init / exit function ordering

The vlib init function subsystem now supports a mix of procedural and
formally-specified ordering constraints. We should eliminate procedural
knowledge wherever possible.

The following schemes are *roughly* equivalent:

static clib_error_t *init_runs_first (vlib_main_t *vm)
{
   clib_error_t *error;

   ... do some stuff...

   if ((error = vlib_call_init_function (init_runs_next)))
     return error;
   ...
}
VLIB_INIT_FUNCTION (init_runs_first);

and

static clib_error_t *init_runs_first (vlib_main_t *vm)
{
   ... do some stuff...
}
VLIB_INIT_FUNCTION (init_runs_first) =
{
    .runs_before = VLIB_INITS("init_runs_next"),
};

The first form will [most likely] call "init_runs_next" on the
spot. The second form means that "init_runs_first" runs before
"init_runs_next," possibly much earlier in the sequence.

Please DO NOT construct sets of init functions where A before B
actually means A *right before* B. It's not necessary - simply combine
A and B - and it leads to hugely annoying debugging exercises when
trying to switch from ad-hoc procedural ordering constraints to formal
ordering constraints.

Change-Id: I5e4353503bf43b4acb11a45fb33c79a5ade8426c
Signed-off-by: Dave Barach <dave@barachs.net>

3 files changed, 12 insertions, 15 deletions

diff --git a/src/plugins/ikev2/ikev2.c b/src/plugins/ikev2/ikev2.c
index 2340137bb9c..e7b2f92941d 100644
--- a/src/plugins/ikev2/ikev2.c
+++ b/src/plugins/ikev2/ikev2.c
@@ -3295,13 +3295,9 @@ clib_error_t *
 ikev2_init (vlib_main_t * vm)
 {
   ikev2_main_t *km = &ikev2_main;
-  clib_error_t *error;
   vlib_thread_main_t *tm = vlib_get_thread_main ();
   int thread_id;
 
-  if ((error = vlib_call_init_function (vm, ipsec_init)))
-    return error;
-
   clib_memset (km, 0, sizeof (ikev2_main_t));
   km->vnet_main = vnet_get_main ();
   km->vlib_main = vm;
@@ -3319,16 +3315,20 @@ ikev2_init (vlib_main_t * vm)
 
   km->sa_by_ispi = hash_create (0, sizeof (uword));
 
-
-  if ((error = vlib_call_init_function (vm, ikev2_cli_init)))
-    return error;
-
   udp_register_dst_port (vm, 500, ikev2_node.index, 1);
 
+  ikev2_cli_reference ();
+
   return 0;
 }
 
-VLIB_INIT_FUNCTION (ikev2_init);
+/* *INDENT-OFF* */
+VLIB_INIT_FUNCTION (ikev2_init) =
+{
+  .runs_after = VLIB_INITS("ipsec_init"),
+};
+/* *INDENT-ON* */
+
 
 static u8
 ikev2_mngr_process_child_sa (ikev2_sa_t * sa, ikev2_child_sa_t * csa)
diff --git a/src/plugins/ikev2/ikev2.h b/src/plugins/ikev2/ikev2.h
index 55731bff975..2feecf73fdb 100644
--- a/src/plugins/ikev2/ikev2.h
+++ b/src/plugins/ikev2/ikev2.h
@@ -422,6 +422,7 @@ uword unformat_ikev2_transform_dh_type (unformat_input_t * input,
 					va_list * args);
 uword unformat_ikev2_transform_esn_type (unformat_input_t * input,
 					 va_list * args);
+void ikev2_cli_reference (void);
 
 #endif /* __included_ikev2_h__ */
 
diff --git a/src/plugins/ikev2/ikev2_cli.c b/src/plugins/ikev2/ikev2_cli.c
index 8801793be0b..0933667c4bd 100644
--- a/src/plugins/ikev2/ikev2_cli.c
+++ b/src/plugins/ikev2/ikev2_cli.c
@@ -584,15 +584,11 @@ VLIB_CLI_COMMAND (ikev2_initiate_command, static) = {
 };
 /* *INDENT-ON* */
 
-
-clib_error_t *
-ikev2_cli_init (vlib_main_t * vm)
+void
+ikev2_cli_reference (void)
 {
-  return 0;
 }
 
-VLIB_INIT_FUNCTION (ikev2_cli_init);
-
 /*
  * fd.io coding-style-patch-verification: ON
  *