Preparing to peer with a production BIRD router turned up two problems.
- packet: most Capability::from_wire arms returned the per-capability
buffer (always empty by then) instead of the bytes following the
capability. The list parser then saw an empty remainder and silently
dropped every later capability. Any OPEN listing extended message, role,
graceful restart, add-path, enhanced route refresh, LLGR, extended next
hop or an unknown capability before the 4-octet ASN capability lost the
ASN, so the peer appeared as AS_TRANS (23456) and a configured
remote_asn was refused with Bad Peer AS. BIRD and FRR both do this.
Single-capability round-trip tests could not catch it; new tests parse
every capability with another following it, and a full BIRD capability
list.
- server: advertise MultiProtocol IPv6 unicast alongside IPv4. Without it
a peer will not accept the IPv6 routes we originate via MP_REACH_NLRI.
- Interop test: byte-for-byte BIRD 2 OPEN is accepted with the right ASN,
and an IPv6 End-of-RIB neither drops the session nor creates a route.
- docs/lab/prod: BIRD config for an announce-only ferrix neighbour
(strict /48 import filter, community scrubbing, unreachable next hop,
import limit, export none, passive) and the matching ferrix config.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
