mac80211: sync dtim_count to TSF

On starting a mesh or AP BSS, the interface dtim_count
countdown should match that of the driver TSF.

Signed-off-by: Thomas Pedersen <twpedersen@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1035,6 +1035,7 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
 		return err;
 	}
 
+	ieee80211_recalc_dtim(local, sdata);
 	ieee80211_bss_info_change_notify(sdata, changed);
 
 	netif_carrier_on(dev);

net/mac80211/debugfs_netdev.c

@@ -474,6 +474,7 @@ static ssize_t ieee80211_if_parse_tsf(
 		}
 	}
 
+	ieee80211_recalc_dtim(local, sdata);
 	return buflen;
 }
 IEEE80211_IF_FILE_RW(tsf);

net/mac80211/ieee80211_i.h

@@ -1800,6 +1800,8 @@ ieee80211_cs_get(struct ieee80211_local *local, u32 cipher,
 int ieee80211_cs_headroom(struct ieee80211_local *local,
 			  struct cfg80211_crypto_settings *crypto,
 			  enum nl80211_iftype iftype);
+void ieee80211_recalc_dtim(struct ieee80211_local *local,
+			   struct ieee80211_sub_if_data *sdata);
 
 #ifdef CONFIG_MAC80211_NOINLINE
 #define debug_noinline noinline

net/mac80211/mesh.c

@@ -807,6 +807,7 @@ int ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata)
 		return -ENOMEM;
 	}
 
+	ieee80211_recalc_dtim(local, sdata);
 	ieee80211_bss_info_change_notify(sdata, changed);
 
 	netif_carrier_on(sdata->dev);

net/mac80211/util.c

@@ -2734,3 +2734,44 @@ int ieee80211_parse_p2p_noa(const struct ieee80211_p2p_noa_attr *attr,
 	return ret;
 }
 EXPORT_SYMBOL(ieee80211_parse_p2p_noa);
+
+void ieee80211_recalc_dtim(struct ieee80211_local *local,
+			   struct ieee80211_sub_if_data *sdata)
+{
+	u64 tsf = drv_get_tsf(local, sdata);
+	u64 dtim_count = 0;
+	u16 beacon_int = sdata->vif.bss_conf.beacon_int * 1024;
+	u8 dtim_period = sdata->vif.bss_conf.dtim_period;
+	struct ps_data *ps;
+	u8 bcns_from_dtim;
+
+	if (tsf == -1ULL || !beacon_int || !dtim_period)
+		return;
+
+	if (sdata->vif.type == NL80211_IFTYPE_AP ||
+	    sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
+		if (!sdata->bss)
+			return;
+
+		ps = &sdata->bss->ps;
+	} else if (ieee80211_vif_is_mesh(&sdata->vif)) {
+		ps = &sdata->u.mesh.ps;
+	} else {
+		return;
+	}
+
+	/*
+	 * actually finds last dtim_count, mac80211 will update in
+	 * __beacon_add_tim().
+	 * dtim_count = dtim_period - (tsf / bcn_int) % dtim_period
+	 */
+	do_div(tsf, beacon_int);
+	bcns_from_dtim = do_div(tsf, dtim_period);
+	/* just had a DTIM */
+	if (!bcns_from_dtim)
+		dtim_count = 0;
+	else
+		dtim_count = dtim_period - bcns_from_dtim;
+
+	ps->dtim_count = dtim_count;
+}