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.

Add some supportive functions for f_tree and EC. These functions are used
by L3VPN code.

 - 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.

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.