The identifier "discovery" named three unrelated subsystems; the FMP
overlay coordinate-lookup subsystem is now consistently "lookup". This
finishes the concept-#1 rename across the shell, config, and metric
layers left after the earlier proto-layer rename:
- Handler module node::handlers::discovery -> node::handlers::lookup, and
reset_discovery_backoff -> reset_lookup_backoff.
- The Node lookup-engine field Node.discovery -> Node.lookup, renamed by
resolved binding so the metrics().discovery and node.discovery config
paths are left untouched.
- The lookup metric types DiscoveryMetrics -> LookupMetrics,
DiscoveryStatsSnapshot -> LookupStatsSnapshot, and Metrics.discovery ->
Metrics.lookup.
Two surfaces cross a stability boundary and ship behind a compatibility
window, both marked in-code for removal at the v2 cutover:
- The control-socket metric family is dual-emitted under both "discovery"
(deprecated alias) and "lookup" so existing dashboards keep working.
- The node.discovery.* config table is split into node.lookup.* (mesh
lookup scalars) and node.rendezvous.* (nostr/lan peer rendezvous).
NodeConfig does not deny unknown fields, so a naive rename would make a
deployed node.discovery: block deserialize into nothing and silently
revert every setting to default. A deprecated all-Option
DiscoveryConfigCompat field captures a legacy block and a new post-parse
Config::normalize_deprecated_keys pass folds it into the new tables with
a one-time deprecation warning.
Flip the packaged fips.yaml templates to the new keys, add legacy/new/
scalar compat parse tests, and record the split and deprecations in the
CHANGELOG. Behavior-neutral; fmt/clippy clean, lib suite green.
Add six forwarding counters that partition transit-forwarded packets by their
tree relationship to the chosen next hop: tree-up (peer is our ancestor),
tree-down (peer is our descendant and the destination is within its subtree),
tree-down-cross (peer is our descendant but the destination is outside its
subtree), cross-link descend (lateral peer, destination within its subtree),
cross-link ascend (lateral peer, destination outside its subtree), and
direct-peer. The six classes sum to forwarded_packets, asserted by a unit
test. Classification is computed from tree coordinates at the transit
chokepoint, so the error-signal routing callers are excluded.
The two "outside the chosen peer's subtree" classes are both up-and-over
forwards but differ in what they depend on. Tree-down-cross is the
dive-to-tree-child cut-through: we forward down to our own child for a
destination not beneath it, which is only possible because the child
advertised cross-link reach upward to us, beyond its own subtree. Its count
measures how much forwarding depends on that upward advertisement, i.e. what
would change if cross-link advertisements were narrowed to subtree-entry only.
Cross-link ascend, by contrast, uses the node's own lateral cross-link learned
from a peer's split-horizon advertisement, so it does not depend on any upward
advertisement.
Surface the counters through the forwarding stats snapshot (control socket,
show_routing and show_status) and reorganize the fipstop routing tab so its
two columns separate own/endpoint traffic (received, delivered, originated)
from forwarded/transit traffic (the route-class breakdown and drop reasons),
with the tree-down-cross line visually flagged.
Store node counters in an atomic metric registry read through &self, and
introduce a shared NodeContext bundle holding the effectively-immutable
fields (config, identity, startup epoch, capability limits). Source the
immutable config and identity reads across the receive hot path, the
handshake/session/mmp/encrypted state machines, and the discovery, tree,
bloom, retry, and lifecycle modules through the context accessors rather
than direct field reads. The Node fields and the context are rebuilt in
lockstep at every mutation site.
The discovery request dedup cache (recent_requests) silently dropped
LookupRequests once it reached MAX_RECENT_DISCOVERY_REQUESTS, with no
counter to surface the condition. Add a DiscoveryReject::ReqDedupCacheFull
reject reason backed by a req_dedup_cache_full counter on DiscoveryStats,
mirroring the existing duplicate-request counter, and record it at the
drop site so the rejection is visible in show_routing.
