mac80211: use nullfunc instead of probe request for connection monitoring

nullfunc frames are better for connection monitoring, because probe requests
are answered even if the AP has already dropped the connection, whereas
nullfunc frames from an unassociated station will trigger a disassoc/deauth
frame from the AP (WLAN_REASON_CLASS3_FRAME_FROM_NONASSOC_STA), which allows
the station to reconnect immediately instead of waiting until it attempts to
transmit the next unicast frame.

This only works on hardware with reliable tx ACK reporting, any other hardware
needs to fall back to the probe request method.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index ff7bc307827b6e59b718f6d95a783b42557b27e5..5bc0745368fec3dcf178b5d3c6af6d92005f2045 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1265,6 +1265,8 @@ void ieee80211_send_nullfunc(struct ieee80211_local *local,
                             int powersave);
 void ieee80211_sta_rx_notify(struct ieee80211_sub_if_data *sdata,
                             struct ieee80211_hdr *hdr);
+void ieee80211_sta_tx_notify(struct ieee80211_sub_if_data *sdata,
+                            struct ieee80211_hdr *hdr);
 void ieee80211_beacon_connection_loss_work(struct work_struct *work);
 
 void ieee80211_wake_queues_by_reason(struct ieee80211_hw *hw,

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 849d9c639add2d7f0656c094d05a0cd29b374d1a..33ffce3ec605c968924495b6806923471c4ec53a 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1034,6 +1034,51 @@ void ieee80211_sta_rx_notify(struct ieee80211_sub_if_data *sdata,
        ieee80211_sta_reset_conn_monitor(sdata);
 }
 
+static void ieee80211_reset_ap_probe(struct ieee80211_sub_if_data *sdata)
+{
+       struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+
+       if (!(ifmgd->flags & (IEEE80211_STA_BEACON_POLL |
+                             IEEE80211_STA_CONNECTION_POLL)))
+           return;
+
+       ifmgd->flags &= ~(IEEE80211_STA_CONNECTION_POLL |
+                         IEEE80211_STA_BEACON_POLL);
+       mutex_lock(&sdata->local->iflist_mtx);
+       ieee80211_recalc_ps(sdata->local, -1);
+       mutex_unlock(&sdata->local->iflist_mtx);
+
+       if (sdata->local->hw.flags & IEEE80211_HW_CONNECTION_MONITOR)
+               return;
+
+       /*
+        * We've received a probe response, but are not sure whether
+        * we have or will be receiving any beacons or data, so let's
+        * schedule the timers again, just in case.
+        */
+       ieee80211_sta_reset_beacon_monitor(sdata);
+
+       mod_timer(&ifmgd->conn_mon_timer,
+                 round_jiffies_up(jiffies +
+                                  IEEE80211_CONNECTION_IDLE_TIME));
+}
+
+void ieee80211_sta_tx_notify(struct ieee80211_sub_if_data *sdata,
+                            struct ieee80211_hdr *hdr)
+{
+       if (!ieee80211_is_data(hdr->frame_control) &&
+           !ieee80211_is_nullfunc(hdr->frame_control))
+           return;
+
+       ieee80211_sta_reset_conn_monitor(sdata);
+
+       if (ieee80211_is_nullfunc(hdr->frame_control) &&
+           sdata->u.mgd.probe_send_count > 0) {
+               sdata->u.mgd.probe_send_count = 0;
+               ieee80211_queue_work(&sdata->local->hw, &sdata->work);
+       }
+}
+
 static void ieee80211_mgd_probe_ap_send(struct ieee80211_sub_if_data *sdata)
 {
        struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
@@ -1049,8 +1094,19 @@ static void ieee80211_mgd_probe_ap_send(struct ieee80211_sub_if_data *sdata)
        if (ifmgd->probe_send_count >= unicast_limit)
                dst = NULL;
 
