From: Olivier Houchard <ohouchard@haproxy.com>
Date: Wed, 2 Apr 2025 10:40:42 +0000 (+0000)
Subject: BUG/MEDIUM: leastconn: Don't try to reposition if the server is down
X-Git-Tag: v3.2-dev9~17
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f59297e49250402650088c89e7c79a1d5291b6ac;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: leastconn: Don't try to reposition if the server is down

It may happen that the server is going down, and fwlc_srv_reposition()
is still called, because streams still attached to the server are
being terminated.
So in fwlc_srv_reposition(), just do nothing if we've been removed from
the tree.

This should fix github issue #2919.

This should not be backported, unless commit
9fe72bba3cf3484577fa1ef00723de08df757996 is also backported.

---

diff --git a/src/lb_fwlc.c b/src/lb_fwlc.c
index c647336c5..354e03d17 100644
--- a/src/lb_fwlc.c
+++ b/src/lb_fwlc.c
@@ -330,6 +330,15 @@ static void fwlc_srv_reposition(struct server *s)
 		return;
 	}
 
+	/*
+	 * We're not in the tree, the server is probably down, don't
+	 * do anything.
+	 */
+	if (unlikely(!s->tree_elt)) {
+		HA_RWLOCK_RDUNLOCK(LBPRM_LOCK, &s->proxy->lbprm.lock);
+		_HA_ATOMIC_STORE(&s->lb_lock, 0);
+		return;
+	}
 	node = eb32_lookup(s->lb_tree, new_key);
 	if (node)
 		tree_elt = container_of(node, struct fwlc_tree_elt, lb_node);
@@ -462,8 +471,7 @@ static void fwlc_srv_reposition(struct server *s)
 
 	__ha_barrier_store();
 
-	if (s->tree_elt)
-                _HA_ATOMIC_DEC(&s->tree_elt->elements);
+	_HA_ATOMIC_DEC(&s->tree_elt->elements);
 
 	/*
 	 * Now lock the existing element, and its target list.