fib: FIB Entry tracking

Instead of all clients directly RR sourcing the entry they are tracking,
use a deidcated 'tracker' object. This tracker object is a entry
delegate and a child of the entry. The clients are then children of the
tracker.
The benefit of this aproach is that each time a new client tracks the
entry it doesn't RR source it. When an entry is sourced all its children
are updated. Thus, new clients tracking an entry is O(n^2). With the
tracker as indirection, the entry is sourced only once.

Type: feature

Change-Id: I5b80bdda6c02057152e5f721e580e786cd840a3b
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/geneve/geneve.c b/src/vnet/geneve/geneve.c
index b0c17e2..dcbdb2f 100644
--- a/src/vnet/geneve/geneve.c
+++ b/src/vnet/geneve/geneve.c
@@ -16,6 +16,7 @@
 #include <vnet/ip/format.h>
 #include <vnet/fib/fib_entry.h>
 #include <vnet/fib/fib_table.h>
+#include <vnet/fib/fib_entry_track.h>
 #include <vnet/mfib/mfib_table.h>
 #include <vnet/adj/adj_mcast.h>
 #include <vnet/interface.h>
@@ -498,12 +499,11 @@
 	   * re-stack accordingly
 	   */
 	  vtep_addr_ref (&t->local);
-	  t->fib_entry_index = fib_table_entry_special_add
-	    (t->encap_fib_index, &tun_remote_pfx, FIB_SOURCE_RR,
-	     FIB_ENTRY_FLAG_NONE);
-	  t->sibling_index = fib_entry_child_add
-	    (t->fib_entry_index, FIB_NODE_TYPE_GENEVE_TUNNEL,
-	     t - vxm->tunnels);
+	  t->fib_entry_index = fib_entry_track (t->encap_fib_index,
+						&tun_remote_pfx,
+						FIB_NODE_TYPE_GENEVE_TUNNEL,
+						t - vxm->tunnels,
+						&t->sibling_index);
 	  geneve_tunnel_restack_dpo (t);
 	}
       else
@@ -605,8 +605,7 @@
       if (!ip46_address_is_multicast (&t->remote))
 	{
 	  vtep_addr_unref (&t->local);
-	  fib_entry_child_remove (t->fib_entry_index, t->sibling_index);
-	  fib_table_entry_delete_index (t->fib_entry_index, FIB_SOURCE_RR);
+	  fib_entry_untrack (t->fib_entry_index, t->sibling_index);
 	}
       else if (vtep_addr_unref (&t->remote) == 0)
 	{