zebra: dont delete pthreads from under themselves

* Rename some things to be less confusing
* Convert client close function to take a client struct rather than a
  task
* Extern client close function and use it when handling SIGTERM

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

zebra/main.c

@@ -134,11 +134,16 @@ static void sigint(void)
 {
 	struct vrf *vrf;
 	struct zebra_vrf *zvrf;
+	struct listnode *ln, *nn;
+	struct zserv *client;
 
 	zlog_notice("Terminating on signal");
 
 	frr_early_fini();
 
+	for (ALL_LIST_ELEMENTS(zebrad.client_list, ln, nn, client))
+		zserv_close_client(client);
+
 	list_delete_all_node(zebrad.client_list);
 	zebra_ptm_finish();
 

zebra/zserv.c

@@ -91,7 +91,7 @@ enum zserv_event {
 	/* The calling client has packets on its input buffer */
 	ZSERV_PROCESS_MESSAGES,
 	/* The calling client wishes to be killed */
-	ZSERV_HANDLE_CLOSE,
+	ZSERV_HANDLE_CLIENT_FAIL,
 };
 
 /*
@@ -160,18 +160,25 @@ static void zserv_log_message(const char *errmsg, struct stream *msg,
 /*
  * Gracefully shut down a client connection.
  *
- * Cancel any pending tasks for the client's thread. Then schedule a task on the
- * main thread to shut down the calling thread.
+ * Cancel any pending tasks for the client's thread. Then schedule a task on
+ * the main thread to shut down the calling thread.
  *
  * Must be called from the client pthread, never the main thread.
  */
-static void zserv_client_close(struct zserv *client)
+static void zserv_client_fail(struct zserv *client)
 {
+	zlog_warn("Client '%s' encountered an error and is shutting down.",
+		  zebra_route_string(client->proto));
+
 	atomic_store_explicit(&client->pthread->running, false,
-			      memory_order_seq_cst);
+			      memory_order_relaxed);
+	if (client->sock > 0) {
+		close(client->sock);
+		client->sock = -1;
+	}
 	THREAD_OFF(client->t_read);
 	THREAD_OFF(client->t_write);
-	zserv_event(client, ZSERV_HANDLE_CLOSE);
+	zserv_event(client, ZSERV_HANDLE_CLIENT_FAIL);
 }
 
 /*
@@ -264,7 +271,7 @@ static int zserv_write(struct thread *thread)
 zwrite_fail:
 	zlog_warn("%s: could not write to %s [fd = %d], closing.", __func__,
 		  zebra_route_string(client->proto), client->sock);
-	zserv_client_close(client);
+	zserv_client_fail(client);
 	return 0;
 }
 
@@ -438,7 +445,7 @@ static int zserv_read(struct thread *thread)
 
 zread_fail:
 	stream_fifo_free(cache);
-	zserv_client_close(client);
+	zserv_client_fail(client);
 	return -1;
 }
 
@@ -605,28 +612,46 @@ static void zserv_client_free(struct zserv *client)
 	XFREE(MTYPE_TMP, client);
 }
 
-/*
- * Finish closing a client.
- *
- * This task is scheduled by a ZAPI client pthread on the main pthread when it
- * wants to stop itself. When this executes, the client connection should
- * already have been closed. This task's responsibility is to gracefully
- * terminate the client thread, update relevant internal datastructures and
- * free any resources allocated by the main thread.
- */
-static int zserv_handle_client_close(struct thread *thread)
+void zserv_close_client(struct zserv *client)
 {
-	struct zserv *client = THREAD_ARG(thread);
-
-	/* synchronously stop thread */
+	/* synchronously stop and join pthread */
 	frr_pthread_stop(client->pthread, NULL);
 
-	/* destroy frr_pthread */
+	if (IS_ZEBRA_DEBUG_EVENT)
+		zlog_debug("Closing client '%s'",
+			   zebra_route_string(client->proto));
+
+	/* if file descriptor is still open, close it */
+	if (client->sock > 0) {
+		close(client->sock);
+		client->sock = -1;
+	}
+
+	thread_cancel_event(zebrad.master, client);
+	THREAD_OFF(client->t_cleanup);
+
+	/* destroy pthread */
 	frr_pthread_destroy(client->pthread);
 	client->pthread = NULL;
 
+	/* remove from client list */
 	listnode_delete(zebrad.client_list, client);
+
+	/* delete client */
 	zserv_client_free(client);
+}
+
+/*
+ * This task is scheduled by a ZAPI client pthread on the main pthread when it
+ * wants to stop itself. When this executes, the client connection should
+ * already have been closed and the thread will most likely have died, but its
+ * resources still need to be cleaned up.
+ */
+static int zserv_handle_client_fail(struct thread *thread)
+{
+	struct zserv *client = THREAD_ARG(thread);
+
+	zserv_close_client(client);
 	return 0;
 }
 
@@ -814,9 +839,9 @@ void zserv_event(struct zserv *client, enum zserv_event event)
 		thread_add_event(zebrad.master, zserv_process_messages, client,
 				 0, NULL);
 		break;
-	case ZSERV_HANDLE_CLOSE:
-		thread_add_event(zebrad.master, zserv_handle_client_close,
-				 client, 0, NULL);
+	case ZSERV_HANDLE_CLIENT_FAIL:
+		thread_add_event(zebrad.master, zserv_handle_client_fail,
+				 client, 0, &client->t_cleanup);
 	}
 }
 
@@ -1037,7 +1062,6 @@ void zserv_init(void)
 {
 	/* Client list init. */
 	zebrad.client_list = list_new();
-	zebrad.client_list->del = (void (*)(void *)) zserv_client_free;
 
 	/* Misc init. */
 	zebrad.sock = -1;

zebra/zserv.h

@@ -73,6 +73,9 @@ struct zserv {
 	struct thread *t_read;
 	struct thread *t_write;
 
+	/* Threads for the main pthread */
+	struct thread *t_cleanup;
+
 	/* default routing table this client munges */
 	int rtm_table;
 
@@ -232,6 +235,18 @@ extern int zserv_send_message(struct zserv *client, struct stream *msg);
  */
 extern struct zserv *zserv_find_client(uint8_t proto, unsigned short instance);
 
+
+/*
+ * Close a client.
+ *
+ * Kills a client's thread, removes the client from the client list and cleans
+ * up its resources.
+ *
+ * client
+ *    the client to close
+ */
+extern void zserv_close_client(struct zserv *client);
+
 #if defined(HANDLE_ZAPI_FUZZING)
 extern void zserv_read_file(char *input);
 #endif