feat(router): ECF predictive mux scheduler (proxy mux mode ecf) - #4240
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Adds WeightModeECF — an Earliest-Completion-First predictive scheduler that holds the next in-order frame off a slower leg when a faster leg will drain the backlog and deliver it sooner, avoiding the head-of-line stalls that goodput/latency weighting causes under path heterogeneity (the MPTCP/MP-QUIC aggregation result). Adapted to skywire's no-TCP-cwnd model: per-leg cwnd -> BDP (rate x RTT), 'has capacity' -> inflight_bytes < BDP (inflight tracked in the selector, drained at the leg's send rate), backlog -> inflight on the fast leg, sigma -> per-leg RTT jitter EWMA. Filter variant (never returns NO-LEG; queues on the fast leg rather than the scheduler holding a frame) so the send path stays non-blocking. Wired as a new WeightMode + 'ecf' distribution end-to-end (selector, native + wasm policy parsers, SetMuxMode RPC, 'proxy mux mode auto|equal|capacity|ecf' CLI). Adaptive preset default left at 'capacity' — ECF is opt-in and unproven live; flipping the default is a one-liner after a live-tuning pass. Deterministic unit tests incl. the canonical fast+10x-slow-leg case. State refreshes on the 5s data-progress cadence for now (RTT/rate/jitter); a ~1s refresh + E2E latency are noted follow-ups.
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Adds
WeightModeECF— an Earliest-Completion-First predictive scheduler that holds the next in-order frame off a slower leg when a faster leg will drain the backlog and deliver it sooner. Goodput/latency-weighted spraying keeps assigning a fraction of in-order frames to slow legs, and since the reorder buffer must deliver in order (never skip), each becomes a head-of-line stall — the MPTCP/MP-QUIC result that weighting alone reaches only ~25% of ideal aggregate. ECF is the predictive hold-back that fixes it.Adapted to skywire’s no-TCP-cwnd model: per-leg cwnd → BDP (
rate × RTT); "has capacity" →inflight_bytes < BDP(inflight tracked in the selector, drained at the leg’s send rate — skywire has no per-leg ack); backlog → inflight on the fast leg; σ → per-leg RTT-jitter EWMA. Filter variant (never returns NO-LEG; queues on the fast leg rather than the scheduler holding a frame) so the send path stays non-blocking — zero send/queue-machinery changes.Wired end-to-end as a new WeightMode +
ecfdistribution (selector, native + wasm policy parsers,SetMuxModeRPC,proxy mux mode auto|equal|capacity|ecfCLI). Adaptive preset default left atcapacity— ECF is opt-in and unproven live, so merging changes no fleet behavior; flipping the default is a one-liner after a live-tuning pass. Deterministic unit tests incl. the canonical fast + 10×-slow-leg case. State refreshes on the 5s data-progress cadence (RTT/rate/jitter); ~1s refresh + E2E latency are noted follow-ups. Developed with AI assistance (Claude).