Latest changes

- Do not create gap in sent packnos when squeezing delayed
  packets.
- sendctl checks for all unacked bytes, not just retx bytes.
- connections with blocked scheduled packets are not tickable
  for sending.

CHANGELOG

@@ -1,3 +1,11 @@
+2018-04-25
+
+    - [BUGFIX] Do not create gap in sent packnos when squeezing delayed
+      packets.
+    - [BUGFIX] sendctl checks for all unacked bytes, not just retx bytes.
+    - [BUGFIX] connections with blocked scheduled packets are not tickable
+      for sending.
+
 2018-04-23
 
     - Fix busy loop: tickable must make progress.  When connection is

src/liblsquic/lsquic_full_conn.c

@@ -2613,6 +2613,14 @@ write_is_possible (struct full_conn *conn)
 }
 
 
+static int
+should_generate_ack (const struct full_conn *conn)
+{
+    return (conn->fc_flags & FC_ACK_QUEUED)
+        || lsquic_send_ctl_lost_ack(&conn->fc_send_ctl);
+}
+
+
 static enum tick_st
 full_conn_ci_tick (lsquic_conn_t *lconn, lsquic_time_t now)
 {
@@ -2708,8 +2716,7 @@ full_conn_ci_tick (lsquic_conn_t *lconn, lsquic_time_t now)
         have_delayed_packets = lsquic_send_ctl_maybe_squeeze_sched(
                                                     &conn->fc_send_ctl);
 
-    if ((conn->fc_flags & FC_ACK_QUEUED) ||
-                            lsquic_send_ctl_lost_ack(&conn->fc_send_ctl))
+    if (should_generate_ack(conn))
     {
         if (have_delayed_packets)
             lsquic_send_ctl_reset_packnos(&conn->fc_send_ctl);
@@ -3317,7 +3324,9 @@ full_conn_ci_is_tickable (lsquic_conn_t *lconn)
     if (!TAILQ_EMPTY(&conn->fc_pub.service_streams))
         return 1;
 
-    if (lsquic_send_ctl_can_send(&conn->fc_send_ctl))
+    if (lsquic_send_ctl_can_send(&conn->fc_send_ctl)
+        && (should_generate_ack(conn) ||
+            !lsquic_send_ctl_sched_is_blocked(&conn->fc_send_ctl)))
     {
         if (lsquic_send_ctl_has_buffered(&conn->fc_send_ctl))
             return 1;

src/liblsquic/lsquic_send_ctl.c

@@ -885,6 +885,15 @@ send_ctl_retx_bytes_out (const struct lsquic_send_ctl *ctl)
 }
 
 
+static unsigned
+send_ctl_all_bytes_out (const struct lsquic_send_ctl *ctl)
+{
+    return ctl->sc_bytes_scheduled
+         + ctl->sc_bytes_unacked_all
+         + ctl->sc_bytes_out;
+}
+
+
 int
 lsquic_send_ctl_pacer_blocked (struct lsquic_send_ctl *ctl)
 {
@@ -902,9 +911,9 @@ __attribute__((weak))
 int
 lsquic_send_ctl_can_send (lsquic_send_ctl_t *ctl)
 {
-    const unsigned n_out = send_ctl_retx_bytes_out(ctl);
-    LSQ_DEBUG("%s: n_out: %u (unacked_retx: %u, out: %u); cwnd: %lu", __func__,
-        n_out, ctl->sc_bytes_unacked_retx, ctl->sc_bytes_out,
+    const unsigned n_out = send_ctl_all_bytes_out(ctl);
+    LSQ_DEBUG("%s: n_out: %u (unacked_all: %u, out: %u); cwnd: %lu", __func__,
+        n_out, ctl->sc_bytes_unacked_all, ctl->sc_bytes_out,
         lsquic_cubic_get_cwnd(&ctl->sc_cubic));
     if (ctl->sc_flags & SC_PACE)
     {
@@ -1041,6 +1050,21 @@ lsquic_send_ctl_scheduled_one (lsquic_send_ctl_t *ctl,
 }
 
