On Mon, Apr 20, 2015 at 10:52 PM, Emmanuel Grumbach
<emmanuel.grumbach@xxxxxxxxx> wrote:
> From: Avri Altman <avri.altman@xxxxxxxxx>
>
> This concerns a bugy behavior of some APs, that advertise themselves
> falsely as supporting U-APSD, but they don't which affects throughput.
> It was detected in iPhones, but recently also with some Netgear models.
> Those devices also advertise their capabilities as SISO, so use that
> and disable U-APSD if connected to a SISO AP.
>
> Signed-off-by: Avri Altman <avri.altman@xxxxxxxxx>
> Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
> ---
[...]
> static bool is_uapsd_supported(struct ieee802_11_elems *elems)
> {
> u8 qos_info;
> + int i;
>
> if (elems->wmm_info && elems->wmm_info_len == 7
> && elems->wmm_info[5] == 1)
> @@ -53,6 +54,22 @@ static bool is_uapsd_supported(struct ieee802_11_elems *elems)
> /* no valid wmm information or parameter element found */
> return false;
>
> + /*
> + * 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.
> + */
> + if (elems->parse_error || !elems->ht_cap_elem)
> + goto mimo;
> +
> + for (i = 1; i < 4; i++) {
> + if (elems->ht_cap_elem->mcs.rx_mask[i])
> + goto mimo;
> + }
> + return false;
> +
> +mimo:
> return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
> }
this is pretty confusing, as MIMO really has nothing to do with uapsd.
i guess this is only some heuristics for "incompatible ap". better
move it into a new function with a name indicating that this is only a
workaround.
this will also improve the function flow, which became a bit weird
with this patch.
Eliad.
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