fix(exit): count distinct silent sources, and stop one address drowning the signal - #216
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…ng the signal The silent-peer record was meant to be the sharpest probe signal an exit produces: a real Bitcoin node always speaks first, so a connection that sends nothing is a scan. On the first prod exit it was 87% our own monitoring. VPSReachabilityProbeWorker dials every published route and closes without sending a byte — functionally a port scan, and indistinguishable from one at this layer. It produced 77 of 89 untagged records, every ~3 minutes, from a single address. A real distributed scan would have been invisible underneath it. Two changes, and the second is the one that matters: - A repeat silent source logs once at `info`, thereafter at `debug`. Counters still move, so nothing is lost from the roll-up. - The roll-up gains `untagged_silent_sources`. Volume alone cannot distinguish a health check from a scan; distinct sources can. 77 connections from 1 source is monitoring, 77 from 60 is an attack, and only the second number tells them apart. The tracked set is bounded at 4096. It is fed by unauthenticated peers, so an unbounded set would be a memory-growth primitive against the exit; past the cap every silent drop reports, keeping the failure direction noisy rather than quiet. A poisoned lock also reports rather than silences. Deliberately not an allowlist of our own prober addresses: that needs config plumbing, goes stale when the checker moves, and would hide the very traffic shape an operator should be able to see. Distinct-source counting is the same insight without a list to maintain. Verified against the live exit's journal, which is where the noise was found. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KUixBponT8tUkebxe8EZuV
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Included review availability: Your plan includes up to 1 review per rolling hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe change adds bounded tracking for distinct silent untagged peer sources. It exposes the count in snapshots and summaries, logs repeated sources at ChangesSilent-source telemetry
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to The change improves silent-source telemetry, but the deployment guidance still omits the intentional logging behavior after the tracking cap is reached, which could confuse operators during saturation; the PR is mergeable with explicit owner follow-up to clarify that behavior. Sequence Diagram(s)sequenceDiagram
participant EgressTelemetry
participant EgressSession
participant TelemetryOutput
EgressTelemetry->>EgressSession: identify silent source
EgressSession->>TelemetryOutput: emit info for first source
EgressSession->>TelemetryOutput: emit debug for repeated source
EgressTelemetry->>TelemetryOutput: emit distinct-source summary
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Pull request overview
This PR improves WASM exit egress telemetry so “silent” untagged connections remain a useful probe signal by (a) deduplicating repeat silent sources in per-connection logs and (b) adding a distinct-source metric to the periodic roll-up, with bounded memory growth.
Changes:
- Deduplicate repeat
Opening::Silentsources: first sighting logs atinfo, repeats atdebug, while counters still increment. - Add
untagged_silent_sourcesto the egress roll-up snapshot and summary log (bounded byMAX_TRACKED_SILENT_SOURCES). - Document the operational motivation and interpretation of distinct-source counting.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| docs/wasm-exit-deployment-design.md | Documents why silent-source dedup + distinct-source counting improves signal quality and why the tracked set is bounded. |
| core/src/transport/wasm/telemetry.rs | Implements bounded silent-source tracking, adds untagged_silent_sources to snapshots/summary, and adds tests for dedup and bounding behavior. |
Suppressed comments (1)
core/src/transport/wasm/telemetry.rs:229
- In
note_silent_source, the poisoned-lock path returnstruewithout recovering/updating the set. Once poisoned, this effectively disables distinct-source tracking (and forces all silent connections to be reportable) even though the underlyingHashSetis likely still usable. Consider usingPoisonError::into_inner()to keep the set functional (and optionally keep returningtrueto stay in the “noisy, never quiet” failure mode).
fn note_silent_source(&self, peer: IpAddr) -> bool {
match self.silent_sources.lock() {
Ok(mut set) => {
if set.len() >= MAX_TRACKED_SILENT_SOURCES {
return true;
}
set.insert(peer)
}
// A poisoned lock must not silence telemetry.
Err(_) => true,
}
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Inline comments:
In `@docs/wasm-exit-deployment-design.md`:
- Around line 209-215: Update the documentation around
VPSReachabilityProbeWorker and silent-source logging to state that repeat
sources downgrade to debug only while silent_sources remains below its
4096-entry tracking cap; after saturation, note_silent_source returns true for
every silent drop, so each drop emits an info record, including known repeats.
