FIB2.0: memory leaks during load-balance update (VPP-475)

some other fixes and enhancemets to address failures in the IPv6 Scale testing:
 - The rate at which VPP sends ARP/ND requests, 1 per-millisecond, is too high. This is reduced to 1 every 10 ms. probably still too high.
 - If an ARP/ND response is received that does not contain a change to the known MAC address, no further processing is done.
 - Added stats to get info about the async FIB walks.
 - When walking FIB entries and performing a load-balance update, it is not necessary to re-insert the LB in the forwarding table.

Change-Id: Ifd47e4bdbce94495f44aaf1b78e7d1395ed870d1
Signed-off-by: Neale Ranns <nranns@cisco.com>

12 files changed, 658 insertions, 333 deletions

diff --git a/vnet/vnet/dpo/load_balance.c b/vnet/vnet/dpo/load_balance.c
index fc788508bdb..6badb0e7c38 100644
--- a/vnet/vnet/dpo/load_balance.c
+++ b/vnet/vnet/dpo/load_balance.c
@@ -650,6 +650,7 @@ load_balance_multipath_update (const dpo_id_t *dpo,
     {
         dpo_reset(&nh->path_dpo);
     }
+    vec_free(nhs);
 
     load_balance_map_unlock(old_lbmi);
 }
diff --git a/vnet/vnet/ethernet/arp.c b/vnet/vnet/ethernet/arp.c
index 45d0dc8e48a..645ff86c274 100644
--- a/vnet/vnet/ethernet/arp.c
+++ b/vnet/vnet/ethernet/arp.c
@@ -459,6 +459,16 @@ vnet_arp_set_ip4_over_ethernet_internal (vnet_main_t * vnm,
 	e->adj_index[link] = ADJ_INDEX_INVALID;
       }
     }
+  else
+    {
+      /*
+       * prevent a DoS attack from the data-plane that
+       * spams us with no-op updates to the MAC address
+       */
+      if (0 == memcmp (e->ethernet_address,
+		       a->ethernet, sizeof (e->ethernet_address)))
+	return -1;
+    }
 
   /* Update time stamp and ethernet address. */
   clib_memcpy (e->ethernet_address, a->ethernet,
diff --git a/vnet/vnet/fib/fib_entry.c b/vnet/vnet/fib/fib_entry.c
index 06922004021..5429da2983d 100644
--- a/vnet/vnet/fib/fib_entry.c
+++ b/vnet/vnet/fib/fib_entry.c
@@ -211,7 +211,7 @@ format_fib_entry (u8 * s, va_list * args)
         if (level >= FIB_ENTRY_FORMAT_DETAIL2)
         {
 
-            FOR_EACH_FIB_FORW_CHAIN(fct)
+            FOR_EACH_FIB_FORW_MPLS_CHAIN(fct)
             {
                 s = format(s, "  %U-chain\n  %U",
                            format_fib_forw_chain_type, fct,
@@ -320,7 +320,7 @@ fib_entry_last_lock_gone (fib_node_t *node)
 
     fib_entry = fib_entry_from_fib_node(node);
 
-    FOR_EACH_FIB_FORW_CHAIN(fct)
+    FOR_EACH_FIB_FORW_MPLS_CHAIN(fct)
     {
 	dpo_reset(&fib_entry->fe_lb[fct]);
     }
@@ -605,7 +605,7 @@ fib_entry_alloc (u32 fib_index,
     fib_entry->fe_export = FIB_NODE_INDEX_INVALID;
     fib_entry->fe_import = FIB_NODE_INDEX_INVALID;
     fib_entry->fe_covered = FIB_NODE_INDEX_INVALID;
-    FOR_EACH_FIB_FORW_CHAIN(fct)
+    FOR_EACH_FIB_FORW_MPLS_CHAIN(fct)
     {
 	dpo_reset(&fib_entry->fe_lb[fct]);
     }
@@ -1309,7 +1309,7 @@ fib_entry_recursive_loop_detect (fib_node_index_t entry_index,
 	     * re-evaluate all the entry's forwarding
 	     * NOTE: this is an inplace modify
 	     */
-	    FOR_EACH_FIB_FORW_CHAIN(fct)
+	    FOR_EACH_FIB_FORW_MPLS_CHAIN(fct)
 	    {
 		if (dpo_id_is_valid(&fib_entry->fe_lb[fct]))
 		{
diff --git a/vnet/vnet/fib/fib_entry_src.c b/vnet/vnet/fib/fib_entry_src.c
index 6107e3e19cd..6ee966bd85f 100644
--- a/vnet/vnet/fib/fib_entry_src.c
+++ b/vnet/vnet/fib/fib_entry_src.c
@@ -369,6 +369,7 @@ fib_entry_src_mk_lb (fib_entry_t *fib_entry,
     load_balance_multipath_update(dpo_lb,
                                   ctx.next_hops,
                                   fib_entry_calc_lb_flags(&ctx));
+    vec_free(ctx.next_hops);
 
     /*
      * if this entry is sourced by the uRPF-exempt source then we
@@ -408,21 +409,33 @@ fib_entry_src_action_install (fib_entry_t *fib_entry,
      */
     fib_forward_chain_type_t fct;
     fib_entry_src_t *esrc;
+    int insert;
 
     fct = fib_entry_get_default_chain_type(fib_entry);
     esrc = fib_entry_src_find(fib_entry, source, NULL);
 
+    /*
+     * Every entry has its own load-balance object. All changes to the entry's
+     * forwarding result in an inplace modify of the load-balance. This means
+     * the load-balance object only needs to be added to the forwarding
+     * DB once, when it is created.
+     */
+    insert = !dpo_id_is_valid(&fib_entry->fe_lb[fct]);
+
     fib_entry_src_mk_lb(fib_entry, esrc, fct, &fib_entry->fe_lb[fct]);
 
-    FIB_ENTRY_DBG(fib_entry, "install: %d",
-		  fib_entry->fe_lb[fct]);
+    ASSERT(dpo_id_is_valid(&fib_entry->fe_lb[fct]));
+    FIB_ENTRY_DBG(fib_entry, "install: %d", fib_entry->fe_lb[fct]);
 