-       ssid = ieee80211_bss_get_ie(ifmgd->associated, WLAN_EID_SSID);
-       ieee80211_send_probe_req(sdata, dst, ssid + 2, ssid[1], NULL, 0);
+       /*
+        * When the hardware reports an accurate Tx ACK status, it's
+        * better to send a nullfunc frame instead of a probe request,
+        * as it will kick us off the AP quickly if we aren't associated
+        * anymore. The timeout will be reset if the frame is ACKed by
+        * the AP.
+        */
+       if (sdata->local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS)
+               ieee80211_send_nullfunc(sdata->local, sdata, 0);
+       else {
+               ssid = ieee80211_bss_get_ie(ifmgd->associated, WLAN_EID_SSID);
+               ieee80211_send_probe_req(sdata, dst, ssid + 2, ssid[1], NULL, 0);
+       }
 
        ifmgd->probe_send_count++;
        ifmgd->probe_timeout = jiffies + IEEE80211_PROBE_WAIT;
@@ -1517,29 +1573,8 @@ static void ieee80211_rx_mgmt_probe_resp(struct ieee80211_sub_if_data *sdata,
        ieee80211_rx_bss_info(sdata, mgmt, len, rx_status, &elems, false);
 
        if (ifmgd->associated &&
-           memcmp(mgmt->bssid, ifmgd->associated->bssid, ETH_ALEN) == 0 &&
-           ifmgd->flags & (IEEE80211_STA_BEACON_POLL |
-                           IEEE80211_STA_CONNECTION_POLL)) {
-               ifmgd->flags &= ~(IEEE80211_STA_CONNECTION_POLL |
-                                 IEEE80211_STA_BEACON_POLL);
-               mutex_lock(&sdata->local->iflist_mtx);
-               ieee80211_recalc_ps(sdata->local, -1);
-               mutex_unlock(&sdata->local->iflist_mtx);
-
-               if (sdata->local->hw.flags & IEEE80211_HW_CONNECTION_MONITOR)
-                       return;
-
-               /*
-                * We've received a probe response, but are not sure whether
-                * we have or will be receiving any beacons or data, so let's
-                * schedule the timers again, just in case.
-                */
-               ieee80211_sta_reset_beacon_monitor(sdata);
-
-               mod_timer(&ifmgd->conn_mon_timer,
-                         round_jiffies_up(jiffies +
-                                          IEEE80211_CONNECTION_IDLE_TIME));
-       }
+           memcmp(mgmt->bssid, ifmgd->associated->bssid, ETH_ALEN) == 0)
+               ieee80211_reset_ap_probe(sdata);
 }
 
 /*
@@ -1891,7 +1926,12 @@ void ieee80211_sta_work(struct ieee80211_sub_if_data *sdata)
                u8 bssid[ETH_ALEN];
 
                memcpy(bssid, ifmgd->associated->bssid, ETH_ALEN);
-               if (time_is_after_jiffies(ifmgd->probe_timeout))
+
+               /* ACK received for nullfunc probing frame */
+               if (!ifmgd->probe_send_count)
+                       ieee80211_reset_ap_probe(sdata);
+
+               else if (time_is_after_jiffies(ifmgd->probe_timeout))
                        run_again(ifmgd, ifmgd->probe_timeout);
 
                else if (ifmgd->probe_send_count < IEEE80211_MAX_PROBE_TRIES) {

diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index 3153c19893b81ebe1309290b41491010cd296999..8695cd11dfd95b8b5df5692ea1a5d6c1a11d5415 100644 (file)
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -155,6 +155,10 @@ static void ieee80211_frame_acked(struct sta_info *sta, struct sk_buff *skb)
 
                ieee80211_queue_work(&local->hw, &local->recalc_smps);
        }
+
+       if ((sdata->vif.type == NL80211_IFTYPE_STATION) &&
+           (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS))
+               ieee80211_sta_tx_notify(sdata, (void *) skb->data);
 }
 
 void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)