Rayhaan JaufeerallyandClaude Fable 5.1
87f96f9389
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>
5.6 KiB
5.6 KiB
RFCs
Tracks which RFCs are implemented, partially implemented, or only represented in the wire format layer.
Legend
- ✅ Implemented — functional end-to-end
- 🟡 Wire format only — parsed and serialised correctly, but not yet acted on
- ❌ Not implemented
Core BGP
RFC 4271 — A Border Gateway Protocol 4 (BGP-4)
https://datatracker.ietf.org/doc/html/rfc4271
The base protocol specification.
| Section | Description | Status |
|---|---|---|
| §4.1 | Message framing (marker, length, type) | ✅ |
| §4.2 | OPEN message | ✅ |
| §4.3 | UPDATE message (path attributes, NLRI, withdrawn routes) | ✅ |
| §4.4 | KEEPALIVE message | ✅ |
| §4.5 | NOTIFICATION message (all error codes and subcodes) | ✅ |
| §8 | FSM — passive (inbound) side: OpenSent → OpenConfirm → Established | ✅ |
| §8 | FSM — active (outbound) side: dial configured peers, exponential retry | ✅ |
| §6.2 | Bad Peer AS check against configured ASN | ✅ |
| §6.8 | Connection collision detection (BGP Identifier comparison, Cease / Connection Collision Resolution) | ✅ |
| §8.1.1 | Optional CollisionDetectEstablishedState (collision_detect_established_state) |
✅ |
| §6.2 | Bad BGP Identifier check (peer using our identifier, or 0.0.0.0) | ✅ |
| §9 | Decision process / best-path selection | ❌ |
| §9 | Adj-RIB-In (per-peer table of received routes) | ✅ |
| §9 | Locally originated routes, advertised to all established peers | ✅ |
| §9 | Loc-RIB / Adj-RIB-Out for routes learned from peers (re-advertisement) | ❌ |
| §9.2 | Hold timer reset on any received message (not only KEEPALIVE) | ✅ |
Capability and Session Extensions
RFC 6793 — BGP Support for Four-Octet Autonomous System (AS) Number Space
https://datatracker.ietf.org/doc/html/rfc6793
| Feature | Status |
|---|---|
AS_TRANS (23456) sentinel |
✅ |
FourByteAsn capability advertisement and parsing |
✅ |
4-byte AS_PATH segment encoding/decoding via ParserContext |
✅ |
| 4-byte ASN negotiation in FSM | ✅ |
RFC 9072 — Extended Optional Parameters Length for BGP OPEN Message
https://datatracker.ietf.org/doc/html/rfc9072
| Feature | Status |
|---|---|
| Parsing extended-length OPEN (0xFF sentinel) | ✅ |
| Serialising extended-length OPEN when options exceed 255 bytes | ✅ |
RFC 2918 — Route Refresh Capability for BGP-4
https://datatracker.ietf.org/doc/html/rfc2918
| Feature | Status |
|---|---|
RouteRefresh capability advertisement |
✅ |
ROUTE-REFRESH message type (5) framing |
✅ |
| AFI/SAFI payload parsing | ❌ |
| Acting on received ROUTE-REFRESH (re-advertising routes) | ❌ |
RFC 7313 — Enhanced Route Refresh Capability for BGP-4
https://datatracker.ietf.org/doc/html/rfc7313
| Feature | Status |
|---|---|
EnhancedRouteRefresh capability wire format |
🟡 |
RFC 4724 — Graceful Restart Mechanism for BGP
https://datatracker.ietf.org/doc/html/rfc4724
| Feature | Status |
|---|---|
GracefulRestart capability wire format |
🟡 |
| Restart state and forwarding preserved across sessions | ❌ |
RFC 9494 — Long-Lived Graceful Restart for BGP
https://datatracker.ietf.org/doc/html/rfc9494
| Feature | Status |
|---|---|
LongLivedGracefulRestart capability wire format |
🟡 |
RFC 8654 — Extended Message Support for BGP
https://datatracker.ietf.org/doc/html/rfc8654
| Feature | Status |
|---|---|
ExtendedMessage capability wire format |
🟡 |
Raising BGP_MAX_MSG_LEN to 65535 when negotiated |
❌ |
Multiprotocol and NLRI
RFC 2858 — Multiprotocol Extensions for BGP-4
https://datatracker.ietf.org/doc/html/rfc2858
| Feature | Status |
|---|---|
MultiProtocol capability advertisement (IPv4 unicast) |
✅ |
MP_REACH_NLRI path attribute (parse, serialise) |
✅ |
MP_UNREACH_NLRI path attribute (parse, serialise) |
✅ |
| IPv4 and IPv6 next-hop encoding | ✅ |
RFC 8950 — Advertising IPv4 Network Layer Reachability Information (NLRI) with an IPv6 Next Hop
https://datatracker.ietf.org/doc/html/rfc8950
| Feature | Status |
|---|---|
ExtendedNextHop capability wire format |
🟡 |
Path Attributes and Communities
RFC 1997 — BGP Communities Attribute
https://datatracker.ietf.org/doc/html/rfc1997
| Feature | Status |
|---|---|
COMMUNITIES path attribute (parse, serialise) |
✅ |
| Attach to locally originated routes | ✅ |
RFC 4360 — BGP Extended Communities Attribute
https://datatracker.ietf.org/doc/html/rfc4360
| Feature | Status |
|---|---|
EXTENDED_COMMUNITIES path attribute (parse, serialise) |
✅ |
| AS-specific, IPv4-address-specific, opaque, route-target, route-origin subtypes | ✅ |
RFC 8092 — BGP Large Communities Attribute
https://datatracker.ietf.org/doc/html/rfc8092
| Feature | Status |
|---|---|
LARGE_COMMUNITIES path attribute (parse, serialise) |
✅ |
| Attach to locally originated routes | ✅ |
Other Capabilities (Wire Format Only)
The following capabilities are parsed and serialised correctly but have no functional behaviour implemented beyond that.
| RFC | Capability | Status |
|---|---|---|
| RFC 5291 | Outbound Route Filtering (ORF) | 🟡 |
| RFC 7911 | ADD-PATH | 🟡 |
| RFC 8205 | BGPsec | 🟡 |
Error Handling
RFC 9687 — BGP Send Hold Timer
https://datatracker.ietf.org/doc/html/rfc9687
| Feature | Status |
|---|---|
SendHoldTimer error code (8) defined |
✅ |
| Send hold timer enforcement | ❌ |