netdev - Re: TBF man page: peakrate must be greater than rate

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Date:   Fri, 3 Sep 2021 09:21:29 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Andy Walker <camtarn@...tarn.org>
Cc:     netdev@...r.kernel.org
Subject: Re: TBF man page: peakrate must be greater than rate

On Fri, 3 Sep 2021 16:48:45 +0100
Andy Walker <camtarn@...tarn.org> wrote:

> Hi,
> 
> I was struggling with the following command line:
> tc qdisc add dev eth1 parent 1:1 handle 10: tbf rate 10.0kbit maxburst
> 10kb latency 50ms peakrate 10kbit mtu 1600
> RTNETLINK answers: Invalid argument
> 
> When I altered peakrate to be 10.1kbit, tbf accepted its parameters.
> 
> Looking in dmesg, I found the following:
> 
> sch_tbf: peakrate 1250 is lower than or equals to rate 1250
> 
> The man page does not specify that peakrate needs to be greater than
> rate. This would probably be a useful addition, as it's easy to assume
> that the two can/should be set to the same value for precise rate
> limiting.
> 
> Thanks,
> Andy

The kernel should be reporting error message via netlink extack
but it isn't.  Anytime user has to look in dmesg to see an error
it is bad.

TBF is old and rarely modified code in the kernel. It looks like
it could use some attention.