Release 2.24.5

- [FEATURE] Improve Delayed ACKs extension and turn it on by default.
- Limit receive history to a finite amount of memory.

CHANGELOG

@@ -1,3 +1,8 @@
+2020-11-24
+    - 2.24.5
+    - [FEATURE] Improve Delayed ACKs extension and turn it on by default.
+    - Limit receive history to a finite amount of memory.
+
 2020-11-18
     - 2.24.4
     - [BUGFIX] Check whether ECN counts are set in ACK struct before using

bin/test_common.c

@@ -1857,6 +1857,11 @@ set_engine_option (struct lsquic_engine_settings *settings,
             settings->es_base_plpmtu = atoi(val);
             return 0;
         }
+        if (0 == strncmp(name, "ptpc_target", 11))
+        {
+            settings->es_ptpc_target = atof(val);
+            return 0;
+        }
         break;
     case 12:
         if (0 == strncmp(name, "idle_conn_to", 12))
@@ -1921,6 +1926,11 @@ set_engine_option (struct lsquic_engine_settings *settings,
             settings->es_ext_http_prio = atoi(val);
             return 0;
         }
+        if (0 == strncmp(name, "ptpc_int_gain", 13))
+        {
+            settings->es_ptpc_int_gain = atof(val);
+            return 0;
+        }
         break;
     case 14:
         if (0 == strncmp(name, "max_streams_in", 14))
@@ -1933,6 +1943,11 @@ set_engine_option (struct lsquic_engine_settings *settings,
             settings->es_progress_check = atoi(val);
             return 0;
         }
+        if (0 == strncmp(name, "ptpc_prop_gain", 14))
+        {
+            settings->es_ptpc_prop_gain = atof(val);
+            return 0;
+        }
         break;
     case 15:
         if (0 == strncmp(name, "allow_migration", 15))
@@ -1945,6 +1960,16 @@ set_engine_option (struct lsquic_engine_settings *settings,
             settings->es_grease_quic_bit = atoi(val);
             return 0;
         }
+        if (0 == strncmp(name, "ptpc_dyn_target", 15))
+        {
+            settings->es_ptpc_dyn_target = atoi(val);
+            return 0;
+        }
+        if (0 == strncmp(name, "ptpc_err_thresh", 15))
+        {
+            settings->es_ptpc_err_thresh = atof(val);
+            return 0;
+        }
         break;
     case 16:
         if (0 == strncmp(name, "proc_time_thresh", 16))
@@ -1957,6 +1982,21 @@ set_engine_option (struct lsquic_engine_settings *settings,
             settings->es_qpack_experiment = atoi(val);
             return 0;
         }
+        if (0 == strncmp(name, "ptpc_periodicity", 16))
+        {
+            settings->es_ptpc_periodicity = atoi(val);
+            return 0;
+        }
+        if (0 == strncmp(name, "ptpc_max_packtol", 16))
+        {
+            settings->es_ptpc_max_packtol = atoi(val);
+            return 0;
+        }
+        if (0 == strncmp(name, "ptpc_err_divisor", 16))
+        {
+            settings->es_ptpc_err_divisor = atof(val);
+            return 0;
+        }
         break;
     case 18:
         if (0 == strncmp(name, "qpack_enc_max_size", 18))

docs/apiref.rst

@@ -743,9 +743,6 @@ settings structure:
 
        Enable delayed ACKs extension.  Allowed values are 0 and 1.
 
-       **Warning**: this is an experimental feature.  Using it will most likely
-       lead to degraded performance.
-
        Default value is :macro:`LSQUIC_DF_DELAYED_ACKS`
 
     .. member:: int             es_timestamps
@@ -1036,7 +1033,7 @@ out of date.  Please check your :file:`lsquic.h` for actual values.*
 
 .. macro:: LSQUIC_DF_DELAYED_ACKS
 
-    Delayed ACKs are off by default.
+    The Delayed ACKs extension is on by default.
 
