vlib: Punt reason allocation listener enable/disable callback

Type: improvement

allow clients that allocate punt reasons to pass a callback function
that is invoked when the first/last client registers to use/listen on
that punt reason. This allows the client to perform some necessary
configs that might not otherwise be enabled.
IPSec uses this callback to register the ESP proto and UDP handling
nodes, that would not otherwise be enabled unless a tunnel was present.

Change-Id: I9759349903f21ffeeb253d4271e619e6bf46054b
Signed-off-by: Neale Ranns <nranns@cisco.com>

2 files changed, 39 insertions, 4 deletions

diff --git a/src/vlib/punt.c b/src/vlib/punt.c
index 7c2daf25ee4..d5e13004caf 100644
--- a/src/vlib/punt.c
+++ b/src/vlib/punt.c
@@ -47,6 +47,21 @@ typedef struct punt_reason_data_t_
    * Clients/owners that have registered this reason
    */
   u32 *pd_owners;
+
+  /**
+   * clients interested/listening to this reason
+   */
+  u32 pd_users;
+
+  /**
+   * function to invoke if a client becomes interested in the code.
+   */
+  punt_interested_listener_t pd_fn;
+
+  /**
+   * Data to pass to the callback
+   */
+  void *pd_data;
 } punt_reason_data_t;
 
 /**
@@ -249,8 +264,8 @@ punt_reg_mk_dp (vlib_punt_reason_t reason)
 }
 
 int
-vlib_punt_register (vlib_punt_hdl_t client, vlib_punt_reason_t reason,
-		    const char *node_name)
+vlib_punt_register (vlib_punt_hdl_t client,
+		    vlib_punt_reason_t reason, const char *node_name)
 {
   vlib_node_t *punt_to, *punt_from;
   punt_client_t *pc;
@@ -298,6 +313,11 @@ vlib_punt_register (vlib_punt_hdl_t client, vlib_punt_reason_t reason,
 
       pri = pr - punt_reg_pool;
 
+      if (0 == punt_reason_data[reason].pd_users++ &&
+	  NULL != punt_reason_data[reason].pd_fn)
+	punt_reason_data[reason].pd_fn (VLIB_ENABLE,
+					punt_reason_data[reason].pd_data);
+
       punt_reg_add (pr);
     }
 
@@ -353,6 +373,10 @@ vlib_punt_unregister (vlib_punt_hdl_t client,
 
       if (0 == pr->pr_locks)
 	{
+	  if (0 == --punt_reason_data[reason].pd_users &&
+	      NULL != punt_reason_data[reason].pd_fn)
+	    punt_reason_data[reason].pd_fn (VLIB_DISABLE,
+					    punt_reason_data[reason].pd_data);
 	  punt_reg_remove (pr);
 	  pool_put (punt_reg_pool, pr);
 	}
@@ -377,7 +401,9 @@ vlib_punt_reason_validate (vlib_punt_reason_t reason)
 
 int
 vlib_punt_reason_alloc (vlib_punt_hdl_t client,
-			const char *reason_name, vlib_punt_reason_t * reason)
+			const char *reason_name,
+			punt_interested_listener_t fn,
+			void *data, vlib_punt_reason_t * reason)
 {
   vlib_punt_reason_t new;
 
@@ -388,6 +414,8 @@ vlib_punt_reason_alloc (vlib_punt_hdl_t client,
   vec_validate (punt_reason_data, new);
   punt_reason_data[new].pd_name = format (NULL, "%s", reason_name);
   punt_reason_data[new].pd_reason = new;
+  punt_reason_data[new].pd_fn = fn;
+  punt_reason_data[new].pd_data = data;
   vec_add1 (punt_reason_data[new].pd_owners, client);
 
   vlib_validate_combined_counter (&punt_counters, new);
diff --git a/src/vlib/punt.h b/src/vlib/punt.h
index 7a3e5da2da6..d93b5eac599 100644
--- a/src/vlib/punt.h
+++ b/src/vlib/punt.h
@@ -56,12 +56,19 @@ typedef int vlib_punt_hdl_t;
  */
 vlib_punt_hdl_t vlib_punt_client_register (const char *who);
 
+typedef void (*punt_interested_listener_t) (vlib_enable_or_disable_t i,
+					    void *data);
+
 /**
  * Allocate a new punt reason
+ * @param fn     - A callback to invoke when an entity becomes [un]interested
+ *                 in the punt code.
+ * @param data   - To be passed in the callback function.
  */
 extern int vlib_punt_reason_alloc (vlib_punt_hdl_t client,
 				   const char *reason_name,
-				   vlib_punt_reason_t * reason);
+				   punt_interested_listener_t fn,
+				   void *data, vlib_punt_reason_t * reason);
 
 /**
  * Validate that a punt reason is assigned