zebra: support FIB override routes

FIB override routes are for routing protocols that establish
shortcut routes, or establish point-to-point routes that should
not be redistributed. Namely this is useful NHRP daemon to come.

Zebra is extended to select two entries from RIB the "best" entry
from routing protocols, and the FIB entry to install to kernel.
FIB override routes are never selected as best entry, and thus
are never adverticed to other routing daemons. The best FIB
override, or if it does not exist the otherwise best RIB is
selected as FIB entry to be installed.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>

1 files changed, 59 insertions, 23 deletions

diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
index 92640872..d06382c3 100644
--- a/zebra/zebra_rib.c
+++ b/zebra/zebra_rib.c
@@ -387,7 +387,7 @@ nexthop_active_ipv4 (struct rib *rib, struct nexthop *nexthop, int set,
 	{
 	  if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	    continue;
-	  if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+	  if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	    break;
 	}
 
@@ -521,7 +521,7 @@ nexthop_active_ipv6 (struct rib *rib, struct nexthop *nexthop, int set,
 	{
 	  if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	    continue;
-	  if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+	  if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	    break;
 	}
 
@@ -633,7 +633,7 @@ rib_match_ipv4_safi (struct in_addr addr, safi_t safi, int skip_bgp,
 	{
 	  if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	    continue;
-	  if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+	  if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	    break;
 	}
 
@@ -778,7 +778,7 @@ rib_lookup_ipv4 (struct prefix_ipv4 *p, vrf_id_t vrf_id)
     {
       if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	continue;
-      if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+      if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	break;
     }
 
@@ -838,7 +838,7 @@ rib_lookup_ipv4_route (struct prefix_ipv4 *p, union sockunion * qgate,
     {
       if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	continue;
-      if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+      if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	break;
     }
 
@@ -904,7 +904,7 @@ rib_match_ipv6 (struct in6_addr *addr, vrf_id_t vrf_id)
 	{
 	  if (CHECK_FLAG (match->status, RIB_ENTRY_REMOVED))
 	    continue;
-	  if (CHECK_FLAG (match->flags, ZEBRA_FLAG_SELECTED))
+	  if (CHECK_FLAG (match->status, RIB_ENTRY_SELECTED_FIB))
 	    break;
 	}
 
@@ -1139,7 +1139,7 @@ rib_uninstall (struct route_node *rn, struct rib *rib)
 {
   rib_table_info_t *info = rn->table->info;
 
-  if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED))
+  if (CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB))
     {
       if (info->safi == SAFI_UNICAST)
         zfpm_trigger_update (rn, "rib_uninstall");
@@ -1259,6 +1259,8 @@ rib_process (struct route_node *rn)
 {
   struct rib *rib;
   struct rib *next;
+  struct rib *old_selected = NULL;
+  struct rib *new_selected = NULL;
   struct rib *old_fib = NULL;
   struct rib *new_fib = NULL;
   int installed = 0;
@@ -1275,6 +1277,11 @@ rib_process (struct route_node *rn)
       /* Currently installed rib. */
       if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED))
         {
+          assert (old_selected == NULL);
+          old_selected = rib;
+        }
+      if (CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB))
+        {
           assert (old_fib == NULL);
           old_fib = rib;
         }
@@ -1291,17 +1298,31 @@ rib_process (struct route_node *rn)
       if (rib->distance == DISTANCE_INFINITY)
         continue;
 
-      new_fib = rib_choose_best(new_fib, rib);
+      if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_FIB_OVERRIDE))
+        new_fib = rib_choose_best(new_fib, rib);
+      else
+        new_selected = rib_choose_best(new_selected, rib);
     } /* RNODE_FOREACH_RIB_SAFE */
 
+  /* If no FIB override route, use the selected route also for FIB */
+  if (new_fib == NULL)
+    new_fib = new_selected;
+
   /* After the cycle is finished, the following pointers will be set:
-   * old_fib --- RIB entry currently having SELECTED
-   * new_fib --- RIB entry that is newly SELECTED
+   * old_selected --- RIB entry currently having SELECTED
+   * new_selected --- RIB entry that is newly SELECTED
+   * old_fib      --- RIB entry currently in kernel FIB
+   * new_fib      --- RIB entry that is newly to be in kernel FIB
+   *
+   * new_selected will get SELECTED flag, and is going to be redistributed
+   * the zclients. new_fib (which can be new_selected) will be installed in kernel.
    */
 
   /* Set real nexthops. */
   if (new_fib)
     nexthop_active_update (rn, new_fib, 1);
+  if (new_selected && new_selected != new_fib)
+     nexthop_active_update (rn, new_selected, 1);
 