     /*
      * insert the adj into the data-plane forwarding trie
      */
-    fib_table_fwding_dpo_update(fib_entry->fe_fib_index,
-				&fib_entry->fe_prefix,
-				&fib_entry->fe_lb[fct]);
+    if (insert)
+    {
+       fib_table_fwding_dpo_update(fib_entry->fe_fib_index,
+                                   &fib_entry->fe_prefix,
+                                   &fib_entry->fe_lb[fct]);
+    }
 
     if (FIB_FORW_CHAIN_TYPE_UNICAST_IP4 == fct ||
 	FIB_FORW_CHAIN_TYPE_UNICAST_IP6 == fct)
diff --git a/vnet/vnet/fib/fib_entry_src_mpls.c b/vnet/vnet/fib/fib_entry_src_mpls.c
index 5145c10977f..79c745acf48 100644
--- a/vnet/vnet/fib/fib_entry_src_mpls.c
+++ b/vnet/vnet/fib/fib_entry_src_mpls.c
@@ -67,30 +67,6 @@ fib_entry_src_mpls_add (fib_entry_src_t *src,
 }
 
 static void
-fib_entry_src_mpls_fwd_update (fib_entry_src_t *src,
-			       const fib_entry_t *fib_entry,
-			       fib_source_t best_source)
-{
-    dpo_id_t dpo = DPO_NULL;
-    mpls_eos_bit_t eos;
-
-    FOR_EACH_MPLS_EOS_BIT(eos)
-    {
-	fib_entry_contribute_forwarding(fib_entry_get_index(fib_entry),
-					(eos ?
-					 FIB_FORW_CHAIN_TYPE_MPLS_EOS :
-					 FIB_FORW_CHAIN_TYPE_MPLS_NON_EOS),
-					&dpo);
-
-	fib_table_entry_special_dpo_update(src->mpls.fesm_lfes[eos],
-					   FIB_SOURCE_SPECIAL,
-					   FIB_ENTRY_FLAG_EXCLUSIVE,
-					   &dpo);
-    }
-    dpo_reset(&dpo);
-}
-
-static void
 fib_entry_src_mpls_set_data (fib_entry_src_t *src,
                              const fib_entry_t *entry,
                              const void *data)
@@ -187,9 +163,15 @@ const static fib_entry_src_vft_t mpls_src_vft = {
     .fesv_add = fib_entry_src_mpls_add,
     .fesv_remove = fib_entry_src_mpls_remove,
     .fesv_format = fib_entry_src_mpls_format,
-    .fesv_fwd_update = fib_entry_src_mpls_fwd_update,
     .fesv_set_data = fib_entry_src_mpls_set_data,
     .fesv_get_data = fib_entry_src_mpls_get_data,
+    /*
+     * .fesv_fwd_update = fib_entry_src_mpls_fwd_update,
+     *  When the forwarding for the IP entry is updated, any MPLS chains
+     * it has created are also updated. Since the MPLS entry will have already
+     * installed that chain/load-balance there is no need to update the netry
+     * FIXME: later: propagate any walk to the children of the MPLS entry. for SR
+     */
 };
 
 void
diff --git a/vnet/vnet/fib/fib_path.c b/vnet/vnet/fib/fib_path.c
index 1b82f46482e..bea17218547 100644
--- a/vnet/vnet/fib/fib_path.c
+++ b/vnet/vnet/fib/fib_path.c
@@ -1801,13 +1801,36 @@ show_fib_path_command (vlib_main_t * vm,
 			unformat_input_t * input,
 			vlib_cli_command_t * cmd)
 {
+    fib_node_index_t pi;
     fib_path_t *path;
 
-    vlib_cli_output (vm, "FIB Path Lists");
-    pool_foreach(path, fib_path_pool,
-    ({
-	vlib_cli_output (vm, "%U", format_fib_path, path);
-    }));
+    if (unformat (input, "%d", &pi))
+    {
+	/*
+	 * show one in detail
+	 */
+	if (!pool_is_free_index(fib_path_pool, pi))
+	{
+	    path = fib_path_get(pi);
+	    u8 *s = fib_path_format(pi, NULL);
+	    s = format(s, "children:");
+	    s = fib_node_children_format(path->fp_node.fn_children, s);
+	    vlib_cli_output (vm, "%s", s);
+	    vec_free(s);
+	}
+	else
+	{
+	    vlib_cli_output (vm, "path %d invalid", pi);
+	}
+    }
+    else
+    {
+	vlib_cli_output (vm, "FIB Paths");
+	pool_foreach(path, fib_path_pool,
+	({
+	    vlib_cli_output (vm, "%U", format_fib_path, path);
+	}));
+    }
 
     return (NULL);
 }
diff --git a/vnet/vnet/fib/fib_path_list.c b/vnet/vnet/fib/fib_path_list.c
index a58274908d4..5cd5096b7d8 100644
--- a/vnet/vnet/fib/fib_path_list.c
+++ b/vnet/vnet/fib/fib_path_list.c
@@ -1188,7 +1188,7 @@ show_fib_path_list_command (vlib_main_t * vm,
 }
 
 VLIB_CLI_COMMAND (show_fib_path_list, static) = {
-  .path = "show fib path list",
+  .path = "show fib path-lists",
   .function = show_fib_path_list_command,
-  .short_help = "show fib path list",
+  .short_help = "show fib path-lists",
 };
diff --git a/vnet/vnet/fib/fib_test.c b/vnet/vnet/fib/fib_test.c
index 3dc9c1d7267..c9a937ba559 100644
--- a/vnet/vnet/fib/fib_test.c
+++ b/vnet/vnet/fib/fib_test.c
@@ -4802,11 +4802,16 @@ fib_test_validate_entry (fib_node_index_t fei,
 {
     const load_balance_t *lb;
     dpo_id_t dpo = DPO_NULL;
+    fib_prefix_t pfx;
+    index_t fw_lbi;
+    u32 fib_index;
     va_list ap;
     int res;
 
     va_start(ap, n_buckets);
 
+    fib_entry_get_prefix(fei, &pfx);
+    fib_index = fib_entry_get_fib_index(fei);
     fib_entry_contribute_forwarding(fei, fct, &dpo);
 
     FIB_TEST_LB((DPO_LOAD_BALANCE == dpo.dpoi_type),
@@ -4816,6 +4821,37 @@ fib_test_validate_entry (fib_node_index_t fei,
 
     res = fib_test_validate_lb_v(lb, n_buckets, ap);
 
+    /*
+     * ensure that the LB contributed by the entry is the
+     * same as the LB in the forwarding tables
+     */
+    switch (pfx.fp_proto)
+    {
+    case FIB_PROTOCOL_IP4:
+	fw_lbi = ip4_fib_forwarding_lookup(fib_index, &pfx.fp_addr.ip4);
+	break;
+    case FIB_PROTOCOL_IP6:
+	fw_lbi = ip6_fib_table_fwding_lookup(&ip6_main, fib_index, &pfx.fp_addr.ip6);
+	break;
+    case FIB_PROTOCOL_MPLS:
+	{
+	    mpls_unicast_header_t hdr;
+
+	    vnet_mpls_uc_set_label(&hdr.label_exp_s_ttl, pfx.fp_label);
+	    vnet_mpls_uc_set_s(&hdr.label_exp_s_ttl, pfx.fp_eos);
+	    hdr.label_exp_s_ttl = clib_host_to_net_u32(hdr.label_exp_s_ttl);
+
+	    fw_lbi = mpls_fib_table_forwarding_lookup(fib_index, &hdr);
+	    break;
+	}
+    default:
+	fw_lbi = 0;
+    }
+    FIB_TEST_LB((fw_lbi == dpo.dpoi_index),
+		"Contributed LB = FW LB: %U\n %U",
+		format_load_balance, fw_lbi, 0,
+		format_load_balance, dpo.dpoi_index, 0);
+
     dpo_reset(&dpo);
 
     va_end(ap);
diff --git a/vnet/vnet/fib/fib_types.h b/vnet/vnet/fib/fib_types.h
index 250aad76e84..4d656565de4 100644
--- a/vnet/vnet/fib/fib_types.h
+++ b/vnet/vnet/fib/fib_types.h
@@ -157,7 +157,12 @@ typedef enum fib_forward_chain_type_t_ {
 #define FIB_FORW_CHAIN_MPLS_NUM (FIB_FORW_CHAIN_TYPE_MPLS_EOS+1)
 
