[Cake] Upstream submission of dual-mode fairness patch

[Pete Heist]

> On Mar 3, 2019, at 8:03 PM, gamanakis at gmail.com wrote:
> 
> For the record, I can replicate it now. I also think that this behavior is expected.
> There is a work-around but it seems like an awful hack:
> 
> ----------8<----------
> diff --git a/sch_cake.c b/sch_cake.c
> index 733b897..08e08f4 100644
> --- a/sch_cake.c
> +++ b/sch_cake.c
> @@ -2216,7 +2216,6 @@ retry:
>                if (q->rate_flags & CAKE_FLAG_INGRESS) {
>                        len = cake_advance_shaper(q, b, skb,
>                                                  now, true);
> -                       flow->deficit -= len;
>                        b->tin_deficit -= len;
>                }
>                flow->dropped++;
> ----------8<----------
> 
> 
> Then the results are:
> 
> IP1, 1 up:	47.18 mbit/s
> IP2, 32 up:	46.99
> IP1, 32 down:	40.98
> IP2, 1 down:	41.34

Yes, thanks for confirming it, this fix equalizes goodput for me as well, although I think we’re in agreement that nothing should actually change in the end(?)

If so, I think we should document this. If it wasn’t obvious to us right away what was happening, then it probably won’t be obvious to others.

If I don’t hear any objection to this in the next couple days, I’ll submit a pull request to tc-adv for tc-cake.8, if that’s the right place to do it.