From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Thu, 2 Jan 2025 09:59:43 +0000 (+0100)
Subject: BUG/MAJOR: mux-quic: properly fix BUG_ON on empty STREAM emission
X-Git-Tag: v3.2-dev3~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ddfd8031f895b448604cbc259f74e6cb7b086b0b;p=thirdparty%2Fhaproxy.git

BUG/MAJOR: mux-quic: properly fix BUG_ON on empty STREAM emission

Properly fix BUG_ON() occurence when QUIC MUX emits only empty STREAM
frames. This was addressed by a previous patch but it causes another
regression so a revert was needed.

BUG_ON() on qcc_build_frms() return value is invalid. Indeed,
qcc_build_frms() may return 0, but this does not imply that frame list
is empty, as encoded frames can have a zero length payload. As such,
simply remove this invalid BUG_ON().

This must be backported up to 3.1.
---

diff --git a/src/mux_quic.c b/src/mux_quic.c
index e3fa05cb48..98b3af41dd 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -2389,7 +2389,9 @@ static int qcc_emit_rs_ss(struct qcc *qcc)
  * error occured during this step, this is considered as fatal. Tx frms is
  * cleared and 0 is returned.
  *
- * Returns the sum of encoded STREAM frames length or 0 if no frame built.
+ * Returns the sum of encoded payload STREAM frames length. Note that 0 can be
+ * returned either if no frame was built or only empty payload frames were
+ * encoded.
  */
 static int qcc_build_frms(struct qcc *qcc, struct list *qcs_failed)
 {
@@ -2505,10 +2507,8 @@ static int qcc_io_send(struct qcc *qcc)
 	/* Encode new STREAM frames if list has been previously cleared. */
 	if (LIST_ISEMPTY(frms) && !LIST_ISEMPTY(&qcc->send_list)) {
 		total = qcc_build_frms(qcc, &qcs_failed);
-		if (!total) {
-			BUG_ON(!LIST_ISEMPTY(frms));
+		if (LIST_ISEMPTY(frms))
 			goto out;
-		}
 	}
 
 	if (qcc_is_pacing_active(qcc->conn)) {