Release 1.17.6

- Add failsafe: resume sending packets after some time

  The change puts a 1-second limit on the amount of time the engine
  will not send packets after some packets are delayed.  This makes
  the library robust in case the user does not unblock the engine
  explicitly using lsquic_engine_send_unsent_packets() call.

- [BUGFIX] Handle corner cases in send controller when packets are
  a) delayed or b) dropped during repackaging.

- [BUGFIX] Memory leak: destroy buffered packets during controller
  cleanup.

CHANGELOG

@@ -1,3 +1,17 @@
+2018-11-29
+    - 1.17.6
+    - Add failsafe: resume sending packets after some time
+
+      The change puts a 1-second limit on the amount of time the engine
+      will not send packets after some packets are delayed.  This makes
+      the library robust in case the user does not unblock the engine
+      explicitly using lsquic_engine_send_unsent_packets() call.
+
+    - [BUGFIX] Handle corner cases in send controller when packets are
+      a) delayed or b) dropped during repackaging.
+    - [BUGFIX] Memory leak: destroy buffered packets during controller
+      cleanup.
+
 2018-11-16
     - 1.17.3
     - [BUGFIX] Do not send STOP_WAITING frames when using Q044

include/lsquic.h

@@ -25,7 +25,7 @@ extern "C" {
 
 #define LSQUIC_MAJOR_VERSION 1
 #define LSQUIC_MINOR_VERSION 17
-#define LSQUIC_PATCH_VERSION 3
+#define LSQUIC_PATCH_VERSION 6
 
 /**
  * Engine flags:

src/liblsquic/lsquic_engine.c

@@ -61,6 +61,8 @@
 #define LSQUIC_LOGGER_MODULE LSQLM_ENGINE
 #include "lsquic_logger.h"
 
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
 
 /* The batch of outgoing packets grows and shrinks dynamically */
 #define MAX_OUT_BATCH_SIZE 1024
@@ -168,6 +170,7 @@ struct lsquic_engine
     lsquic_time_t                      last_sent;
     unsigned                           n_conns;
     lsquic_time_t                      deadline;
+    lsquic_time_t                      resume_sending_at;
     struct out_batch                   out_batch;
 };
 
@@ -1025,6 +1028,7 @@ send_batch (lsquic_engine_t *engine, struct conns_out_iter *conns_iter,
     if (n_sent < (int) n_to_send)
     {
         engine->pub.enp_flags &= ~ENPUB_CAN_SEND;
+        engine->resume_sending_at = now + 1000000;
         LSQ_DEBUG("cannot send packets");
         EV_LOG_GENERIC_EVENT("cannot send packets");
     }
@@ -1272,6 +1276,15 @@ process_connections (lsquic_engine_t *engine, conn_iter_f next_conn,
     TAILQ_INIT(&ticked_conns);
     reset_deadline(engine, now);
 
+    if (!(engine->pub.enp_flags & ENPUB_CAN_SEND)
+                                        && now > engine->resume_sending_at)
+    {
+        LSQ_NOTICE("failsafe activated: resume sending packets again after "
+                    "timeout");
+        EV_LOG_GENERIC_EVENT("resume sending packets again after timeout");
+        engine->pub.enp_flags |= ENPUB_CAN_SEND;
+    }
+
     i = 0;
     while ((conn = next_conn(engine))
           )
@@ -1412,8 +1425,8 @@ lsquic_engine_quic_versions (const lsquic_engine_t *engine)
 int
 lsquic_engine_earliest_adv_tick (lsquic_engine_t *engine, int *diff)
 {
-    const lsquic_time_t *next_time;
-    lsquic_time_t now;
+    const lsquic_time_t *next_attq_time;
+    lsquic_time_t now, next_time;
 
     if (((engine->flags & ENG_PAST_DEADLINE)
                                     && lsquic_mh_count(&engine->conns_out))
@@ -1423,12 +1436,24 @@ lsquic_engine_earliest_adv_tick (lsquic_engine_t *engine, int *diff)
         return 1;
     }
 
