bgpd: conditional advertisement

Implemented as per the feature description given in the source link.

Descriprion:
The BGP conditional advertisement feature uses the non-exist-map or exist-map
and the advertise-map keywords of the neighbor advertise-map command in order
to track routes by the route prefix.

non-exist-map :
If a route prefix is not present in output of the non-exist-map command, then
the route specified by the advertise-map command is announced.

exist-map :
If a route prefix is present in output of the exist-map command, then the route
specified by the advertise-map command is announced.

The conditional BGP announcements are sent in addition to the normal
announcements that a BGP router sends to its peers.

The conditional advertisement process is triggered by the BGP scanner process,
which runs every 60 seconds. This means that the maximum time for the conditional
advertisement to take effect is 60 seconds. The conditional advertisement can take
effect sooner, depending on when the tracked route is removed from the BGP table
and when the next instance of the BGP scanner occurs.

Sample Configuration on DUT
---------------------------
Router2# show running-config
Building configuration...

Current configuration:
!
frr version 7.6-dev-MyOwnFRRVersion
frr defaults traditional
hostname router
log file /var/log/frr/bgpd.log
log syslog informational
hostname Router2
service integrated-vtysh-config
!
debug bgp updates in
debug bgp updates out
!
debug route-map
!
ip route 200.200.0.0/16 blackhole
ipv6 route 2001:db8::200/128 blackhole
!
interface enp0s9
 ip address 10.10.10.2/24
!
interface enp0s10
 ip address 10.10.20.2/24
!
interface lo
 ip address 2.2.2.2/24
 ipv6 address 2001:db8::2/128
!
router bgp 2
 bgp log-neighbor-changes
 no bgp ebgp-requires-policy
 neighbor 10.10.10.1 remote-as 1
 neighbor 10.10.20.3 remote-as 3
 !
 address-family ipv4 unicast
  network 2.2.2.0/24
  network 200.200.0.0/16
  neighbor 10.10.10.1 soft-reconfiguration inbound
  neighbor 10.10.10.1 advertise-map ADVERTISE non-exist-map CONDITION
  neighbor 10.10.20.3 soft-reconfiguration inbound
 exit-address-family
 !
 address-family ipv6 unicast
  network 2001:db8::2/128
  network 2001:db8::200/128
  neighbor 10.10.10.1 activate
  neighbor 10.10.10.1 soft-reconfiguration inbound
  neighbor 10.10.10.1 advertise-map ADVERTISE_6 non-exist-map CONDITION_6
  neighbor 10.10.20.3 activate
  neighbor 10.10.20.3 soft-reconfiguration inbound
 exit-address-family
!
access-list CONDITION seq 5 permit 3.3.3.0/24
access-list ADVERTISE seq 5 permit 2.2.2.0/24
access-list ADVERTISE seq 6 permit 200.200.0.0/16
access-list ADVERTISE seq 7 permit 20.20.0.0/16
!
ipv6 access-list ADVERTISE_6 seq 5 permit 2001:db8::2/128
ipv6 access-list CONDITION_6 seq 5 permit 2001:db8::3/128
!
route-map ADVERTISE permit 10
 match ip address ADVERTISE
!
route-map CONDITION permit 10
 match ip address CONDITION
!
route-map ADVERTISE_6 permit 10
 match ipv6 address ADVERTISE_6
!
route-map CONDITION_6 permit 10
 match ipv6 address CONDITION_6
!
line vty
!
end
Router2#

Withdraw when non-exist-map prefixes present in BGP table:
----------------------------------------------------------
Router2# show ip bgp all wide

For address family: IPv4 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 1.1.1.0/24                                   10.10.10.1                                     0             0 1 i
*> 2.2.2.0/24                                   0.0.0.0                                        0         32768 i
*> 3.3.3.0/24                                   10.10.20.3                                     0             0 3 i
*> 200.200.0.0/16                               0.0.0.0                                        0         32768 i

Displayed  4 routes and 4 total paths

For address family: IPv6 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 2001:db8::1/128                              fe80::a00:27ff:fecb:ad57                       0             0 1 i
*> 2001:db8::2/128                              ::                                             0         32768 i
*> 2001:db8::3/128                              fe80::a00:27ff:fe76:6738                       0             0 3 i
*> 2001:db8::200/128                            ::                                             0         32768 i

Displayed  4 routes and 4 total paths
Router2#

Router2# show ip bgp neighbors 10.10.10.1
BGP neighbor is 10.10.10.1, remote AS 1, local AS 2, external link

!--- Output suppressed.

