mirrors/bird
mirrors/bird
0
0
Fork 0
mirror of https://gitlab.nic.cz/labs/bird.git synced 2025-03-12 09:28:46 +00:00
Code Releases Activity

Nest: Improve export counter handling

Browse Source 
One of previous workarounds for phantom route avoidance breaks export
counters by expanding sending of spurious withdraws, which are send when
we are not sure whether we have advertised that routes in the past.
If not, then export counter is decreased, but it was not increased
before, so it overflows under zero.

The patch fixes that by sending spurious withdraws, but not counting them
on export counter. That may lead to error in the other direction, but
that happens only as a race condition (i.e., in normal operation filters
return proper values about old route export state).
This commit is contained in:
Ondrej Zajicek (work) 2019-02-19 16:00:30 +01:00
parent b4438e40ef
commit 2dd9800ab5
1 changed files with 26 additions and 13 deletions

39
nest/rt-table.c

@ -426,35 +426,48 @@ rt_notify_basic(struct announce_hook *ah, net *net, rte *new0, rte *old0, int re
* reconfiguration and the end of refeed - if a newly filtered * reconfiguration and the end of refeed - if a newly filtered
* route disappears during this period, proper withdraw is not * route disappears during this period, proper withdraw is not
* sent (because old would be also filtered) and the route is * sent (because old would be also filtered) and the route is
* not refeeded (because it disappeared before that). Therefore, * not refeeded (because it disappeared before that). This is
* we also do not try to run the filter on old routes that are * handled below as a special case.
* older than the last filter change.
*/ */
if (new) if (new)
new = export_filter(ah, new, &new_free, &tmpa, 0); new = export_filter(ah, new, &new_free, &tmpa, 0);
if (old && !(refeed || ((old->lastmod <= ah->last_out_filter_change) && if (old && !refeed)
(p != old->sender->proto))))
old = export_filter(ah, old, &old_free, NULL, 1); old = export_filter(ah, old, &old_free, NULL, 1);
if (!new && !old) if (!new && !old)
{ {
/* /*
* As mentioned above, 'old' value may be incorrect in some race conditions. * As mentioned above, 'old' value may be incorrect in some race conditions.
* We generally ignore it with the exception of withdraw to pipe protocol. * We generally ignore it with two exceptions:
* In that case we rather propagate unfiltered withdraws regardless of *
* export filters to ensure that when a protocol is flushed, its routes are * First, withdraw to pipe protocol. In that case we rather propagate
* removed from all tables. Possible spurious unfiltered withdraws are not * unfiltered withdraws regardless of export filters to ensure that when a
* problem here as they are ignored if there is no corresponding route at * protocol is flushed, its routes are removed from all tables. Possible
* the other end of the pipe. We directly call rt_notify() hook instead of * spurious unfiltered withdraws are not problem here as they are ignored if
* there is no corresponding route at the other end of the pipe.
*
* Second, recent filter change. If old route is older than filter change,
* then it was previously evaluated by a different filter and we do not know
* whether it was really propagated. In that case we rather send spurious
* withdraw than do nothing and possibly cause phantom routes.
*
* In both cases wqe directly call rt_notify() hook instead of
* do_rt_notify() to avoid logging and stat counters. * do_rt_notify() to avoid logging and stat counters.
*/ */
int pipe_withdraw = 0, filter_change = 0;
#ifdef CONFIG_PIPE #ifdef CONFIG_PIPE
if ((p->proto == &proto_pipe) && !new0 && (p != old0->sender->proto)) pipe_withdraw = (p->proto == &proto_pipe) && !new0;
p->rt_notify(p, ah->table, net, NULL, old0, NULL);
#endif #endif
filter_change = old0 && (old0->lastmod <= ah->last_out_filter_change);
if ((pipe_withdraw || filter_change) && (p != old0->sender->proto))
{
stats->exp_withdraws_accepted++;
p->rt_notify(p, ah->table, net, NULL, old0, NULL);
}
return; return;
} }