zebra: remove useless deleted route_entries promptly

Zebra accumulates route-entry objects and then processes them
as a group. If that rib processing is delayed, because the
dataplane/fib programming has built up a queue e.g., zebra can
hold multiple deleted route objects in memory. At scale, this can
be a problem. Delete unneeded route entries promptly, if they
can't contribute to rib processing.

Signed-off-by: Mark Stapp <mjs@voltanet.io>

diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
index 88f6ec2634f238326d6373ca0217a95f85bf5fbf..eb6587f82fca2db7fb146907de50b6542d79ae32 100644 (file)
--- a/zebra/zebra_rib.c
+++ b/zebra/zebra_rib.c
@@ -2933,8 +2933,10 @@ int rib_add_multipath_nhe(afi_t afi, safi_t safi, struct prefix *p,
        struct nhg_hash_entry *nhe = NULL;
        struct route_table *table;
        struct route_node *rn;
-       struct route_entry *same = NULL;
+       struct route_entry *same = NULL, *first_same = NULL;
        int ret = 0;
+       int same_count = 0;
+       rib_dest_t *dest;
 
        if (!re || !re_nhe)
                return -1;
@@ -3002,14 +3004,22 @@ int rib_add_multipath_nhe(afi_t afi, safi_t safi, struct prefix *p,
         * for the install don't do a route replace.
         */
        RNODE_FOREACH_RE (rn, same) {
-               if (CHECK_FLAG(same->status, ROUTE_ENTRY_REMOVED))
+               if (CHECK_FLAG(same->status, ROUTE_ENTRY_REMOVED)) {
+                       same_count++;
                        continue;
+               }
 
                /* Compare various route_entry properties */
-               if (rib_compare_routes(re, same))
-                       break;
+               if (rib_compare_routes(re, same)) {
+                       same_count++;
+
+                       if (first_same == NULL)
+                               first_same = same;
+               }
        }
 
+       same = first_same;
+
        /* If this route is kernel/connected route, notify the dataplane. */
        if (RIB_SYSTEM_ROUTE(re)) {
                /* Notify dataplane */
@@ -3019,8 +3029,9 @@ int rib_add_multipath_nhe(afi_t afi, safi_t safi, struct prefix *p,
        /* Link new re to node.*/
        if (IS_ZEBRA_DEBUG_RIB) {
                rnode_debug(rn, re->vrf_id,
-                           "Inserting route rn %p, re %p (%s) existing %p",
-                           rn, re, zebra_route_string(re->type), same);
+                           "Inserting route rn %p, re %p (%s) existing %p, same_count %d",
+                           rn, re, zebra_route_string(re->type), same,
+                           same_count);
 
                if (IS_ZEBRA_DEBUG_RIB_DETAILED)
                        route_entry_dump(p, src_p, re);
@@ -3034,6 +3045,24 @@ int rib_add_multipath_nhe(afi_t afi, safi_t safi, struct prefix *p,
        if (same)
                rib_delnode(rn, same);
 
+       /* See if we can remove some RE entries that are queued for
+        * removal, but won't be considered in rib processing.
+        */
+       dest = rib_dest_from_rnode(rn);
+       RNODE_FOREACH_RE_SAFE (rn, re, same) {
+               if (CHECK_FLAG(re->status, ROUTE_ENTRY_REMOVED)) {
+                       /* If the route was used earlier, must retain it. */
+                       if (dest && re == dest->selected_fib)
+                               continue;
+
+                       if (IS_ZEBRA_DEBUG_RIB)
+                               rnode_debug(rn, re->vrf_id, "rn %p, removing unneeded re %p",
+                                           rn, re);
+
+                       rib_unlink(rn, re);
+               }
+       }
+
        route_unlock_node(rn);
        return ret;
 }