[Cake] Upstream submission of dual-mode fairness patch

[Pete Heist]

> On Mar 1, 2019, at 3:40 PM, Georgios Amanakis <gamanakis at gmail.com> wrote:
> 
> Thanks for testing Pete! The unfairness you see occurs if you shape
> ingress using ifb on the same interface you shape egress, right?
> Sounds puzzling to me, and I don't have an explanation right now.

Yes, same interface, so it’s:

apu2a eth0 <—> apu1a eth0 / apu1a eth0.3300 <—> apu2b eth0.3300

Of course, the VLAN interfaces have 4 bytes of extra overhead, which should be accounted for by ether-vlan.

It’s possible there’s some quirkiness here with apu1a, which has a Realtek Ethernet interface with the r8169 driver. With this driver, I find that setting rx-vlan-offload off (ethtool -K eth0 rxvlan off) doubles routed throughput when one-armed routing. That probably shouldn’t be. Nevertheless, the same thing happens with or without that offload enabled.

Or it’s just something in this old kernel again. If I ever have a rig like this with a newer kernel I’ll try it.