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.
Add option 'netlink rx buffer' to specify netlink socket receive buffer
size. Uses SO_RCVBUFFORCE, so it can override rmem_max limit.
Thanks to Trisha Biswas and Michal for the original patches.
Add strict checking for netlink KRT dumps to avoid PMTU cache records
from FNHE table dump along with KRT.
Linux Kernel added FNHE table dump to the netlink API in patch:
8d3b68cd37.1561131177.git.sbrivio@redhat.com/
Therefore, since Linux 5.3 these route cache entries are dumped together
with regular routes during periodic KRT scans, which in some cases may be
huge amount of useless data. This can be avoided by using strict checking
for netlink dumps:
https://lore.kernel.org/netdev/20181008031644.15989-1-dsahern@kernel.org/
The patch mitigates the risk of receiving unknown and potentially large
number of FNHE records that would block BIRD I/O in each sync. There is a
known issue caused by the GRE tunnels on Linux that seems to be creating
one FNHE record for each destination IP address that is routed through
the tunnel, even when the PMTU equals to GRE interface MTU.
Thanks to Tomas Hlavacek for the original patch.
Kernel uses cloned routes to keep route cache entries, but reports them
together with regular routes. They were skipped implicitly as they
do not have rtm_protocol filled. Add explicit check for cloned flag
and skip such routes explicitly.
Also, improve debug logs of skipped routes.
Add option to socket interface for nonlocal binding, i.e. binding to an
IP address that is not present on interfaces. This behaviour is enabled
when SKF_FREEBIND socket flag is set. For Linux systems, it is
implemented by IP_FREEBIND socket flag.
Minor changes done by commiter.
Currently, BIRD ignores dead routes to consider them absent. But it also
ignores its own routes and thus it can not correctly manage such routes
in some cases. This patch makes an exception for routes with proto bird
when ignoring dead routes, so they can be properly updated or removed.
Thanks to Alexander Zubkov for the original patch.
With net.ipv4.conf.XXX.ignore_routes_with_linkdown sysctl, a user can
ensure the kernel does not use a route whose target interface is down.
Such route is marked with a 'dead' / RTNH_F_DEAD flag.
Ignore these routes or multipath nexthops during scan.
Thanks to Vincent Bernat for the original patch.
For ECMP routes, RTA_FLOW attribute must be set per-nexthop, not
per-route. Our corresponding krt_realm attribute is per-route.
Thanks to Mikhail Petrov for the bugreport.
Add support for RTA_MULTIPATH attribute parsing for AF_MPLS routes.
BIRD is capable of installing a multipath route into kernel on Linux,
but it would not be seen because parsing fails. This made BIRD attempt
to install the same route repeatedly.
(The patch minorly updated by committer)
When dynamic BGP with remote range is configured, MD5SIG needs to use
newer socket option (TCP_MD5SIG_EXT) to specify remote addres range for
listening socket.
Thanks to Adam Kułagowski for the suggestion.
Accept RTA_VIA attribute in all cases. The old code always used
RTA_GATEWAY for IPv4 / IPv6 and RTA_VIA for MPLS. The new code uses
RTA_VIA in cases where AF of network and AF of nexthop differs.
Use route replace netlink op instead of delete+add netlink ops for kernel
IPv4 route replace. This avoids some packetloss during route replace.
Still use the old behavior for IPv6, as some kernel bugs are hidden in
IPv6 ECMP handling.
Instead of separate scans for IPv4, IPv6 and MPLS, do one AF_UNSPEC scan.
This also avoids kernel issue when kernel reported IPv4 and IPv6 routes
during MPLS scan if MPLS is not active.
This is a major change of how the filters are interpreted. If everything
works how it should, it should not affect you unless you are hacking the
filters themselves.
Anyway, this change should make a huge improvement in the filter performance
as previous benchmarks showed that our major problem lies in the
recursion itself.
There are also some changes in nest and protocols, related mostly to
spreading const declarations throughout the whole BIRD and also to
refactored dynamic attribute definitions. The need of these came up
during the whole work and it is too difficult to split out these
not-so-related changes.
This is a fundamental change of an original (1999) concept of route
processing inside BIRD. During import/export, there was a temporary
ea_list created which was to be used instead of the another one inside
the route itself.
This led to some confusion, quirks, and strange filter code that handled
extended route attributes. Dropping it now.
The protocol interface has changed in an uniform way -- the
`struct ea_list *attrs` argument has been removed from store_tmp_attrs(),
import_control(), rt_notify() and get_route_info().
This patch adds support for source-specific IPv6 routes to BIRD core.
This is based on Dean Luga's original patch, with the review comments
addressed. SADR support is added to network address parsing in confbase.Y
and to the kernel protocol on Linux.
Currently there is no way to mix source-specific and non-source-specific
routes (i.e., SADR tables cannot be connected to non-SADR tables).
Thanks to Toke Hoiland-Jorgensen for the original patch.
Minor changes by Ondrej Santiago Zajicek.
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.
Starting from Linux 4.11, IPv6 ECMP routes are now notified using
RTA_MULTIPATH, like IPv4 ones. The patch adds support for RTA_MULTIPATH
parsing for IPv6 routes. This also enables to parse ECMP alien routes
correctly.
Thanks to Vincent Bernat for the original patch.
Add proper support for per-nexthop onlink flag in routes to handle next
hop addresses that are not covered by interface IP ranges. Supported by
kernel and static protocols.
Thanks to Vincent Bernat for the idea.