 For address family: IPv4 Unicast
  Update group 9, subgroup 5
  Packet Queue length 0
  Inbound soft reconfiguration allowed
  Community attribute sent to this neighbor(all)
  Condition NON_EXIST, Condition-map *CONDITION, Advertise-map *ADVERTISE, status: Withdraw
  1 accepted prefixes

 For address family: IPv6 Unicast
  Update group 10, subgroup 6
  Packet Queue length 0
  Inbound soft reconfiguration allowed
  Community attribute sent to this neighbor(all)
  Condition NON_EXIST, Condition-map *CONDITION_6, Advertise-map *ADVERTISE_6, status: Withdraw
  1 accepted prefixes

!--- Output suppressed.

Router2#

Here 2.2.2.0/24 & 200.200.0.0/16 (prefixes in advertise-map) are withdrawn
by conditional advertisement scanner as the prefix(3.3.3.0/24) specified
by non-exist-map is present in BGP table.

Router2# show ip bgp all neighbors 10.10.10.1 advertised-routes wide

For address family: IPv4 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 1.1.1.0/24                                   0.0.0.0                                                      0 1 i
*> 3.3.3.0/24                                   0.0.0.0                                                      0 3 i

Total number of prefixes 2

For address family: IPv6 Unicast
BGP table version is 8, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 2001:db8::1/128                              ::                                                           0 1 i
*> 2001:db8::3/128                              ::                                                           0 3 i
*> 2001:db8::200/128                            ::                                             0         32768 i

Total number of prefixes 3
Router2#

Advertise when non-exist-map prefixes not present in BGP table:
---------------------------------------------------------------
After Removing 3.3.3.0/24 (prefix present in non-exist-map),
2.2.2.0/24 & 200.200.0.0/16 (prefixes present in advertise-map) are advertised

Router2# show ip bgp all wide

For address family: IPv4 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 1.1.1.0/24                                   10.10.10.1                                     0             0 1 i
*> 2.2.2.0/24                                   0.0.0.0                                        0         32768 i
*> 200.200.0.0/16                               0.0.0.0                                        0         32768 i

Displayed  3 routes and 3 total paths

For address family: IPv6 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 2001:db8::1/128                              fe80::a00:27ff:fecb:ad57                       0             0 1 i
*> 2001:db8::2/128                              ::                                             0         32768 i
*> 2001:db8::200/128                            ::                                             0         32768 i

Displayed  3 routes and 3 total paths
Router2#

Router2# show ip bgp neighbors 10.10.10.1

!--- Output suppressed.

 For address family: IPv4 Unicast
  Update group 9, subgroup 5
  Packet Queue length 0
  Inbound soft reconfiguration allowed
  Community attribute sent to this neighbor(all)
  Condition NON_EXIST, Condition-map *CONDITION, Advertise-map *ADVERTISE, status: Advertise
  1 accepted prefixes

 For address family: IPv6 Unicast
  Update group 10, subgroup 6
  Packet Queue length 0
  Inbound soft reconfiguration allowed
  Community attribute sent to this neighbor(all)
  Condition NON_EXIST, Condition-map *CONDITION_6, Advertise-map *ADVERTISE_6, status: Advertise
  1 accepted prefixes

!--- Output suppressed.

