[Cake] [lede-project/source] Add support for cake qdisc (#72)

[Toke Høiland-Jørgensen]

moeller0 <moeller0 at gmx.de> writes:

> So, my take on this is that we want to be able to re-map DSCP to zero. On
> ingress if we do not trust our upstream to do the right thing on egress if we do
> not want to leak internal information to our upstream. As far as I can tell DSCP
> is supposed to be domain specific and I consider a home net equivalent with a
> domain. This is why I tried to argue for the existing squash/wash combination.
> Since Dave had already implemented the squashing on ingress per iptables in SQM,
> we will still be able to offer this functionality in SQM independent on whether
> cake offers this natively or not (but note the sqm implementation re-mapped
> after using the DSCP marks)*. I tried to divine which mis-feature Jonathan
> referred to and remembered his unhappiness with that feature, and since I really
> want to see cake go somewhere I am fine with “sacrificing” this feature to make
> upstreaming more likely.

I'm guessing this was probably discussed before and I've simply
forgotten; but why does this (rewriting dscp bits) need to be part of
the qdisc when you can do it with iptables?

-Toke