 .. macro:: LSQUIC_DF_MAX_UDP_PAYLOAD_SIZE_RX
 

docs/conf.py

@@ -26,7 +26,7 @@
 # The short X.Y version
 version = u'2.24'
 # The full version, including alpha/beta/rc tags
-release = u'2.24.4'
+release = u'2.24.5'
 
 
 # -- General configuration ---------------------------------------------------

include/lsquic.h

@@ -25,7 +25,7 @@ extern "C" {
 
 #define LSQUIC_MAJOR_VERSION 2
 #define LSQUIC_MINOR_VERSION 24
-#define LSQUIC_PATCH_VERSION 4
+#define LSQUIC_PATCH_VERSION 5
 
 /**
  * Engine flags:
@@ -350,8 +350,21 @@ typedef struct ssl_ctx_st * (*lsquic_lookup_cert_f)(
 /** Turn spin bit on by default */
 #define LSQUIC_DF_SPIN 1
 
-/** Turn off delayed ACKs extension by default */
-#define LSQUIC_DF_DELAYED_ACKS 0
+/** Turn on delayed ACKs extension by default */
+#define LSQUIC_DF_DELAYED_ACKS 1
+
+/**
+ * Defaults for the Packet Tolerance PID Controller (PTPC) used by the
+ * Delayed ACKs extension:
+ */
+#define LSQUIC_DF_PTPC_PERIODICITY 3
+#define LSQUIC_DF_PTPC_MAX_PACKTOL 150
+#define LSQUIC_DF_PTPC_DYN_TARGET 1
+#define LSQUIC_DF_PTPC_TARGET 1.0
+#define LSQUIC_DF_PTPC_PROP_GAIN 0.8
+#define LSQUIC_DF_PTPC_INT_GAIN 0.35
+#define LSQUIC_DF_PTPC_ERR_THRESH 0.05
+#define LSQUIC_DF_PTPC_ERR_DIVISOR 0.05
 
 /** Turn on timestamp extension by default */
 #define LSQUIC_DF_TIMESTAMPS 1
@@ -847,9 +860,6 @@ struct lsquic_engine_settings {
     /**
      * Enable delayed ACKs extension.  Allowed values are 0 and 1.
      *
-     * Warning: this is an experimental feature.  Using it will most likely
-     * lead to degraded performance.
-     *
      * Default value is @ref LSQUIC_DF_DELAYED_ACKS
      */
     int             es_delayed_acks;
@@ -962,6 +972,39 @@ struct lsquic_engine_settings {
      * Default value is @ref LSQUIC_DF_QPACK_EXPERIMENT.
      */
     int             es_qpack_experiment;
+
+    /**
+     * Settings for the Packet Tolerance PID Controller (PTPC) used for
+     * the Delayed ACKs logic.  Periodicity is how often the number of
+     * incoming ACKs is sampled.  Periodicity's units is the number of
+     * RTTs. Target is the average number of incoming ACKs per RTT we
+     * want to achieve.  Error threshold defines the range of error values
+     * within which no action is taken.  For example, error threshold of
+     * 0.03 means that adjustment actions will be taken only when the
+     * error is outside of the [-0.03, 0.03] range.  Proportional and
+     * integral gains have their usual meanings described here:
+     *      https://en.wikipedia.org/wiki/PID_controller#Controller_theory
+     *
+     * The average is normalized as follows:
+     *    AvgNormalized = Avg * e / Target      # Where 'e' is 2.71828...
+     *
+     * The error is then calculated as ln(AvgNormalized) - 1.  This gives
+     * us a logarithmic scale that is convenient to use for adjustment
+     * calculations.  The error divisor is used to calculate the packet
+     * tolerance adjustment:
+     *    Adjustment = Error / ErrorDivisor
+     *
+     * WARNING.  The library comes with sane defaults.  Only fiddle with
+     * these knobs if you know what you are doing.
+     */
+    unsigned es_ptpc_periodicity;   /* LSQUIC_DF_PTPC_PERIODICITY */
+    unsigned es_ptpc_max_packtol;   /* LSQUIC_DF_PTPC_MAX_PACKTOL */
+    int      es_ptpc_dyn_target;    /* LSQUIC_DF_PTPC_DYN_TARGET */
+    float    es_ptpc_target,        /* LSQUIC_DF_PTPC_TARGET */
+             es_ptpc_prop_gain,     /* LSQUIC_DF_PTPC_PROP_GAIN */
+             es_ptpc_int_gain,      /* LSQUIC_DF_PTPC_INT_GAIN */
+             es_ptpc_err_thresh,    /* LSQUIC_DF_PTPC_ERR_THRESH */
+             es_ptpc_err_divisor;   /* LSQUIC_DF_PTPC_ERR_DIVISOR */
 };
 