   /* Update kernel if FIB entry has changed */
   if (old_fib != new_fib
@@ -1309,20 +1330,15 @@ rib_process (struct route_node *rn)
     {
         if (old_fib && old_fib != new_fib)
           {
-            if (! new_fib)
-              redistribute_delete (&rn->p, old_fib);
-
             if (! RIB_SYSTEM_ROUTE (old_fib) && (! new_fib || RIB_SYSTEM_ROUTE (new_fib)))
               rib_update_kernel (rn, old_fib, NULL);
-            UNSET_FLAG (old_fib->flags, ZEBRA_FLAG_SELECTED);
+            UNSET_FLAG (old_fib->status, RIB_ENTRY_SELECTED_FIB);
           }
 
         if (new_fib)
           {
             /* Install new or replace existing FIB entry */
-            SET_FLAG (new_fib->flags, ZEBRA_FLAG_SELECTED);
-            redistribute_add (&rn->p, new_fib);
-
+            SET_FLAG (new_fib->status, RIB_ENTRY_SELECTED_FIB);
             if (! RIB_SYSTEM_ROUTE (new_fib))
               rib_update_kernel (rn, old_fib, new_fib);
           }
@@ -1346,6 +1362,26 @@ rib_process (struct route_node *rn)
         rib_update_kernel (rn, NULL, new_fib);
     }
 
+  /* Redistribute SELECTED entry */
+  if (old_selected != new_selected
+      || (new_selected && CHECK_FLAG (new_selected->status, RIB_ENTRY_CHANGED)))
+    {
+      if (old_selected)
+        {
+          if (! new_selected)
+            redistribute_delete (&rn->p, old_selected);
+          if (old_selected != new_selected)
+            UNSET_FLAG (old_selected->flags, ZEBRA_FLAG_SELECTED);
+        }
+
+      if (new_selected)
+        {
+          /* Install new or replace existing redistributed entry */
+          SET_FLAG (new_selected->flags, ZEBRA_FLAG_SELECTED);
+          redistribute_add (&rn->p, new_selected);
+        }
+     }
+
   /* Remove all RIB entries queued for removal */
   RNODE_FOREACH_RIB_SAFE (rn, rib, next)
     {
@@ -1947,7 +1983,7 @@ void rib_lookup_and_pushup (struct prefix_ipv4 * p)
    */
   RNODE_FOREACH_RIB (rn, rib)
   {
-    if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED) &&
+    if (CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB) &&
       ! RIB_SYSTEM_ROUTE (rib))
     {
       changed = 1;
@@ -2098,7 +2134,7 @@ rib_delete_ipv4 (int type, int flags, struct prefix_ipv4 *p,
       if (CHECK_FLAG (rib->status, RIB_ENTRY_REMOVED))
         continue;
 
-      if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED))
+      if (CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB))
 	fib = rib;
 
       if (rib->type != type)
@@ -2146,7 +2182,7 @@ rib_delete_ipv4 (int type, int flags, struct prefix_ipv4 *p,
 	  for (nexthop = fib->nexthop; nexthop; nexthop = nexthop->next)
 	    UNSET_FLAG (nexthop->flags, NEXTHOP_FLAG_FIB);
 
-	  UNSET_FLAG (fib->flags, ZEBRA_FLAG_SELECTED);
+	  UNSET_FLAG (fib->status, RIB_ENTRY_SELECTED_FIB);
 	}
       else
 	{
@@ -2675,7 +2711,7 @@ rib_delete_ipv6 (int type, int flags, struct prefix_ipv6 *p,
       if (CHECK_FLAG(rib->status, RIB_ENTRY_REMOVED))
         continue;
 
-      if (CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED))
+      if (CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB))
 	fib = rib;
 
       if (rib->type != type)
@@ -2724,7 +2760,7 @@ rib_delete_ipv6 (int type, int flags, struct prefix_ipv6 *p,
 	  for (nexthop = fib->nexthop; nexthop; nexthop = nexthop->next)
 	    UNSET_FLAG (nexthop->flags, NEXTHOP_FLAG_FIB);
 
-	  UNSET_FLAG (fib->flags, ZEBRA_FLAG_SELECTED);
+	  UNSET_FLAG (fib->status, RIB_ENTRY_SELECTED_FIB);
 	}
       else
 	{
@@ -3058,7 +3094,7 @@ rib_close_table (struct route_table *table)
     for (rn = route_top (table); rn; rn = route_next (rn))
       RNODE_FOREACH_RIB (rn, rib)
         {
-          if (!CHECK_FLAG (rib->flags, ZEBRA_FLAG_SELECTED))
+          if (!CHECK_FLAG (rib->status, RIB_ENTRY_SELECTED_FIB))
 	    continue;
 
           if (info->safi == SAFI_UNICAST)