Re: Question on beacon-miss offloading.

[Ben Greear <greearb@candelatech.com>]

On 06/15/2015 08:35 AM, Ben Greear wrote:
> On 06/14/2015 10:36 PM, Michal Kazior wrote:
>> On 12 June 2015 at 17:37, Ben Greear <greearb@candelatech.com> wrote:
>>> On 06/11/2015 11:03 PM, Michal Kazior wrote:
>>>> On 12 June 2015 at 01:38, Ben Greear <greearb@candelatech.com> wrote:
>>>>> On 06/11/2015 02:07 PM, Ben Greear wrote:
>>>>>> In my ath10k CT firmware, I am disabling the beacon-miss offloading
>>>>>> to save space and because it will not work with lots of virtual
>>>>>> stations.
>>>>>>
>>>>>> But, it must be that I need some way to tell the stack that this
>>>>>> feature is not enabled, because when suddenly kill my AP, then
>>>>>> the ath10k station connected to it shows endless 'beacon loss' events
>>>>>> in 'iw events' output, but it never actually loses connection.
>>>>>>
>>>>>> Stock firmware works fine, so probably I just need to disable
>>>>>> some feature flag when registering the ath10k hardware
>>>>>> when using CT firmware.
>>>>>>
>>>>>> With stock firmware, I see a quick dissassociation due to inactivity.
>>>>>>
>>>>>> I am having poor luck finding how a driver tells the stack
>>>>>> it has beacon miss offload or not, so, does anyone know how
>>>>>> this is controlled?
>>>>>
>>>>> I still am not sure why stock firmware works, but it appears
>>>>> the reason mine is failing is that the ACK status for mgt frames
>>>>> is always set to TRUE since the ath10k wmi-mgt-tx API is so
>>>>> lame.  So, mac80211 does a probe, ath10k lies and says it was
>>>>> acked, and mac80211 then things all is well for another few
>>>>> seconds.
>>>>
>>>> mac80211 shouldn't do a Probe Req to an AP on beacon loss because
>>>> ath10k advertises it supports tx-status report. Hence mac80211 should
>>>> use NullFunc frames which shouldn't go through wmi-mgmt-tx but htt
>>>> tx-frm.
>>>>
>>>> But then again: NullFunc status reporting via htt tx-frm was broken on
>>>> 10.1 if memory serves right. I believe it was fixed in 10.2 or 10.2.4.
>>>>
>>>> This problem has been effectively obscured on stock 10.1 by the
>>>> offloaded beacon miss.
>>>
>>> Thanks for the hint.  I was able to fix my firmware to properly
>>> return htt tx status, and now it appears to work properly.
>>>
>>> A quick throughput test works as well, so hopefully no regressions.
>>>
>>> I guess the NulFunc related comment is incorrect for 10.1 stock firmware?
>>>
>>> Maybe some others?
>>>
>>> static void ath10k_tx_htt(struct ath10k *ar, struct sk_buff *skb)
>>> {
>>>         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
>>>         int ret = 0;
>>>
>>>         if (ar->htt.target_version_major >= 3) {
>>>                 /* Since HTT 3.0 there is no separate mgmt tx command */
>>>                 ret = ath10k_htt_tx(&ar->htt, skb);
>>>                 goto exit;
>>>         }
>>>
>>>         if (ieee80211_is_mgmt(hdr->frame_control)) {
>>>                 if (test_bit(ATH10K_FW_FEATURE_HAS_WMI_MGMT_TX,
>>>                              ar->fw_features)) {
>>>                         if (skb_queue_len(&ar->wmi_mgmt_tx_queue) >=
>>>                             ATH10K_MAX_NUM_MGMT_PENDING) {
>>>                                 ath10k_warn(ar, "reached WMI management transmit queue limit\n");
>>>                                 ret = -EBUSY;
>>>                                 goto exit;
>>>                         }
>>>
>>>                         skb_queue_tail(&ar->wmi_mgmt_tx_queue, skb);
>>>                         ieee80211_queue_work(ar->hw, &ar->wmi_mgmt_tx_work);
>>>                 } else {
>>>                         ret = ath10k_htt_mgmt_tx(&ar->htt, skb);
>>>                 }
>>>         } else if (!test_bit(ATH10K_FW_FEATURE_HAS_WMI_MGMT_TX,
>>>                              ar->fw_features) &&
>>>                    ieee80211_is_nullfunc(hdr->frame_control)) {
>>>                 /* FW does not report tx status properly for NullFunc frames
>>>                  * unless they are sent through mgmt tx path. mac80211 sends
>>>                  * those frames when it detects link/beacon loss and depends
>>>                  * on the tx status to be correct. */
>>>                 ret = ath10k_htt_mgmt_tx(&ar->htt, skb);
>>>         } else {
>>>                 ret = ath10k_htt_tx(&ar->htt, skb);
>>>         }
>>
>> The NullFunc workaround was originally done for 999.999.0.636 but
>> should be true for 10.1 as well with the sole exception the latter
>> doesn't have htt-mgmt-tx to workaround the problem.
> 
> Is it correct to say that this logic is completely broken for stock 10.1 firmware
> because null-func frames are not management frames, so the packet goes out the
> ath10k_htt_mgmt_tx call, and stock 10.1 does not properly do tx status
> for htt-tx frames?
> 
> 
> And slightly different question:  Once I put in proper htt ACK reporting into
> my firmware, I notice that stations often loose connectivity when they are
> idle.  I captured a sniff, and it appears the null-func packets are sent,
> but the header is not requesting an explicit ACK, and the AP does not ACK it,
> so connection is lost.
> 
> I guess that the null-func frames should be requesting explicit ACK?

This patch below (with firmware fix to make it actually pay attention
to this special TID in station mode), fixes the null-func to be non-qos
frames and get immediate ack.  This in turn seems to fix the disconnect
issue I was facing, though I need to test some more to be sure.

This seem reasonable, maybe even for upstream?

[greearb@ben-dt2 ath10k]$ git diff
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 6ca48e3..610447e 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -2213,6 +2213,9 @@ static u8 ath10k_tx_h_get_tid(struct ieee80211_hdr *hdr)
        if (ieee80211_is_mgmt(hdr->frame_control))
                return HTT_DATA_TX_EXT_TID_MGMT;

+       if (ieee80211_is_nullfunc(hdr->frame_control))
+               return HTT_DATA_TX_EXT_TID_NON_QOS_MCAST_BCAST;
+
        if (!ieee80211_is_data_qos(hdr->frame_control))
                return HTT_DATA_TX_EXT_TID_NON_QOS_MCAST_BCAST;


Thanks,
Ben



-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com


_______________________________________________
ath10k mailing list
ath10k@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/ath10k