mac80211: add WMM admission control support

Use the currently existing APIs between mac80211 and the low
level driver to implement WMM admission control.

The low level driver needs to report the media time used by
each transmitted packet in ieee80211_tx_status. Based on that
information, mac80211 will modify the QoS parameters of the
admission controlled Access Category when the limit is
reached. Once the original QoS parameters can be restored,
mac80211 will do so.

One issue with this approach is that management frames will
also erroneously be downgraded, but the upside is that the
implementation is simple. In the future, it can be extended
to driver- or device-based implementations that are better.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 138 insertions, 4 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index fb6561509caf..4d9b4d165ce8 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1606,6 +1606,95 @@ void ieee80211_dfs_cac_timer_work(struct work_struct *work)
 	mutex_unlock(&sdata->local->mtx);
 }
 
+static bool
+__ieee80211_sta_handle_tspec_ac_params(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+	bool ret;
+	int ac;
+
+	if (local->hw.queues < IEEE80211_NUM_ACS)
+		return false;
+
+	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+		struct ieee80211_sta_tx_tspec *tx_tspec = &ifmgd->tx_tspec[ac];
+		int non_acm_ac;
+		unsigned long now = jiffies;
+
+		if (tx_tspec->action == TX_TSPEC_ACTION_NONE &&
+		    tx_tspec->admitted_time &&
+		    time_after(now, tx_tspec->time_slice_start + HZ)) {
+			tx_tspec->consumed_tx_time = 0;
+			tx_tspec->time_slice_start = now;
+
+			if (tx_tspec->downgraded)
+				tx_tspec->action =
+					TX_TSPEC_ACTION_STOP_DOWNGRADE;
+		}
+
+		switch (tx_tspec->action) {
+		case TX_TSPEC_ACTION_STOP_DOWNGRADE:
+			/* take the original parameters */
+			if (drv_conf_tx(local, sdata, ac, &sdata->tx_conf[ac]))
+				sdata_err(sdata,
+					  "failed to set TX queue parameters for queue %d\n",
+					  ac);
+			tx_tspec->action = TX_TSPEC_ACTION_NONE;
+			tx_tspec->downgraded = false;
+			ret = true;
+			break;
+		case TX_TSPEC_ACTION_DOWNGRADE:
+			if (time_after(now, tx_tspec->time_slice_start + HZ)) {
+				tx_tspec->action = TX_TSPEC_ACTION_NONE;
+				ret = true;
+				break;
+			}
+			/* downgrade next lower non-ACM AC */
+			for (non_acm_ac = ac + 1;
+			     non_acm_ac < IEEE80211_NUM_ACS;
+			     non_acm_ac++)
+				if (!(sdata->wmm_acm & BIT(7 - 2 * non_acm_ac)))
+					break;
+			/* The loop will result in using BK even if it requires
+			 * admission control, such configuration makes no sense
+			 * and we have to transmit somehow - the AC selection
+			 * does the same thing.
+			 */
+			if (drv_conf_tx(local, sdata, ac,
+					&sdata->tx_conf[non_acm_ac]))
+				sdata_err(sdata,
+					  "failed to set TX queue parameters for queue %d\n",
+					  ac);
+			tx_tspec->action = TX_TSPEC_ACTION_NONE;
+			ret = true;
+			schedule_delayed_work(&ifmgd->tx_tspec_wk,
+				tx_tspec->time_slice_start + HZ - now + 1);
+			break;
+		case TX_TSPEC_ACTION_NONE:
+			/* nothing now */
+			break;
+		}
+	}
+
+	return ret;
+}
+
+void ieee80211_sta_handle_tspec_ac_params(struct ieee80211_sub_if_data *sdata)
+{
+	if (__ieee80211_sta_handle_tspec_ac_params(sdata))
+		ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_QOS);
+}
+
+static void ieee80211_sta_handle_tspec_ac_params_wk(struct work_struct *work)
+{
+	struct ieee80211_sub_if_data *sdata;
+
+	sdata = container_of(work, struct ieee80211_sub_if_data,
+			     u.mgd.tx_tspec_wk.work);
+	ieee80211_sta_handle_tspec_ac_params(sdata);
+}
+
 /* MLME */
 static bool ieee80211_sta_wmm_params(struct ieee80211_local *local,
 				     struct ieee80211_sub_if_data *sdata,
@@ -1690,12 +1779,14 @@ static bool ieee80211_sta_wmm_params(struct ieee80211_local *local,
 		params.uapsd = uapsd;
 
