I always need a miracle to connect with iwlwifi

Felipe Contreras felipe.contreras
Fri Nov 8 06:18:51 PST 2013

On Fri, Nov 8, 2013 at 8:06 AM, Krishna Chaitanya
<chaitanya.mgit at gmail.com> wrote:
> On Fri, Nov 8, 2013 at 6:44 PM, Felipe Contreras
> <felipe.contreras at gmail.com> wrote:
>> On Fri, Nov 8, 2013 at 2:35 AM, Felipe Contreras
>> <felipe.contreras at gmail.com> wrote:
>>> On Sat, Nov 2, 2013 at 2:05 PM, Krishna Chaitanya
>>> <chaitanya.mgit at gmail.com> wrote:
>>>> Also one more thing you said N900 uses mac80211 and it has no issues, but as
>>>> its a embedded device it might running an older kernel where the
>>>> handling might be
>>>> different, so we need to try with the same kernel you are facing an
>>>> issue with the
>>>> a driver which advertises IEEE80211_HW_NEED_DTIM_BEFORE_ASSOC.
>>> Yes it was running an older kernel, but I just compiled v3.12 and ran
>>> it on the N900, and still everything works fine.
>>>> (or) if you a have a compilation environment try commenting the advertisement of
>>>> IEEE80211_HW_NEED_DTIM_BEFORE_ASSOC in the iwlwifi DVM driver and
>>>> try to reproduce the issue.
>>> After commenting that flag everything works fine :)
> Oh, great. That was just to corner the problem, that means we are not getting
> the required beacon  before the association, but we only wait for 1 beacon here
> may be we to wait for some number of beacons before giving up the association??
> Johannes??

But we are receiving 0 beacons, waiting for more than 1 won't help.
BTW, why NEED_DTIM_BEFORE_ASSOC if the device doesn't *need* the DTIM
before the association?

>>> What are the next steps?
>> I tried to add some debugging to see what's going on, and indeed the
>> beacon packets are lost, I added debugging as low in the chain as I
>> could (iwlagn_rx_reply_rx()), and I don't see them there. However,
>> when I enable the monitor mode, I see them. What's going on?
> In the captures you shared all the beacons are malformed, so
> probably they failed the CRC check. iwlwifi drops all the CRC failed
> packets. (doth MVM and DVM)

Before iwlagn_rx_reply_rx()?

> Not sure how you are receiving the beacons in the monitor mode.

I don't know what kismet does, but I can see my debugging is printing them.

> BTW did you tried capturing the beacons in other devices and see if they
> are really malformed, or is it just iwlwifi interpreting them wrongly.?

I haven't managed to do that yet.

This is what I'm doing:

--- a/drivers/net/wireless/iwlwifi/dvm/rx.c
+++ b/drivers/net/wireless/iwlwifi/dvm/rx.c
@@ -919,6 +919,11 @@ static int iwlagn_rx_reply_rx(struct iwl_priv *priv,
        ampdu_status = iwlagn_translate_rx_status(priv,

+       if (ieee80211_is_beacon(header->frame_control)) {
+               print_hex_dump(KERN_INFO, "iwlwifi: dump: ", DUMP_PREFIX_OFFSET,
+                               16, 1, header, len, true);
+       }
        if ((unlikely(phy_res->cfg_phy_cnt > 20))) {
                IWL_DEBUG_DROP(priv, "dsp size out of range [0,20]: %d\n",

Felipe Contreras

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