mac80211: inform the driver about update of dtim_period

Currently, when the driver requires the DTIM period,
mac80211 will wait to hear a beacon before association.
This behavior is suboptimal since some drivers may be
able to deal with knowing the DTIM period after the
association, if they get it at all.

To address this, notify the drivers with bss_info_changed
with the new BSS_CHANGED_DTIM_PERIOD flag when the DTIM
becomes known. This might be when changing to associated,
or later when the entire association was done with only
probe response information.

Rename the hardware flag for the current behaviour to
IEEE80211_HW_NEED_DTIM_BEFORE_ASSOC to more accurately
reflect its behaviour. IEEE80211_HW_NEED_DTIM_PERIOD is
no longer accurate as all drivers get the DTIM period
now, just not before association.

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

1 files changed, 44 insertions, 30 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index d79b9cd72fc5..a5dba67bbe0b 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1445,7 +1445,7 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 
 	ieee80211_led_assoc(local, 1);
 
-	if (local->hw.flags & IEEE80211_HW_NEED_DTIM_PERIOD) {
+	if (sdata->u.mgd.assoc_data->have_beacon) {
 		/*
 		 * If the AP is buggy we may get here with no DTIM period
 		 * known, so assume it's 1 which is the only safe assumption
@@ -1453,6 +1453,7 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
 		 * probably just won't work at all.
 		 */
 		bss_conf->dtim_period = sdata->u.mgd.dtim_period ?: 1;
+		bss_info_changed |= BSS_CHANGED_DTIM_PERIOD;
 	} else {
 		bss_conf->dtim_period = 0;
 	}
@@ -2548,13 +2549,14 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 	chan = chanctx_conf->def.chan;
 	rcu_read_unlock();
 
-	if (ifmgd->assoc_data && !ifmgd->assoc_data->have_beacon &&
+	if (ifmgd->assoc_data && ifmgd->assoc_data->need_beacon &&
 	    ether_addr_equal(mgmt->bssid, ifmgd->assoc_data->bss->bssid)) {
 		ieee802_11_parse_elems(mgmt->u.beacon.variable,
 				       len - baselen, &elems);
 
 		ieee80211_rx_bss_info(sdata, mgmt, len, rx_status, &elems);
 		ifmgd->assoc_data->have_beacon = true;
+		ifmgd->assoc_data->need_beacon = false;
 		/* continue assoc process */
 		ifmgd->assoc_data->timeout = jiffies;
 		run_again(ifmgd, ifmgd->assoc_data->timeout);
@@ -2711,6 +2713,19 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 				     elems.wmm_param_len))
 		changed |= BSS_CHANGED_QOS;
 
+	/*
+	 * If we haven't had a beacon before, tell the driver about the
+	 * DTIM period now.
+	 */
+	if (!bss_conf->dtim_period) {
+		/* a few bogus AP send dtim_period = 0 or no TIM IE */
+		if (elems.tim)
+			bss_conf->dtim_period = elems.tim->dtim_period ?: 1;
+		else
+			bss_conf->dtim_period = 1;
+		changed |= BSS_CHANGED_DTIM_PERIOD;
+	}
+
 	if (elems.erp_info && elems.erp_info_len >= 1) {
 		erp_valid = true;
 		erp_value = elems.erp_info[0];
@@ -2989,7 +3004,8 @@ void ieee80211_sta_work(struct ieee80211_sub_if_data *sdata)
 
 	if (ifmgd->assoc_data &&
 	    time_after(jiffies, ifmgd->assoc_data->timeout)) {
-		if (!ifmgd->assoc_data->have_beacon ||
+		if ((ifmgd->assoc_data->need_beacon &&
+		     !ifmgd->assoc_data->have_beacon) ||
 		    ieee80211_do_assoc(sdata)) {
 			u8 bssid[ETH_ALEN];
 
@@ -3776,6 +3792,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 	struct ieee80211_bss *bss = (void *)req->bss->priv;
 	struct ieee80211_mgd_assoc_data *assoc_data;
+	const struct cfg80211_bss_ies *beacon_ies;
 	struct ieee80211_supported_band *sband;
 	const u8 *ssidie, *ht_ie, *vht_ie;
 	int i, err;
@@ -3941,38 +3958,35 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 	if (err)
 		goto err_clear;
 
-	if (sdata->local->hw.flags & IEEE80211_HW_NEED_DTIM_PERIOD) {
-		const struct cfg80211_bss_ies *beacon_ies;
+	rcu_read_lock();
+	beacon_ies = rcu_dereference(req->bss->beacon_ies);
 
-		rcu_read_lock();
-		beacon_ies = rcu_dereference(req->bss->beacon_ies);
-		if (!beacon_ies) {
-			/*
-			 * Wait up to one beacon interval ...
-			 * should this be more if we miss one?
-			 */
-			sdata_info(sdata, "waiting for beacon from %pM\n",
-				   ifmgd->bssid);
-			assoc_data->timeout =
-				TU_TO_EXP_TIME(req->bss->beacon_interval);
-		} else {
-			const u8 *tim_ie = cfg80211_find_ie(WLAN_EID_TIM,
-							    beacon_ies->data,
-							    beacon_ies->len);
-			if (tim_ie && tim_ie[1] >=
-					sizeof(struct ieee80211_tim_ie)) {
-				const struct ieee80211_tim_ie *tim;
-				tim = (void *)(tim_ie + 2);
-				ifmgd->dtim_period = tim->dtim_period;
-			}
-			assoc_data->have_beacon = true;
-			assoc_data->timeout = jiffies;
+	if (sdata->local->hw.flags & IEEE80211_HW_NEED_DTIM_BEFORE_ASSOC &&
+	    !beacon_ies) {
+		/*
+		 * Wait up to one beacon interval ...
+		 * should this be more if we miss one?
+		 */
+		sdata_info(sdata, "waiting for beacon from %pM\n",
+			   ifmgd->bssid);
+		assoc_data->timeout = TU_TO_EXP_TIME(req->bss->beacon_interval);
+		assoc_data->need_beacon = true;
+	} else if (beacon_ies) {
+		const u8 *tim_ie = cfg80211_find_ie(WLAN_EID_TIM,
+						    beacon_ies->data,
+						    beacon_ies->len);
+		if (tim_ie && tim_ie[1] >= sizeof(struct ieee80211_tim_ie)) {
+			const struct ieee80211_tim_ie *tim;
+			tim = (void *)(tim_ie + 2);
+			ifmgd->dtim_period = tim->dtim_period;
 		}
-		rcu_read_unlock();
-	} else {
 		assoc_data->have_beacon = true;
 		assoc_data->timeout = jiffies;
+	} else {
+		assoc_data->timeout = jiffies;
 	}
+	rcu_read_unlock();
+
 	run_again(ifmgd, assoc_data->timeout);
 
 	if (bss->corrupt_data) {