bgpd: allow bestpath to handle mutliple locally-originated paths

Current code in bgp bestpath selection would accept the newest
locally originated path as the best path.  Making the selection
non-deterministic.  Modify the code to always come to the
same bestpath conclusion when you have multiple locally originated
paths in bestpath selection.

Before:

eva# conf
eva(config)# router bgp 323
eva(config-router)# address-family ipv4 uni
eva(config-router-af)# redistribute connected
eva(config-router-af)# network 192.168.161.0/24
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (2 available, best #1, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (Origin)
      Last update: Wed Sep 16 15:03:03 2020
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin incomplete, metric 0, weight 32768, valid, sourced
      Last update: Wed Sep 16 15:02:52 2020
eva(config-router-af)# no redistribute connected
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (First path received)
      Last update: Wed Sep 16 15:03:03 2020
eva(config-router-af)#  redistribute connected
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (2 available, best #2, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin incomplete, metric 0, weight 32768, valid, sourced
      Last update: Wed Sep 16 15:03:32 2020
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (Origin)
      Last update: Wed Sep 16 15:03:03 2020
eva(config-router-af)#

Notice the route choosen depends on order received

Fixed behavior:

eva# conf
eva(config)# router bgp 323
eva(config-router)# address-family ipv4 uni
eva(config-router-af)# redistribute connected
eva(config-router-af)# network 192.168.161.0/24
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (2 available, best #1, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (Origin)
      Last update: Wed Sep 16 15:03:03 2020
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin incomplete, metric 0, weight 32768, valid, sourced
      Last update: Wed Sep 16 15:02:52 2020
eva(config-router-af)# no redistribute connected
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (First path received)
      Last update: Wed Sep 16 15:03:03 2020
eva(config-router-af)#  redistribute connected
eva(config-router-af)# do show bgp ipv4 uni 192.168.161.0
BGP routing table entry for 192.168.161.0/24
Paths: (2 available, best #2, table default)
  Not advertised to any peer
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin incomplete, metric 0, weight 32768, valid, sourced
      Last update: Wed Sep 16 15:03:32 2020
  Local
    0.0.0.0(eva) from 0.0.0.0 (192.168.161.245)
      Origin IGP, metric 0, weight 32768, valid, sourced, local, bestpath-from-AS Local, best (Origin)
      Last update: Wed Sep 16 15:03:03 2020
eva(config-router-af)#

Ticket: CM-31490
Found-by: Trey Aspelund <taspelund@nvidia.com>
Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index 43ba4ceef619ebb278847ab91a753aab780c9ffb..84fc1d9c84bedf0fcf4e6e40caa87d9779886225 100644 (file)
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -550,6 +550,7 @@ static int bgp_path_info_cmp(struct bgp *bgp, struct bgp_path_info *new,
        bool same_esi;
        bool old_proxy;
        bool new_proxy;
+       bool new_origin, exist_origin;
 
        *paths_eq = 0;
 
@@ -794,8 +795,12 @@ static int bgp_path_info_cmp(struct bgp *bgp, struct bgp_path_info *new,
         *  - BGP_ROUTE_AGGREGATE
         *  - BGP_ROUTE_REDISTRIBUTE
         */
-       if (!(new->sub_type == BGP_ROUTE_NORMAL ||
-             new->sub_type == BGP_ROUTE_IMPORTED)) {
+       new_origin = !(new->sub_type == BGP_ROUTE_NORMAL ||
+                      new->sub_type == BGP_ROUTE_IMPORTED);
+       exist_origin = !(exist->sub_type == BGP_ROUTE_NORMAL ||
+                        exist->sub_type == BGP_ROUTE_IMPORTED);
+
+       if (new_origin && !exist_origin) {
                *reason = bgp_path_selection_local_route;
                if (debug)
                        zlog_debug(
@@ -804,8 +809,7 @@ static int bgp_path_info_cmp(struct bgp *bgp, struct bgp_path_info *new,
                return 1;
        }
 
-       if (!(exist->sub_type == BGP_ROUTE_NORMAL ||
-             exist->sub_type == BGP_ROUTE_IMPORTED)) {
+       if (!new_origin && exist_origin) {
                *reason = bgp_path_selection_local_route;
                if (debug)
                        zlog_debug(