Re: iwd not connecting on Raspberry Pi with Raspbian

[Denis Kenzior <denkenz@gmail.com>]

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Hi Patrick,

On 8/30/20 8:38 AM, Patrick Häcker wrote:
> Hi Denis,
> 
> thanks for the answer!
> 
>> This is a brcmfmac card right?  We have seen some weirdness with brcmfmac
>> where it simply refuses to perform the handshake (which is what is
>> happening in your case).  The handshake times out (reason: 15 =
>> MMPDU_REASON_CODE_4WAY_HANDSHAKE_TIMEOUT).
>>
>> The strange part is that it does work in other setups and it seems to be a
>> combination of AP or some other weird factor that screws this up.  Have you
>> tried different brcmfmac firmware versions?
> Yes, it's a brcmfmac card. I speculate, that it had some state, which iwd did
> not expect due to booting up with wpa_supplicant and only switching to iwd
> afterwards (it worked after I removed wpa_supplicant and rebooted).

There isn't really any state for iwd to be confused by.   Once a CMD_DISCONNECT 
is issued, or the device brought into IF_OPER_DOWN state, the kernel / driver 
should clean up any state associated with the previous connection.

iwd tries to reset as much of the driver as possible at startup, by 
deleting/re-creating the default interface and power-cycling the card. 
Unfortunately brcmfmac doesn't support the first part either.

The issue is likely that wpa_s uses handshake offload (with handshake handled by 
the firmware) and iwd does not.  This maybe leads to the firmware or driver 
being confused possibly due to some missing cleanups.  But that's a kernel 
driver / firmware issue, not a problem in iwd.

> 
> Therefore I did not try different brcmfmac firmware versions. I am probably
> using this firmware:
>> brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip
>>      BCM4345/6
>> brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4345/6 wl0: Mar 23 2020
>>      02:19:54 version 7.45.206 (r725000 CY) FWID 01-88ee44ea
> 
>>>> src/wiphy.c:wiphy_reg_notify() Notification of command Reg Change(36)
>>>> src/wiphy.c:wiphy_update_reg_domain() New reg domain country code for
>>>>
>>>>       (global) is DE
>>
>> Seems like the kernel is switching the regulatory domain here, right after
>> we try to connect.  I wonder if you can use iw to set this prior to
>> triggering the connection with iwd.  Does anything change?
> Actually, the reg domain is set before to the correct value (DE in my case, I
> have double-checked that, when I saw the message in the logs). I am not sure
> why it's switching.  I am on channel 13, so with an US/default reg domain I
> couldn't access the 2-GHz-Wi-Fi.

Okay, we can seemingly rule that out then...

> 
>>>> src/netdev.c:netdev_link_notify() event 16 on ifindex 3
>>>> src/netdev.c:netdev_mlme_notify() MLME notification Disconnect(48)
>>>> src/netdev.c:netdev_disconnect_event()
>>>> Received Deauthentication event, reason: 2, from_ap: false
>>
>> And here we see the firmware using an incorrect password somehow and
>> triggering a disconnect by itself, without iwd's input.  I think James had
>> the exact same issue on RPI4, and we determined that the firmware/driver
>> was just borked...
> The provided password was definitely correct, as it's provided by a file and
> working now without being changed in between. But it might be, that the
> firmware/driver ended up with a wrong authentication somehow, although the
> correct password was provided.
> 
>>>> src/station.c:station_disconnect_event() 3
>>>> src/station.c:station_disassociated() 3
>>>> src/station.c:station_enter_state() Old State: connecting, new state:
>>>> disconnected >
>>>
>>> I could imagine, that there is still a kernel module missing, but this is
>>> just guessing. Any hints how to continue debugging?
>>
>> This is a driver / firmware problem.  You say that wpa_s works correctly.
>> Can you capture iwmon traces of both wpa_s and iwd trying to connect to the
>> same AP and share that with us?
> I wanted to use iwmon already before. Unfortunately, it does not work on this
> system:
>> Wireless monitor ver 1.8
>> Failed to create monitor interface nlmon: Unknown error -95
> There is (to me) no obvious error in its strace, but I am omitting it here, as
> it is probably a separate issue and I am not sure if anyone is interested in
> solving that problem.

You do not have nlmon (CONFIG_NLMON) compiled into the kernel or perhaps the 
nlmon module is not loaded.

> 
> So where to go from here on? The principle issue (iwd in Raspbian) is solved.
> But if someone is interested to find and fix the root cause to avoid the
> removing/rebooting procedure on the Raspberry Pi in the future, I can assist
> with this (although my time is limited mostly to weekends).
> My gut feeling is, that we need to fix that issue before suggesting to have iwd
> as default on a Raspberry.
> 

Not sure, but so far it really sounds like you need to start a thread on 
linux-wireless and get brcmfmac maintainer's attention.

Regards,
-Denis