Three independent reviews (hijack resistance, reliability, code health)
of the whole tree. This is what they found that could let a bad route in
or take the daemon down.
Hijacks:
- A route had two paths on a two-octet session, AS_PATH and AS4_PATH,
read in two places by two rules. A peer could make the origin checked
on import differ from the one checked at revalidation, and get an
RPKI-invalid route into the table. AS4_PATH is now merged into AS_PATH
once, on receipt (RFC 6793 §4.2.3), and nothing else knows of it.
- The next hop is judged on import: it must be usable, agreed on
(RFC 8950), and by default the peer itself.
- Our own originated prefixes are not taken from other networks.
- A route for a network the machine is on is never put in the kernel.
- Paths with an AS_SET are refused (RFC 9774).
- A configured peer gets one session, not one per BGP Identifier.
- More IPv6 special-purpose prefixes are bogons.
Reliability:
- A batch of requests the kernel refused could overflow the netlink
socket and end the daemon. The socket has room now, a lost answer or a
silent kernel means asking what is there, and neither is fatal.
- Working the routes out again within the grace period after a restart
no longer drops the routes being kept.
- That work can no longer be put off for ever by interface changes.
- Peers whose sessions keep failing are slowed down.
- Unused attribute sets are swept when they pile up, not only each
minute.
- Log lines a peer can cause are said once in a while.
- An RTR answer is bounded in size and time; data cannot expire between
two refreshes.
- The shard of a key is taken from a stirred hash: neighbouring bits of
the hash proved alike for prefixes in a row. The test that showed it,
failing one run in sixteen, is deterministic now.
The lab has a phase, hijacks, in which FRR tries the first three.
route::apply is a struct with methods instead of nested closures, and
the kernel task's loop is shorter.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
