daemon: per-peer path watchdog — heal a single dead peer path in place#401
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2026-07-17 incident: one peer's NAT/relay session died (list-agents unreachable for hours) while 8 other peers stayed healthy — so the global rx-watchdog never fired (any live peer keeps PktsRecv moving), and the only remedy was a full daemon restart, which drops EVERY session and costs minutes of re-establishment on a NAT'd link. Nothing health-checks an individual peer mapping: the tunnel keepalive is fire-and-forget (the receiver silently swallows it), so it keeps NAT mappings warm but verifies nothing. Add pathwatch.go (L4): every Ready peer already refreshes lastInboundDecrypt at least every ~30s via bidirectional keepalives. A peer silent past 55s gets up to 3 pong-soliciting probes; still silent → that ONE peer's path is reset in place via the same sequence as `pilotctl prefer-direct` (drop cached resolve + tunnel, preserve relay-active, clear rekey cooldowns, proactively push a fresh PILA) — extracted from the IPC handler into the shared resetPeerPath. Worst- case detection ≈85s, recovery ~1 RTT, healthy sessions untouched. Reset is rate-limited per peer (2min cooldown); disable with -no-path-watch. Events: tunnel.path_suspect / tunnel.path_recovered. Backward compatible with the whole deployed fleet — no wire changes: the probe is a plain PortPing control frame with a non-empty payload. Verified against the v1.10.0, v1.10.0-rc5 and -rc7 trees (the fleet runs rc6-dev): their isTunnelKeepalive only swallows EMPTY frames, so the probe reaches handleControlPacket and gets a pong; old peers' own keepalives independently keep refreshing our liveness signal, so an old peer is never falsely reset. The compat invariant is pinned by TestPathProbeIsNotSwallowedByOldKeepaliveFilter. Tests: probe/reset/recovery/cooldown/prune state machine, relay-state preservation in resetPeerPath, keepalive-filter compat. pkg/daemon green under -race for the new tests and under the -short CI gate. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Problem (2026-07-17 incident)
One peer's NAT/relay session died (list-agents unreachable for hours) while 8 other peers stayed healthy. The global rx-watchdog never fires in this shape — any single live peer keeps
PktsRecvmoving — and nothing health-checks an individual peer mapping: the tunnel keepalive is fire-and-forget (receiver silently swallows it; it warms the NAT mapping but verifies nothing). The only remedy was a full daemon restart — which drops every session and costs minutes of re-establishment on a NAT'd link (measured: mechanical restart 4s, functional recovery to service agents 4-15+ min).Fix
New
pathwatch.go(L4), per-peer feedback loop:lastInboundDecrypt≤~30s via bidirectional keepalives (all daemon versions). Silent > 55s → up to 3 pong-soliciting probes (one per 10s tick).pilotctl prefer-directsequence, now extracted as the sharedresetPeerPath(drop cached resolve + tunnel, preserve relay-active / clear pin, clear rekey cooldowns, proactively push fresh PILA). Healthy sessions untouched. Worst-case detection ≈ 85s; recovery ~1 RTT.-no-path-watchto disable; eventstunnel.path_suspect/tunnel.path_recovered; panic boundary per tick.Backward compatibility (the hard requirement)
Zero wire changes. The probe is a plain
ProtoControl/PortPingframe with a non-empty payload:rc6-dev, between the two): theirisTunnelKeepaliveonly swallows empty frames, so the probe passes the filter, reacheshandleControlPacket, and gets a pong (present in all three trees).TestPathProbeIsNotSwallowedByOldKeepaliveFilteras a tripwire.Tests
State machine (healthy/probe/reset/cooldown/prune), relay-state preservation in
resetPeerPath, keepalive-filter compat. New tests green under-race; fullpkg/daemon/...green under the-shortCI gate. (TestIPCServer_MaxClientsCap/TestWriteLoopExitsOnWriteDeadlinefail locally on clean main and v1.12.7 too — pre-existing non-short-only, unrelated.)Post-merge validation plan
Release, update this laptop, then reproduce the original failure live (wifi→hotspot switch mid-session) and confirm list-agents reachability self-heals within ~85s with zero manual restarts.
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