[Cake] overhead and mpu

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Tue Sep 5 11:33:40 EDT 2017

On 05/09/17 15:37, Ryan Mounce wrote:
> +1
> It would also be nice for tc to know whether the overhead has been
> explicitly configured and report appropriately. In my case I use cake
> on a VLAN sub-interface that happens to have a hard_header_len of 18
> after the 802.1q tag, and then use the docsis keyword to more
> explicitly configure the overhead in case I move to an untagged
> interface in the future. tc -s qdisc can't tell the difference and
> reports 'raw mpu 64' rather than 'overhead 18 mpu 64'.

The almost reality is that you could do whatever you want with the LEDE 
patch that adds cake awareness to iproute2's tc.  The challenge comes in 
keeping it up to date with whatever lands in 'cake master' and 'cake 
aware tc master'

I say almost reality because some on the LEDE committers list question 
things (rightly) if you're not pointing at master. For these reasons 
(and others) I've been reluctant to point LEDE cake at the cobalt branch 
so the 'in test' features of cobalt (and matching tc) are not being 
exercised there (ingress mode, "Voice tin traffic sometimes delayed by 
more than one bulk packet in best effort" 'solution' except it doesn't 
appear to have solved it)

Either the cobalt branch features need to get into master (and someone 
update the LEDE cake & iproute2 packages) OR someone needs to take the 
step to point LEDE cake at cobalt (and update the packages etc etc)

Cake on LEDE is currently without a maintainer and the cake list & repo 
has been incredibly quiet for the past 4+ months.

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