Terminology cleanup: The import_control hook is now called preexport.

Once upon a time, far far away, there were the old Bird developers
discussing what direction of route flow shall be called import and
export. They decided to say "import to protocol" and "export to table"
when speaking about a protocol. When speaking about a table, they
spoke about "importing to table" and "exporting to protocol".

The latter terminology was adopted in configuration, then also the
bird CLI in commit ea2ae6d started to use it (in year 2009). Now
it's 2018 and the terminology is the latter. Import is from protocol to
table, export is from table to protocol. Anyway, there was still an
import_control hook which executed right before route export.

One thing is funny. There are two commits in April 1999 with just two
minutes between them. The older announces the final settlement
on config terminology, the newer uses the other definition. Let's see
their commit messages as the git-log tool shows them (the newer first):

    commit 9e0e485
    Author: Martin Mares <[email protected]>
    Date:   Mon Apr 5 20:17:59 1999 +0000

	Added some new protocol hooks (look at the comments for better explanation):

		make_tmp_attrs          Convert inline attributes to ea_list
		store_tmp_attrs         Convert ea_list to inline attributes
		import_control          Pre-import decisions

    commit 5056c55
    Author: Martin Mares <[email protected]>
    Date:   Mon Apr 5 20:15:31 1999 +0000

	Changed syntax of attaching filters to protocols to hopefully the final
	version:

		EXPORT <filter-spec>    for outbound routes (i.e., those announced
					by BIRD to the rest of the world).
		IMPORT <filter-spec>    for inbound routes (i.e., those imported
					by BIRD from the rest of the world).

	where <filter-spec> is one of:

		ALL                     pass all routes
		NONE                    drop all routes
		FILTER <name>           use named filter
		FILTER { <filter> }     use explicitly defined filter

	For all protocols, the default is IMPORT ALL, EXPORT NONE. This includes
	the kernel protocol, so that you need to add EXPORT ALL to get the previous
	configuration of kernel syncer (as usually, see doc/bird.conf.example for
	a bird.conf example :)).

Let's say RIP to this almost 19-years-old inconsistency. For now, if you
import a route, it is always from protocol to table. If you export a
route, it is always from table to protocol.

And they lived happily ever after.

nest/proto-hooks.c

@@ -258,16 +258,16 @@ void store_tmp_attrs(rte *e, ea_list *attrs)
 { DUMMY; }
 
 /**
- * import_control - pre-filtering decisions on route import
- * @p: protocol instance the route is going to be imported to
+ * preexport - pre-filtering decisions before route export
+ * @p: protocol instance the route is going to be exported to
  * @e: the route in question
  * @attrs: extended attributes of the route
  * @pool: linear pool for allocation of all temporary data
  *
- * The import_control() hook is called as the first step of a exporting
+ * The preexport() hook is called as the first step of a exporting
  * a route from a routing table to the protocol instance. It can modify
- * route attributes and force acceptance or rejection of the route regardless
- * of user-specified filters. See rte_announce() for a complete description
+ * route attributes and force acceptance or rejection of the route before
+ * the user-specified filters are run. See rte_announce() for a complete description
  * of the route distribution process.
  *
  * The standard use of this hook is to reject routes having originated
@@ -276,7 +276,7 @@ void store_tmp_attrs(rte *e, ea_list *attrs)
  * Result: 1 if the route has to be accepted, -1 if rejected and 0 if it
  * should be passed to the filters.
  */
-int import_control(struct proto *p, rte **e, ea_list **attrs, struct linpool *pool)
+int preexport(struct proto *p, rte **e, ea_list **attrs, struct linpool *pool)
 { DUMMY; }
 
