When both ends dial each other, exactly one TCP connection must survive
and both ends must pick the same one. Previously ferrix relied on the
other router to sort this out and could briefly hold two sessions.
- collision: a shared map keyed by the peer's BGP Identifier holds the one
connection currently preferred for that peer plus a kill signal. Each
connection calls admit() on receiving the peer's OPEN. The connection
initiated by the higher BGP Identifier wins; the loser gets Cease /
Connection Collision Resolution, whether it is the new connection or an
existing one in OpenConfirm running in another task.
- A collision with an Established session closes the new connection (RFC
default). The optional CollisionDetectEstablishedState is available as
collision_detect_established_state: a restarted peer's new connection
then replaces the stale session at once instead of being refused until
the hold timer expires. Enabled in the lab config.
- Two connections opened by the same side: the newer wins.
- OPEN validation rejects a peer using our own BGP Identifier or 0.0.0.0
with Bad BGP Identifier; collision resolution needs distinct identifiers.
- OpenConfirm no longer times out instantly when the negotiated hold time
is zero.
- Sessions record which side opened them; shown as "opened by" on the
status page and as `direction` in /api/peers. New counter
bgp_connection_collisions_total{closed}.
- Tests: unit tests for the rule (including that both ends agree), and
integration tests for simultaneous open in both identifier orders and
both arrival orders, Established default, restart replacement with route
flush, distinct identifiers, slot release, and Bad BGP Identifier.
Existing fan-out test now gives its two peers distinct identifiers.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Phase 4 of the teaching demo: the daemon now brings up its own sessions.
- New dialer task per configured peer: connect with a timeout, run the
same FSM as the passive side, back off exponentially (from
connect_retry_seconds, capped at two minutes) and retry forever. Stays
idle while a session with the same remote IP and ASN already exists.
- The peer's OPEN must carry the configured ASN, otherwise the session is
refused with a Bad Peer AS notification. Inbound connections from a
configured peer's address get the same check plus the configured name
and hold time.
- SessionRegistry tracks configured peers and their dial state
(Idle / Connecting / Backoff with last error and retry time).
- /api/peers merges configured peers with live sessions so the page shows
peers that are down, why, and when the next attempt is; unconfigured
inbound sessions are listed after them.
- fake_peer gains --listen so it can stand in for a router the daemon
dials.
- Integration tests: dial and establish, reconnect after the peer closes,
wrong ASN refused, inbound from a configured address checked and named.
Not implemented: RFC 4271 §6.8 collision detection; a real router on the
other end resolves the rare race by closing one connection.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Phase 2 of the teaching demo: everything the status page will need is now
reachable over HTTP.
- New crate crates/web (axum). JSON endpoints for status, peers, local
routes (announce / withdraw), received routes, the exact UPDATE bytes a
local route produces per session, and well-known community names.
Communities are accepted as ASN:VALUE or by name (NO_EXPORT, BLACKHOLE,
...); large communities as A:B:C. Policy errors map to 403/409/422.
- GET /api/events is a server-sent event stream merging session up/down,
local route and Adj-RIB-In changes, with lag notifications.
- GET /metricz serves Prometheus metrics; the server crate now counts
messages sent/received by type and sessions established.
- The runnable main moves from crates/server to bin/bgp so it can depend
on both server and web without a cycle. `cargo run -- config.textpb`.
- Config gains http_endpoint; unset disables the API.
- Integration tests drive the API against a live server with a real BGP
peer, including verifying the wire view matches the bytes the peer got.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Phase 1 of the BGP teaching demo: the daemon can now originate routes and
advertise them to every established peer.
- rib: add LocalRib actor holding locally originated routes with owner,
origin, AS-path prepend, MED, standard and large communities. Enforces a
LocalRibPolicy (prefix allowlist, per-owner limit, owner match on
replace/withdraw) and emits LocalRibEvents.
- server: add SessionRegistry with per-session outbound queues; sessions
register on Established and deregister via a drop guard. Emits
SessionEvent::{Up,Down}.
- server: advertiser task fans LocalRib changes out to all sessions and
replays the table to new sessions. UPDATE builders handle IPv4 (legacy
NLRI) and IPv6 (MP_REACH/MP_UNREACH).
- fsm: merge the timer and timer-less established loops into one select!
with an outbound branch; reset the hold timer on any received message
per RFC 4271 §8.2.2 (previously only on KEEPALIVE).
- config: new local_route_policy proto message.
- packet: fix Communitites typo, expose CommunitiesPathAttribute inner vec.
- primitives: IpPrefix::contains.
- integration tests: announce/withdraw/replay/fan-out/policy coverage.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