 /* Initialize `settings' to default values */

src/liblsquic/lsquic_alarmset.c

@@ -48,6 +48,7 @@ const char *const lsquic_alid2str[] =
     [AL_SESS_TICKET] = "SESS_TICKET",
     [AL_BLOCKED_KA] = "BLOCKED_KA",
     [AL_MTU_PROBE]  = "MTU_PROBE",
+    [AL_PACK_TOL]   = "PACK_TOL",
 };
 
 

src/liblsquic/lsquic_alarmset.h

@@ -38,6 +38,7 @@ enum alarm_id {
     AL_PATH_CHAL_3,
     AL_SESS_TICKET,
     AL_BLOCKED_KA,      /* Blocked Keep-Alive */
+    AL_PACK_TOL,        /* Calculate packet tolerance */
     MAX_LSQUIC_ALARMS
 };
 
@@ -59,6 +60,7 @@ enum alarm_id_bit {
     ALBIT_SESS_TICKET = 1 << AL_SESS_TICKET,
     ALBIT_BLOCKED_KA  = 1 << AL_BLOCKED_KA,
     ALBIT_MTU_PROBE = 1 << AL_MTU_PROBE,
+    ALBIT_PACK_TOL = 1 << AL_PACK_TOL,
 };
 
 
@@ -92,6 +94,9 @@ lsquic_alarmset_init_alarm (lsquic_alarmset_t *, enum alarm_id,
 #define lsquic_alarmset_are_set(alarmset, flags) \
                             ((alarmset)->as_armed_set & (flags))
 
+#define lsquic_alarmset_is_inited(alarmset_, al_id_) (                  \
+    (alarmset_)->as_alarms[al_id_].callback)
+
 /* Timers "fire," alarms "ring." */
 void
 lsquic_alarmset_ring_expired (lsquic_alarmset_t *, lsquic_time_t now);

src/liblsquic/lsquic_enc_sess_ietf.c

@@ -647,8 +647,10 @@ gen_trans_params (struct enc_sess_iquic *enc_sess, unsigned char *buf,
     }
     if (settings->es_delayed_acks)
     {
-        params.tp_numerics[TPI_MIN_ACK_DELAY] = 10000;    /* TODO: make into a constant? make configurable? */
+        params.tp_numerics[TPI_MIN_ACK_DELAY] = TP_MIN_ACK_DELAY;
         params.tp_set |= 1 << TPI_MIN_ACK_DELAY;
+        params.tp_numerics[TPI_MIN_ACK_DELAY_02] = TP_MIN_ACK_DELAY;
+        params.tp_set |= 1 << TPI_MIN_ACK_DELAY_02;
     }
     if (settings->es_timestamps)
     {
@@ -1687,6 +1689,17 @@ get_peer_transport_params (struct enc_sess_iquic *enc_sess)
     }
 