 /**

nest/protocol.h

@@ -191,12 +191,12 @@ struct proto {
    *	   ifa_notify	Notify protocol about interface address changes.
    *	   rt_notify	Notify protocol about routing table updates.
    *	   neigh_notify	Notify protocol about neighbor cache events.
-   *	   make_tmp_attrs  Construct ea_list from private attrs stored in rte.
+   *	   make_tmp_attrs  Construct ea_list from private attrs stored in rta.
    *	   store_tmp_attrs Store private attrs back to rta. The route MUST NOT be cached.
-   *	   import_control  Called as the first step of the route importing process.
+   *	   preexport  Called as the first step of the route exporting process.
    *			It can construct a new rte, add private attributes and
-   *			decide whether the route shall be imported: 1=yes, -1=no,
-   *			0=process it through the import filter set by the user.
+   *			decide whether the route shall be exported: 1=yes, -1=no,
+   *			0=process it through the export filter set by the user.
    *	   reload_routes   Request channel to reload all its routes to the core
    *			(using rte_update()). Returns: 0=reload cannot be done,
    *			1= reload is scheduled and will happen (asynchronously).
@@ -210,7 +210,7 @@ struct proto {
   void (*neigh_notify)(struct neighbor *neigh);
   struct ea_list *(*make_tmp_attrs)(struct rte *rt, struct linpool *pool);
   void (*store_tmp_attrs)(struct rte *rt);
-  int (*import_control)(struct proto *, struct rte **rt, struct linpool *pool);
+  int (*preexport)(struct proto *, struct rte **rt, struct linpool *pool);
   void (*reload_routes)(struct channel *);
   void (*feed_begin)(struct channel *, int initial);
   void (*feed_end)(struct channel *);

nest/route.h

@@ -271,7 +271,7 @@ static inline int rte_is_filtered(rte *r) { return !!(r->flags & REF_FILTERED);
 #define RA_ANY		3		/* Announcement of any route change */
 #define RA_MERGED	4		/* Announcement of optimal route merged with next ones */
 
-/* Return value of import_control() callback */
+/* Return value of preexport() callback */
 #define RIC_ACCEPT	1		/* Accepted by protocol */
 #define RIC_PROCESS	0		/* Process it through import filter */
 #define RIC_REJECT	-1		/* Rejected by protocol */

nest/rt-show.c

@@ -133,7 +133,7 @@ rt_show_net(struct cli *c, net *n, struct rt_show_data *d)
       else if (d->export_mode)
 	{
 	  struct proto *ep = ec->proto;
-	  int ic = ep->import_control ? ep->import_control(ep, &e, c->show_pool) : 0;
+	  int ic = ep->preexport ? ep->preexport(ep, &e, c->show_pool) : 0;
 
 	  if (ec->ra_mode == RA_OPTIMAL || ec->ra_mode == RA_MERGED)
 	    pass = 1;

nest/rt-table.c

@@ -407,7 +407,7 @@ export_filter_(struct channel *c, rte *rt0, rte **rt_free, linpool *pool, int si
 
   rte_make_tmp_attrs(&rt, pool);
 
-  v = p->import_control ? p->import_control(p, &rt, pool) : 0;
+  v = p->preexport ? p->preexport(p, &rt, pool) : 0;
   if (v < 0)
     {
       if (silent)
@@ -873,7 +873,7 @@ rt_notify_merged(struct channel *c, net *net, rte *new_changed, rte *old_changed
  * routing table @tab) changes In that case @old stores the old route
  * from the same protocol.
  *
- * For each appropriate protocol, we first call its import_control()
+ * For each appropriate protocol, we first call its preexport()
  * hook which performs basic checks on the route (each protocol has a
  * right to veto or force accept of the route before any filter is
  * asked) and adds default values of attributes specific to the new
@@ -1473,7 +1473,7 @@ rt_examine(rtable *t, net_addr *a, struct proto *p, struct filter *filter)
 