 
+/* This mimics the logic in lsquic_send_ctl_next_packet_to_send(): we want
+ * to check whether the first scheduled packet cannot be sent.
+ */
+int
+lsquic_send_ctl_sched_is_blocked (const struct lsquic_send_ctl *ctl)
+{
+    const lsquic_packet_out_t *packet_out
+                            = TAILQ_FIRST(&ctl->sc_scheduled_packets);
+    return ctl->sc_n_consec_rtos
+        && 0 == ctl->sc_next_limit
+        && packet_out
+        && !(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK));
+}
+
+
 lsquic_packet_out_t *
 lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
 {
@@ -1298,6 +1322,28 @@ lsquic_send_ctl_set_tcid0 (lsquic_send_ctl_t *ctl, int tcid0)
 }
 
 
+/* Need to assign new packet numbers to all packets following the first
+ * dropped packet to eliminate packet number gap.
+ */
+static void
+send_ctl_repackno_sched_tail (struct lsquic_send_ctl *ctl,
+                              struct lsquic_packet_out *pre_dropped)
+{
+    struct lsquic_packet_out *packet_out;
+
+    assert(pre_dropped);
+
+    ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
+    for (packet_out = TAILQ_NEXT(pre_dropped, po_next); packet_out;
+                            packet_out = TAILQ_NEXT(packet_out, po_next))
+    {
+        packet_out->po_flags |= PO_REPACKNO;
+        if (packet_out->po_flags & PO_ENCRYPTED)
+            send_ctl_release_enc_data(ctl, packet_out);
+    }
+}
+
+
 /* The controller elides this STREAM frames of stream `stream_id' from
  * scheduled and buffered packets.  If a packet becomes empty as a result,
  * it is dropped.
@@ -1341,20 +1387,8 @@ lsquic_send_ctl_elide_stream_frames (lsquic_send_ctl_t *ctl, uint32_t stream_id)
         }
     }
 
-    /* Need to assign new packet numbers to all packets following the first
-     * dropped packet to eliminate packet number gap.
-     */
     if (pre_dropped)
-    {
-        ctl->sc_cur_packno = lsquic_senhist_largest(&ctl->sc_senhist);
-        for (packet_out = TAILQ_NEXT(pre_dropped, po_next); packet_out;
-                                packet_out = TAILQ_NEXT(packet_out, po_next))
-        {
-            packet_out->po_flags |= PO_REPACKNO;
-            if (packet_out->po_flags & PO_ENCRYPTED)
-                send_ctl_release_enc_data(ctl, packet_out);
-        }
-    }
+        send_ctl_repackno_sched_tail(ctl, pre_dropped);
 
     for (n = 0; n < sizeof(ctl->sc_buffered_packets) /
                                 sizeof(ctl->sc_buffered_packets[0]); ++n)
@@ -1456,10 +1490,12 @@ int
 lsquic_send_ctl_squeeze_sched (lsquic_send_ctl_t *ctl)
 {
     struct lsquic_packet_out *packet_out, *next;
+    struct lsquic_packet_out *pre_dropped;
 #ifndef NDEBUG
     int pre_squeeze_logged = 0;
 #endif
 
+    pre_dropped = NULL;
     for (packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets); packet_out;
                                                             packet_out = next)
     {
@@ -1477,6 +1513,9 @@ lsquic_send_ctl_squeeze_sched (lsquic_send_ctl_t *ctl)
                 LOG_PACKET_Q(&ctl->sc_scheduled_packets,
                                         "unacked packets before squeezing");
 #endif
+            if (!pre_dropped)
+                pre_dropped = TAILQ_PREV(packet_out, lsquic_packets_tailq,
+                                                                    po_next);
             send_ctl_sched_remove(ctl, packet_out);
             LSQ_DEBUG("Dropping packet %"PRIu64" from scheduled queue",
                 packet_out->po_packno);
@@ -1484,6 +1523,9 @@ lsquic_send_ctl_squeeze_sched (lsquic_send_ctl_t *ctl)
         }
     }
 
+    if (pre_dropped)
+        send_ctl_repackno_sched_tail(ctl, pre_dropped);
+
 #ifndef NDEBUG
     if (pre_squeeze_logged)
         LOG_PACKET_Q(&ctl->sc_scheduled_packets,

src/liblsquic/lsquic_send_ctl.h

@@ -276,4 +276,7 @@ lsquic_send_ctl_pacer_blocked (struct lsquic_send_ctl *);
     lsquic_send_ctl_sanity_check(ctl);                          \
 } while (0)
 
+int
+lsquic_send_ctl_sched_is_blocked (const struct lsquic_send_ctl *);
+
 #endif