-    next_time = attq_next_time(engine->attq);
-    if (!next_time)
-        return 0;
+    next_attq_time = attq_next_time(engine->attq);
+    if (engine->pub.enp_flags & ENPUB_CAN_SEND)
+    {
+        if (next_attq_time)
+            next_time = *next_attq_time;
+        else
+            return 0;
+    }
+    else
+    {
+        if (next_attq_time)
+            next_time = MIN(*next_attq_time, engine->resume_sending_at);
+        else
+            next_time = engine->resume_sending_at;
+    }
 
     now = lsquic_time_now();
-    *diff = (int) ((int64_t) *next_time - (int64_t) now);
+    *diff = (int) ((int64_t) next_time - (int64_t) now);
     return 1;
 }
 

src/liblsquic/lsquic_packet_out.h

@@ -94,6 +94,7 @@ typedef struct lsquic_packet_out
         PO_IPv6     = (1 <<20),         /* Set if pmi_allocate was passed is_ipv6=1,
                                          *   otherwise unset.
                                          */
+        PO_LIMITED  = (1 <<21),         /* Used to credit sc_next_limit if needed. */
     }                  po_flags;
     enum quic_ft_bit   po_frame_types:16; /* Bitmask of QUIC_FRAME_* */
     unsigned short     po_data_sz;      /* Number of usable bytes in data */

src/liblsquic/lsquic_send_ctl.c

@@ -858,7 +858,8 @@ send_ctl_next_packno (lsquic_send_ctl_t *ctl)
 void
 lsquic_send_ctl_cleanup (lsquic_send_ctl_t *ctl)
 {
-    lsquic_packet_out_t *packet_out;
+    lsquic_packet_out_t *packet_out, *next;
+    unsigned n;
     lsquic_senhist_cleanup(&ctl->sc_senhist);
     while ((packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets)))
     {
@@ -881,6 +882,16 @@ lsquic_send_ctl_cleanup (lsquic_send_ctl_t *ctl)
         TAILQ_REMOVE(&ctl->sc_lost_packets, packet_out, po_next);
         send_ctl_destroy_packet(ctl, packet_out);
     }
+    for (n = 0; n < sizeof(ctl->sc_buffered_packets) /
+                                sizeof(ctl->sc_buffered_packets[0]); ++n)
+    {
+        for (packet_out = TAILQ_FIRST(&ctl->sc_buffered_packets[n].bpq_packets);
+                                                packet_out; packet_out = next)
+        {
+            next = TAILQ_NEXT(packet_out, po_next);
+            send_ctl_destroy_packet(ctl, packet_out);
+        }
+    }
     pacer_cleanup(&ctl->sc_pacer);
 #if LSQUIC_SEND_STATS
     LSQ_NOTICE("stats: n_total_sent: %u; n_resent: %u; n_delayed: %u",
@@ -1083,6 +1094,7 @@ lsquic_packet_out_t *
 lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
 {
     lsquic_packet_out_t *packet_out;
+    int dec_limit;
 
   get_packet:
     packet_out = TAILQ_FIRST(&ctl->sc_scheduled_packets);
@@ -1093,10 +1105,12 @@ lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
                     !(packet_out->po_frame_types & (1 << QUIC_FRAME_ACK)))
     {
         if (ctl->sc_next_limit)
-            --ctl->sc_next_limit;
+            dec_limit = 1;
         else
             return NULL;
     }
+    else
+        dec_limit = 0;
 
     send_ctl_sched_remove(ctl, packet_out);
     if (packet_out->po_flags & PO_REPACKNO)
@@ -1116,6 +1130,13 @@ lsquic_send_ctl_next_packet_to_send (lsquic_send_ctl_t *ctl)
     }
 
     ctl->sc_bytes_out += packet_out_total_sz(packet_out);
+    if (dec_limit)
+    {
+        --ctl->sc_next_limit;
+        packet_out->po_flags |= PO_LIMITED;
+    }
+    else
+        packet_out->po_flags &= ~PO_LIMITED;
     return packet_out;
 }
 
@@ -1126,6 +1147,8 @@ lsquic_send_ctl_delayed_one (lsquic_send_ctl_t *ctl,
 {
     send_ctl_sched_prepend(ctl, packet_out);
     ctl->sc_bytes_out -= packet_out_total_sz(packet_out);
+    if (packet_out->po_flags & PO_LIMITED)
+        ++ctl->sc_next_limit;
     LSQ_DEBUG("packet %"PRIu64" has been delayed", packet_out->po_packno);
 #if LSQUIC_SEND_STATS
     ++ctl->sc_stats.n_delayed;