_vif *vif,
u64 color_bitmap, gfp_t gfp)
{
struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
+ struct ieee80211_link_data *link = &sdata->deflink;
if (sdata->vif.bss_conf.color_change_active || sdata->vif.bss_conf.csa_active)
return;
- cfg80211_obss_color_collision_notify(sdata->dev, color_bitmap, gfp);
+ if (delayed_work_pending(&link->color_collision_detect_work))
+ return;
+
+ link->color_bitmap = color_bitmap;
+ /* queue the color collision detection event every 500 ms in order to
+ * avoid sending too much netlink messages to userspace.
+ */
+ ieee80211_queue_delayed_work(&sdata->local->hw,
+ &link->color_collision_detect_work,
+ msecs_to_jiffies(500)); /* 500 ms */
}
EXPORT_SYMBOL_GPL(ieee80211_obss_color_collision_notify);
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index d16606e84e22..7ca9bde3c6d2 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -974,6 +974,8 @@ struct ieee80211_link_data {
struct cfg80211_chan_def csa_chandef;
struct work_struct color_change_finalize_work;
+ struct delayed_work color_collision_detect_work;
+ u64 color_bitmap;
/* context reservation -- protected with chanctx_mtx */
struct ieee80211_chanctx *reserved_chanctx;
@@ -1929,6 +1931,7 @@ int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev,
/* color change handling */
void ieee80211_color_change_finalize_work(struct work_struct *work);
+void ieee80211_color_collision_detection_work(struct work_struct *work);
/* interface handling */
#define MAC80211_SUPPORTED_FEATURES_TX (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM | \
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 23ed13f15067..1ef970b457d1 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -541,6 +541,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do
cancel_work_sync(&sdata->deflink.color_change_finalize_work);
cancel_delayed_work_sync(&sdata->deflink.dfs_cac_timer_work);
+ cancel_delayed_work_sync(&sdata->deflink.color_collision_detect_work);
if (sdata->wdev.cac_started) {
chandef = sdata->vif.bss_conf.chandef;
diff --git a/net/mac80211/link.c b/net/mac80211/link.c
index d1f5a9f7c647..acab8309d2d6 100644
--- a/net/mac80211/link.c
+++ b/net/mac80211/link.c
@@ -39,6 +39,8 @@ void ieee80211_link_init(struct ieee80211_sub_if_data *sdata,
ieee80211_csa_finalize_work);
INIT_WORK(&link->color_change_finalize_work,
ieee80211_color_change_finalize_work);
+ INIT_DELAYED_WORK(&link->color_collision_detect_work,
+ ieee80211_color_collision_detection_work);
INIT_LIST_HEAD(&link->assigned_chanctx_list);
INIT_LIST_HEAD(&link->reserved_chanctx_list);
INIT_DELAYED_WORK(&link->dfs_cac_timer_work,
Attachment:
signature.asc
Description: PGP signature