Introduce a typed RejectReason enum and a NodeStats::record_reject
dispatch so every receive-path rejection-and-return site bumps a
machine-readable per-subsystem counter while keeping its operator-facing
log line. The top-level variants mirror the existing NodeStats subsystem
split (Tree, Bloom, Discovery, Forwarding) and add Handshake, Session,
Mmp, and Transport categories; HandshakeStats, SessionStats, and MmpStats
are new sub-stats.
Wired clusters: tree and MMP outbound sign-failure; the FSP session
unknown-session and state-machine cluster; the Noise IK handshake
state-machine cluster (msg1/msg2); and the decode / crypto / cap /
semantic tail across bloom, discovery, forwarding, mmp, and tree. The
TreeStats::ancestry_invalid counter, present since the scaffold but never
incremented, is now bumped from the validate_semantics ancestry rejection.
Several handshake, MMP, tree, and discovery paths that previously had no
counter at all are now counted, including the send_lookup_response
no-route drop (DiscoveryStats::resp_no_route).
Existing direct counters at the bloom / discovery / forwarding sites are
retained alongside the new dispatch while the rollout is in progress (the
bloom_poison tests expect the transitional +2 delta); a later change
collapses the duplicate increment.
A malformed FilterAnnounce whose fill ratio produces an implausibly
high false-positive rate is mostly useless for routing and, once
merged into our outgoing filter via bitwise OR, propagates the
saturated state to tree peers one hop per announce tick. A saturated
filter also made estimated_count() return f64::INFINITY, which
compute_mesh_size summed into its cached estimate.
handle_filter_announce now rejects inbound FilterAnnounce whose
derived FPR exceeds `node.bloom.max_inbound_fpr` (new config field,
default 0.05 ≈ fill 0.549 at k=5). Rejection is silent on the wire,
logs at WARN, and increments a new `bloom.fill_exceeded` counter. The
peer's prior stored filter and filter_sequence are left unchanged so
a single rejected announce does not wipe the peer's existing
contribution to aggregation.
After a successful outgoing FilterAnnounce send, a rate-limited WARN
fires if our own filter's FPR exceeds the same cap, surfacing
aggregation drift. Limited to once per 60 seconds via a new
Node.last_self_warn field.
BloomFilter::estimated_count() now takes max_fpr and returns
Option<f64>. Returns None for saturated filters (regardless of cap)
or when the filter's FPR exceeds max_fpr. Callers updated: debug
logs render None as "—", the Debug impl uses f64::INFINITY as "no
cap" and prints "saturated" instead of inf, control-socket JSON
emits null, and compute_mesh_size propagates None into the already-
Option<u64> estimated_mesh_size field.
Replace discovery flooding with bloom-filter-guided tree routing:
lookups sent only to tree peers (parent + children) whose bloom
filter contains the target. If no tree peer matches, fall back to
non-tree peers with bloom matches before dropping the request. This
produces single-path forwarding through the spanning tree (90%
traffic reduction) while recovering from dead ends caused by stale
bloom filters, tree restructuring, or transit node failures.
Remove visited bloom filter from LookupRequest wire format (-257
bytes per request). Tree routing is inherently loop-free; request_id
dedup handles edge cases during tree restructuring. Add response-
forwarded flag to prevent response routing loops from convergent
request paths.
Add originator-side exponential backoff (30s base, 300s cap) after
lookup timeouts and bloom misses. Backoff resets on topology changes
(parent switch, new peer, first RTT, reconnection).
Add transit-side per-target rate limiting (2s minimum interval) for
forwarded lookups as defense-in-depth.
Add discovery retry within the timeout window (default: send at T=0,
retry at T=5s, fail at T=10s) to compensate for single-path fragility.
Lookups with zero eligible tree peers fail immediately.
Improve discovery logging: promote key events to info (initiation,
success, timeout with failure count). Add debug logging for dedup,
pending packet retry, backoff suppression, forward rate limiting,
and backoff reset.
New config: discovery.backoff_base_secs, backoff_max_secs,
forward_min_interval_secs, retry_interval_secs, max_attempts.
