Re: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

Re: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

[Kalle Valo]

Randy Dunlap <rdunlap@infradead.org> writes:

> [add netdev mailing list + 2 patch signers]

Adding also linux-wireless. It's always best to send questions about any
wireless issues to linux-wireless

> On 3/3/20 7:34 PM, Mancini, Jason wrote:
>> [I can't seem to access the linux-net ml per kernel.org faq, apology
>> in advance.]
>> 
>> This change, which I think first appeared for v5.5-rc1, basically
>> within seconds, knocks out our [apparently buggy] Comcast wifi for
>> about 2-3 minutes.  Is there a boot option (or similar) where I can
>> achieve prior kernel behavior?  Otherwise I am stuck on kernel 5.4
>> (or Win10) it seems, or forever compiling custom kernels for my
>> choice of distribution [as I don't have physical access to the router
>> in question.]
>> Thanks!
>> Jason
>> 
>> ================
>> 
>> 127eef1d46f80056fe9f18406c6eab38778d8a06 is the first bad commit
>> commit 127eef1d46f80056fe9f18406c6eab38778d8a06
>> Author: Yan-Hsuan Chuang <yhchuang@realtek.com>
>> Date:   Wed Oct 2 14:35:23 2019 +0800

Can you try if this fixes it:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next.git/commit/?id=74c3d72cc13401f9eb3e3c712855e9f8f2d2682b

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

RE: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

[Tony Chuang]

Kalle Valo <kvalo@codeaurora.org> writes:
> 
> Randy Dunlap <rdunlap@infradead.org> writes:
> 
> > [add netdev mailing list + 2 patch signers]
> 
> Adding also linux-wireless. It's always best to send questions about any
> wireless issues to linux-wireless
> 
> > On 3/3/20 7:34 PM, Mancini, Jason wrote:
> >> [I can't seem to access the linux-net ml per kernel.org faq, apology
> >> in advance.]
> >>
> >> This change, which I think first appeared for v5.5-rc1, basically
> >> within seconds, knocks out our [apparently buggy] Comcast wifi for
> >> about 2-3 minutes.  Is there a boot option (or similar) where I can
> >> achieve prior kernel behavior?  Otherwise I am stuck on kernel 5.4
> >> (or Win10) it seems, or forever compiling custom kernels for my
> >> choice of distribution [as I don't have physical access to the router
> >> in question.]
> >> Thanks!
> >> Jason
> >>
> >> ================
> >>
> >> 127eef1d46f80056fe9f18406c6eab38778d8a06 is the first bad commit
> >> commit 127eef1d46f80056fe9f18406c6eab38778d8a06
> >> Author: Yan-Hsuan Chuang <yhchuang@realtek.com>
> >> Date:   Wed Oct 2 14:35:23 2019 +0800
> 
> Can you try if this fixes it:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next.gi
> t/commit/?id=74c3d72cc13401f9eb3e3c712855e9f8f2d2682b
> 

Kalle is providing the right possible patch to fix it.

The first bad commit you found, that causes this issue, introduced TX-AMSDU.
But we found that enabling TX-AMSDU on 2.4G band is not working while
connecting to some APs. So, you can try if the patch provided by Kalle works.
(I hope so). Otherwise, you can enable the kernel log debug mask by:
echo 0xffffffff > /sys/module/rtw88/parameters/debug_mask.
And collect the log to see if there's anything wrong.

Yen-Hsuan

Re: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

[Mancini, Jason]

[AMD Official Use Only - Internal Distribution Only]

I tested Kalle's patch.  Laptop connects via 5GHz band by default.  Comcast router still
crashed in a hurry.  I blocked (via NM.conf) the 5GHz mac of the router, and rebooted
the laptop. Checked that the router was using 2.4 for the laptop.  Still hung the router!

What I've done temporarily is change the unlimited return value from 0 to 4000.
Somewhere around 5325 the Comcast router gets cranky/weird, and at 5350 it is
resetting the wifi stack (without resetting the entire router).

So there's no boot time flag to turn the feature off currently?

Jason

RE: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

[Tony Chuang]

> [AMD Official Use Only - Internal Distribution Only]
> 
> I tested Kalle's patch.  Laptop connects via 5GHz band by default.  Comcast
> router still
> crashed in a hurry.  I blocked (via NM.conf) the 5GHz mac of the router, and
> rebooted
> the laptop. Checked that the router was using 2.4 for the laptop.  Still hung
> the router!
> 
> What I've done temporarily is change the unlimited return value from 0 to
> 4000.
> Somewhere around 5325 the Comcast router gets cranky/weird, and at 5350
> it is
> resetting the wifi stack (without resetting the entire router).
> 
> So there's no boot time flag to turn the feature off currently?
> 

Unfortunately, no, there's no flag to turn off this.

But, from your experiments, if you applied that patch,
("rtw88: disable TX-AMSDU on 2.4G band") connect to AP on 2.4G, and still crash
the Comcast AP, then it looks like it's not TX-AMSDU to be blamed.

Assume the return value you mentioned is max_rc_amsdu_len, if you always
return 1, it will just disable all of the AMSDU process.
You can try it, and to see if sending AMSDU will crash the router or not.

Yen-Hsuan

Re: v5.5-rc1 and beyond insta-kills some Comcast wifi routers

[Jason Mancini]

On 3/4/20 2:41 AM, Tony Chuang wrote:
> Unfortunately, no, there's no flag to turn off this.
> But, from your experiments, if you applied that patch,
> ("rtw88: disable TX-AMSDU on 2.4G band") connect to AP on 2.4G, and still crash
> the Comcast AP, then it looks like it's not TX-AMSDU to be blamed.
>
> Assume the return value you mentioned is max_rc_amsdu_len, if you always
> return 1, it will just disable all of the AMSDU process.
> You can try it, and to see if sending AMSDU will crash the router or not.
>
> Yen-Hsuan

(Specifically, this Comcast router is "Arris TG1682G" firmware 10.1.27B.SIP.PC20.CT hardware version 9.0)

I re-tested tonight, here are the results, from *unpatched* kernels:

(1) 2.4G only w/5G disabled via router control panel: kernel 5.5/5.6 seemingly doesn't upset router.
(2) 5G only w/2.4G disabled via router control panel: kernel 5.5/5.6 definitely kill router wifi.
(3) 5G only w/2.4G disabled via router control panel: plus get_max_amsdu_len forced to return 1: kernel 5.6-rc4 seemingly doesn't upset router.

As you can see, the suggested patch isn't going to help result (2), and apparently isn't needed for (1).  And this router's 5G seems
allergic to amsdu per (3), so somehow amsdu is involved it seems.

Well, I'll just work around it with (3) custom kernels, or (1) leave the router in 2.4G mode.  But be aware that apparently there's at least
one common buggy wifi router that's going to puke on 5G + amsdu.

Jason