Sometimes RxBitrate of 1000 Kbit/s

["Patrick Häcker" <pat_h@web.de>]

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Hello all,

from time to time my RxBitrate (sometimes the TxBitrate, too) goes down to
1000 Kbit/s, whereas it otherwise is in the usual 5 to 6 digit range. This
seems to especially happen some time after waking up from standby (S3), maybe
also from hibernate (S4).

When it happens, wireless usage is super slow to non-existent.

Restarting iwd immediately solves the problem. I routinely also reloaded the
involved kernel modules, but I think this was unnecessary as I
skipped it the last few times and only restarted iwd and this was enough to
get it back to a working state.

Naturally, it seems to occur every few hours, but I might be able to trigger
it more often with extensive standby cycles, but I am not sure.

That's how it looks when it happens (although TxBitrate is often still in the
normal 5 to 6 digit rate; please note ExpectedThroughput being much larger
than TxBitrate or RxBitrate):
# iwctl station wlan0 show
                                 Station: wlan0
--------------------------------------------------------------------------------
  Settable  Property              Value
--------------------------------------------------------------------------------
            Scanning              no
            State                 connected
            Connected network     *redacted*
            IPv4 address          192.168.0.10
            ConnectedBss          98:9b:cb:4b:b1:cc
            Frequency             2412
            Security              WPA3-Personal
            RSSI                  -44 dBm
            AverageRSSI           -55 dBm
            TxBitrate             1000 Kbit/s
            RxBitrate             1000 Kbit/s
            ExpectedThroughput    56906 Kbit/s

This is how it looks after restarting iwd:
# systemctl restart iwd
# iwctl station wlan0 show
                                 Station: wlan0
--------------------------------------------------------------------------------
  Settable  Property              Value
--------------------------------------------------------------------------------
            Scanning              no
            State                 connected
            Connected network     *redacted*
            IPv4 address          192.168.0.10
            ConnectedBss          98:9b:cb:4b:b1:cd
            Frequency             5180
            Security              WPA3-Personal
            RSSI                  -72 dBm
            AverageRSSI           -72 dBm
            RxMode                802.11n
            RxMCS                 9
            TxMode                802.11n
            TxMCS                 3
            TxBitrate             60000 Kbit/s
            RxBitrate             60000 Kbit/s
            ExpectedThroughput    31125 Kbit/s

Please note, that currently the router steers clients towards either 2.4 GHz
or 5 GHz. I already tried to restrict the client to either of both frequency
bands, but that did not seem to avoid the problem.

# uname -a
Linux mmm 6.0.0-2-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.0.5-1 (2022-10-28)
x86_64 GNU/Linux

(Probably) involved kernel modules:
rt2800usb rt2x00usb rt2800lib rt2x00lib mac80211 cfg80211

The device is a USB device
Ralink Technology, Corp. RT5572 Wireless Adapter

Any tips how to debug this?

From https://iwd.wiki.kernel.org/debugging I would assume, that IWD_GENL_DEBUG
might the relevant environment variable, but I am really not sure.
I could obviously implement some kind of watchdog checking the output of iwctl
every some seconds and restarting iwd in case, but I would avoid that if there
is a cleaner solution available.

I think is problem started to occur some months ago. It might be related with
some kernel or iwd update some time ago. But due to the long time until
occuring, a sound bisect might take more than a week.

Kind regards
Patrick

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