zebra: add more logs/asserts to rib work queue code

  * zebra/zebra_rib.c: (rib_queue_add, rib_queue_init) Add some more
    logs and asserts.

From: Subbaiah Venkata <svenkata@google.com>
Signed-off-by: Avneesh Sachdev <avneesh@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@diac24.net>
diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
index 580b75b..0035eb6 100644
--- a/zebra/zebra_rib.c
+++ b/zebra/zebra_rib.c
@@ -1271,14 +1271,30 @@
 static void
 rib_queue_add (struct zebra_t *zebra, struct route_node *rn)
 {
+  char buf[INET_ADDRSTRLEN];
+  assert (zebra && rn);
   
   if (IS_ZEBRA_DEBUG_RIB_Q)
-    {
-      char buf[INET6_ADDRSTRLEN];
+    inet_ntop (AF_INET, &rn->p.u.prefix, buf, INET_ADDRSTRLEN);
 
-      zlog_info ("%s: %s/%d: work queue added", __func__,
-		 inet_ntop (rn->p.family, &rn->p.u.prefix, buf, INET6_ADDRSTRLEN),
-		 rn->p.prefixlen);
+  /* Pointless to queue a route_node with no RIB entries to add or remove */
+  if (!rn->info)
+    {
+      zlog_debug ("%s: called for route_node (%p, %d) with no ribs",
+                  __func__, rn, rn->lock);
+      zlog_backtrace(LOG_DEBUG);
+      return;
+    }
+
+  if (IS_ZEBRA_DEBUG_RIB_Q)
+    zlog_info ("%s: %s/%d: work queue added", __func__, buf, rn->p.prefixlen);
+
+  assert (zebra);
+
+  if (zebra->ribq == NULL)
+    {
+      zlog_err ("%s: work_queue does not exist!", __func__);
+      return;
     }
 
   /*
@@ -1293,6 +1309,11 @@
     work_queue_add (zebra->ribq, zebra->mq);
 
   rib_meta_queue_add (zebra->mq, rn);
+
+  if (IS_ZEBRA_DEBUG_RIB_Q)
+    zlog_debug ("%s: %s/%d: rn %p queued", __func__, buf, rn->p.prefixlen, rn);
+
+  return;
 }
 
 /* Create new meta queue.
@@ -1320,6 +1341,8 @@
 static void
 rib_queue_init (struct zebra_t *zebra)
 {
+  assert (zebra);
+  
   if (! (zebra->ribq = work_queue_new (zebra->master, 
                                        "route_node processing")))
     {
@@ -1335,7 +1358,11 @@
   zebra->ribq->spec.hold = rib_process_hold_time;
   
   if (!(zebra->mq = meta_queue_new ()))
+  {
     zlog_err ("%s: could not initialise meta queue!", __func__);
+    return;
+  }
+  return;
 }
 
 /* RIB updates are processed via a queue of pointers to route_nodes.