BUG/MINOR: quic: ignore congestion window on probing for MUX wakeup

qc_notify_send() is used to wake up the MUX layer for sending. This
function first ensures that all sending condition are met to avoid to
wake up the MUX for unnecessarily.

One of this condition is to check if there is room in the congestion
window. However, when probe packets must be sent due to a PTO
expiration, RFC 9002 explicitely mentions that the congestion window
must be ignored which was not the case prior to this patch.

This commit fixes this by first setting <pto_probe> of 01RTT packet
space before invoking qc_notify_send(). This ensures that congestion
window won't be checked anymore to wake up the MUX layer until probing
packets are sent.

This commit replaces the following one which was not sufficient :
  commit e25fce03ebe3307bc104d1f81356108e271d2bc3
  BUG/MINOR: quic: Dysfunctional 01RTT packet number space probing

This should be backported up to 2.7.

diff --git a/src/quic_conn.c b/src/quic_conn.c
index 529e99777e87557fcf5f75f9108635a33988a0ee..f4a36f0e4ad8d81b16afc2b87143e603edfcd67d 100644 (file)
--- a/src/quic_conn.c
+++ b/src/quic_conn.c
@@ -5188,6 +5188,7 @@ struct task *qc_process_timer(struct task *task, void *ctx, unsigned int state)
                        }
                }
                else if (pktns == &qc->pktns[QUIC_TLS_PKTNS_01RTT]) {
+                       pktns->tx.pto_probe = QUIC_MAX_NB_PTO_DGRAMS;
                        /* Wake up upper layer if waiting to send new data. */
                        if (!qc_notify_send(qc)) {
                                TRACE_STATE("needs to probe 01RTT packet number space", QUIC_EV_CONN_TXPKT, qc);
@@ -8107,14 +8108,22 @@ void qc_notify_close(struct quic_conn *qc)
        TRACE_LEAVE(QUIC_EV_CONN_CLOSE, qc);
 }
 
-/* Wake-up upper layer if waiting for send to be ready.
+/* Wake-up upper layer for sending if all conditions are met :
+ * - room in congestion window or probe packet to sent
+ * - socket FD ready to sent or listener socket used
  *
  * Returns 1 if upper layer has been woken up else 0.
  */
 int qc_notify_send(struct quic_conn *qc)
 {
+       const struct quic_pktns *pktns = &qc->pktns[QUIC_TLS_PKTNS_01RTT];
+
        if (qc->subs && qc->subs->events & SUB_RETRY_SEND) {
-               if (quic_path_prep_data(qc->path) &&
+               /* RFC 9002 7.5. Probe Timeout
+                *
+                * Probe packets MUST NOT be blocked by the congestion controller.
+                */
+               if ((quic_path_prep_data(qc->path) || pktns->tx.pto_probe) &&
                    (!qc_test_fd(qc) || !fd_send_active(qc->fd))) {
                        tasklet_wakeup(qc->subs->tasklet);
                        qc->subs->events &= ~SUB_RETRY_SEND;