   /* Rest is stripped down export_filter() */
   rte_make_tmp_attrs(&rt, rte_update_pool);
-  int v = p->import_control ? p->import_control(p, &rt, rte_update_pool) : 0;
+  int v = p->preexport ? p->preexport(p, &rt, rte_update_pool) : 0;
   if (v == RIC_PROCESS)
     v = (f_run(filter, &rt, rte_update_pool, FF_SILENT) <= F_ACCEPT);
 

proto/babel/babel.c

@@ -2104,7 +2104,7 @@ babel_prepare_attrs(struct linpool *pool, ea_list *next, uint metric, u64 router
 
 
 static int
-babel_import_control(struct proto *P, struct rte **new, struct linpool *pool UNUSED)
+babel_preexport(struct proto *P, struct rte **new, struct linpool *pool UNUSED)
 {
   struct rta *a = (*new)->attrs;
 
@@ -2228,7 +2228,7 @@ babel_init(struct proto_config *CF)
 
   P->if_notify = babel_if_notify;
   P->rt_notify = babel_rt_notify;
-  P->import_control = babel_import_control;
+  P->preexport = babel_preexport;
   P->make_tmp_attrs = babel_make_tmp_attrs;
   P->store_tmp_attrs = babel_store_tmp_attrs;
   P->rte_better = babel_rte_better;

proto/bgp/attrs.c

@@ -1371,7 +1371,7 @@ bgp_free_prefix(struct bgp_channel *c, struct bgp_prefix *px)
  */
 
 int
-bgp_import_control(struct proto *P, rte **new, struct linpool *pool UNUSED)
+bgp_preexport(struct proto *P, rte **new, struct linpool *pool UNUSED)
 {
   rte *e = *new;
   struct proto *SRC = e->attrs->src->proto;

proto/bgp/bgp.c

@@ -1533,7 +1533,7 @@ bgp_init(struct proto_config *CF)
   struct bgp_config *cf = (struct bgp_config *) CF;
 
   P->rt_notify = bgp_rt_notify;
-  P->import_control = bgp_import_control;
+  P->preexport = bgp_preexport;
   P->neigh_notify = bgp_neigh_notify;
   P->reload_routes = bgp_reload_routes;
   P->feed_begin = bgp_feed_begin;

proto/bgp/bgp.h

@@ -533,7 +533,7 @@ int bgp_rte_mergable(rte *pri, rte *sec);
 int bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best);
 struct rte *bgp_rte_modify_stale(struct rte *r, struct linpool *pool);
 void bgp_rt_notify(struct proto *P, struct channel *C, net *n, rte *new, rte *old);
-int bgp_import_control(struct proto *, struct rte **, struct linpool *);
+int bgp_preexport(struct proto *, struct rte **, struct linpool *);
 int bgp_get_attr(struct eattr *e, byte *buf, int buflen);
 void bgp_get_route_info(struct rte *, byte *buf);
 

proto/ospf/ospf.c

@@ -101,7 +101,7 @@
 #include <stdlib.h>
 #include "ospf.h"
 
-static int ospf_import_control(struct proto *P, rte **new, struct linpool *pool);
+static int ospf_preexport(struct proto *P, rte **new, struct linpool *pool);
 static struct ea_list *ospf_make_tmp_attrs(struct rte *rt, struct linpool *pool);
 static void ospf_store_tmp_attrs(struct rte *rt);
 static void ospf_reload_routes(struct channel *C);
@@ -315,7 +315,7 @@ ospf_init(struct proto_config *CF)
   P->rt_notify = ospf_rt_notify;
   P->if_notify = ospf_if_notify;
   P->ifa_notify = cf->ospf2 ? ospf_ifa_notify2 : ospf_ifa_notify3;
-  P->import_control = ospf_import_control;
+  P->preexport = ospf_preexport;
   P->reload_routes = ospf_reload_routes;
   P->make_tmp_attrs = ospf_make_tmp_attrs;
   P->store_tmp_attrs = ospf_store_tmp_attrs;
@@ -434,7 +434,7 @@ ospf_disp(timer * timer)
 
