Merge pull request #15025 from donaldsharp/dplane_fpm_nl_wedgied

zebra: Prevent possible wedged fpm write

zebra/dplane_fpm_nl.c

@@ -47,6 +47,12 @@
 #define SOUTHBOUND_DEFAULT_ADDR INADDR_LOOPBACK
 #define SOUTHBOUND_DEFAULT_PORT 2620
 
+/*
+ * Time in seconds that if the other end is not responding
+ * something terrible has gone wrong.  Let's fix that.
+ */
+#define DPLANE_FPM_NL_WEDGIE_TIME 15
+
 /**
  * FPM header:
  * {
@@ -93,6 +99,7 @@ struct fpm_nl_ctx {
 	struct event *t_event;
 	struct event *t_nhg;
 	struct event *t_dequeue;
+	struct event *t_wedged;
 
 	/* zebra events. */
 	struct event *t_lspreset;
@@ -1367,6 +1374,18 @@ static void fpm_rmac_reset(struct event *t)
 			&fnc->t_rmacwalk);
 }
 
+static void fpm_process_wedged(struct event *t)
+{
+	struct fpm_nl_ctx *fnc = EVENT_ARG(t);
+
+	zlog_warn("%s: Connection unable to write to peer for over %u seconds, resetting",
+		  __func__, DPLANE_FPM_NL_WEDGIE_TIME);
+
+	atomic_fetch_add_explicit(&fnc->counters.connection_errors, 1,
+				  memory_order_relaxed);
+	FPM_RECONNECT(fnc);
+}
+
 static void fpm_process_queue(struct event *t)
 {
 	struct fpm_nl_ctx *fnc = EVENT_ARG(t);
@@ -1411,9 +1430,13 @@ static void fpm_process_queue(struct event *t)
 				  processed_contexts, memory_order_relaxed);
 
 	/* Re-schedule if we ran out of buffer space */
-	if (no_bufs)
-		event_add_timer(fnc->fthread->master, fpm_process_queue, fnc, 0,
+	if (no_bufs) {
+		event_add_event(fnc->fthread->master, fpm_process_queue, fnc, 0,
 				&fnc->t_dequeue);
+		event_add_timer(fnc->fthread->master, fpm_process_wedged, fnc,
+				DPLANE_FPM_NL_WEDGIE_TIME, &fnc->t_wedged);
+	} else
+		EVENT_OFF(fnc->t_wedged);
 
 	/*
 	 * Let the dataplane thread know if there are items in the
@@ -1617,7 +1640,7 @@ static int fpm_nl_process(struct zebra_dplane_provider *prov)
 	if (atomic_load_explicit(&fnc->counters.ctxqueue_len,
 				 memory_order_relaxed)
 	    > 0)
-		event_add_timer(fnc->fthread->master, fpm_process_queue, fnc, 0,
+		event_add_event(fnc->fthread->master, fpm_process_queue, fnc, 0,
 				&fnc->t_dequeue);
 
 	/* Ensure dataplane thread is rescheduled if we hit the work limit */