TCP COPA (mvfst-inspired) — Linux Congestion Control Module

This repository contains a Linux TCP congestion control implementation inspired by Meta’s mvfst COPA design.

Thnings to keep in mind about this implementation

• Much smaller delta (deltaParam)
  The algorithm uses a smaller delta_param_fp than mvfst’s default. This reduces delay sensitivity issues that can otherwise overshoot pacing rate and produce abnormal sawtooth behavior (I use fixed point arithmetic which I suspect exacerbates the problem).

• Bad RTT samples are filtered out
  RTT updates ignore invalid and delayed-ACK samples (rs->rtt_us < 0 or rs->is_ack_delayed), so minRTT/standing-RTT tracking is fed with cleaner measurements.

-**Segmentation offloading I am fairly confident that this will misbehave when segmentation offloading is present. Beware.

RTT signals

• minRTT: simple minimum over a configurable window (copa_min_rtt_win_sec, default 10s).
• Standing RTT: two-half-window min-filter (optional; controlled by copa_use_rtt_standing).

Build

This module is compiled against the BBRv3 kernel found here (the v3 branch).

make load
make enable