bgpd: Paths, received from shutdown peer, not deleted

Issue:
In a scaled setup, (where number of nets > BGP_CLEARING_BATCH_MAX_DESTS
for walk_batch_table_helper), when peer is shutdown, it is seen some
of the paths are not deleted, which are received from that peer.

Fix:
This is due to, in clear_batch_rib_helper, once walk_batch_table_helper
returns after BGP_CLEARING_BATCH_MAX_DESTS is reached, we just break
from inner loop for the afi/safi for loops. So during walk for next
afi/safi that 'ret' state is overwritten with new state. Also the
resume context is overwritten. This causes to lose the start point
for next walk, some nets are skipped forever. So they are not marked
for deletion anymore. To fix this, we immediately return from current
run. This will have resume state to be stored correctly, and next walk
will start from there.

Testing:
32 ecmp paths were received from the shutdown peer
Before fix:
show bgp ipv6 2052:52:1:167::/64
BGP routing table entry for 2052:52:1:167::/64, version 495
Paths: (246 available, best #127, table default)
  Not advertised to any peer

<snip>
  4200165500 4200165002
    2021:21:51:101::2(spine-5) from spine-5(2021:21:51:101::2) (6.0.0.17)
    (fe80::202:ff:fe00:55) (prefer-global)
      Origin incomplete, valid, external, multipath
      Last update: Fri Apr  4 17:25:05 2025
  4200165500 4200165002
    2021:21:11:116::2(spine-1) from spine-1(2021:21:11:116::2) (0.0.0.0)
    (fe80::202:ff:fe00:3d) (prefer-global)<<<<path not deleted
      Origin incomplete, valid, external
      Last update: Fri Apr  4 17:25:05 2025
  4200165500 4200165002
    2021:21:11:115::2(spine-1) from spine-1(2021:21:11:115::2) (0.0.0.0)
    (fe80::202:ff:fe00:3d) (prefer-global)<<<<path not deleted
      Origin incomplete, valid, external
      Last update: Fri Apr  4 17:25:05 2025
<snip>

 32 paths are supposed to be withdrawn:
root@leaf-1:mgmt:# vtysh -c "show bgp ipv6 2052:52:1:167::/64" | grep "prefer-global" | wc -l
256
root@leaf-1:mgmt# vtysh -c "show bgp ipv6 2052:52:1:167::/64" | grep "prefer-global" | wc -l
246<<should be 224, but showing 246, which is wrong
After fix:
 32 paths are supposed to be withdrawn:
root@leaf-1:mgmt:# vtysh -c "show bgp ipv6 2052:52:1:167::/64" | grep "prefer-global" | wc -l
256
root@leaf-1:mgmt:# vtysh -c "show bgp ipv6 2052:52:1:167::/64" | grep "prefer-global" | wc -l
224<<<shows correctly

Signed-off-by: Soumya Roy <souroy@nvidia.com>

diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index bb87406048b3ebf02456b64b60b6d5469e5e3227..993029a9196fb38068e411708a7de34df97c8015 100644 (file)
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -6825,6 +6825,16 @@ static int clear_batch_rib_helper(struct bgp_clearing_info *cinfo)
                         */
                        UNSET_FLAG(cinfo->flags, BGP_CLEARING_INFO_FLAG_RESUME);
                }
+
+               /* Return immediately, otherwise the 'ret' state will be overwritten
+                * by next afi/safi. Also resume state stored for current afi/safi
+                * in walk_batch_table_helper, will be overwritten. This may cause to
+                * skip the nets to be walked again, so they won't be marked for deletion
+                * from BGP table
+                */
+               if (ret != 0)
+                       return ret;
+
                safi = SAFI_UNICAST;
        }
        return ret;