This reverts commit 2c137591.

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.

This reverts commit cee0cd14.
This change is not needed in version 2 and the surrounding code has
disappeared mostly in version 3.

Add support for bgp_otc in filters and warning for configuration
inside confederations.

Eugene Bogomazov authored 2 years ago and Ondřej Zajíček committed 2 years ago

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.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

For loops allow to iterate over elements in compound data like BGP paths
or community lists. The syntax is:

  for [ <type> ] <variable> in <expr> do <command-body>

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Allow variable declarations mixed with code, also in nested blocks with
proper scoping, and with variable initializers. E.g:

function fn(int a)
{
  int b;
  int c = 10;

  if a > 20 then
  {
    b = 30;
    int d = c * 2;
    print a, b, c, d;
  }

  string s = "Hello";
}

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

When f_line is done, we have to pop the stack frame. The old code just
removed nominal number of args/vars. Change it to use stored ventry value
modified by number of returned values. This allows to allocate variables
on a stack frame during execution of f_lines instead of just at start.

But we need to know the number of returned values for a f_line. It is 1
for term, 0 for cmd. Store that to f_line during linearization.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Command sequences in curly braces used a separate nonterminal in grammar.
Handle them as a regular command.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

When a new variable used the same name as an existing symbol in an outer
scope, then offset number was defined based on a scope of the existing
symbol ($3) instead of a scope of the new symbol (sym_). That can lead
to two variables sharing the same memory slot.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Soft scopes are anonymous scopes that most likely do not contain any
symbol, so allocating regular scope is postponed when it is really
needed.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Direct recursion almost worked, just crashed on function signature check.
Split function parsing such that function signature is saved before
function body is processed. Recursive calls are marked so they can be
avoided during f_same() and similar code walking.

Also, include tower of hanoi solver as a test case.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Equality comparison is defined on all values, even of different
types, but we still want to do constant promotion if possible.

Alexander Zubkov authored 3 years ago and Ondřej Zajíček committed 2 years ago

Add literal for empty set [], which works both for tree-based sets
and prefix sets by using existing constant promotion mechanism.

Minor changes by committer.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Use struct f_val as a common argument for as_path_filter(), as suggested
by Alexander Zubkov. That allows to use NULL sets as valid arguments.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

All instructions with a return value (i.e. expressions, ones with
non-zero outval, third argument in INST()) should declare their return
type. Check that automatically by M4 macros.

Set outval of FI_RETURN to 0. The instruction adds one value to stack,
but syntactically it is a statement, not an expression.

Add fake return type declaration to FI_CALL, otherwise the automatic
check would fail builds.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Keep list of function parameters in f_line and use it to verify
types of arguments for function calls. Only static type checks
are implemented.

Ondřej Zajíček authored 3 years ago and Ondřej Zajíček committed 2 years ago

Pass instructions of function call arguments as vararg arguments to
FI_CALL instruction constructor and move necessary magic from parser
code to interpreter / instruction code.

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.

When writing flow4 { dst 2001:db8::dead:beef/128; }, BIRD crashed on an
not-well-debuggable segfault as it tried to copy the whole 128-bit
prefix into an IPv4-sized memory.

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 fix neighbor removal
which were changing seqno requests to multicast ones instead of removing
them.

Fixes: ebd5751c ("Babel: Seqno requests are properly decoupled from
neighbors when the underlying interface disappears").

Based on the patch from Toke Høiland-Jørgensen <toke@toke.dk>,
bug reported by Stefan Haller <stefan.haller@stha.de>, thanks.

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.