Replaces the unconditional `CoordCache::clear()` calls at parent-switch,
become-root, and loop-detection sites with two targeted invalidation
methods scoped to what actually makes an entry stale:
- `invalidate_via_node(node_addr)`: drop entries whose cached
destination ancestry contains `node_addr`. Used at parent-position-
change sites — our prefix changed, so destinations downstream of
us have stale-prefix coords.
- `invalidate_other_roots(current_root)`: drop entries rooted under
a different root than the current one. Used at root-change sites.
Under the previous global flush, parent switches blanked the cache
across the board, leaving `find_next_hop` returning `None` for every
non-direct-peer destination until the cache passively re-warmed via
incoming TreeAnnounces / SessionSetup. Surgical invalidation
preserves entries that remain correct after the topology change.
The cached coord describes a destination's tree position; that
position only goes stale relative to our own routing decisions when
our own prefix changes (entries we are downstream of) or the root
changes (entries in a different tree). Peer removal does not
invalidate cached coords: `Node::find_next_hop` recomputes the
next-hop decision on every call against the current peer set, bloom
filters, and tree state, and Discovery already triggers on
`no route to destination` errors when a destination becomes
unroutable through us. The peer-removal site retains the original
"no cache invalidation" behavior.
Each method returns the count of entries removed for observability.
Unit tests cover each method against the cases enumerated in the
acceptance criterion.
Extend the fipsctl control query interface with visibility into internal
state critical for protocol security auditing, mesh troubleshooting, and
operational monitoring.
New command:
fipsctl show identity-cache
Lists every node identity cached by the daemon (learned from DNS
resolution, peer handshakes, sessions, and static config). Shows
npub, IPv6 address, display name, and LRU age alongside the
configured cache capacity.
Extended queries:
show peers — Noise session counters (send_counter, highest received
counter) for rekey urgency assessment. Per-peer replay suppression
and consecutive decrypt failure counts for active attack detection.
Session index visibility for hijack analysis. Rekey lifecycle
state (in_progress, draining, K-bit epoch).
show sessions — Handshake resend count during establishment for
connectivity debugging. Rekey and session health fields
(session_start, K-bit, coords warmup, drain state) when
established.
show cache — Individual coordinate cache entries with tree
coordinates, depth, path MTU, and age. Enables route-level
debugging by showing exactly which destinations have cached
routes and via what tree path. Renames the top-level count
field from "entries" to "count" for clarity.
show routing — Pending discovery lookups expanded from count to
per-target detail (attempt number, age, last sent). Pending
TUN packet queue depth for backpressure visibility. Connection
retry state per peer (retry count, next attempt, auto-reconnect
flag).
Updates fipstop to match the revised show_cache and show_routing
response schemas. Updates README monitoring section with the complete
fipsctl command list.
Co-authored-by: Johnathan Corgan <johnathan@corganlabs.com>
Add min_mtu (u16) to LookupRequest and path_mtu (u16) to
LookupResponse, enabling the discovery system to report transport
MTU capability along the lookup path.
LookupRequest carries min_mtu (origin's minimum MTU requirement,
default 0 = no requirement). LookupResponse carries path_mtu
(initialized to u16::MAX by the target, reduced by transit nodes
via min(path_mtu, outgoing_link_mtu) on the reverse path).
path_mtu is a transit annotation like SessionDatagram.path_mtu and
is NOT included in the proof signature. The originator stores the
discovered path_mtu in CacheEntry alongside cached coordinates.
Wire format: +2 bytes each for LookupRequest and LookupResponse.
Transit nodes cache destination coordinates when they forward
SessionSetup messages (via try_warm_coord_cache). These coord_cache
entries have a 5-minute TTL, after which they expire. Once expired,
the transit node can no longer forward data packets for that
destination — find_next_hop returns None and the node sends
CoordsRequired errors back to the source. This creates a permanent
routing failure for any multi-hop path after 5 minutes of the initial
session establishment, even if traffic is actively flowing.
The root cause was that find_next_hop used coord_cache.get(), a
read-only lookup that checks expiry but never extends it. Active
forwarding did not keep the cache warm. Meanwhile, get_and_touch()
existed but only updated last_used without extending expires_at.
Fix:
- find_next_hop now calls coord_cache.get_and_touch() instead of get()
- get_and_touch now calls entry.refresh() instead of entry.touch(),
which extends expires_at by the default TTL on each access
- find_next_hop signature changed from &self to &mut self to allow
the mutable cache access
This ensures that as long as traffic flows through a transit node,
the coord_cache entries stay warm and routing continues to work.
Entries still expire after 5 minutes of inactivity as designed.
Johnathan Corgan
Tim O'SheaandJohnathan Corgan