     LSQ_DEBUG("have peer transport parameters (%zu bytes)", bufsz);
+    if (LSQ_LOG_ENABLED(LSQ_LOG_DEBUG))
+    {
+        params_str = lsquic_mm_get_4k(&enc_sess->esi_enpub->enp_mm);
+        if (params_str)
+        {
+            lsquic_hexdump(params_buf, bufsz, params_str, 0x1000);
+            LSQ_DEBUG("transport parameters (%zd bytes):\n%s", bufsz,
+                                                            params_str);
+            lsquic_mm_put_4k(&enc_sess->esi_enpub->enp_mm, params_str);
+        }
+    }
     if (0 > (version == LSQVER_ID27 ? lsquic_tp_decode_27
                 : lsquic_tp_decode)(params_buf, bufsz,
                             !(enc_sess->esi_flags & ESI_SERVER),
@@ -3343,8 +3356,10 @@ lsquic_enc_sess_ietf_gen_quic_ctx (
     }
     if (settings->es_delayed_acks)
     {
-        params.tp_numerics[TPI_MIN_ACK_DELAY] = 10000;    /* TODO: make into a constant? make configurable? */
+        params.tp_numerics[TPI_MIN_ACK_DELAY] = TP_MIN_ACK_DELAY;
         params.tp_set |= 1 << TPI_MIN_ACK_DELAY;
+        params.tp_numerics[TPI_MIN_ACK_DELAY_02] = TP_MIN_ACK_DELAY;
+        params.tp_set |= 1 << TPI_MIN_ACK_DELAY_02;
     }
     if (settings->es_timestamps)
     {

src/liblsquic/lsquic_engine.c

@@ -382,6 +382,14 @@ lsquic_engine_init_settings (struct lsquic_engine_settings *settings,
     settings->es_cc_rtt_thresh   = LSQUIC_DF_CC_RTT_THRESH;
     settings->es_optimistic_nat  = LSQUIC_DF_OPTIMISTIC_NAT;
     settings->es_ext_http_prio   = LSQUIC_DF_EXT_HTTP_PRIO;
+    settings->es_ptpc_periodicity= LSQUIC_DF_PTPC_PERIODICITY;
+    settings->es_ptpc_max_packtol= LSQUIC_DF_PTPC_MAX_PACKTOL;
+    settings->es_ptpc_dyn_target = LSQUIC_DF_PTPC_DYN_TARGET;
+    settings->es_ptpc_target     = LSQUIC_DF_PTPC_TARGET;
+    settings->es_ptpc_prop_gain  = LSQUIC_DF_PTPC_PROP_GAIN;
+    settings->es_ptpc_int_gain   = LSQUIC_DF_PTPC_INT_GAIN;
+    settings->es_ptpc_err_thresh = LSQUIC_DF_PTPC_ERR_THRESH;
+    settings->es_ptpc_err_divisor= LSQUIC_DF_PTPC_ERR_DIVISOR;
 }
 
 

src/liblsquic/lsquic_full_conn.c

@@ -81,6 +81,9 @@ enum stream_if { STREAM_IF_STD, STREAM_IF_HSK, STREAM_IF_HDR, N_STREAM_IFS };
 #define MAX_RETR_PACKETS_SINCE_LAST_ACK 2
 #define ACK_TIMEOUT                     25000
 
+/* Maximum number of ACK ranges that can fit into gQUIC ACK frame */
+#define MAX_ACK_RANGES 256
+
 /* IMPORTANT: Keep values of FC_SERVER and FC_HTTP same as LSENG_SERVER
  * and LSENG_HTTP.
  */
@@ -661,7 +664,7 @@ new_conn_common (lsquic_cid_t cid, struct lsquic_engine_public *enpub,
     conn->fc_pub.all_streams = lsquic_hash_create();
     if (!conn->fc_pub.all_streams)
         goto cleanup_on_error;
-    lsquic_rechist_init(&conn->fc_rechist, 0);
+    lsquic_rechist_init(&conn->fc_rechist, 0, MAX_ACK_RANGES);
     if (conn->fc_flags & FC_HTTP)
     {
         conn->fc_pub.u.gquic.hs = lsquic_headers_stream_new(
@@ -4411,7 +4414,7 @@ lsquic_gquic_full_conn_srej (struct lsquic_conn *lconn)
 
     /* Reset receive history */
     lsquic_rechist_cleanup(&conn->fc_rechist);
-    lsquic_rechist_init(&conn->fc_rechist, 0);
+    lsquic_rechist_init(&conn->fc_rechist, 0, MAX_ACK_RANGES);
 
     /* Reset send controller state */
     lsquic_send_ctl_cleanup(&conn->fc_send_ctl);