Re: d80211: How does TX flow control work?

[Jan Kiszka <jan.kiszka@web.de>]

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Jan Kiszka wrote:
> Johannes Berg wrote:
>>> The actual problem was meanwhile identified: shorewall happened to
>>> overwrite the queueing discipline of wmaster0 with pfifo_fast. I found
>>> the magic knob to tell shorewall to no longer do this (at least until I
>>> want to manage traffic control that way...), but I still wonder if it is
>>> an acceptable situation. Currently, the user can intentionally or
>>> accidentally screw up the stack this way.
>> I don't seem to be able to do that:
>>
>> # tc qdisc change dev wmaster0 pfifo
>> RTNETLINK answers: Invalid argument
>>
>> # tc qdisc replace dev wmaster0 pfifo
>> RTNETLINK answers: Invalid argument
>>
>> what exactly does shorewall do?
>>
> 
> Don't recall... need to re-test... lacking time. :(
> 
> Just one note: I observed this on a 2.6.19 kernel - in case there is a
> difference to the latest.
> 

Now I came across this issue once again. It is still present, I just
observed it over the latest rt2x00 tree after updating shorewall and
forgetting to fix its config.

I redirected tc to some logging filter, and this is what shorewall does
when "CLEAR_TC=Yes" is set in shorewall.conf:

...
tc qdisc del dev wmaster0 root
tc qdisc del dev wmaster0 ingress
tc qdisc del dev wlan0 root
tc qdisc del dev wlan0 ingress

HTH,
Jan


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