zebra: Add a timer to nexthop group deletion

Before deleting nexthop groups, that are installed,
from the system, start a timer and hold the nexthop
group for that time.

Suppose you have this scenario

a) create a static route with 1 x ecmp
      creates a nhg with 1 x ecmp
b) create a static route with 2 x ecmp
      creates a nhg with 2 x ecmp
      deletes a's nhg
c) create a static route with 3 x ecmp
      creates a nhg with 3 x ecmp
      deletes b's nhg
d) create a different route with 1 x ecmp
      creates another 1 x ecmp ( since a's ecmp was deleted )
e) create a different route with 2 x ecmp
      creates another 2 x ecmp ( since b's ecmp was deleted )

If you don't delete the nhg, start a timer, the nhg's used
in steps a and b can be reused for steps d and e.  This reduces
overhead work with zebra <-> kernel interactions and improves
the speed of the system.

So modify the code to note that an installed nexthop group should
be kept around a bit and hopefully reused.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/zebra/zebra_vty.c b/zebra/zebra_vty.c
index be19b07d9..88752edb9 100644
--- a/zebra/zebra_vty.c
+++ b/zebra/zebra_vty.c
@@ -1433,14 +1433,22 @@ static void show_nexthop_group_out(struct vty *vty, struct nhg_hash_entry *nhe)
 	struct nhg_connected *rb_node_dep = NULL;
 	struct nexthop_group *backup_nhg;
 	char up_str[MONOTIME_STRLEN];
+	char time_left[MONOTIME_STRLEN];
 
 	uptime2str(nhe->uptime, up_str, sizeof(up_str));
 
 	vty_out(vty, "ID: %u (%s)\n", nhe->id, zebra_route_string(nhe->type));
-	vty_out(vty, "     RefCnt: %u\n", nhe->refcnt);
+	vty_out(vty, "     RefCnt: %u", nhe->refcnt);
+	if (thread_is_scheduled(nhe->timer))
+		vty_out(vty, " Time to Deletion: %s",
+			thread_timer_to_hhmmss(time_left, sizeof(time_left),
+					       nhe->timer));
+	vty_out(vty, "\n");
+
 	vty_out(vty, "     Uptime: %s\n", up_str);
 	vty_out(vty, "     VRF: %s\n", vrf_id_to_name(nhe->vrf_id));
 
+
 	if (CHECK_FLAG(nhe->flags, NEXTHOP_GROUP_VALID)) {
 		vty_out(vty, "     Valid");
 		if (CHECK_FLAG(nhe->flags, NEXTHOP_GROUP_INSTALLED))