 #define FOR_EACH_FIB_FORW_CHAIN(_item)			  \
-    for (_item = FIB_FORW_CHAIN_TYPE_ETHERNET;   	  \
+    for (_item = FIB_FORW_CHAIN_TYPE_UNICAST_IP4;   	  \
+	 _item <= FIB_FORW_CHAIN_TYPE_ETHERNET;		  \
+	 _item++)
+
+#define FOR_EACH_FIB_FORW_MPLS_CHAIN(_item)		  \
+    for (_item = FIB_FORW_CHAIN_TYPE_UNICAST_IP4;   	  \
 	 _item <= FIB_FORW_CHAIN_TYPE_MPLS_EOS;		  \
 	 _item++)
 
diff --git a/vnet/vnet/fib/fib_walk.c b/vnet/vnet/fib/fib_walk.c
index 79e3ad0b242..bb1a2ac564a 100644
--- a/vnet/vnet/fib/fib_walk.c
+++ b/vnet/vnet/fib/fib_walk.c
@@ -78,6 +78,11 @@ typedef struct fib_walk_t_
     u32 fw_n_visits;
 
     /**
+     * Time the walk started
+     */
+    f64 fw_start_time;
+
+    /**
      * The reasons this walk is occuring.
      * This is a vector ordered in time. The reasons and the front were started
      * first, and so should be acted first when a node is visisted.
@@ -112,8 +117,8 @@ typedef enum fib_walk_queue_stats_t_
 
 #define FOR_EACH_FIB_WALK_QUEUE_STATS(_wqs)   \
     for ((_wqs) = FIB_WALK_SCHEDULED;         \
-         (_wqs) < FIB_WALK_QUEUE_STATS_NUM;   \
-         (_wqs)++)
+	 (_wqs) < FIB_WALK_QUEUE_STATS_NUM;   \
+	 (_wqs)++)
 
 /**
  * The names of the walk stats
@@ -154,6 +159,28 @@ static fib_walk_queues_t fib_walk_queues;
  */
 static const char * const fib_walk_priority_names[] = FIB_WALK_PRIORITIES;
 
+/**
+ * @brief Histogram stats on the lenths of each walk in elemenets visisted.
+ * Store upto 1<<23 elements in increments of 1<<10
+ */
+#define HISTOGRAM_VISITS_PER_WALK_MAX (1<<23)
+#define HISTOGRAM_VISITS_PER_WALK_INCR (1<<10)
+#define HISTOGRAM_VISITS_PER_WALK_N_BUCKETS \
+    (HISTOGRAM_VISITS_PER_WALK_MAX/HISTOGRAM_VISITS_PER_WALK_INCR)
+static u64 fib_walk_hist_vists_per_walk[HISTOGRAM_VISITS_PER_WALK_N_BUCKETS];
+
+/**
+ * @brief History of state for the last 128 walks
+ */
+#define HISTORY_N_WALKS 128
+static u32 history_last_walk_pos;
+typedef struct fib_walk_history_t_ {
+    u32 fwh_n_visits;
+    f64 fwh_duration;
+    fib_node_ptr_t fwh_parent;
+} fib_walk_history_t;
+static fib_walk_history_t fib_walk_history[HISTORY_N_WALKS];
+
 u8*
 format_fib_walk_priority (u8 *s, va_list ap)
 {
@@ -207,13 +234,37 @@ fib_walk_queue_get_front (fib_walk_priority_t prio)
 static void
 fib_walk_destroy (fib_walk_t *fwalk)
 {
+    u32 bucket;
+
     if (FIB_NODE_INDEX_INVALID != fwalk->fw_prio_sibling)
     {
-        fib_node_list_elt_remove(fwalk->fw_prio_sibling);
+	fib_node_list_elt_remove(fwalk->fw_prio_sibling);
     }
     fib_node_child_remove(fwalk->fw_parent.fnp_type,
-                          fwalk->fw_parent.fnp_index,
-                          fwalk->fw_dep_sibling);
+			  fwalk->fw_parent.fnp_index,
+			  fwalk->fw_dep_sibling);
+
+    /*
+     * add the stats to the continuous histogram collection.
+     */
+    bucket = (fwalk->fw_n_visits / HISTOGRAM_VISITS_PER_WALK_INCR);
+    bucket = (bucket > HISTOGRAM_VISITS_PER_WALK_MAX ?
+	      HISTOGRAM_VISITS_PER_WALK_MAX - 1 :
+	      bucket);
+    fib_walk_hist_vists_per_walk[bucket]++;
+
+    /*
+     * save stats to the recent history
+     */
+
+    fib_walk_history[history_last_walk_pos].fwh_n_visits =
+	fwalk->fw_n_visits;
+    fib_walk_history[history_last_walk_pos].fwh_duration =
+	vlib_time_now(vlib_get_main()) - fwalk->fw_start_time;
+    fib_walk_history[history_last_walk_pos].fwh_parent =
+	fwalk->fw_parent;
+
+    history_last_walk_pos = (history_last_walk_pos + 1) % HISTORY_N_WALKS;
 
     fib_node_deinit(&fwalk->fw_node);
     pool_put(fib_walk_pool, fwalk);
@@ -252,7 +303,7 @@ fib_walk_advance (fib_node_index_t fwi)
 
