Merge pull request FRRouting#18819 from donaldsharp/path_info_fixup

Fix bestpath reason being incorrectly set in some cases

Author: ton31337

bgpd/bgp_route.c

@@ -3348,6 +3348,9 @@ void bgp_best_selection(struct bgp *bgp, struct bgp_dest *dest,
 	}
 
 	if (do_mpath && new_select) {
+		bool first_reason = true;
+		enum bgp_path_selection_reason ignore;
+
 		for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = pi->next) {
 			if (debug)
 				bgp_path_info_path_with_addpath_rx_str(
@@ -3373,10 +3376,10 @@ void bgp_best_selection(struct bgp *bgp, struct bgp_dest *dest,
 				if (!peer_established(pi->peer->connection))
 					continue;
 
-			bgp_path_info_cmp(bgp, pi, new_select, &paths_eq,
-					  mpath_cfg, debug, pfx_buf, afi, safi,
-					  &dest->reason);
+			bgp_path_info_cmp(bgp, pi, new_select, &paths_eq, mpath_cfg, debug, pfx_buf,
+					  afi, safi, first_reason ? &dest->reason : &ignore);
 
+			first_reason = false;
 			if (paths_eq) {
 				if (debug)
 					zlog_debug(

tests/topotests/bgp_bestpath_reason/r1/frr.conf

@@ -0,0 +1,22 @@
+!
+hostname r1
+!
+debug bgp bestpath 192.168.199.0/24
+!
+interface r1-eth0
+ ip address 192.16.2.1/24
+!
+interface r1-eth1
+ ip address 192.16.3.1/24
+!
+interface r1-eth2
+ ip address 192.16.4.1/24
+!
+router bgp 65001
+ timers bgp 1 10
+ bgp router-id 1.1.1.1
+ no bgp ebgp-requires-policy
+ neighbor 192.16.2.2 remote-as 65024
+ neighbor 192.16.3.3 remote-as 65003
+ neighbor 192.16.4.4 remote-as 65024
+!

tests/topotests/bgp_bestpath_reason/r2/frr.conf

@@ -0,0 +1,23 @@
+!
+hostname r2
+!
+interface r2-eth0
+    ip address 192.16.2.2/24
+!
+interface r2-eth1
+    ip address 192.168.199.2/24
+!
+router bgp 65024
+ timers bgp 1 10
+ bgp router-id 1.1.1.2
+ no bgp ebgp-requires-policy
+ neighbor 192.16.2.1 remote-as 65001
+ !
+ address-family ipv4 unicast
+  network 192.168.199.0/24
+  neighbor 192.16.2.1 route-map set-med out
+ exit-address-family
+!
+route-map set-med permit 10
+ set metric 200
+!

tests/topotests/bgp_bestpath_reason/r3/frr.conf

@@ -0,0 +1,24 @@
+!
+hostname r3
+!
+interface r3-eth0
+ ip address 192.16.3.3/24
+!
+interface r3-eth1
+ ip address 192.168.199.3/24
+!
+router bgp 65003
+ timers bgp 1 10
+ bgp router-id 1.1.1.3
+ no bgp ebgp-requires-policy
+ neighbor 192.16.3.1 remote-as 65001
+ !
+ address-family ipv4 unicast
+  network 192.168.199.0/24
+  no neighbor 192.16.3.1 activate
+  neighbor 192.16.3.1 route-map set-med out
+ exit-address-family
+!
+route-map set-med permit 10
+ set metric 150
+!

tests/topotests/bgp_bestpath_reason/r4/frr.conf

@@ -0,0 +1,24 @@
+!
+hostname r4
+!
+interface r4-eth0
+ ip address 192.16.4.4/24
+!
+interface r4-eth1
+ ip address 192.168.199.4/24
+!
+router bgp 65024
+ timers bgp 1 10
+ bgp router-id 1.1.1.4
+ no bgp ebgp-requires-policy
+ neighbor 192.16.4.1 remote-as 65001
+ !
+ address-family ipv4 unicast
+  network 192.168.199.0/24
+  no neighbor 192.16.4.1 activate
+  neighbor 192.16.4.1 route-map set-med out
+ exit-address-family
+!
+route-map set-med permit 10
+ set metric 100
+!