The Babel RTT extension employs metric smoothing to dampen route
oscillations in the face of varying RTT values between two peers[0].
This patch implements such dampening in Bird, roughly following the
implementation in babeld (i.e., using the same exponential function
definition). The main difference is that we calculate everything in the
native Bird microsecond time unit (and increase constants accordingly), and
that we split out the smoothed metric calculation in two function variants,
one that has no side effects and one that does.
[0] https://arxiv.org/pdf/1403.3488.pdf
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
This adds support to the Babel protocol for the RTT extension specified in
draft-ietf-babel-rtt-extension. While this extension is not yet at the RFC
stage, it is one of the more useful extensions to Babel[0], so it seems
worth having in Bird as well.
The extension adds timestamps to Hello and IHU TLVs and uses these to
compute an RTT to each neighbour. An extra per-neighbour cost is then
computed from the RTT based on a minimum and maximum interval and cost
value specified in the configuration. The primary use case for this is
improving routing in a geographically distributed tunnel-based overlay
network.
The implementation follows the babeld implementation when picking constants
and default configuration values. It also uses the same RTT smoothing
algorithm as babeld, and follows it in adding a new 'tunnel' interface type
which enables RTT by default.
[0] https://alioth-lists.debian.net/pipermail/babel-users/2022-April/003932.html
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Add a current_time_now() function which gets an immediate monotonic
timestamp instead of using the cached value from the event loop. This is
useful for callers that need precise times, such as the Babel RTT
measurement code.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
The Babel seqno request code keeps track of which seqno requests are
outstanding for a neighbour by putting them onto a per-neighbour list. When
reusing a seqno request, it will try to remove this node, but if the seqno
request in question was a multicast request with no neighbour attached this
will result in a crash because it tries to remove a list node that wasn't
added to any list.
Fix this by making the list remove conditional. Also add a check so that
seqno requests are only reused if the neighbour also matches, allowing
multiple outstanding requests for the same router ID.
Fixes: ebd5751cde ("Babel: Seqno requests are properly decoupled from neighbors when the underlying interface disappears")
Reported-by: Stefan Haller <stefan.haller@stha.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
When there is a continuos stream of CLI commands, cli_get_command()
always returns 1 (there is a new command). Anyway, the socket receive
buffer was reset only when there was no command at all, leading to a
strange behavior: after a while, the CLI receive buffer came to its end,
then read() was called with zero size buffer, it returned 0 which was
interpreted as EOF.
The patch fixes that by resetting the buffer position after each command
and moving remaining data at the beginning of buffer.
Thanks to Maria Matejka for examining the bug and for the original bugfix.
The import table does not work reliably together with re-evaluation of
routes due to recursive next hops or flowspec validation. We will at
least document that here, as import tables are completely redesigned and
this issue is fixed in BIRD 3.x branch.
Netlink support was added to FreeBSD recently. It is not as full-featured
as its Linux counterpart yet, however the added subset is enough to make
a routing daemon work. Specifically, it supports multiple tables,
multipath, nexthops and nexthops groups. No MPLS support yet.
The attached change adds 'bsd-netlink’ sysconf target, allowing to build
both netlink & rtsock versions on FreeBSD.
The effective keepalive time now scales relative to the negotiated
hold time, to maintain proportion between the keepalive time and the
hold time. This avoids issues when both keepalive and hold times
were configured, the hold time was negotiated to a smaller value,
but the keepalive time stayed the same.
Add new options 'min hold time' and 'min keepalive time', which reject
session attempts with too small hold time.
Improve validation of config options an their documentation.
Thanks to Alexander Zubkov and Sergei Goriunov for suggestions.
When filtered routes (enabled by 'import keep filtered' option) are
updated, they trigger announcements by rte_announce(). For regular
channels (e.g. type RA_OPTIMAL or RA_ANY) such announcement is just
ignored, but in case of RA_ACCEPTED (BGP peer with 'secondary' option)
it just reannounces the old (and still valid) best route.
The patch ensures that such no-change is ignored even for these channels.
BIRD keeps a previous (old) configuration for the purpose of undo. The
existing code frees it after a new configuration is successfully parsed
during reconfiguration. That causes memory usage spikes as there are
temporarily three configurations (old, current, and new). The patch
changes it to free the old one before parsing the new one (as user
already requested a new config). The disadvantage is that undo is
not available after failed reconfiguration.