     /*
      * this walk function is re-entrant - walks acan spawn walks.
-     * fib_walk_t objects come from a pool, so they can realloc. we need 
+     * fib_walk_t objects come from a pool, so they can realloc. we need
      * to retch from said pool at the appropriate times.
      */
     fwalk = fib_walk_get(fwi);
@@ -261,42 +312,79 @@ fib_walk_advance (fib_node_index_t fwi)
 
     if (more_elts)
     {
-        vec_foreach(ctx, fwalk->fw_ctx)
-        {
-            wrc = fib_node_back_walk_one(&sibling, ctx);
-
-            fwalk = fib_walk_get(fwi);
-            fwalk->fw_n_visits++;
-
-            if (FIB_NODE_BACK_WALK_MERGE == wrc)
-            {
-                /*
-                 * this walk has merged with the one further along the node's
-                 * dependecy list.
-                 */
-                return (FIB_WALK_ADVANCE_MERGE);
-            }
-        }
-        /*
-         * move foward to the next node to visit
-         */
-        more_elts = fib_node_list_advance(fwalk->fw_dep_sibling);
+	vec_foreach(ctx, fwalk->fw_ctx)
+	{
+	    wrc = fib_node_back_walk_one(&sibling, ctx);
+
+	    fwalk = fib_walk_get(fwi);
+	    fwalk->fw_n_visits++;
+
+	    if (FIB_NODE_BACK_WALK_MERGE == wrc)
+	    {
+		/*
+		 * this walk has merged with the one further along the node's
+		 * dependecy list.
+		 */
+		return (FIB_WALK_ADVANCE_MERGE);
+	    }
+	}
+	/*
+	 * move foward to the next node to visit
+	 */
+	more_elts = fib_node_list_advance(fwalk->fw_dep_sibling);
     }
 
     if (more_elts)
     {
-        return (FIB_WALK_ADVANCE_MORE);
+	return (FIB_WALK_ADVANCE_MORE);
     }
 
     return (FIB_WALK_ADVANCE_DONE);
 }
 
 /**
- * First guesses as to good values
+ * @breif Enurmerate the times of sleep between walks
  */
-#define SHORT_SLEEP 1e-8
-#define LONG_SLEEP  1e-3
-#define QUOTA       1e-4
+typedef enum fib_walk_sleep_type_t_
+{
+    FIB_WALK_SHORT_SLEEP,
+    FIB_WALK_LONG_SLEEP,
+} fib_walk_sleep_type_t;
+
+#define FIB_WALK_N_SLEEP (FIB_WALK_LONG_SLEEP+1)
+
+/**
+ * @brief Durations for the sleep types
+ */
+static f64 fib_walk_sleep_duration[] = {
+    [FIB_WALK_LONG_SLEEP] = 1e-3,
+    [FIB_WALK_SHORT_SLEEP] = 1e-8,
+};
+
+/**
+ * @brief The time quota for a walk. When more than this amount of time is
+ * spent, the walk process will yield.
+ */
+static f64 quota = 1e-4;
+
+/**
+ * Histogram on the amount of work done (in msecs) in each walk
+ */
+#define N_TIME_BUCKETS 128
+#define TIME_INCREMENTS (N_TIME_BUCKETS/2)
+static u64 fib_walk_work_time_taken[N_TIME_BUCKETS];
+
+/**
+ * Histogram on the number of nodes visted in each quota
+ */
+#define N_ELTS_BUCKETS 128
+static u32 fib_walk_work_nodes_visisted_incr = 2;
+static u64 fib_walk_work_nodes_visited[N_ELTS_BUCKETS];
+
+/**
+ * Histogram of the sleep lengths
+ */
+static u64 fib_walk_sleep_lengths[2];
 
 /**
  * @brief Service the queues
@@ -304,64 +392,89 @@ fib_walk_advance (fib_node_index_t fwi)
  */
 f64
 fib_walk_process_queues (vlib_main_t * vm,
-                         const f64 quota)
+			 const f64 quota)
 {
+    f64 start_time, consumed_time;
+    fib_walk_sleep_type_t sleep;
     fib_walk_priority_t prio;
     fib_walk_advance_rc_t rc;
     fib_node_index_t fwi;
     fib_walk_t *fwalk;
+    u32 n_elts;
+    i32 bucket;
 
-    f64 sleep_time, start_time; // , vector_rate;
-
+    consumed_time = 0;
     start_time = vlib_time_now(vm);
+    n_elts = 0;
 
     FOR_EACH_FIB_WALK_PRIORITY(prio)
     {
-        while (0 != fib_walk_queue_get_size(prio))
-        {
-            fwi = fib_walk_queue_get_front(prio);
-
-            /*
-             * set this walk as executing
-             */
-            fwalk = fib_walk_get(fwi);
-            fwalk->fw_flags |= FIB_WALK_FLAG_EXECUTING;
-
-            do
-            {
-                rc = fib_walk_advance(fwi);
-            } while (((vlib_time_now(vm) - start_time) < quota) &&
-                     (FIB_WALK_ADVANCE_MORE == rc));
-
-            /*
-             * if this walk has no more work then pop it from the queue
-             * and move on to the next.
-             */
-            if (FIB_WALK_ADVANCE_MORE != rc)
-            {
-                fwalk = fib_walk_get(fwi);
-                fib_walk_destroy(fwalk);
-                fib_walk_queues.fwqs_queues[prio].fwq_stats[FIB_WALK_COMPLETED]++;
-            }
-            else
-            {
-                /*
-                 * passed our work quota. sleep time.
-                 */
-                fwalk = fib_walk_get(fwi);
-                fwalk->fw_flags &= ~FIB_WALK_FLAG_EXECUTING;
-                sleep_time = SHORT_SLEEP;
-                goto that_will_do_for_now;
-            }
-        }
+	while (0 != fib_walk_queue_get_size(prio))
+	{
+	    fwi = fib_walk_queue_get_front(prio);
+
+	    /*
+	     * set this walk as executing
+	     */
+	    fwalk = fib_walk_get(fwi);
+	    fwalk->fw_flags |= FIB_WALK_FLAG_EXECUTING;
+
+	    do
+	    {
+		rc = fib_walk_advance(fwi);
+		n_elts++;
+		consumed_time = (vlib_time_now(vm) - start_time);
+	    } while ((consumed_time < quota) &&
+		     (FIB_WALK_ADVANCE_MORE == rc));
+
+	    /*
+	     * if this walk has no more work then pop it from the queue
+	     * and move on to the next.
+	     */
+	    if (FIB_WALK_ADVANCE_MORE != rc)
+	    {
+		fwalk = fib_walk_get(fwi);
+		fib_walk_destroy(fwalk);
+		fib_walk_queues.fwqs_queues[prio].fwq_stats[FIB_WALK_COMPLETED]++;
+	    }
+	    else
+	    {
+		/*
+		 * passed our work quota. sleep time.
+		 */
+		fwalk = fib_walk_get(fwi);
+		fwalk->fw_flags &= ~FIB_WALK_FLAG_EXECUTING;
+		sleep = FIB_WALK_SHORT_SLEEP;
+		goto that_will_do_for_now;
+	    }
+	}
     }
     /*
      * got to the end of all the work
      */
-    sleep_time = LONG_SLEEP;
+    sleep = FIB_WALK_LONG_SLEEP;
 
 that_will_do_for_now:
-    return (sleep_time);
+
+    /*
+     * collect the stats:
+     *  - for the number of nodes visisted we store 128 increments
+     *  - for the time consumed we store quota/TIME_INCREMENTS increments.
+     */
+    bucket = ((n_elts/fib_walk_work_nodes_visisted_incr) > N_ELTS_BUCKETS ?
+	      N_ELTS_BUCKETS-1 :
+	      n_elts/fib_walk_work_nodes_visisted_incr);
+    ++fib_walk_work_nodes_visited[bucket];
+
+    bucket = (consumed_time - quota) / (quota / TIME_INCREMENTS);
+    bucket += N_TIME_BUCKETS/2;
+    bucket = (bucket < 0 ? 0 : bucket);
+    bucket = (bucket > N_TIME_BUCKETS-1 ? N_TIME_BUCKETS-1 : bucket);
+    ++fib_walk_work_time_taken[bucket];
+
+    ++fib_walk_sleep_lengths[sleep];
+
+    return (fib_walk_sleep_duration[sleep]);
 }
 