 		mlme_dbg(sdata,
-			 "WMM queue=%d aci=%d acm=%d aifs=%d cWmin=%d cWmax=%d txop=%d uapsd=%d\n",
+			 "WMM queue=%d aci=%d acm=%d aifs=%d cWmin=%d cWmax=%d txop=%d uapsd=%d, downgraded=%d\n",
 			 queue, aci, acm,
 			 params.aifs, params.cw_min, params.cw_max,
-			 params.txop, params.uapsd);
+			 params.txop, params.uapsd,
+			 ifmgd->tx_tspec[queue].downgraded);
 		sdata->tx_conf[queue] = params;
-		if (drv_conf_tx(local, sdata, queue, &params))
+		if (!ifmgd->tx_tspec[queue].downgraded &&
+		    drv_conf_tx(local, sdata, queue, &params))
 			sdata_err(sdata,
 				  "failed to set TX queue parameters for queue %d\n",
 				  queue);
@@ -1958,6 +2049,10 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 	}
 	mutex_unlock(&local->mtx);
 
+	/* existing TX TSPEC sessions no longer exist */
+	memset(ifmgd->tx_tspec, 0, sizeof(ifmgd->tx_tspec));
+	cancel_delayed_work_sync(&ifmgd->tx_tspec_wk);
+
 	sdata->encrypt_headroom = IEEE80211_ENCRYPT_HEADROOM;
 }
 
@@ -2010,9 +2105,46 @@ out:
 	mutex_unlock(&local->mtx);
 }
 
+static void ieee80211_sta_tx_wmm_ac_notify(struct ieee80211_sub_if_data *sdata,
+					   struct ieee80211_hdr *hdr,
+					   u16 tx_time)
+{
+	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+	u16 tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
+	int ac = ieee80211_ac_from_tid(tid);
+	struct ieee80211_sta_tx_tspec *tx_tspec = &ifmgd->tx_tspec[ac];
+	unsigned long now = jiffies;
+
+	if (likely(!tx_tspec->admitted_time))
+		return;
+
+	if (time_after(now, tx_tspec->time_slice_start + HZ)) {
+		tx_tspec->consumed_tx_time = 0;
+		tx_tspec->time_slice_start = now;
+
+		if (tx_tspec->downgraded) {
+			tx_tspec->action = TX_TSPEC_ACTION_STOP_DOWNGRADE;
+			schedule_delayed_work(&ifmgd->tx_tspec_wk, 0);
+		}
+	}
+
+	if (tx_tspec->downgraded)
+		return;
+
+	tx_tspec->consumed_tx_time += tx_time;
+
+	if (tx_tspec->consumed_tx_time >= tx_tspec->admitted_time) {
+		tx_tspec->downgraded = true;
+		tx_tspec->action = TX_TSPEC_ACTION_DOWNGRADE;
+		schedule_delayed_work(&ifmgd->tx_tspec_wk, 0);
+	}
+}
+
 void ieee80211_sta_tx_notify(struct ieee80211_sub_if_data *sdata,
-			     struct ieee80211_hdr *hdr, bool ack)
+			     struct ieee80211_hdr *hdr, bool ack, u16 tx_time)
 {
+	ieee80211_sta_tx_wmm_ac_notify(sdata, hdr, tx_time);
+
 	if (!ieee80211_is_data(hdr->frame_control))
 	    return;
 
@@ -3834,6 +3966,8 @@ void ieee80211_sta_setup_sdata(struct ieee80211_sub_if_data *sdata)
 		    (unsigned long) sdata);
 	setup_timer(&ifmgd->chswitch_timer, ieee80211_chswitch_timer,
 		    (unsigned long) sdata);
+	INIT_DELAYED_WORK(&ifmgd->tx_tspec_wk,
+			  ieee80211_sta_handle_tspec_ac_params_wk);
 
 	ifmgd->flags = 0;
 	ifmgd->powersave = sdata->wdev.ps;