Hi,
ieee80211_recalc_ps is enabling power save before the 4-way Handshake
completes in station mode. This can potentially delay when the station
is authorized to send/receive traffic. Specifically, this is a problem
when dynamic power save is disabled and the station must therefore
send PS-Polls (or U-APSD trigger frames) for retrieve downlink EAPOL
frames. This may result in a failed 4-way Handshake if the AP's (or
authenticators) timing requirements are strict and/or dependent on the
beacon interval etc. It also increases total roaming time, which
becomes an issue if the station is part of a VoIP solution.
I've also found at least one AP (Cisco1252) whose's U-APSD
implementation is broken if power save is enabled before the 4-way
Handshake completes; it will not deliver the buffered downlink EAPOL
frames to the station in response to U-APSD trigger frames, despite
the fact that the AP is advertising traffic in the TIM.
Something like the following prevents powersave from being enabled
before the 4-way handshake completes, but we still need to call
ieee80211_recalc_ps again after WLAN_STA_AUTHORIZED is set and I'm not
sure the best place for that. Any ideas or alternate approaches that
may solve this problem?
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index cc984bd..64d92d5 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -613,6 +613,37 @@ static void ieee80211_change_ps(struct
ieee80211_local *local)
}
}
+static bool ieee80211_powersave_allowed(struct ieee80211_sub_if_data *sdata)
+{
+ struct ieee80211_if_managed *mgd = &sdata->u.mgd;
+ struct sta_info *sta = NULL;
+ u32 sta_flags = 0;
+
+ if (!mgd->powersave)
+ return false;
+
+ if (!mgd->associated)
+ return false;
+
+ if (!mgd->associated->beacon_ies)
+ return false;
+
+ if (mgd->flags & (IEEE80211_STA_BEACON_POLL |
+ IEEE80211_STA_CONNECTION_POLL))
+ return false;
+
+ rcu_read_lock();
+ sta = sta_info_get(sdata, mgd->bssid);
+ if (sta)
+ sta_flags = get_sta_flags(sta);
+ rcu_read_unlock();
+
+ if (!(sta_flags & WLAN_STA_AUTHORIZED))
+ return false;
+
+ return true;
+}
+
/* need to hold RTNL or interface lock */
void ieee80211_recalc_ps(struct ieee80211_local *local, s32 latency)
{
@@ -647,11 +678,7 @@ void ieee80211_recalc_ps(struct ieee80211_local
*local, s32 late
count++;
}
- if (count == 1 && found->u.mgd.powersave &&
- found->u.mgd.associated &&
- found->u.mgd.associated->beacon_ies &&
- !(found->u.mgd.flags & (IEEE80211_STA_BEACON_POLL |
- IEEE80211_STA_CONNECTION_POLL))) {
+ if (count == 1 && ieee80211_powersave_allowed(found)) {
struct ieee80211_conf *conf = &local->hw.conf;
s32 beaconint_us;
--
Jason Young
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