Upload limiter overshoots under certain conditions with CoDel scheduler

[User1337]

When using FQ_CoDel as the scheduler, the configured upload limit overshoots when doing iperf3 --bidir (bidirectional load). This does not happen with the non-bufferbloat schedulers such as QFQ, RR, WFQ, etc. I remember this happening on FQ_Pie as well, but I am affected by this issue so I can not confirm this.

The limiter mostly works except in isolated cases like this. I am using floating rules for both in/out.

Example:
iperf3 -c dal.speedtest.clouvider.net -p 5205 --bidir -t 400

For example, if I set a 9Mbps limit I will see 11Mbps on the WAN traffic graph. 5Mbps becomes ~6.11, so it's non-linear.

[User1337]

Turns out the bufferbloat limiters do not limit ACKs. How can I make it also limit ACKs?