Make async hooks code use the 'recursions' array

Async hooks are the last feature using the client->fetchhandle and
client->query.fetch pointers.  Update ns_query_hookasync() and
query_hookresume() so that they use a dedicated slot in the 'recursions'
array.  Note that async hooks are still not expected to initiate
recursion if one was already started by a prior ns_query_recurse() call,
so the REQUIRE assertion in ns_query_hookasync() needs to check the
RECTYPE_NORMAL slot rather than the RECTYPE_HOOK one.

lib/ns/include/ns/query.h

@@ -46,6 +46,7 @@ typedef enum {
 	RECTYPE_NORMAL,
 	RECTYPE_PREFETCH,
 	RECTYPE_RPZ,
+	RECTYPE_HOOK,
 	RECTYPE_COUNT,
 } ns_query_rectype_t;
 
@@ -59,6 +60,8 @@ typedef enum {
 	((client)->query.recursions[RECTYPE_PREFETCH].handle)
 #define HANDLE_RECTYPE_RPZ(client) \
 	((client)->query.recursions[RECTYPE_RPZ].handle)
+#define HANDLE_RECTYPE_HOOK(client) \
+	((client)->query.recursions[RECTYPE_HOOK].handle)
 
 /*%
  * Helper macros for accessing dns_fetch_t pointers for a specific recursion a
@@ -70,6 +73,8 @@ typedef enum {
 	((client)->query.recursions[RECTYPE_PREFETCH].fetch)
 #define FETCH_RECTYPE_RPZ(client) \
 	((client)->query.recursions[RECTYPE_RPZ].fetch)
+#define FETCH_RECTYPE_HOOK(client) \
+	((client)->query.recursions[RECTYPE_HOOK].fetch)
 
 /*%
  * nameserver recursion parameters, to uniquely identify a recursion

lib/ns/query.c

@@ -6693,12 +6693,11 @@ query_hookresume(isc_task_t *task, isc_event_t *event) {
 	UNLOCK(&client->manager->reclock);
 
 	/*
-	 * This event is running under a client task, so it's safe to detach
-	 * the fetch handle.  And it should be done before resuming query
-	 * processing below, since that may trigger another recursion or
-	 * asynchronous hook event.
+	 * The fetch handle should be detached before resuming query processing
+	 * below, since that may trigger another recursion or asynchronous hook
+	 * event.
 	 */
-	isc_nmhandle_detach(&client->fetchhandle);
+	isc_nmhandle_detach(&HANDLE_RECTYPE_HOOK(client));
 
 	client->state = NS_CLIENTSTATE_WORKING;
 
@@ -6814,7 +6813,7 @@ ns_query_hookasync(query_ctx_t *qctx, ns_query_starthookasync_t runasync,
 
 	REQUIRE(NS_CLIENT_VALID(client));
 	REQUIRE(client->query.hookactx == NULL);
-	REQUIRE(client->query.fetch == NULL);
+	REQUIRE(FETCH_RECTYPE_NORMAL(client) == NULL);
 
 	result = check_recursionquota(client);
 	if (result != ISC_R_SUCCESS) {
@@ -6837,12 +6836,11 @@ ns_query_hookasync(query_ctx_t *qctx, ns_query_starthookasync_t runasync,
 	 * attribute won't be checked anywhere.
 	 *
 	 * Hook-based asynchronous processing cannot coincide with normal
-	 * recursion, so we can safely use fetchhandle here.  Unlike in
-	 * ns_query_recurse(), we attach to the handle only if 'runasync'
-	 * succeeds. It should be safe since we're either in the client
-	 * task or pausing it.
+	 * recursion.  Unlike in ns_query_recurse(), we attach to the handle
+	 * only if 'runasync' succeeds. It should be safe since we're either in
+	 * the client task or pausing it.
 	 */
-	isc_nmhandle_attach(client->handle, &client->fetchhandle);
+	isc_nmhandle_attach(client->handle, &HANDLE_RECTYPE_HOOK(client));
 	return (ISC_R_SUCCESS);
 
 cleanup:

tests/ns/query_test.c

@@ -709,11 +709,11 @@ hook_async_common(void *arg, void *data, isc_result_t *resultp,
 		}
 	} else {
 		/*
-		 * Resume from the completion of async event.
-		 * fetchhandle should have been detached so that we can start
-		 * another async event or DNS recursive resolution.
+		 * Resume from the completion of async event.  The fetch handle
+		 * should have been detached so that we can start another async
+		 * event or DNS recursive resolution.
 		 */
-		INSIST(qctx->client->fetchhandle == NULL);
+		INSIST(HANDLE_RECTYPE_HOOK(qctx->client) == NULL);
 		asdata->async = false;
 		switch (hookpoint) {
 		case NS_QUERY_GOT_ANSWER_BEGIN: