path: root/bgpd/bgp_conditional_adv.c

/*
 * BGP Conditional advertisement
 * Copyright (C) 2020  Samsung R&D Institute India - Bangalore.
 *			Madhurilatha Kuruganti
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#include "bgpd/bgp_conditional_adv.h"
#include "bgpd/bgp_vty.h"

static route_map_result_t
bgp_check_rmap_prefixes_in_bgp_table(struct bgp_table *table,
				     struct route_map *rmap)
{
	struct attr dummy_attr = {0};
	struct bgp_dest *dest;
	struct bgp_path_info *pi;
	struct bgp_path_info path = {0};
	struct bgp_path_info_extra path_extra = {0};
	const struct prefix *dest_p;
	route_map_result_t ret = RMAP_DENYMATCH;

	for (dest = bgp_table_top(table); dest; dest = bgp_route_next(dest)) {
		dest_p = bgp_dest_get_prefix(dest);
		assert(dest_p);

		for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = pi->next) {
			dummy_attr = *pi->attr;

			/* Fill temp path_info */
			prep_for_rmap_apply(&path, &path_extra, dest, pi,
					    pi->peer, &dummy_attr);

			RESET_FLAG(dummy_attr.rmap_change_flags);

			ret = route_map_apply(rmap, dest_p, &path);
			bgp_attr_flush(&dummy_attr);

			if (ret == RMAP_PERMITMATCH) {
				bgp_dest_unlock_node(dest);
				if (BGP_DEBUG(update, UPDATE_OUT))
					zlog_debug(
						"%s: Condition map routes present in BGP table",
						__func__);

				return ret;
			}
		}
	}

	if (BGP_DEBUG(update, UPDATE_OUT))
		zlog_debug("%s: Condition map routes not present in BGP table",
			   __func__);

	return ret;
}

static void bgp_conditional_adv_routes(struct peer *peer, afi_t afi,
				       safi_t safi, struct bgp_table *table,
				       struct route_map *rmap,
				       enum update_type update_type)
{
	bool addpath_capable;
	struct bgp_dest *dest;
	struct bgp_path_info *pi;
	struct bgp_path_info path;
	struct peer_af *paf;
	const struct prefix *dest_p;
	struct update_subgroup *subgrp;
	struct attr advmap_attr = {0}, attr = {0};
	struct bgp_path_info_extra path_extra = {0};
	route_map_result_t ret;

	paf = peer_af_find(peer, afi, safi);
	if (!paf)
		return;

	subgrp = PAF_SUBGRP(paf);
	/* Ignore if subgroup doesn't exist (implies AF is not negotiated) */
	if (!subgrp)
		return;

	subgrp->pscount = 0;
	SET_FLAG(subgrp->sflags, SUBGRP_STATUS_TABLE_REPARSING);

	if (BGP_DEBUG(update, UPDATE_OUT))
		zlog_debug("%s: %s routes to/from %s for %s", __func__,
			   update_type == UPDATE_TYPE_ADVERTISE ? "Advertise"
								: "Withdraw",
			   peer->host, get_afi_safi_str(afi, safi, false));

	addpath_capable = bgp_addpath_encode_tx(peer, afi, safi);

	for (dest = bgp_table_top(table); dest; dest = bgp_route_next(dest)) {
		dest_p = bgp_dest_get_prefix(dest);
		assert(dest_p);

		for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = pi->next) {
			advmap_attr = *pi->attr;

			/* Fill temp path_info */
			prep_for_rmap_apply(&path, &path_extra, dest, pi,
					    pi->peer, &advmap_attr);

			RESET_FLAG(advmap_attr.rmap_change_flags);

			ret = route_map_apply(rmap, dest_p, &path);
			if (ret != RMAP_PERMITMATCH ||
			    !bgp_check_selected(pi, peer, addpath_capable, afi,
						safi)) {
				bgp_attr_flush(&advmap_attr);
				continue;
			}

			/* Skip route-map checks in
			 * subgroup_announce_check while executing from
			 * the conditional advertise scanner process.
			 * otherwise when route-map is also configured
			 * on same peer, routes in advertise-map may not
			 * be advertised as expected.
			 */
			if (update_type == UPDATE_TYPE_ADVERTISE &&
			    subgroup_announce_check(dest, pi, subgrp, dest_p,
						    &attr, &advmap_attr)) {
				bgp_adj_out_set_subgroup(dest, subgrp, &attr,
							 pi);
			} else {
				/* If default originate is enabled for
				 * the peer, do not send explicit
				 * withdraw. This will prevent deletion
				 * of default route advertised through
				 * default originate.
				 */
				if (CHECK_FLAG(peer->af_flags[afi][safi],
					       PEER_FLAG_DEFAULT_ORIGINATE) &&
				    is_default_prefix(dest_p))
					break;

				bgp_adj_out_unset_subgroup(
					dest, subgrp, 1,
					bgp_addpath_id_for_peer(
						peer, afi, safi,
						&pi->tx_addpath));
			}
			bgp_attr_flush(&advmap_attr);
		}
	}
	UNSET_FLAG(subgrp->sflags, SUBGRP_STATUS_TABLE_REPARSING);
}

/* Handler of conditional advertisement timer event.
 * Each route in the condition-map is evaluated.
 */
static void bgp_conditional_adv_timer(struct thread *t)
{
	afi_t afi;
	safi_t safi;
	int pfx_rcd_safi;
	struct bgp *bgp = NULL;
	struct peer *peer = NULL;
	struct peer_af *paf = NULL;
	struct bgp_table *table = NULL;
	struct bgp_filter *filter = NULL;
	struct listnode *node, *nnode = NULL;
	struct update_subgroup *subgrp = NULL;
	route_map_result_t ret;
	bool advmap_table_changed = false;

	bgp = THREAD_ARG(t);
	assert(bgp);

	thread_add_timer(bm->master, bgp_conditional_adv_timer, bgp,
			 bgp->condition_check_period, &bgp->t_condition_check);

	/* loop through each peer and check if we have peers with
	 * advmap_table_change attribute set, to make sure we send
	 * conditional advertisements properly below.
	 * peer->advmap_table_change is added on incoming BGP UPDATES,
	 * but here it's used for outgoing UPDATES, hence we need to
	 * check if at least one peer got advmap_table_change.
	 */
	for (ALL_LIST_ELEMENTS_RO(bgp->peer, node, peer)) {
		if (peer->advmap_table_change) {
			advmap_table_changed = true;
			break;
		}
	}

	/* loop through each peer and advertise or withdraw routes if
	 * advertise-map is configured and prefix(es) in condition-map
	 * does exist(exist-map)/not exist(non-exist-map) in BGP table
	 * based on condition(exist-map or non-exist map)
	 */
	for (ALL_LIST_ELEMENTS(bgp->peer, node, nnode, peer)) {
		if (!CHECK_FLAG(peer->flags, PEER_FLAG_CONFIG_NODE))
			continue;

		if (!peer_established(peer))
			continue;

		FOREACH_AFI_SAFI (afi, safi) {
			if (!peer->afc_nego[afi][safi])
				continue;

			/* labeled-unicast routes are installed in the unicast
			 * table so in order to display the correct PfxRcd value
			 * we must look at SAFI_UNICAST
			 */
			pfx_rcd_safi = (safi == SAFI_LABELED_UNICAST)
					       ? SAFI_UNICAST
					       : safi;

			table = bgp->rib[afi][pfx_rcd_safi];
			if (!table)
				continue;

			filter = &peer->filter[afi][safi];

			if (!filter->advmap.aname || !filter->advmap.cname
			    || !filter->advmap.amap || !filter->advmap.cmap)
				continue;

			if (!peer->advmap_config_change[afi][safi] &&
			    !advmap_table_changed)
				continue;

			if (BGP_DEBUG(update, UPDATE_OUT)) {
				if (peer->advmap_table_change)
					zlog_debug(
						"%s: %s - routes changed in BGP table.",
						__func__, peer->host);
				if (peer->advmap_config_change[afi][safi])
					zlog_debug(
						"%s: %s for %s - advertise/condition map configuration is changed.",
						__func__, peer->host,
						get_afi_safi_str(afi, safi,
								 false));
			}

