Four failure modes observed in-house since the polling-first refactor
(709fdf4):
1. Half-open DTLS sessions where the socket stays writable but the peer
has gone silent. Ping sends succeed against a wedged peer because
RT-OCF doesn't reliably emit a RST; only successful polls prove the
session is live.
- PollScheduler exposes last_success_ts (bumped on every 2.05).
- KeepaliveTask takes liveness_fn(); ticks fail if no 2.05 in the
last 60s, even when the ping send succeeded.
- Bridge force-closes the session after 120s unreachable so
run_forever() breaks out of sess.join() and reconnects.
2. RT-OCF cascade under load. One wedged path can eat 8s of timeout,
the next tier tick fires immediately and stacks another attempt,
and the device wedges harder.
- PollTier.timeout_s per-tier override (hot=2s, warm=4s, sweep=15s).
- On TimeoutError, the href goes into a 5-60s cooldown via the
existing _defer_until mechanism.
- take_window_stats() now reports successful-poll RTT separately
from a timeout count, exposed as the "Poll Timeouts (window)"
diagnostic entity in HA.
- Active-window throttle: if the previous health window saw >=3
timeouts and is_active=True, drop back to idle cadence -- stops
stacking polls on a stalled responder.
3. OBSERVE table aging across cloud-auth blips. The device stays
DTLS-reachable but the on-device stack clears its observer table
during the blip, so push delivery stays dead even after upstream
recovers.
- New ObserveRefreshTask per bridge; every 6h derregs all current
observer tokens and re-subscribes on the existing session.
4. Oven lamp/door coupling. Oven hardware auto-drives the lamp from
door state but /mode/vs/0 is warm-tier (30s) so HA showed stale lamp
during a cook.
- Track door + lamp value-change timestamps in descriptor_state.
When the door transition is newer, derive lamp from door_open.
When an HA optimistic write is newer, the cache value wins.
Also: ANSI-coloured WARNING/ERROR lines (NO_COLOR=1 opt-out), jittered
reconnect backoff so dryer + oven don't sync up after a router blip.
In-house verification: running on dryer + oven since 2026-06-03.
Major session of local-OCF reverse engineering against the NV7000BS
oven and DV5000T dryer. Surfaces a working set of HA entities for the
oven and resolves several Samsung-quirk regressions in the bridge's
write path.
Key behavioural fixes:
- OBSERVE registrations now use single-byte tokens. Samsung RT-OCF
silently drops registrations with TKL>1; same 4-byte tokens work
fine for GET/POST. Symptom was that writes returned 2.04 but the
appliance never pushed state changes.
- Per-session random starting tokens + MID. Samsung retains observer
state across DTLS reconnects from the same cert; reusing tokens on
reconnect silently no-ops.
- OBSERVE deregister sent on DtlsCoapSession.close(), with a stop-
watcher thread in PushBridge.session_once() so SIGINT/SIGTERM
actually reaches close() instead of hanging in sess.join().
- pyOpenSSL is not thread-safe — reader-loop conn.* calls now hold
the same _send_lock the sender uses, dispatching decrypted packets
outside the lock so the auto-ACK send doesn't deadlock.
- Periodic CoAP Ping (RFC 7252 §4.4) keepalive to keep DTLS warm.
- Post-write Block2 fetchback REMOVED. It was the root cause of
every "setpoint/operationTime/modes revert ~3s after write"
symptom — Samsung's stack treats a read on a freshly-written
resource as a signal to invalidate that write. OBSERVE pushes
keep HA in sync without the verification GET.
HA-facing changes (oven):
- New entities: Lamp (light), Sound (switch), Fast preheat, Natural
steam, Setpoint (number), Cook time (number), Stop cycle (button).
- Cooking mode surfaced as a read-only sensor — the oven owns the
modes field once a cycle is active and rolls local writes back.
- Cook time writes operationTime + remainingTime on
/operational/state/vs/0 (discovered via OBSERVE capture of
SmartThings mid-cycle changes — UpperTimerSet on /mode/vs/0
options is vestigial and doesn't drive the running cycle).
- New cycle_active MQTT availability topic. Writes the oven only
honours mid-cycle (setpoint, cook time, fast preheat, natural
steam, stop) gate on it via avail_with_cycle / avail_with_remote_
and_cycle. Sound + Lamp remain always-available.
- Cycle Start deliberately NOT exposed. Every byte-level approxi-
mation of SmartThings's working start sequence is rejected at
the firmware level. Empty discovery payloads remove the previous
Start button and Cooking-mode select cleanly from HA.
Diagnostics:
- DEBUG_BRIDGE=1 env var enables verbose tracing (rx CON/NON/ACK/
RST per frame, full link-tree dump at seed, /oic/res directory,
REP changes on /operational/state, /oven, /power, mode options).
Quiet in production.
Jack Nagy