 /**
@@ -369,25 +482,25 @@ that_will_do_for_now:
  */
 static uword
 fib_walk_process (vlib_main_t * vm,
-                  vlib_node_runtime_t * node,
-                  vlib_frame_t * f)
+		  vlib_node_runtime_t * node,
+		  vlib_frame_t * f)
 {
     f64 sleep_time;
 
-    sleep_time = SHORT_SLEEP;
+    sleep_time = fib_walk_sleep_duration[FIB_WALK_SHORT_SLEEP];
 
     while (1)
     {
-        vlib_process_wait_for_event_or_clock(vm, sleep_time);
+	vlib_process_wait_for_event_or_clock(vm, sleep_time);
 
-        /*
-         * there may be lots of event queued between the processes,
-         * but the walks we want to schedule are in the priority queues,
-         * so we ignore the process events.
-         */
-        vlib_process_get_events(vm, NULL);
+	/*
+	 * there may be lots of event queued between the processes,
+	 * but the walks we want to schedule are in the priority queues,
+	 * so we ignore the process events.
+	 */
+	vlib_process_get_events(vm, NULL);
 
-        sleep_time = fib_walk_process_queues(vm, QUOTA);
+	sleep_time = fib_walk_process_queues(vm, quota);
     }
 
     /*
@@ -407,12 +520,12 @@ VLIB_REGISTER_NODE (fib_walk_process_node,static) = {
 
 /**
  * @brief Allocate a new walk object
- */ 
+ */
 static fib_walk_t *
 fib_walk_alloc (fib_node_type_t parent_type,
-                fib_node_index_t parent_index,
-                fib_walk_flags_t flags,
-                fib_node_back_walk_ctx_t *ctx)
+		fib_node_index_t parent_index,
+		fib_walk_flags_t flags,
+		fib_node_back_walk_ctx_t *ctx)
 {
     fib_walk_t *fwalk;
 
@@ -426,6 +539,8 @@ fib_walk_alloc (fib_node_type_t parent_type,
     fwalk->fw_parent.fnp_index = parent_index;
     fwalk->fw_parent.fnp_type = parent_type;
     fwalk->fw_ctx = NULL;
+    fwalk->fw_start_time = vlib_time_now(vlib_get_main());
+    fwalk->fw_n_visits = 0;
 
     /*
      * make a copy of the backwalk context so the depth count remains
@@ -445,14 +560,14 @@ fib_walk_alloc (fib_node_type_t parent_type,
  */
 static index_t
 fib_walk_prio_queue_enquue (fib_walk_priority_t prio,
-                            fib_walk_t *fwalk)
+			    fib_walk_t *fwalk)
 {
     index_t sibling;
 
     sibling = fib_node_list_push_front(fib_walk_queues.fwqs_queues[prio].fwq_queue,
-                                       0,
-                                       FIB_NODE_TYPE_WALK,
-                                       fib_walk_get_index(fwalk));
+				       0,
+				       FIB_NODE_TYPE_WALK,
+				       fib_walk_get_index(fwalk));
     fib_walk_queues.fwqs_queues[prio].fwq_stats[FIB_WALK_SCHEDULED]++;
 
     /*
@@ -461,40 +576,40 @@ fib_walk_prio_queue_enquue (fib_walk_priority_t prio,
      * the process will drain the queues
      */
     vlib_process_signal_event(vlib_get_main(),
-                              fib_walk_process_node.index,
-                              FIB_WALK_EVENT,
-                              FIB_WALK_EVENT);
+			      fib_walk_process_node.index,
+			      FIB_WALK_EVENT,
+			      FIB_WALK_EVENT);
 
     return (sibling);
 }
 
 void
 fib_walk_async (fib_node_type_t parent_type,
-                fib_node_index_t parent_index,
-                fib_walk_priority_t prio,
-                fib_node_back_walk_ctx_t *ctx)
+		fib_node_index_t parent_index,
+		fib_walk_priority_t prio,
+		fib_node_back_walk_ctx_t *ctx)
 {
     fib_walk_t *fwalk;
 
     if (FIB_NODE_GRAPH_MAX_DEPTH < ++ctx->fnbw_depth)
     {
-        /*
-         * The walk has reached the maximum depth. there is a loop in the graph.
-         * bail.
-         */
-        return;
+	/*
+	 * The walk has reached the maximum depth. there is a loop in the graph.
+	 * bail.
+	 */
+	return;
     }
 
     fwalk = fib_walk_alloc(parent_type,
-                           parent_index,
-                           FIB_WALK_FLAG_ASYNC,
-                           ctx);
+			   parent_index,
+			   FIB_WALK_FLAG_ASYNC,
+			   ctx);
 
     fwalk->fw_dep_sibling = fib_node_child_add(parent_type,
-                                               parent_index,
-                                               FIB_NODE_TYPE_WALK,
-                                               fib_walk_get_index(fwalk));
-    
+					       parent_index,
+					       FIB_NODE_TYPE_WALK,
+					       fib_walk_get_index(fwalk));
+
     fwalk->fw_prio_sibling = fib_walk_prio_queue_enquue(prio, fwalk);
 }
 
@@ -507,8 +622,8 @@ fib_walk_async (fib_node_type_t parent_type,
  */
 void
 fib_walk_sync (fib_node_type_t parent_type,
-               fib_node_index_t parent_index,
-               fib_node_back_walk_ctx_t *ctx)
+	       fib_node_index_t parent_index,
+	       fib_node_back_walk_ctx_t *ctx)
 {
     fib_walk_advance_rc_t rc;
     fib_node_index_t fwi;
@@ -516,92 +631,92 @@ fib_walk_sync (fib_node_type_t parent_type,
 
     if (FIB_NODE_GRAPH_MAX_DEPTH < ++ctx->fnbw_depth)
     {
-        /*
-         * The walk has reached the maximum depth. there is a loop in the graph.
-         * bail.
-         */
-        return;
+	/*
+	 * The walk has reached the maximum depth. there is a loop in the graph.
+	 * bail.
+	 */
+	return;
     }
 
     fwalk = fib_walk_alloc(parent_type,
-                           parent_index,
-                           FIB_WALK_FLAG_SYNC,
-                           ctx);
+			   parent_index,
+			   FIB_WALK_FLAG_SYNC,
+			   ctx);
 
