mac80211: use ps-poll when dynamic power save mode is disabled

When a directed tim bit is set, mac80211 currently disables power save
ands sends a null frame to the AP. But if dynamic power save is
disabled, mac80211 will not enable power save ever gain. Fix this by
adding ps-poll functionality to mac80211. When a directed tim bit is
set, mac80211 sends a ps-poll frame to the AP and checks for the more
data bit in the returned data frames.

Using ps-poll is slower than waking up with null frame, but it's saves more
power in cases where the traffic is low. Userspace can control if either
ps-poll or null wakeup method is used by enabling and disabling dynamic
power save.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 51 insertions, 3 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 05c8d13d39b6..169f10c51042 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -511,6 +511,39 @@ static void ieee80211_send_deauth_disassoc(struct ieee80211_sub_if_data *sdata,
         ieee80211_tx_skb(sdata, skb, ifsta->flags & IEEE80211_STA_MFP_ENABLED);
 }
 
+void ieee80211_send_pspoll(struct ieee80211_local *local,
+                           struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+        struct ieee80211_pspoll *pspoll;
+        struct sk_buff *skb;
+        u16 fc;
+
+        skb = dev_alloc_skb(local->hw.extra_tx_headroom + sizeof(*pspoll));
+        if (!skb) {
+                printk(KERN_DEBUG "%s: failed to allocate buffer for "
+                       "pspoll frame\n", sdata->dev->name);
+                return;
+        }
+        skb_reserve(skb, local->hw.extra_tx_headroom);
+
+        pspoll = (struct ieee80211_pspoll *) skb_put(skb, sizeof(*pspoll));
+        memset(pspoll, 0, sizeof(*pspoll));
+        fc = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_PSPOLL | IEEE80211_FCTL_PM;
+        pspoll->frame_control = cpu_to_le16(fc);
+        pspoll->aid = cpu_to_le16(ifsta->aid);
+
+        /* aid in PS-Poll has its two MSBs each set to 1 */
+        pspoll->aid |= cpu_to_le16(1 << 15 | 1 << 14);
+
+        memcpy(pspoll->bssid, ifsta->bssid, ETH_ALEN);
+        memcpy(pspoll->ta, sdata->dev->dev_addr, ETH_ALEN);
+
+        ieee80211_tx_skb(sdata, skb, 0);
+
+        return;
+}
+
 /* MLME */
 static void ieee80211_sta_def_wmm_params(struct ieee80211_sub_if_data *sdata,
                                          struct ieee80211_bss *bss)
@@ -1868,9 +1901,24 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
                 directed_tim = ieee80211_check_tim(&elems, ifsta->aid);
 
                 if (directed_tim) {
-                        local->hw.conf.flags &= ~IEEE80211_CONF_PS;
-                        ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
-                        ieee80211_send_nullfunc(local, sdata, 0);
+                        if (local->hw.conf.dynamic_ps_timeout > 0) {
+                                local->hw.conf.flags &= ~IEEE80211_CONF_PS;
+                                ieee80211_hw_config(local,
+                                                    IEEE80211_CONF_CHANGE_PS);
+                                ieee80211_send_nullfunc(local, sdata, 0);
+                        } else {
+                                local->pspolling = true;
+
+                                /*
+                                 * Here is assumed that the driver will be
+                                 * able to send ps-poll frame and receive a
+                                 * response even though power save mode is
+                                 * enabled, but some drivers might require
+                                 * to disable power save here. This needs
+                                 * to be investigated.
+                                 */
+                                ieee80211_send_pspoll(local, sdata);
+                        }
                 }
         }