Router2#
Router2# show ip bgp all neighbors 10.10.10.1 advertised-routes wide

For address family: IPv4 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 1.1.1.0/24                                   0.0.0.0                                                      0 1 i
*> 2.2.2.0/24                                   0.0.0.0                                        0         32768 i
*> 200.200.0.0/16                               0.0.0.0                                        0         32768 i

Total number of prefixes 3

For address family: IPv6 Unicast
BGP table version is 9, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 2
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network                                      Next Hop                                  Metric LocPrf Weight Path
*> 2001:db8::1/128                              ::                                                           0 1 i
*> 2001:db8::2/128                              ::                                             0         32768 i
*> 2001:db8::200/128                            ::                                             0         32768 i

Total number of prefixes 3
Router2#

Signed-off-by: Madhuri Kuruganti <k.madhuri@samsung.com>

1 files changed, 142 insertions, 0 deletions

diff --git a/bgpd/bgp_conditional_adv.h b/bgpd/bgp_conditional_adv.h
new file mode 100644
index 0000000000..cd857958a2
--- /dev/null
+++ b/bgpd/bgp_conditional_adv.h
@@ -0,0 +1,142 @@
+/*
+ * BGP Conditional advertisement
+ * Copyright (C) 2020  Samsung Research Institute 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
+ */
+
+#ifndef _FRR_BGP_CONDITION_ADV_H
+#define _FRR_BGP_CONDITION_ADV_H
+#include <zebra.h>
+#include "prefix.h"
+#include "bgpd/bgp_addpath.h"
+#include "bgpd/bgp_attr.h"
+#include "bgpd/bgpd.h"
+#include "bgpd/bgp_debug.h"
+#include "bgpd/bgp_route.h"
+#include "bgpd/bgp_updgrp.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Polling time for monitoring condition-map routes in route table */
+#define CONDITIONAL_ROUTES_POLL_TIME 60
+
+#define FOREACH_ACCESS_LIST_FILTER(alist, filter)                              \
+	for (filter = alist->head; filter; filter = filter->next)
+
+static inline bool is_rmap_valid(struct route_map *rmap)
+{
+	if (!rmap || !rmap->head)
+		return false;
+
+	/* Doesn't make sense to configure advertise
+	 * or condition map in deny/any clause.
+	 */
+	if (rmap->head->type != RMAP_PERMIT)
+		return false;
+
+	/* If a match command is not present, all routes match the clause */
+	if (!rmap->head->match_list.head)
+		return false;
+
+	return true;
+}
+
+static inline afi_t get_afi_from_match_rule(const char *str)
+{
+	if (!strcmp(str, "ip address"))
+		return AFI_IP;
+	else if (!strcmp(str, "ipv6 address"))
+		return AFI_IP6;
+	else
+		return AFI_MAX;
+}
+
+static inline bool advertise_dest_routes(struct update_subgroup *subgrp,
+					 struct bgp_dest *dest,
+					 struct peer *peer, afi_t afi,
+					 safi_t safi, int addpath_capable,
+					 bool advertise)
+{
+	struct attr attr;
+	struct bgp_path_info *pi = NULL;
+	const struct prefix *dest_p = NULL;
+	bool route_advertised = false;
+
+	dest_p = (struct prefix *)bgp_dest_get_prefix(dest);
+	if (!dest_p)
+		return route_advertised;
+
+	for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = pi->next) {
+		if (CHECK_FLAG(pi->flags, BGP_PATH_SELECTED)
+		    || (addpath_capable
+			&& bgp_addpath_tx_path(peer->addpath_type[afi][safi],
+					       pi))) {
+
+			/* 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 (advertise
+			    && subgroup_announce_check(dest, pi, subgrp, dest_p,
+						       &attr, true)) {
+				bgp_adj_out_set_subgroup(dest, subgrp, &attr,
+							 pi);
+				route_advertised = true;
+			} 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));
+				route_advertised = true;
+			}
+		}
+	}
+	return route_advertised;
+}
+
+struct bgp_dest *bgp_dest_matches_filter_prefix(struct bgp_table *table,
+						struct filter *filter);
+extern enum route_map_cmd_result_t
+bgp_check_rmap_prefixes_in_bgp_table(struct bgp_table *table,
+				     struct route_map *rmap);
+extern void bgp_conditional_adv_enable(struct peer *peer, afi_t afi,
+				       safi_t safi);
+extern void bgp_conditional_adv_disable(struct peer *peer, afi_t afi,
+					safi_t safi);
+extern bool bgp_conditional_adv_routes(struct peer *peer, afi_t afi,
+				       safi_t safi, struct bgp_table *table,
+				       struct route_map *rmap, bool advertise);
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _FRR_BGP_CONDITION_ADV_H */