Route flags are mosty internal state of rtable, they are not significant
to whether a route has changed. With the old code, all routes received as
a part of enhanced route refresh are always re-announced to other peers
due to change in REF_STALE.

Update for one of previous patches, handles the the issue for
first-accepted mode of route propagation.

When area is reconfigured to a different type, we need to flush LSAs as
they may not be valid (e.g. NSSA-LSA for non-NSSA area). Also, when we
have have just one OSPF area and that changes type, we could restart OSPF
as there is no state to keep anyway. That solves issue with different
handling of external routes exported to OSPF based of main area type.

External LSAs originated by OSPF routers with VPN-PE behavior enabled are
marked by DN flag and they are ignored by other OSPF routers with VPN-PE
enabled.

As we do not have much usage for it yet.

One of previous workarounds for phantom route avoidance breaks export
counters by expanding sending of spurious withdraws, which are send when
we are not sure whether we have advertised that routes in the past.
If not, then export counter is decreased, but it was not increased
before, so it overflows under zero.

The patch fixes that by sendung spurious withdraws, but not counting them
on export counter. That may lead to error in the other direction, but that
happens only as a race condition (i.e., in normal operation filters
return proper values about old route export state).

Thanks to Michal Nowak for reporting the issue.

Direct acknowledgements should be send as unicast to a corresponding
neighbor. Only delayed acks should be send as multicast to all/designated
routers.

Master may free last DBDES packet immediately. Slave must wait dead
interval before freeing last DBDES packet and then reject duplicate
DBDES packets with SeqNumberMismatch.

After SeqNumberMismatch/BadLSReq, we should continue with the old
seqnum++. The old code tries to do that by n->adj, but it was set
nowhere.

As it is specified in RFC 2328. The old code just provided warning.

Using dummy net instead. This should help with performance on rejected
routes.

The earlier fix loosen conditions for not running filters on old
route when deciding about route propagation to a protocol to avoid
issues with ghost routes in some race conditions.

Unfortunately, the fix also caused back-propagation of withdraws. For
regular updates, back-propagation is prevented in import_control hooks,
but these are not called on withdraws. For them, import_control hooks
are called on old routes instead, changing (old, NULL) notification
to (NULL, NULL), which is ignored. By not calling export processing
in some cases, the withdraw is not ignored and is back-propagated.

This patch fixes that by contract conditions so the earlier fix is not
applied to back-propagated updates.

Thanks to Igor Podlesny for notification.

When going up, uncleaned old channel state may trigger unexpected
conditions crashing bird.

Add support for OSPFv2 Opaque LSAs (RFC 5250) and for Router Information
LSA (RFC 7770). The second part is here mainly for testing opaque LSAs.

Also includes minor cleanup of help.

Current FreeBSD kernels require SA records for both directions.

Thanks to Joseph Mulloy and Andrey V. Elsukov for reporting and
solving the issue.

Minor cleanups, updates and clarifications. Also removes (incomplete
and well-known) build steps from README, as they are better described
in INSTALL.

Since v2 we have multiple listening BGP sockets, and each BGP protocol
has associated one of them. Use listening socket that accepted the
incoming connection as a key in the dispatch process so only BGP
protocols assocaited with that listening socket can be selected.
This is necesary for proper dispatch when VRFs are used.

It may happen that the LLv6 address for given iface is not defined during
BGP start, so we postpone the check to the the session establishment.

FreeBSD silently changes TTL to 1 when MSG_DONTROUTE is used, even when
it is explicitly set to another value. That breaks TTL security sockets,
including BFD which always uses TTL 255. Bad FreeBSD!

This protocol is highly experimental and nobody should use it in
production. Anyway it may help you getting some insight into what eats
so much time in filter processing.

In some circumstances (old LSA flushed but not acknowledged and not
removed) origination of a new LSA may wrongly triggers LSA collision
code. The patch fixes that.

Thanks to Asbjorn Mikkelsen for the bugreport and @mdelagueronniere
for the original patch.

Extend 'next hop keep' and 'next hop self' options to have boolean values
(enabled / disabled) and also values 'ibgp'/ 'ebgp' to restrict it to
routes received from IBGP / EBGP. This allows to have it enabled by
default in some cases, matches features of other implementations, and
allows to handle some strange cases like EBGP border router with 'next
hop self' also doing IBGP route reflecting.

Change default of 'next hop keep' to enabled for route servers, and
'ibgp' for route reflectors.

Update documentation for these options.