The live throughput test found it: a 3-second run delivered 104 packets and stopped after 50 milliseconds. The rate check exempted the first 50 ms entirely, meaning to be lenient at startup. The effect was the opposite. A sender could dump an unbounded burst into that free window, and the instant the check switched on it compared those bytes against 50 ms worth of allowance and refused everything until real time caught up. Every short test passed — downtrain sends 50 packets, big_send seven — and every sustained send died about fifty milliseconds in. A token bucket (allowance = burst + rate x elapsed) has no such cliff; it is smooth from t=0. The burst is 100 ms of the allowed rate, floored at one ordinary datagram so a single packet is never refused outright. The floor is deliberately one datagram: at 8 kbps a 64 KB floor would be sixty-four seconds' worth, which is precisely the instant dump the ceiling exists to prevent. The existing rate test caught that when I first tried it, and it was right. Second half of the same bug: callers treated any refusal as terminal. TryAllow now says why, so a sender can pace through a transient "too fast just now" and still stop dead on a spent budget or an expired grant. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Echolot app
The production Android client (spec). Native Kotlin + Jetpack Compose. Multi-module; built bottom-up from a verifiable protocol spine.
Modules
| Module | Type | Status |
|---|---|---|
core-protocol |
pure Kotlin/JVM | done — client half of probe-protocol.md, verified live against the server |
core-measurement |
pure Kotlin/JVM | planned — measurement-schema.md types |
core-probe |
Android lib | planned — app-tier probes, ported from echolot-prober |
core-shizuku |
Android lib | planned — dual-path executor (UserService + newProcess fallback) |
app |
Android app | planned — Compose UI |
core-protocol is deliberately Android-free so it builds and unit-tests on any JDK (no Android
SDK) and can run integration tests against a live server.
core-protocol
Implements the control plane (SPKI-pinned enrollment/profile/sessions via HttpsURLConnection —
Android-API-1 compatible, hostname verification off because trust is the pin), the HKDF-SHA256
session-key schedule, and the binary ELT1 UDP data plane (HMAC gate, ECHO + observation block,
MTU probe) — byte-compatible with the Go server.
./gradlew :core-protocol:test # unit tests (crypto vectors, wire round-trip)
scripts/test-fmr.sh # live end-to-end test against the deployed server
test-fmr.sh mints an enrollment token over SSH, enrolls via the public control plane, computes
the SPKI pin from the served cert, and runs LiveServerTest — proving the client speaks the wire
protocol to the real server (enroll → profile → session → echo+observation → MTU → observations).
The live test self-skips when ECHOLOT_LIVE_* env vars are absent, so unit runs and CI stay green
offline.