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Rayhaan JaufeerallyandClaude Fable 5.1 e2de44ba78 feature: active dialer for configured peers

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>

2026-09-16 23:22:08 +02:00

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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§4.3	UPDATE message (path attributes, NLRI, withdrawn routes)	✅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 (router-ID comparison)	❌
§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	❌

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