From: Christopher Faulet <cfaulet@haproxy.com>
Date: Fri, 10 Oct 2025 12:32:04 +0000 (+0200)
Subject: BUG/MEDIUM: apppet: Improve spinning loop detection with the new API
X-Git-Tag: v3.3-dev10~33
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=54b7539d6;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: apppet: Improve spinning loop detection with the new API

Conditions to detect the spinning loop for applets based on the new API are
not accurrate. We cannot continue to check the channel's buffers state to
know if an applet has made some progress. At least, we must also check the
applet's buffers.

After digging to find the right way to do, it was clear that the best is to
use something similar to what is performed for the streams, namely, checking
read and write events. And in fact, it is quite easy to do with the new
API. So let's do so.

This patch must be backported as far as 3.0.
---

diff --git a/src/applet.c b/src/applet.c
index b71096ae9..4b55bf9b5 100644
--- a/src/applet.c
+++ b/src/applet.c
@@ -898,6 +898,7 @@ struct task *task_process_applet(struct task *t, void *context, unsigned int sta
 	struct appctx *app = context;
 	struct stconn *sc;
 	unsigned int rate;
+	int did_send, did_recv;
 
 	TRACE_ENTER(APPLET_EV_PROCESS, app);
 
@@ -925,6 +926,7 @@ struct task *task_process_applet(struct task *t, void *context, unsigned int sta
 	sc = appctx_sc(app);
 
 	sc_applet_sync_send(sc);
+	did_send = (sc_oc(sc)->flags & CF_WRITE_EVENT);
 
 	/* We always pretend the applet can't get and doesn't want to
 	 * put, it's up to it to change this if needed. This ensures
@@ -940,7 +942,7 @@ struct task *task_process_applet(struct task *t, void *context, unsigned int sta
 	if (b_data(&app->outbuf) || se_fl_test(app->sedesc, SE_FL_MAY_FASTFWD_PROD))
 		applet_have_more_data(app);
 
-	sc_applet_sync_recv(sc);
+	did_recv = sc_applet_sync_recv(sc);
 
 	if (!se_fl_test(app->sedesc, SE_FL_WANT_ROOM)) {
 		/* Handle EOI/EOS/ERROR outside of data transfer. But take care
@@ -966,11 +968,7 @@ struct task *task_process_applet(struct task *t, void *context, unsigned int sta
 	}
 
 	/* measure the call rate and check for anomalies when too high */
-	if (((b_size(sc_ib(sc)) && sc->flags & SC_FL_NEED_BUFF) || // asks for a buffer which is present
-	     (b_size(sc_ib(sc)) && !b_data(sc_ib(sc)) && sc->flags & SC_FL_NEED_ROOM) || // asks for room in an empty buffer
-	     (b_data(sc_ob(sc)) && sc_is_send_allowed(sc)) || // asks for data already present
-	     (!b_data(sc_ib(sc)) && b_data(sc_ob(sc)) && // didn't return anything ...
-	      (!(sc_oc(sc)->flags & CF_WRITE_EVENT) && (sc->flags & SC_FL_SHUT_WANTED))))) { // ... and left data pending after a shut
+	if (!did_recv && !did_send) {
 		rate = update_freq_ctr(&app->call_rate, 1);
 		if (rate >= 100000 && app->call_rate.prev_ctr) // looped like this more than 100k times over last second
 			stream_dump_and_crash(&app->obj_type, read_freq_ctr(&app->call_rate));