From: Avri Altman <avri.altman@xxxxxxxxx>
There are a few APs our there that advertise U-APSD
capabilities but don't implement it right which leads to
poor traffic. These APs don't support MIMO or don't even
support HT. Use this heuristic to detect them and disable
U-APSD accordingly.
Signed-off-by: Avri Altman <avri.altman@xxxxxxxxx>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
---
net/mac80211/scan.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 7bb6a93..3791c8a 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -39,6 +39,28 @@ void ieee80211_rx_bss_put(struct ieee80211_local *local,
container_of((void *)bss, struct cfg80211_bss, priv));
}
+/*
+ * An incompatible AP workaround:
+ * if the AP does not advertise MIMO capabilities disable U-APSD.
+ * iPhones, among others, advertise themselves as U-APSD capable when
+ * they aren't. Avoid connecting to those devices in U-APSD enabled.
+ */
+static bool broken_uapsd_workarounds(struct ieee802_11_elems *elems)
+{
+ int i;
+
+ /* iPhone 4/4s with this problem doesn't have ht_capa */
+ if (!elems->ht_cap_elem)
+ return true;
+
+ for (i = 1; i < 4; i++) {
+ if (elems->ht_cap_elem->mcs.rx_mask[i])
+ return false;
+ }
+
+ return true;
+}
+
static bool is_uapsd_supported(struct ieee802_11_elems *elems)
{
u8 qos_info;
@@ -53,6 +75,9 @@ static bool is_uapsd_supported(struct ieee802_11_elems *elems)
/* no valid wmm information or parameter element found */
return false;
+ if (broken_uapsd_workarounds(elems))
+ return false;
+
return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
}
--
2.1.4
--
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