 
 /**
- * ospf_import_control - accept or reject new route from nest's routing table
+ * ospf_preexport - accept or reject new route from nest's routing table
  * @P: OSPF protocol instance
  * @new: the new route
  * @attrs: list of attributes
@@ -444,7 +444,7 @@ ospf_disp(timer * timer)
  * import to the filters.
  */
 static int
-ospf_import_control(struct proto *P, rte **new, struct linpool *pool UNUSED)
+ospf_preexport(struct proto *P, rte **new, struct linpool *pool UNUSED)
 {
   struct ospf_proto *p = (struct ospf_proto *) P;
   struct ospf_area *oa = ospf_main_area(p);

proto/pipe/pipe.c

@@ -98,7 +98,7 @@ pipe_rt_notify(struct proto *P, struct channel *src_ch, net *n, rte *new, rte *o
 }
 
 static int
-pipe_import_control(struct proto *P, rte **ee, struct linpool *p UNUSED)
+pipe_preexport(struct proto *P, rte **ee, struct linpool *p UNUSED)
 {
   struct proto *pp = (*ee)->sender->proto;
 
@@ -179,7 +179,7 @@ pipe_init(struct proto_config *CF)
   struct pipe_config *cf = (void *) CF;
 
   P->rt_notify = pipe_rt_notify;
-  P->import_control = pipe_import_control;
+  P->preexport = pipe_preexport;
   P->reload_routes = pipe_reload_routes;
 
   pipe_configure_channels(p, cf);

proto/radv/radv.c

@@ -28,7 +28,7 @@
  * processes asynchronous events (specified by RA_EV_* codes), and radv_timer(),
  * which triggers sending RAs and computes the next timeout.
  *
- * The RAdv protocol could receive routes (through radv_import_control() and
+ * The RAdv protocol could receive routes (through radv_preexport() and
  * radv_rt_notify()), but only the configured trigger route is tracked (in
  * &active var).  When a radv protocol is reconfigured, the connected routing
  * table is examined (in radv_check_active()) to have proper &active value in
@@ -396,7 +396,7 @@ radv_net_match_trigger(struct radv_config *cf, net *n)
 }
 
 int
-radv_import_control(struct proto *P, rte **new, struct linpool *pool UNUSED)
+radv_preexport(struct proto *P, rte **new, struct linpool *pool UNUSED)
 {
   // struct radv_proto *p = (struct radv_proto *) P;
   struct radv_config *cf = (struct radv_config *) (P->cf);
@@ -580,7 +580,7 @@ radv_init(struct proto_config *CF)
 
   P->main_channel = proto_add_channel(P, proto_cf_main_channel(CF));
 
-  P->import_control = radv_import_control;
+  P->preexport = radv_preexport;
   P->rt_notify = radv_rt_notify;
   P->if_notify = radv_if_notify;
   P->ifa_notify = radv_ifa_notify;

sysdep/unix/krt.c

@@ -579,7 +579,7 @@ krt_export_net(struct krt_proto *p, net *net, rte **rt_free)
 
   rte_make_tmp_attrs(&rt, krt_filter_lp);
 
-  /* We could run krt_import_control() here, but it is already handled by KRF_INSTALLED */
+  /* We could run krt_preexport() here, but it is already handled by KRF_INSTALLED */
 
   if (filter == FILTER_ACCEPT)
     goto accept;
@@ -940,7 +940,7 @@ krt_store_tmp_attrs(rte *rt)
 }
 
 static int
-krt_import_control(struct proto *P, rte **new, struct linpool *pool UNUSED)
+krt_preexport(struct proto *P, rte **new, struct linpool *pool UNUSED)
 {
   // struct krt_proto *p = (struct krt_proto *) P;
   rte *e = *new;
@@ -1085,7 +1085,7 @@ krt_init(struct proto_config *CF)
 
   p->p.main_channel = proto_add_channel(&p->p, proto_cf_main_channel(CF));
 
-  p->p.import_control = krt_import_control;
+  p->p.preexport = krt_preexport;
   p->p.rt_notify = krt_rt_notify;
   p->p.if_notify = krt_if_notify;
   p->p.reload_routes = krt_reload_routes;