From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Wed, 22 Dec 2021 10:29:05 +0000 (+0100)
Subject: BUG/MINOR: quic: upgrade rdlock to wrlock for ODCID removal
X-Git-Tag: v2.6-dev1~229
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=250ac42754547ac86b9e947cc772e92aa5f3e22e;p=thirdparty%2Fhaproxy.git

BUG/MINOR: quic: upgrade rdlock to wrlock for ODCID removal

When a quic_conn is found in the DCID tree, it can be removed from the
first ODCID tree. However, this operation must absolutely be run under a
write-lock to avoid race condition. To avoid to use the lock too
frequently, node.leaf_p is checked. This value is set to NULL after
ebmb_delete.
---

diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 624cb35510..500814fd1f 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -3863,6 +3863,8 @@ static struct quic_conn *retrieve_qc_conn_from_cid(struct quic_rx_packet *pkt,
 	struct quic_conn *qc = NULL;
 	struct ebmb_node *node;
 	struct quic_connection_id *id;
+	/* set if the quic_conn is found in the second DCID tree */
+	int found_in_dcid = 0;
 
 	HA_RWLOCK_RDLOCK(QUIC_LOCK, &l->rx.cids_lock);
 
@@ -3892,14 +3894,21 @@ static struct quic_conn *retrieve_qc_conn_from_cid(struct quic_rx_packet *pkt,
 
 	id = ebmb_entry(node, struct quic_connection_id, node);
 	qc = id->qc;
+	found_in_dcid = 1;
+
+ end:
+	HA_RWLOCK_RDUNLOCK(QUIC_LOCK, &l->rx.cids_lock);
 
 	/* If found in DCIDs tree, remove the quic_conn from the ODCIDs tree.
 	 * If already done, this is a noop.
+	 *
+	 * node.leaf_p is first checked to avoid unnecessary locking.
 	 */
-	ebmb_delete(&qc->odcid_node);
-
- end:
-	HA_RWLOCK_RDUNLOCK(QUIC_LOCK, &l->rx.cids_lock);
+	if (found_in_dcid && qc->odcid_node.node.leaf_p) {
+		HA_RWLOCK_WRLOCK(QUIC_LOCK, &l->rx.cids_lock);
+		ebmb_delete(&qc->odcid_node);
+		HA_RWLOCK_WRUNLOCK(QUIC_LOCK, &l->rx.cids_lock);
+	}
 
 	return qc;
 }