     fwalk->fw_dep_sibling = fib_node_child_add(parent_type,
-                                               parent_index,
-                                               FIB_NODE_TYPE_WALK,
-                                               fib_walk_get_index(fwalk));
+					       parent_index,
+					       FIB_NODE_TYPE_WALK,
+					       fib_walk_get_index(fwalk));
     fwi = fib_walk_get_index(fwalk);
 
     while (1)
     {
-        /*
-         * set this walk as executing
-         */
-        fwalk->fw_flags |= FIB_WALK_FLAG_EXECUTING;
-
-        do
-        {
-            rc = fib_walk_advance(fwi);
-        } while (FIB_WALK_ADVANCE_MORE == rc);
-
-
-        /*
-         * this walk function is re-entrant - walks can spawn walks.
-         * fib_walk_t objects come from a pool, so they can realloc. we need 
-         * to re-fetch from said pool at the appropriate times.
-         */
-        fwalk = fib_walk_get(fwi);
-
-        if (FIB_WALK_ADVANCE_MERGE == rc)
-        {
-            /*
-             * this sync walk merged with an walk in front.
-             * by reqeusting a sync walk the client wanted all children walked,
-             * so we ditch the walk object in hand and continue with the one
-             * we merged into
-             */
-            fib_node_ptr_t merged_walk;
-
-            fib_node_list_elt_get_next(fwalk->fw_dep_sibling, &merged_walk);
-
-            ASSERT(FIB_NODE_INDEX_INVALID != merged_walk.fnp_index);
-            ASSERT(FIB_NODE_TYPE_WALK == merged_walk.fnp_type);
-
-            fib_walk_destroy(fwalk);
-
-            fwi = merged_walk.fnp_index;
-            fwalk = fib_walk_get(fwi);            
-
-            if (FIB_WALK_FLAG_EXECUTING & fwalk->fw_flags)
-            {
-                /*
-                 * we are executing a sync walk, and we have met with another
-                 * walk that is also executing. since only one walk executs at once
-                 * (there is no multi-threading) this implies we have met ourselves
-                 * and hence the is a loop in the graph.
-                 * This function is re-entrant, so the walk object we met is being
-                 * acted on in a stack frame below this one. We must therefore not
-                 * continue with it now, but let the stack unwind and along the
-                 * appropriate frame to read the depth count and bail.
-                 */
-                fwalk = NULL;
-                break;
-            }
-        }
-        else
-        {
-            /*
-             * the walk reached the end of the depdency list.
-             */
-            break;
-        }
+	/*
+	 * set this walk as executing
+	 */
+	fwalk->fw_flags |= FIB_WALK_FLAG_EXECUTING;
+
+	do
+	{
+	    rc = fib_walk_advance(fwi);
+	} while (FIB_WALK_ADVANCE_MORE == rc);
+
+
+	/*
+	 * this walk function is re-entrant - walks can spawn walks.
+	 * fib_walk_t objects come from a pool, so they can realloc. we need
+	 * to re-fetch from said pool at the appropriate times.
+	 */
+	fwalk = fib_walk_get(fwi);
+
+	if (FIB_WALK_ADVANCE_MERGE == rc)
+	{
+	    /*
+	     * this sync walk merged with an walk in front.
+	     * by reqeusting a sync walk the client wanted all children walked,
+	     * so we ditch the walk object in hand and continue with the one
+	     * we merged into
+	     */
+	    fib_node_ptr_t merged_walk;
+
+	    fib_node_list_elt_get_next(fwalk->fw_dep_sibling, &merged_walk);
+
+	    ASSERT(FIB_NODE_INDEX_INVALID != merged_walk.fnp_index);
+	    ASSERT(FIB_NODE_TYPE_WALK == merged_walk.fnp_type);
+
+	    fib_walk_destroy(fwalk);
+
+	    fwi = merged_walk.fnp_index;
+	    fwalk = fib_walk_get(fwi);
+
+	    if (FIB_WALK_FLAG_EXECUTING & fwalk->fw_flags)
+	    {
+		/*
+		 * we are executing a sync walk, and we have met with another
+		 * walk that is also executing. since only one walk executs at once
+		 * (there is no multi-threading) this implies we have met ourselves
+		 * and hence the is a loop in the graph.
+		 * This function is re-entrant, so the walk object we met is being
+		 * acted on in a stack frame below this one. We must therefore not
+		 * continue with it now, but let the stack unwind and along the
+		 * appropriate frame to read the depth count and bail.
+		 */
+		fwalk = NULL;
+		break;
+	    }
+	}
+	else
+	{
+	    /*
+	     * the walk reached the end of the depdency list.
+	     */
+	    break;
+	}
     }
 
     if (NULL != fwalk)
     {
-        fib_walk_destroy(fwalk);
+	fib_walk_destroy(fwalk);
     }
 }
 
@@ -629,7 +744,7 @@ static fib_walk_t*
 fib_walk_get_from_node (fib_node_t *node)
 {
     return ((fib_walk_t*)(((char*)node) -
-                          STRUCT_OFFSET_OF(fib_walk_t, fw_node)));
+			  STRUCT_OFFSET_OF(fib_walk_t, fw_node)));
 }
 
 /**
@@ -652,21 +767,21 @@ fib_walk_back_walk_notify (fib_node_t *node,
      */
     vec_foreach(old, fwalk->fw_ctx)
     {
-        /*
-         * we can merge walks if the reason for the walk is the same.
-         */
-        if (old->fnbw_reason == ctx->fnbw_reason)
-        {
-            /*
-             * copy the largest of the depth values. in the presence of a loop,
-             * the same walk will merge with itself. if we take the smaller depth
-             * then it will never end.
-             */
-            old->fnbw_depth = ((old->fnbw_depth >= ctx->fnbw_depth) ?
-                                old->fnbw_depth : 
-                                ctx->fnbw_depth);
-            goto out;
-        }
+	/*
+	 * we can merge walks if the reason for the walk is the same.
+	 */
+	if (old->fnbw_reason == ctx->fnbw_reason)
+	{
+	    /*
+	     * copy the largest of the depth values. in the presence of a loop,
+	     * the same walk will merge with itself. if we take the smaller depth
+	     * then it will never end.
+	     */
+	    old->fnbw_depth = ((old->fnbw_depth >= ctx->fnbw_depth) ?
+				old->fnbw_depth :
+				ctx->fnbw_depth);
+	    goto out;
+	}
     }
 
     /*
@@ -696,7 +811,7 @@ fib_walk_module_init (void)
 
