This is optional check described in RFC 4271. Although this can be also
done by filters, it is widely implemented option in BGP implementations.
Thanks to Eugene Bogomazov for the original patch.
Change of some options requires route refresh, but when import table is
active, channel reload is done from it instead of doing full route
refresh. So in this case we request it internally.
The patch implements optional internal export table to a channel and
hooks it to BGP so it can be used as Adj-RIB-Out. When enabled, all
exported (post-filtered) routes are stored there. An export table can be
examined using e.g. 'show route export table bgp1.ipv4'.
Several BGP channel options (including 'next hop self') could be
reconfigured without session reset, with just route refeed/refresh.
The patch improves reconfiguration code to do it that way.
When 'graceful down' command is entered, protocols are shut down
with regard to graceful restart. Namely Kernel protocol does
not remove routes and BGP protocol does not send notification,
just closes the connection.
Useful for implementation of agents implementing the SNMP-BGP MIB, which
requires the local AS of a session to be specified.
Thanks to Jan-Philipp Litza for the patch.
Support for dynamically spawning BGP protocols for incoming connections.
Use 'neighbor range' to specify range of valid neighbor addresses, then
incoming connections from these addresses spawn new BGP instances.
When BGP connection is opened, it may happen that rx hook (with remote
OPEN) is called before tx hook (for local OPEN). Therefore, we need to do
internal changes (like setting local_caps) synchronously with OPENSENT
transition and we need to ensure that OPEN is sent before KEEPALIVE.
Allow to specify just 'internal' or 'external' for remote neighbor
instead of specific ASN. In the second case that means BGP peers with
any non-local ASNs are accepted.
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.
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.
The patch implements optional internal import table to a channel and
hooks it to BGP so it can be used as Adj-RIB-In. When enabled, all
received (pre-filtered) routes are stored there and import filters can
be re-evaluated without explicit route refresh. An import table can be
examined using e.g. 'show route import table bgp1.ipv4'.
When a new channel is found during reconfiguration, do force restart
of the protocol, like with any other un-reconfigurable change.
The old behavior was that the new channel was added but remained in down
state, even if the protocol was up, so a manual protocol restart was
often necessary.
In the future this should be improved such that a reconfigurable
channel addition (e.g. direct) is accepted and channel is started,
while an un-reconfigurable addition forces protocol restart.
Once upon a time, far far away, there were the old Bird developers
discussing what direction of route flow shall be called import and
export. They decided to say "import to protocol" and "export to table"
when speaking about a protocol. When speaking about a table, they
spoke about "importing to table" and "exporting to protocol".
The latter terminology was adopted in configuration, then also the
bird CLI in commit ea2ae6dd0 started to use it (in year 2009). Now
it's 2018 and the terminology is the latter. Import is from protocol to
table, export is from table to protocol. Anyway, there was still an
import_control hook which executed right before route export.
One thing is funny. There are two commits in April 1999 with just two
minutes between them. The older announces the final settlement
on config terminology, the newer uses the other definition. Let's see
their commit messages as the git-log tool shows them (the newer first):
commit 9e0e485e50
Author: Martin Mares <mj@ucw.cz>
Date: Mon Apr 5 20:17:59 1999 +0000
Added some new protocol hooks (look at the comments for better explanation):
make_tmp_attrs Convert inline attributes to ea_list
store_tmp_attrs Convert ea_list to inline attributes
import_control Pre-import decisions
commit 5056c559c4
Author: Martin Mares <mj@ucw.cz>
Date: Mon Apr 5 20:15:31 1999 +0000
Changed syntax of attaching filters to protocols to hopefully the final
version:
EXPORT <filter-spec> for outbound routes (i.e., those announced
by BIRD to the rest of the world).
IMPORT <filter-spec> for inbound routes (i.e., those imported
by BIRD from the rest of the world).
where <filter-spec> is one of:
ALL pass all routes
NONE drop all routes
FILTER <name> use named filter
FILTER { <filter> } use explicitly defined filter
For all protocols, the default is IMPORT ALL, EXPORT NONE. This includes
the kernel protocol, so that you need to add EXPORT ALL to get the previous
configuration of kernel syncer (as usually, see doc/bird.conf.example for
a bird.conf example :)).
Let's say RIP to this almost 19-years-old inconsistency. For now, if you
import a route, it is always from protocol to table. If you export a
route, it is always from table to protocol.
And they lived happily ever after.
The new MRT protocol is responsible for periodic RIB table dumps in the
MRT format (RFC 6396). Also the existing code for BGP4MP MRT dumps is
refactored and splitted between BGP to MRT protocols, will be more
integrated into MRT in the future.
