Increase default MAC learn limit and check it in learn-update path

1. Increase default MAC learn limit from 1M to 8M entries.
2. Check MAC learn limit in MAC learning update path.
3. Allow disable of want_l2_macs_events to set MAC learn limit
4. Other minor cleanups

Change-Id: I62438440937b5fa455e16f4a2e4d910277753395
Signed-off-by: John Lo <loj@cisco.com>

src/vnet/l2/l2.api

@@ -134,7 +134,6 @@ autoreply define l2fib_add_del
 };
 
 /** \brief Register to recive L2 MAC events for leanred and aged MAC
-    Will also change MAC learn limit to L2LEARN_INFORM_LIMIT
     @param client_index - opaque cookie to identify the sender
     @param context - sender context, to match reply w/ request
     @param learn_limit - MAC learn limit, 0 => default to 1000

src/vnet/l2/l2_api.c

@@ -284,7 +284,10 @@ vl_api_want_l2_macs_events_t_handler (vl_api_want_l2_macs_events_t * mp)
     {
       lm->client_pid = 0;
       lm->client_index = 0;
-      lm->global_learn_limit = L2LEARN_DEFAULT_LIMIT;
+      if (learn_limit)
+	lm->global_learn_limit = learn_limit;
+      else
+	lm->global_learn_limit = L2LEARN_DEFAULT_LIMIT;
     }
 
 exit:

src/vnet/l2/l2_fib.c

@@ -1021,7 +1021,7 @@ l2fib_scan (vlib_main_t * vm, f64 start_time, u8 event_only)
 
 	      if (PREDICT_FALSE (evt_idx >= fm->max_macs_in_event))
 		{
-		  /* evet message full, sent it and start a new one */
+		  /* event message full, send it and start a new one */
 		  if (q && (q->cursize < q->maxsize))
 		    {
 		      mp->n_macs = htonl (evt_idx);

src/vnet/l2/l2_learn.c

@@ -131,6 +131,8 @@ l2learn_process (vlib_node_runtime_t * node,
 
       if (PREDICT_TRUE (!update))
 	return;
+      else if (msm->global_learn_count > msm->global_learn_limit)
+	return;			/* Above learn limit - do not update */
     }
   else if (result0->raw == ~0)
     {

src/vnet/l2/l2_learn.h

@@ -46,7 +46,7 @@ typedef struct
   vnet_main_t *vnet_main;
 } l2learn_main_t;
 
-#define L2LEARN_DEFAULT_LIMIT (L2FIB_NUM_BUCKETS * 16)
+#define L2LEARN_DEFAULT_LIMIT (L2FIB_NUM_BUCKETS * 128)
 
 l2learn_main_t l2learn_main;