New stats: req_backoff_suppressed, req_forward_rate_limited,
req_bloom_miss, req_no_tree_peer, req_fallback_forwarded.
Removed: req_already_visited, visited bloom filter.
Implement hop-by-hop ECN congestion signaling through the FMP layer,
transport-level congestion detection via kernel drop counters, and
chaos harness integration for end-to-end validation.
FMP/session ECN plumbing:
- Thread ce_flag parsed at link layer through dispatch_link_message,
handle_session_datagram, handle_session_payload, and
handle_encrypted_session_msg to session delivery
- Replace hardcoded false in session-layer record_recv() with actual
ce_flag, activating ecn_ce_count tracking in session MMP
ECN congestion detection and CE relay:
- Add EcnConfig (node.ecn.*) with configurable loss_threshold (5%)
and etx_threshold (3.0) for transit congestion detection
- Add send_encrypted_link_message_with_ce() that ORs FLAG_CE into FMP
header flags; original method delegates with ce_flag=false
- Compute outgoing_ce = incoming_ce || local congestion on next-hop
link, enabling hop-by-hop CE relay through transit nodes
IPv6 ECN-CE marking:
- Mark ECN-CE (0b11) in IPv6 Traffic Class on received DataPackets
before TUN delivery when FMP CE flag is set
- Only marks ECN-capable packets (ECT(0)/ECT(1)); Not-ECT packets
unchanged per RFC 3168
Transport congestion abstraction and UDP kernel drop detection:
- Add TransportCongestion struct to transport layer for transport-
agnostic local congestion indicators
- Replace tokio::UdpSocket with AsyncFd<socket2::Socket> using
libc::recvmsg() with ancillary data parsing
- Enable SO_RXQ_OVFL for kernel receive buffer drop counter on every
packet, wiring up previously-stubbed UdpStats.kernel_drops
- Add TransportDropState for per-transport delta tracking with 1s
tick sampling via sample_transport_congestion()
- Extend detect_congestion() with transport kernel drop check
alongside MMP loss metrics
Congestion monitoring and control:
- Add CongestionStats (ce_forwarded, ce_received, congestion_detected,
kernel_drop_events) to NodeStats with snapshot serialization
- Wire counters into forwarding path, session handler, and transport
drop sampling with rate-limited warn logging (5s interval)
- Expose congestion data in show_routing control query and
ecn_ce_count in show_mmp peer entries
- Add congestion counters to fipstop routing tab in two-column layout
Chaos harness integration:
- Add query_routing(), query_transports(), snapshot_all_congestion()
to chaos control module
- Add congestion/kernel-drop log analysis in logs module
- Add congestion-stress scenario: 10-node tree, 1 Mbps bandwidth,
5-10% netem loss, heavy iperf3 traffic
- Add IngressConfig for tc ingress policing with per-peer policer
filters simulating upstream bandwidth bottlenecks
- Add iperf3 JSON result capture to traffic manager for throughput
measurement across scenarios
- Add ECN A/B test scenarios (ecn-ab-on/off.yaml) with ingress
policing and comparison script
- Enable TCP ECN negotiation (tcp_ecn=1 sysctl) in container
entrypoint for end-to-end CE propagation
Tests:
- 10 ECN unit/integration tests: mark_ipv6_ecn_ce variants, CE relay
chain (3-node propagation), EcnConfig serde roundtrip
- 3 transport drop congestion detection unit tests
Documentation:
- Update fips-mesh-layer.md: replace outdated CE Echo stub with full
ECN Congestion Signaling section covering detection logic, CE relay,
IPv6 marking, session tracking, and monitoring counters
- Update fips-configuration.md: add node.ecn.* parameter table and
ecn block in complete reference YAML
- Update fips-transport-layer.md: add Congestion Reporting section
with TransportCongestion struct, congestion() trait method, and
per-transport status; document AsyncFd/recvmsg/SO_RXQ_OVFL in UDP
- Update chaos README: add congestion/ECN scenario docs, ingress
traffic control, and iperf3 JSON capture sections
- Update README.md: add ECN to features list and "What works today";
update transport and tooling entries
Johnathan Corgan