     FOR_EACH_FIB_WALK_PRIORITY(prio)
     {
-        fib_walk_queues.fwqs_queues[prio].fwq_queue = fib_node_list_create();
+	fib_walk_queues.fwqs_queues[prio].fwq_queue = fib_node_list_create();
     }
 
     fib_node_register_type(FIB_NODE_TYPE_WALK, &fib_walk_vft);
@@ -711,60 +826,125 @@ format_fib_walk (u8* s, va_list ap)
     fwalk = fib_walk_get(fwi);
 
     return (format(s, "  parent:{%s:%d} visits:%d flags:%d",
-                   fib_node_type_get_name(fwalk->fw_parent.fnp_type),
-                   fwalk->fw_parent.fnp_index,
-                   fwalk->fw_n_visits,
-                   fwalk->fw_flags));
+		   fib_node_type_get_name(fwalk->fw_parent.fnp_type),
+		   fwalk->fw_parent.fnp_index,
+		   fwalk->fw_n_visits,
+		   fwalk->fw_flags));
 }
 
 static clib_error_t *
 fib_walk_show (vlib_main_t * vm,
-               unformat_input_t * input,
-               vlib_cli_command_t * cmd)
+	       unformat_input_t * input,
+	       vlib_cli_command_t * cmd)
 {
     fib_walk_queue_stats_t wqs;
     fib_walk_priority_t prio;
     fib_node_ptr_t sibling;
     fib_node_index_t fwi;
     fib_walk_t *fwalk;
-    int more_elts;
+    int more_elts, ii;
+    u8 *s = NULL;
 
+#define USEC 1000000
+    vlib_cli_output(vm, "FIB Walk Quota = %.2fusec:", quota * USEC);
     vlib_cli_output(vm, "FIB Walk queues:");
 
     FOR_EACH_FIB_WALK_PRIORITY(prio)
     {
-        vlib_cli_output(vm, " %U priority queue:",
-                        format_fib_walk_priority, prio);
-        vlib_cli_output(vm, "  Stats: ");
-
-        FOR_EACH_FIB_WALK_QUEUE_STATS(wqs)
-        {
-            vlib_cli_output(vm, "    %U:%d",
-                            format_fib_walk_queue_stats, wqs,
-                            fib_walk_queues.fwqs_queues[prio].fwq_stats[wqs]);
-        }
-        vlib_cli_output(vm, "  Occupancy:%d",
-                        fib_node_list_get_size(
-                            fib_walk_queues.fwqs_queues[prio].fwq_queue));
-
-        more_elts = fib_node_list_get_front(
-                        fib_walk_queues.fwqs_queues[prio].fwq_queue,
-                        &sibling);
-
-        while (more_elts)
-        {
-            ASSERT(FIB_NODE_INDEX_INVALID != sibling.fnp_index);
-            ASSERT(FIB_NODE_TYPE_WALK == sibling.fnp_type);
-
-            fwi = sibling.fnp_index;
-            fwalk = fib_walk_get(fwi);            
-
-            vlib_cli_output(vm, "  %U", format_fib_walk, fwi);
-
-            more_elts = fib_node_list_elt_get_next(fwalk->fw_prio_sibling,
-                                                   &sibling);
-        }
+	vlib_cli_output(vm, " %U priority queue:",
+			format_fib_walk_priority, prio);
+	vlib_cli_output(vm, "  Stats: ");
+
+	FOR_EACH_FIB_WALK_QUEUE_STATS(wqs)
+	{
+	    vlib_cli_output(vm, "    %U:%d",
+			    format_fib_walk_queue_stats, wqs,
+			    fib_walk_queues.fwqs_queues[prio].fwq_stats[wqs]);
+	}
+	vlib_cli_output(vm, "  Occupancy:%d",
+			fib_node_list_get_size(
+			    fib_walk_queues.fwqs_queues[prio].fwq_queue));
+
+	more_elts = fib_node_list_get_front(
+			fib_walk_queues.fwqs_queues[prio].fwq_queue,
+			&sibling);
+
+	while (more_elts)
+	{
+	    ASSERT(FIB_NODE_INDEX_INVALID != sibling.fnp_index);
+	    ASSERT(FIB_NODE_TYPE_WALK == sibling.fnp_type);
+
+	    fwi = sibling.fnp_index;
+	    fwalk = fib_walk_get(fwi);
+
+	    vlib_cli_output(vm, "  %U", format_fib_walk, fwi);
+
+	    more_elts = fib_node_list_elt_get_next(fwalk->fw_prio_sibling,
+						   &sibling);
+	}
+    }
+
+    vlib_cli_output(vm, "Histogram Statistics:");
+    vlib_cli_output(vm, " Number of Elements visit per-quota:");
+    for (ii = 0; ii < N_ELTS_BUCKETS; ii++)
+    {
+	if (0 != fib_walk_work_nodes_visited[ii])
+	    s = format(s, "%d:%d ",
+		       (ii * fib_walk_work_nodes_visisted_incr),
+		       fib_walk_work_nodes_visited[ii]);
+    }
+    vlib_cli_output(vm, "  %v", s);
+    vec_free(s);
+
+    vlib_cli_output(vm, " Time consumed per-quota (Quota=%f usec):", quota*USEC);
+    s = format(s, "0:%d ", fib_walk_work_time_taken[0]);
+    for (ii = 1; ii < N_TIME_BUCKETS; ii++)
+    {
+	if (0 != fib_walk_work_time_taken[ii])
+	    s = format(s, "%d:%d ", (u32)((((ii - N_TIME_BUCKETS/2) *
+					   (quota / TIME_INCREMENTS)) + quota) *
+					 USEC),
+		       fib_walk_work_time_taken[ii]);
+    }
+    vlib_cli_output(vm, "  %v", s);
+    vec_free(s);
+
+    vlib_cli_output(vm, " Sleep Types:");
+    vlib_cli_output(vm, "  Short  Long:");
+    vlib_cli_output(vm, "  %d %d:",
+		    fib_walk_sleep_lengths[FIB_WALK_SHORT_SLEEP],
+		    fib_walk_sleep_lengths[FIB_WALK_LONG_SLEEP]);
+
+    vlib_cli_output(vm, " Number of Elements visited per-walk:");
+    for (ii = 0; ii < HISTOGRAM_VISITS_PER_WALK_N_BUCKETS; ii++)
+    {
+	if (0 != fib_walk_hist_vists_per_walk[ii])
+	    s = format(s, "%d:%d ",
+		       ii*HISTOGRAM_VISITS_PER_WALK_INCR,
+		       fib_walk_hist_vists_per_walk[ii]);
     }
+    vlib_cli_output(vm, "  %v", s);
+    vec_free(s);
+
+
+    vlib_cli_output(vm, "Brief History (last %d walks):", HISTORY_N_WALKS);
+    ii = history_last_walk_pos;
+    do
+    {
+	if (0 != fib_walk_history[ii].fwh_n_visits)
+	{
+	    vlib_cli_output(
+		vm, " %s:%d visits:%d duration:%.2f ",
+		fib_node_type_get_name(fib_walk_history[ii].fwh_parent.fnp_type),
+		fib_walk_history[ii].fwh_parent.fnp_index,
+		fib_walk_history[ii].fwh_n_visits,
+		fib_walk_history[ii].fwh_duration);
+	}
+
+	ii = (ii + 1) % HISTORY_N_WALKS;
+    } while (ii != history_last_walk_pos);
+
+
     return (NULL);
 }
 
