The MPLS subsystem manages MPLS labels and handles their allocation to
MPLS-aware routing protocols. These labels are then attached to IP or VPN
routes representing label switched paths -- LSPs.
There was already a preliminary MPLS support consisting of MPLS label
net_addr, MPLS routing tables with static MPLS routes, remote labels in
next hops, and kernel protocol support.
This patch adds the MPLS domain as a basic structure representing local
label space with dynamic label allocator and configurable label ranges.
To represent LSPs, allocated local labels can be attached as route
attributes to IP or VPN routes with local labels as attributes.
There are several steps for handling LSP routes in routing protocols --
deciding to which forwarding equivalence class (FEC) the LSP route
belongs, allocating labels for new FECs, announcing MPLS routes for new
FECs, attaching labels to LSP routes. The FEC map structure implements
basic code for managing FECs in routing protocols, therefore existing
protocols can be made MPLS-aware by adding FEC map and delegating
most work related to local label management to it.
In general, private_id is sparse and protocols may want to map some
internal values directly into it. For example, L3VPN needs to
map VPN route discriminators to private_id.
OTOH, u32 is enough for global_id, as these identifiers are dense.
Add a new protocol offering route aggregation.
User can specify list of route attributes in the configuration file and
run route aggregation on the export side of the pipe protocol. Routes are
sorted and for every group of equivalent routes new route is created and
exported to the routing table. It is also possible to specify filter
which will run for every route before aggregation.
Furthermore, it will be possible to set attributes of new routes
according to attributes of the aggregated routes.
This is a work in progress.
Original work by Igor Putovny, subsequent cleanups and finalization by
Maria Matejka.
- Manage BMP state through bmp_peer, bmp_stream, bmp_table structures
- Use channels and rt_notify() hook for route announcements
- Add support for post-policy monitoring
- Send End-of-RIB even when there is no routes
- Remove rte_update_in_notify() hook from import tables
- Update import tables to support channels
- Add bmp_hack (no feed / no flush) flag to channels
Initial implementation of a basic subset of the BMP (BGP Monitoring
Protocol, RFC 7854) from Akamai team. Submitted for further review
and improvement.
There were some confusion about validity and usage of pflags, which
caused incorrect usage after some flags from (now removed) protocol-
specific area were moved to pflags.
We state that pflags:
- Are secondary data used by protocol-specific hooks
- Can be changed on an existing route (in contrast to copy-on-write
for primary data)
- Are irrelevant for propagation (not propagated when changed)
- Are specific to a routing table (not propagated by pipe)
The patch did these fixes:
- Do not compare pflags in rte_same(), as they may keep cached values
like BGP_REF_STALE, causing spurious propagation.
- Initialize pflags to zero in rte_get_temp(), avoid initialization in
protocol code, fixing at least two forgotten initializations (krt
and one case in babel).
- Improve documentation about pflags
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.
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.
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.
Passing protocol to preexport was in fact a historical relic from the
old times when channels weren't a thing. Refactoring that to match
current extensibility needs.
Use timer (configurable as 'gc period') to schedule routing table
GC/pruning to ensure that prune is done on time but not too often.
Randomize GC timers to avoid concentration of GC events from different
tables in one loop cycle.
Fix a bug that caused minimum inter-GC interval be 5 us instead of 5 s.
Make default 'gc period' adaptive based on number of routing tables,
from 10 s for small setups to 600 s for large ones.
In marge multi-table RS setup, the patch improved time of flushing
a downed peer from 20-30 min to <2 min and removed 40s latencies.
The prefix hash table in BGP used the same hash function as the rtable.
When a batch of routes are exported during feed/flush to the BGP, they
all have similar hash values, so they are all crowded in a few slots in
the BGP prefix table (which is much smaller - around the size of the
batch - and uses higher bits from hash values), making it much slower due
to excessive collisions. Use a different hash function to avoid this.
Also, increase the batch size to fill 4k BGP packets and increase minimum
BGP bucket and prefix hash sizes to avoid back and forth resizing during
flushes.
This leads to order of magnitude faster flushes (on my test data).
The prune loop may may rebuild the prefix trie and therefore invalidate
walk state for asynchronous walks (used in 'show route in' cmd). Fix it
by adding locking that keeps the old trie in memory until current walks
are done.
In future this could be improved by rebuilding trie walk states (by
lookup for last found prefix) after the prefix trie rebuild.
When rtable is pruned and network fib nodes are removed, we also need to
prune prefix trie. Unfortunately, rebuilding prefix trie takes long time
(got about 400 ms for 1M networks), so must not be atomic, we have to
rebuild a new trie while current one is still active. That may require
some considerable amount of temporary memory, so we do that only if
we expect significant trie size reduction.
Implement flowspec validation procedure as described in RFC 8955 sec. 6
and RFC 9117. The Validation procedure enforces that only routers in the
forwarding path for a network can originate flowspec rules for that
network.
The patch adds new mechanism for tracking inter-table dependencies, which
is necessary as the flowspec validation depends on IP routes, and flowspec
rules must be revalidated when best IP routes change.
The validation procedure is disabled by default and requires that
relevant IP table uses trie, as it uses interval queries for subnets.
Attach a prefix trie to IP/VPN/ROA tables. Use it for net_route() and
net_roa_check(). This leads to 3-5x speedups for IPv4 and 5-10x
speedup for IPv6 of these calls.
TODO:
- Rebuild the trie during rt_prune_table()
- Better way to avoid trie_add_prefix() in net_get() for existing tables
- Make it configurable (?)
Pipes copy the original rte with old values, so they require rte to be
exported with stored tmpattrs. Other protocols access stored attributes
using eattr list, so they require rte to be exported with expanded
tmpattrs. This is temporary hack, we plan to remove whoe tmpattr mechanism.
Thanks to Paul Donohue for the bugreport.
In most cases of export there is no need to store back temporary
attributes to rte, as receivers (protocols) access eattr list anyway.
But pipe copies the original rte with old values, so we should store
tmpattrs also during export.
Thanks to Paul Donohue for the bugreport.