			/* cmap (route-map attached to exist-map or
			 * non-exist-map) map validation
			 */
			ret = bgp_check_rmap_prefixes_in_bgp_table(
				table, filter->advmap.cmap);

			/* Derive conditional advertisement status from
			 * condition and return value of condition-map
			 * validation.
			 */
			if (filter->advmap.condition == CONDITION_EXIST)
				filter->advmap.update_type =
					(ret == RMAP_PERMITMATCH)
						? UPDATE_TYPE_ADVERTISE
						: UPDATE_TYPE_WITHDRAW;
			else
				filter->advmap.update_type =
					(ret == RMAP_PERMITMATCH)
						? UPDATE_TYPE_WITHDRAW
						: UPDATE_TYPE_ADVERTISE;

			/*
			 * Update condadv update type so
			 * subgroup_announce_check() can properly apply
			 * outbound policy according to advertisement state
			 */
			paf = peer_af_find(peer, afi, safi);
			if (paf && (SUBGRP_PEER(PAF_SUBGRP(paf))
					    ->filter[afi][safi]
					    .advmap.update_type !=
				    filter->advmap.update_type)) {
				/* Handle change to peer advmap */
				if (BGP_DEBUG(update, UPDATE_OUT))
					zlog_debug(
						"%s: advmap.update_type changed for peer %s, adjusting update_group.",
						__func__, peer->host);

				update_group_adjust_peer(paf);
			}

			/* Send regular update as per the existing policy.
			 * There is a change in route-map, match-rule, ACLs,
			 * or route-map filter configuration on the same peer.
			 */
			if (peer->advmap_config_change[afi][safi]) {

				if (BGP_DEBUG(update, UPDATE_OUT))
					zlog_debug(
						"%s: Configuration is changed on peer %s for %s, send the normal update first.",
						__func__, peer->host,
						get_afi_safi_str(afi, safi,
								 false));
				if (paf) {
					update_subgroup_split_peer(paf, NULL);
					subgrp = paf->subgroup;

					if (subgrp && subgrp->update_group)
						subgroup_announce_table(
							paf->subgroup, NULL);
				}
				peer->advmap_config_change[afi][safi] = false;
			}

			/* Send update as per the conditional advertisement */
			bgp_conditional_adv_routes(peer, afi, safi, table,
						   filter->advmap.amap,
						   filter->advmap.update_type);
		}
		peer->advmap_table_change = false;
	}
}

void bgp_conditional_adv_enable(struct peer *peer, afi_t afi, safi_t safi)
{
	struct bgp *bgp = peer->bgp;

	assert(bgp);

	/* This flag is used to monitor conditional routes status in BGP table,
	 * and advertise/withdraw routes only when there is a change in BGP
	 * table w.r.t conditional routes
	 */
	peer->advmap_config_change[afi][safi] = true;

	/* advertise-map is already configured on at least one of its
	 * neighbors (AFI/SAFI). So just increment the counter.
	 */
	if (++bgp->condition_filter_count > 1) {
		if (BGP_DEBUG(update, UPDATE_OUT))
			zlog_debug("%s: condition_filter_count %d", __func__,
				   bgp->condition_filter_count);

		return;
	}

	/* Register for conditional routes polling timer */
	if (!thread_is_scheduled(bgp->t_condition_check))
		thread_add_timer(bm->master, bgp_conditional_adv_timer, bgp, 0,
				 &bgp->t_condition_check);
}

void bgp_conditional_adv_disable(struct peer *peer, afi_t afi, safi_t safi)
{
	struct bgp *bgp = peer->bgp;

	assert(bgp);

	/* advertise-map is not configured on any of its neighbors or
	 * it is configured on more than one neighbor(AFI/SAFI).
	 * So there's nothing to do except decrementing the counter.
	 */
	if (--bgp->condition_filter_count != 0) {
		if (BGP_DEBUG(update, UPDATE_OUT))
			zlog_debug("%s: condition_filter_count %d", __func__,
				   bgp->condition_filter_count);

		return;
	}

	/* Last filter removed. So cancel conditional routes polling thread. */
	THREAD_OFF(bgp->t_condition_check);
}