add plugin_register param telling the source

The plugin `plugin_register` API has a new parameter `source` indicating
whether the plugin is loaded from a view or a zone.

This extra parameter enables the plugin to fail early during
initialization if a plugin written to be used in a zone exclusively
is loaded at a view level, or vice versa.

bin/named/server.c

@@ -5417,7 +5417,7 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 	}
 
 	if (plugin_list != NULL) {
-		ns_hook_data_t hookdata = {};
+		ns_hook_data_t hookdata = { .source = NS_HOOKSOURCE_VIEW };
 
 		INSIST(view->hooktable == NULL);
 		ns_hooktable_create(view->mctx, &hookdata.hooktable);

bin/named/zoneconf.c

@@ -2125,7 +2125,7 @@ named_zone_loadplugins(dns_zone_t *zone, const cfg_obj_t *config,
 	}
 
 	if (tpluginlist != NULL || zpluginlist != NULL) {
-		ns_hook_data_t hookdata = {};
+		ns_hook_data_t hookdata = { .source = NS_HOOKSOURCE_ZONE };
 		isc_mem_t *zmctx = dns_zone_getmctx(zone);
 
 		ns_hooktable_create(zmctx, &hookdata.hooktable);

bin/plugins/filter-a.c

@@ -326,10 +326,13 @@ cleanup:
 isc_result_t
 plugin_register(const char *parameters, const void *cfg, const char *cfg_file,
 		unsigned long cfg_line, isc_mem_t *mctx, void *actx,
-		ns_hooktable_t *hooktable, void **instp) {
+		ns_hooktable_t *hooktable, ns_hooksource_t source,
+		void **instp) {
 	filter_instance_t *inst = NULL;
 	isc_result_t result = ISC_R_SUCCESS;
 
+	UNUSED(source);
+
 	isc_log_write(NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_HOOKS, ISC_LOG_INFO,
 		      "registering 'filter-a' "
 		      "module from %s:%lu, %s parameters",

bin/plugins/filter-aaaa.c

@@ -329,10 +329,13 @@ cleanup:
 isc_result_t
 plugin_register(const char *parameters, const void *cfg, const char *cfg_file,
 		unsigned long cfg_line, isc_mem_t *mctx, void *actx,
-		ns_hooktable_t *hooktable, void **instp) {
+		ns_hooktable_t *hooktable, ns_hooksource_t source,
+		void **instp) {
 	filter_instance_t *inst = NULL;
 	isc_result_t result = ISC_R_SUCCESS;
 
+	UNUSED(source);
+
 	isc_log_write(NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_HOOKS, ISC_LOG_INFO,
 		      "registering 'filter-aaaa' "
 		      "module from %s:%lu, %s parameters",

lib/ns/hooks.c

@@ -239,8 +239,10 @@ ns_plugin_register(const char *modpath, const char *parameters, const void *cfg,
 	isc_log_write(NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_HOOKS, ISC_LOG_INFO,
 		      "registering plugin '%s'", modpath);
 
+	INSIST(hookdata->source != NS_HOOKSOURCE_UNDEFINED);
 	CHECK(plugin->register_func(parameters, cfg, cfg_file, cfg_line, mctx,
-				    actx, hookdata->hooktable, &plugin->inst));
+				    actx, hookdata->hooktable, hookdata->source,
+				    &plugin->inst));
 
 	ISC_LIST_APPEND(*hookdata->plugins, plugin, link);
 

lib/ns/include/ns/hooks.h

@@ -59,10 +59,11 @@
  * contains a function pointer to a hook action and a pointer to data which is
  * to be passed to the action function when it is called.
  *
- * Each view has its own separate hook table, populated by loading plugin
- * modules specified in the "plugin" statements in named.conf.  There is also a
- * special, global hook table (ns__hook_table) that is only used by libns unit
- * tests and whose existence can be safely ignored by plugin modules.
+ * Each view and zone has its own separate hook table, populated by loading
+ * plugin modules specified in the "plugin" statements in named.conf. (See
+ * `ZONE-SPECIFIC PLUGINS` section below.) There is also a special, global
+ * hook table (ns__hook_table) that is only used by libns unit tests and
+ * whose existence can be safely ignored by plugin modules.
  *
  * Hook actions are functions which:
  *
@@ -366,6 +367,14 @@
  *   looked up.  `NS_QUERY_DONE_BEGIN` could be called if an
  *   authoritative zone has been used, but in some flows (for
  *   instance, bad cookie handling), it would be skipped.
+ *
+ * The `plugin_register` function (defined by each plugin and called
+ * when the plugin is loaded) has a `ns_hooksource_t source` parameter.
+ * It indicates whether the plugin has been loaded at the zone level
+ * (`NS_HOOKSOURCE_ZONE`) or at the view level (`NS_HOOKSOURCE_VIEW`).
+ * While this can be ignored if it doesn't matter where the plugin is
+ * loaded, it can also be checked to enforce that the plugin is loaded
+ * only at the zone or view level.
  */
 
 /*!
@@ -476,9 +485,16 @@ typedef struct ns_hook_resume {
  * Wrapper struct holding hook/plugins owning data structures used and owned by
  * zones and views having registered plugins.
  */
+typedef enum {
+	NS_HOOKSOURCE_UNDEFINED,
+	NS_HOOKSOURCE_VIEW,
+	NS_HOOKSOURCE_ZONE
+} ns_hooksource_t;
+
 typedef struct ns_hook_data {
 	ns_hooktable_t *hooktable;
 	ns_plugins_t   *plugins;
+	ns_hooksource_t source;
 } ns_hook_data_t;
 
 /*
@@ -497,7 +513,8 @@ typedef struct ns_hook_data {
 typedef isc_result_t
 ns_plugin_register_t(const char *parameters, const void *cfg, const char *file,
 		     unsigned long line, isc_mem_t *mctx, void *actx,
-		     ns_hooktable_t *hooktable, void **instp);
+		     ns_hooktable_t *hooktable, ns_hooksource_t source,
+		     void **instp);
 /*%<
  * Called when registering a new plugin.
  *