@@ -773,3 +953,75 @@ VLIB_CLI_COMMAND (fib_walk_show_command, static) = {
     .short_help = "show fib walk",
     .function = fib_walk_show,
 };
+
+static clib_error_t *
+fib_walk_set_quota (vlib_main_t * vm,
+		    unformat_input_t * input,
+		    vlib_cli_command_t * cmd)
+{
+    clib_error_t * error = NULL;
+    f64 new_quota;
+
+    if (unformat (input, "%f", &new_quota))
+    {
+	quota = new_quota;
+    }
+    else
+    {
+	error = clib_error_return(0 , "Pass a float value");
+    }
+
+    return (error);
+}
+
+VLIB_CLI_COMMAND (fib_walk_set_quota_command, static) = {
+    .path = "set fib walk quota",
+    .short_help = "set fib walk quota",
+    .function = fib_walk_set_quota,
+};
+
+static clib_error_t *
+fib_walk_set_histogram_elements_size (vlib_main_t * vm,
+				      unformat_input_t * input,
+				      vlib_cli_command_t * cmd)
+{
+    clib_error_t * error = NULL;
+    u32 new;
+
+    if (unformat (input, "%d", &new))
+    {
+	fib_walk_work_nodes_visisted_incr = new;
+    }
+    else
+    {
+	error = clib_error_return(0 , "Pass an int value");
+    }
+
+    return (error);
+}
+
+VLIB_CLI_COMMAND (fib_walk_set_histogram_elements_size_command, static) = {
+    .path = "set fib walk histogram elements size",
+    .short_help = "set fib walk histogram elements size",
+    .function = fib_walk_set_histogram_elements_size,
+};
+
+static clib_error_t *
+fib_walk_clear (vlib_main_t * vm,
+		unformat_input_t * input,
+		vlib_cli_command_t * cmd)
+{
+    memset(fib_walk_hist_vists_per_walk, 0, sizeof(fib_walk_hist_vists_per_walk));
+    memset(fib_walk_history, 0, sizeof(fib_walk_history));
+    memset(fib_walk_work_time_taken, 0, sizeof(fib_walk_work_time_taken));
+    memset(fib_walk_work_nodes_visited, 0, sizeof(fib_walk_work_nodes_visited));
+    memset(fib_walk_sleep_lengths, 0, sizeof(fib_walk_sleep_lengths));
+
+    return (NULL);
+}
+
+VLIB_CLI_COMMAND (fib_walk_clear_command, static) = {
+    .path = "clear fib walk",
+    .short_help = "clear fib walk",
+    .function = fib_walk_clear,
+};
diff --git a/vnet/vnet/ip/ip6_neighbor.c b/vnet/vnet/ip/ip6_neighbor.c
index 57359f7adf3..fdec2d4a0f2 100644
--- a/vnet/vnet/ip/ip6_neighbor.c
+++ b/vnet/vnet/ip/ip6_neighbor.c
@@ -427,6 +427,17 @@ vnet_set_ip6_ethernet_neighbor (vlib_main_t * vm,
     n->key = k;
     n->adj_index = ADJ_INDEX_INVALID;
   }
+  else
+  {
+    /*
+     * prevent a DoS attack from the data-plane that
+     * spams us with no-op updates to the MAC address
+     */
+    if (0 == memcmp(n->link_layer_address,
+		    link_layer_address,
+		    n_bytes_link_layer_address))
+      return -1;
+  }
 
   /* Update time stamp and ethernet address. */
   clib_memcpy (n->link_layer_address,
diff --git a/vnet/vnet/ip/lookup.h b/vnet/vnet/ip/lookup.h
index 97f776cb09d..d3a180fa192 100644
--- a/vnet/vnet/ip/lookup.h
+++ b/vnet/vnet/ip/lookup.h
@@ -200,52 +200,49 @@ typedef struct ip_adjacency_t_ {
   u8 ia_nh_proto;
 
   union {
-    union {
-	/**
-	 * IP_LOOKUP_NEXT_ARP/IP_LOOKUP_NEXT_REWRITE
-	 *
-	 * neighbour adjacency sub-type;
-	 */
-	struct {
-	    ip46_address_t next_hop;
-	} nbr;
-	/**
-	 * IP_LOOKUP_NEXT_MIDCHAIN
-	 *
-	 * A nbr adj that is also recursive. Think tunnels.
-	 * A nbr adj can transition to be of type MDICHAIN
-	 * so be sure to leave the two structs with the next_hop
-	 * fields aligned.
-	 */
-	struct {
-	    /**
-	     * The recursive next-hop
-	     */
-	    ip46_address_t next_hop;
-            /**
-             * The node index of the tunnel's post rewrite/TX function.
-             */
-            u32 tx_function_node;
-	    /**
-	     * The next DPO to use
-	     */
-	    dpo_id_t next_dpo;
-
-	    /**
-	     * A function to perform the post-rewrite fixup
-	     */
-	    adj_midchain_fixup_t fixup_func;
-	} midchain;
-	/**
-	 * IP_LOOKUP_NEXT_GLEAN
-	 *
-	 * Glean the address to ARP for from the packet's destination
-	 */
-	struct {
-	    ip46_address_t receive_addr;
-	} glean;
-    } sub_type;
-  };
+    /**
+     * IP_LOOKUP_NEXT_ARP/IP_LOOKUP_NEXT_REWRITE
+     *
+     * neighbour adjacency sub-type;
+     */
+      struct {
+	  ip46_address_t next_hop;
+      } nbr;
+      /**
+       * IP_LOOKUP_NEXT_MIDCHAIN
+       *
+       * A nbr adj that is also recursive. Think tunnels.
+       * A nbr adj can transition to be of type MDICHAIN
+       * so be sure to leave the two structs with the next_hop
+       * fields aligned.
+       */
+      struct {
+	  /**
+	   * The recursive next-hop
+	   */
+	  ip46_address_t next_hop;
+	  /**
+	   * The node index of the tunnel's post rewrite/TX function.
+	   */
+	  u32 tx_function_node;
+	  /**
+	   * The next DPO to use
+	   */
+	  dpo_id_t next_dpo;
+	  /**
+	   * A function to perform the post-rewrite fixup
+	   */
+	  adj_midchain_fixup_t fixup_func;
+      } midchain;
+      /**
+       * IP_LOOKUP_NEXT_GLEAN
+       *
+       * Glean the address to ARP for from the packet's destination
+       */
+      struct {
+	  ip46_address_t receive_addr;
+      } glean;
+  } sub_type;
 
   CLIB_CACHE_LINE_ALIGN_MARK(cacheline1);
 
@@ -333,11 +330,6 @@ typedef enum {
 
 struct ip_lookup_main_t;
 
-typedef void (* ip_add_del_adjacency_callback_t) (struct ip_lookup_main_t * lm,
-						  u32 adj_index,
-						  ip_adjacency_t * adj,
-						  u32 is_del);
-
 typedef struct ip_lookup_main_t {
   /* Adjacency heap. */
   ip_adjacency_t * adjacency_heap;