MINOR: mux_quic/pacing: display pacing info on show quic

To improve debugging, extend "show quic" output to report if pacing is
activated on a connection. Two values will be displayed for pacing :

* a new counter paced_sent_ctr is defined in QCC structure. It will be
  incremented each time an emission is interrupted due to pacing.

* pacing engine now saves the number of datagrams sent in the last paced
  emission. This will be helpful to ensure burst parameter is valid.

include/haproxy/mux_quic-t.h

@@ -71,6 +71,7 @@ struct qcc {
 		uint64_t buf_in_flight; /* sum of currently allocated Tx buffer sizes */
 		struct list frms; /* list of STREAM frames ready for sent */
 		struct quic_pacer pacer; /* engine used to pace emission */
+		int paced_sent_ctr; /* counter for when emission is interrupted due to pacing */
 	} tx;
 
 	uint64_t largest_bidi_r; /* largest remote bidi stream ID opened. */

include/haproxy/quic_pacing-t.h

@@ -7,6 +7,8 @@
 struct quic_pacer {
 	const struct quic_cc *cc; /* Congestion controler algo used for this connection */
 	ullong next; /* Nanosecond timestamp at which the next emission should be conducted */
+
+	int last_sent; /* Number of datagrams sent during last paced emission */
 };
 
 #endif /* _HAPROXY_QUIC_PACING_T_H */

src/mux_quic.c

@@ -2443,6 +2443,7 @@ static int qcc_io_send(struct qcc *qcc)
 		/* qcc_send_frames cannot return 1 if pacing not used. */
 		BUG_ON(!qcc_is_pacing_active(qcc->conn));
 		qcc_wakeup_pacing(qcc);
+		++qcc->tx.paced_sent_ctr;
 	}
 	else if (!LIST_ISEMPTY(&qcc->tx.frms)) {
 		/* Deallocate frames that the transport layer has rejected. */
@@ -2799,17 +2800,22 @@ static void qcc_purge_sending(struct qcc *qcc)
 	struct quic_pacer *pacer = &qcc->tx.pacer;
 	struct list *frms = &qcc->tx.frms;
 	enum quic_tx_err ret = QUIC_TX_ERR_PACING;
+	int sent = 0;
 
 	/* This function is reserved for pacing usage. */
 	BUG_ON(!qcc_is_pacing_active(qcc->conn));
 
 	/* Only restart emission if pacing delay is reached. */
-	if (quic_pacing_expired(pacer))
+	if (quic_pacing_expired(pacer)) {
 		ret = qc_send_mux(qcc->conn->handle.qc, frms, pacer);
+		sent = 1;
+	}
 
 	if (ret == QUIC_TX_ERR_PACING) {
 		BUG_ON(LIST_ISEMPTY(frms));
 		qcc_wakeup_pacing(qcc);
+		if (sent)
+			++qcc->tx.paced_sent_ctr;
 	}
 	else if (ret == QUIC_TX_ERR_FATAL) {
 		TRACE_DEVEL("error on sending", QMUX_EV_QCC_SEND, qcc->conn);
@@ -2960,8 +2966,10 @@ static int qmux_init(struct connection *conn, struct proxy *prx,
 
 	qcc->tx.buf_in_flight = 0;
 
-	if (qcc_is_pacing_active(conn))
+	if (qcc_is_pacing_active(conn)) {
 		quic_pacing_init(&qcc->tx.pacer, &conn->handle.qc->path->cc);
+		qcc->tx.paced_sent_ctr = 0;
+	}
 
 	if (conn_is_back(conn)) {
 		qcc->next_bidi_l    = 0x00;
@@ -3594,6 +3602,12 @@ void qcc_show_quic(struct qcc *qcc)
 	              qcc, qcc->flags, (ullong)qcc->nb_sc, (ullong)qcc->nb_hreq,
 	              (ullong)qcc->tx.buf_in_flight, (ullong)qc->path->cwnd);
 
+	if (qcc_is_pacing_active(qcc->conn)) {
+		chunk_appendf(&trash, "  pacing int_sent=%d last_sent=%d\n",
+		              qcc->tx.paced_sent_ctr,
+		              qcc->tx.pacer.last_sent);
+	}
+
 	node = eb64_first(&qcc->streams_by_id);
 	while (node) {
 		struct qcs *qcs = eb64_entry(node, struct qcs, by_id);

src/quic_pacing.c

@@ -12,4 +12,5 @@ int quic_pacing_expired(const struct quic_pacer *pacer)
 void quic_pacing_sent_done(struct quic_pacer *pacer, int sent)
 {
 	pacer->next = now_mono_time() + pacer->cc->algo->pacing_rate(pacer->cc) * sent;
+	pacer->last_sent = sent;
 }