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316e7002c1
uBridge's window mode gained the semantics the B.2 spec asked for — `tc window_drop <if> <start> <outage> <pct> [<period> [<jitter>]]`: a single outage that traffic passes before *and* after, recurring flaps with period >= outage, and a per-cycle jitter — so the kernel-only `window_drop` filter type is now exposed: - validation mirrors the tc grammar (3-5 params, ranges, period >= outage, jitter cap) and adds window_drop to KERNEL_ONLY_FILTERS; filter_inactive_filters keeps start=0 — unlike every other filter a zero first parameter means "the outage starts now", not "disabled". - `_ubridge_apply_ebpf_drops` sends `tc window_drop` (positional pass-through) and turns the mode off explicitly when absent, under the same ebpf=1 gate. - FILTERS entry (Start/Outage/Chance/Period/Jitter) + available_filters. The schedule is relative to the apply: reconcile re-sets the classifier on every apply, so any filter change, node restart or link reset restarts the window. Verified on a two-container kernel link, 15/15: a single outage [1000, 1500, 100] arrives per-seq as [0..4, 13..19] (passing before the window, dropped inside, passing after); recurring 1000/2000 ms = 52 % round trip (duty cycle); period == outage = permanent outage; period < outage = 409 before uBridge; jittered flap keeps the ~50 % duty cycle; 30 % chance on a permanent window = 53 % round trip against the per-direction theory 1-0.7^2 = 51 %; coexist with netem; node restart restores; available_filters kernel vs relay (409 + hidden); teardown clean. P6b re-run as a regression on the same uBridge build: 13/13. Worth recording for the next rebuild: the first delivered window program loaded as root but reported ebpf=0 through gns3-server — the verifier's non-root path loses the loop counter's bound, treats the catch-up loop as unbounded and rejects the *whole* program (E2BIG, 8193 pending states), which also took frequency_drop and quota down, with ebpf=0 as the only symptom. Smaller trip caps did not help; the loop had to go (uBridge 572ca0c), on top of a Makefile header-dependency fix (53e34bb) that had been shipping a stale program object.