Memory unmapping causes slow address space fragmentation, leading in
extreme cases to failing to allocate pages at all. Removing this problem
by keeping all the pages allocated to us, yet calling madvise() to let
kernel dispose of them.
This adds a little complexity and overhead as we have to keep the
pointers to the free pages, therefore to hold e.g. 1 GB of 4K pages with
8B pointers, we have to store 2 MB of data.
Define scope for anonymous filters, and also explicitly distinguish block
scopes and function/filter scopes instead of using anonymous / named
distinction.
Anonymous filters forgot to push scope, so variables for them were in
fact defined in the top scope and therefore they shared a frame. This got
broken after rework of variables, which assumed that there is a named
scope for every function/filter.
While onlink flag is meaningful only with explicit next hops, it can be
defined also on direct routes. Parse it also in this case to avoid
periodic updates of the same route.
Thanks to Marcin Saklak for the bugreport.
Add BGP channel option 'next hop prefer global' that modifies BGP
recursive next hop resolution to use global next hop IPv6 address instead
of link-local next hop IPv6 address for immediate next hop of received
routes.
It is useful to distinguish whehter channel config returned from
channel_config_get() was allocated new, or existing from template.
Caller may want to initialize new ones.
- When next hop is reset to local IP, we should remove BGP label stack,
as it is related to original next hop
- BGP next hop or immediate next hop from one VRF should not be passed
to another VRF, as they are different IP namespaces
In principle, the channel list is a list of parent struct proto and can
contain general structures of type struct channel, That is useful e.g.
for adding MPLS channels to BGP.
Changes in commit eb937358 broke setting of channel preference for alien
routes learned during scan. The preference was set only for async routes.
Move common attribute processing part of functions krt_learn_async() and
krt_learn_async() to a separate function to have only one place for such
changes.
In some specific configurations, it was possible to send BIRD into an
infinite loop of recursive next hop resolution. This was caused by route
priority inversion.
To prevent priority inversions affecting other next hops, we simply
refuse to resolve any next hop if the best route for the matching prefix
is recursive or any other route with the same preference is recursive.
Next hop resolution doesn't change route priority, therefore it is
perfectly OK to resolve BGP next hops e.g. by an OSPF route, yet if the
same (or covering) prefix is also announced by iBGP, by retraction of
the OSPF route we would get a possible priority inversion.
Seems like the previous patch was too optimistic, as route replace is
still broken even in Linux 4.19 LTS (but fixed in Linux 5.10 LTS) for:
ip route add 2001:db8::/32 via fe80::1 dev eth0
ip route replace 2001:db8::/32 dev eth0
It ends with two routes instead of just the second.
The issue is limited to direct and special type (e.g. unreachable)
routes, the patch restricts route replace for cases when the new route
is a regular route (with a next hop address).
When IPv6 ECMP support first appeared in Linux kernel, it used different
API than IPv4 ECMP. Individual next hops were updated and announced
separately, instead of using RTA_MULTIPATH as in IPv4. This has several
drawbacks and requires complex code to merge received notifications to
one multipath route.
When Linux came with IPv6 RTA_MULTIPATH support, the initial versions
were somewhat buggy, so we kept using the old API for updates (splitting
multipath routes to sequences of route updates), while accepting both
old-style routes and RTA_MULTIPATH routes in scans / notifications.
As IPv6 RTA_MULTIPATH support is here for a long time, this patch fully
switches Netlink to the IPv6 RTA_MULTIPATH API and removes old complex
code for handling individual next hop announces.
The required Linux version is at least 4.11 for reliable operation.
Thanks to Daniel Gröber for the original patch.
Remove compile-time sysdep option CONFIG_ALL_TABLES_AT_ONCE, replace it
with runtime ability to run either separate table scans or shared scan.
On Linux, use separate table scans by default when the netlink socket
option NETLINK_GET_STRICT_CHK is available, but retreat to shared scan
when it fails.
Running separate table scans has advantages where some routing tables are
managed independently, e.g. when multiple routing daemons are running on
the same machine, as kernel routing table modification performance is
significantly reduced when the table is modified while it is being
scanned.
Thanks Daniel Gröber for the original patch and Toke Høiland-Jørgensen
for suggestions.
Implement BGP roles as described in RFC 9234. It is a mechanism for
route leak prevention and automatic route filtering based on common BGP
topology relationships. It defines role capability (controlled by 'local
role' option) and OTC route attribute, which is used for automatic route
filtering and leak detection.
Minor changes done by commiter.