Example:
protocol mrt {
table "*";
filename "%N_%F_%T.mrt";
period 60;
}
It is partially based on the old MRT code from Pavel Tvrdik.
The old timer interface is still kept, but implemented by new timers. The
plan is to switch from the old inteface to the new interface, then clean
it up.
The patch implements BGP Administrative Shutdown Communication (RFC 8203)
allowing BGP operators to pass messages related to BGP session
administrative shutdown/restart. It handles both transmit and receive of
shutdown messages. Messages are logged and may be displayed by show
protocol all command.
Thanks to Job Snijders for the basic patch.
Add basic VRF (virtual routing and forwarding) support. Protocols can be
associated with VRFs, such protocols will be restricted to interfaces
assigned to the VRF (as reported by Linux kernel) and will use sockets
bound to the VRF. E.g., different multihop BGP instances can use diffent
kernel routing tables to handle BGP TCP connections.
The VRF support is preliminary, currently there are several limitations:
- Recent Linux kernels (4.11) do not handle correctly sockets bound
to interaces that are part of VRF, so most protocols other than multihop
BGP do not work. This will be fixed by future kernel versions.
- Neighbor cache ignores VRFs. Breaks config with the same prefix on
local interfaces in different VRFs. Not much problem as single hop
protocols do not work anyways.
- Olock code ignores VRFs. Breaks config with multiple BGP peers with the
same IP address in different VRFs.
- Incoming BGP connections are not dispatched according to VRFs.
Breaks config with multiple BGP peers with the same IP address in
different VRFs. Perhaps we would need some kernel API to read VRF of
incoming connection? Or probably use multiple listening sockets in
int-new branch.
- We should handle master VRF interface up/down events and perhaps
disable associated protocols when VRF goes down. Or at least disable
associated interfaces.
- Also we should check if the master iface is really VRF iface and
not some other kind of master iface.
- BFD session request dispatch should be aware of VRFs.
- Perhaps kernel protocol should read default kernel table ID from VRF
iface so it is not necessary to configure it.
- Perhaps we should have per-VRF default table.
Covers IPv4/VPNv4 routes with IPv6 next hop (RFC 5549), IPv6 routes with
IPv4 next hop (RFC 4798) and VPNv6 routes with IPv4 next hop (RFC 4659).
Unfortunately it also makes next hop hooks more messy.
Each BGP channel now could have two IGP tables, one for IPv4 next hops,
the other for IPv6 next hops.
Basic support for SAFI 4 and 128 (MPLS labeled IP and VPN) for IPv4 and
IPv6. Should work for route reflector, but does not properly handle
originating routes with next hop self.
Based on patches from Jan Matejka.
Prefix and bucket tables are initialized when entering established state
but not explicitly freed when leaving it (that is handled by protocol
restart). With graceful restart, BGP may enter and leave established
state multiple times without hard protocol restart causing memory leak.
Add code for manipulation with TCP-MD5 keys in the IPsec SA/SP database
at FreeBSD systems. Now, BGP MD5 authentication (RFC 2385) keys are
handled automatically on both Linux and FreeBSD.
Based on patches from Pavel Tvrdik.
In BIRD, RX has lower priority than TX with the exception of RX from
control socket. The patch replaces heuristic based on socket type with
explicit mark and uses it for both control socket and BGP session waiting
to be established.
This should avoid an issue when during heavy load, outgoing connection
could connect (TX event), send open, but then failed to receive OPEN /
establish in time, not sending notifications between and therefore
got hold timer expired error from the neighbor immediately after it
finally established the connection.
When a BGP session was established by an outgoing connection with
Graceful Restart behavior negotiated, a pending incoming connection in
OpenSent state, and another incoming connection was received, then the
outgoing connection (and whole BGP session) was closed, but the old
incoming connection was just overwritten by the new one. That later
caused a crash when the hold timer from the old connection fired.
The patch adds support for channels, structures connecting protocols and
tables and handling most interactions between them. The documentation is
missing yet.
Permit specifying neighbor address, AS number and port independently.
Add 'interface' parameter for specifying interface for link-local
sessions independently.
Thanks to Alexander V. Chernikov for the original patch.
This is more consistent with common usage and also with the behavior of
other implementations (Cisco, Juniper).
Also changes the default for gw mode to be based solely on
direct/multihop.
Neighbor events related to received route next hops got mixed up with
sticky neighbor node for an IP of the BGP peer. If a neighbor for a next
hop disappears, BGP session is shut down.