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core/src/transport/wasm/telemetry.rsdocs/wasm-exit-deployment-design.md
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…eption Two review follow-ups. snapshot() mapped a poisoned silent_sources mutex to 0 distinct sources. That understates a scan at exactly the moment the number matters, and contradicts the documented saturating behaviour. Both call sites now recover the guard with into_inner(): the set is only read and inserted into, so its contents stay meaningful after a panic elsewhere. note_silent_source recovers too, which keeps dedup working rather than falling back to reporting everything. The design note claimed repeats always drop to debug. They do not: once the tracked set hits the cap, note_silent_source returns early and every silent drop logs at info again, because tracking stops rather than evicting. Documented rather than changed — the noisy direction is the safe one past the cap. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KUixBponT8tUkebxe8EZuV
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Pull request overview
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
Suppressed comments (1)
core/src/transport/wasm/telemetry.rs:354
- The
debug!branch logspeer = %self.peerbut uses a differentmessagestring ("untagged peer (repeat silent source)"). Elsewhere the codebase assumes the only event that may carry apeerfield is the one whose message is exactly "untagged peer" (see wasm-server/tests/bitcoin_egress.rs:491-499). Consider keeping the message constant and adding a structured field (e.g.repeat_silent_source=true) while only changing the log level.
debug!(
peer = %self.peer,
opening = %self.opening,
opening_bytes,
outcome = %self.outcome,
duration_ms,
"untagged peer (repeat silent source)"
);
The type exists to accumulate fields — every counter worth surfacing lands on it — so each addition is otherwise a source-breaking change for anything constructing it by literal or matching it exhaustively. Nothing outside spark-core does either today (checked: the only references are in telemetry.rs and the mod.rs re-export, and the crate is a path dependency), so this is future-proofing rather than a fix. It costs nothing: in-crate construction is unaffected, and wasm-server still builds. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KUixBponT8tUkebxe8EZuV
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Pull request overview
Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.
Suppressed comments (1)
core/src/transport/wasm/telemetry.rs:359
- The debug path for repeat silent sources logs
peer = %self.peerbut changes the event message to"untagged peer (repeat silent source)". In this codebase, the log message string is used as the identifier for the one event allowed to carry apeerfield (see wasm-server/tests/bitcoin_egress.rs:491-499). Changing the message here risks breaking that invariant (and any downstream log parsing) whenever debug-level logs are enabled.
Consider keeping the message exactly "untagged peer" for both branches and adding a structured flag like repeat_silent_source=true (and/or reported=false) to distinguish the deduped debug event, instead of changing the message string.
opening = %self.opening,
opening_bytes,
outcome = %self.outcome,
duration_ms,
"untagged peer (repeat silent source)"
The signal was 87% our own monitoring
The silent-peer record is meant to be the sharpest probe signal an exit produces — a real Bitcoin node always speaks first, so a connection that sends nothing is a scan. Read off the live prod exit's journal:
35.233.177.182isgoogleusercontent.com.VPSReachabilityProbeWorkerdials every published route and closes without sending a byte (reachable.go:75-78) — functionally a port scan, and indistinguishable from one at this layer.So 77 of 89 untagged records were ours, from one address. A real distributed scan would have been invisible underneath it.
Two changes; the second is the one that matters
info, thereafter atdebug. Counters still move, so nothing is lost from the roll-up.untagged_silent_sources. Volume alone cannot tell a health check from a scan; distinct sources can — 77 connections from 1 source is monitoring, 77 from 60 is an attack, and only the second number separates them.Why not an allowlist
Allowlisting our prober's addresses needs config plumbing, goes stale the moment the checker moves or scales, and would hide the traffic shape an operator should be able to see. Distinct-source counting is the same insight with nothing to maintain.
Bounds
The tracked set is capped at 4096 because it is fed by unauthenticated peers — unbounded, it is a memory-growth primitive against the exit. Past the cap every silent drop reports, and a poisoned lock also reports: the failure direction is noisy, never quiet.
Tests
a_repeat_silent_source_is_reported_oncesources=1distinct_sources_separate_a_scan_from_a_health_checksources1 vs 30non_silent_openings_are_always_reportedtracked_silent_sources_are_boundedReverting the dedup makes the first test fail. Full suite: 1001 passed, 0 failed; fmt and clippy clean.
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Summary by CodeRabbit
New Features
Bug Fixes
Documentation