Merge pull request #15968 from miri64/congure/feat/congure_abe

congure_abe: initial import of TCP Alternative Backoff with ECN for CongURE

sys/Makefile.dep

@@ -37,6 +37,10 @@ ifneq (,$(filter congure_%,$(USEMODULE)))
   USEMODULE += congure
 endif
 
+ifneq (,$(filter congure_abe,$(USEMODULE)))
+  USEMODULE += congure_reno_methods
+endif
+
 ifneq (,$(filter congure_quic,$(USEMODULE)))
   USEMODULE += ztimer_msec
 endif

sys/congure/Kconfig

@@ -8,6 +8,7 @@ if !TEST_KCONFIG
 menu "CongURE congestion control abstraction"
     depends on USEMODULE_CONGURE
 
+rsource "abe/Kconfig"
 rsource "mock/Kconfig"
 rsource "quic/Kconfig"
 rsource "reno/Kconfig"
@@ -23,6 +24,7 @@ menuconfig MODULE_CONGURE
 
 if MODULE_CONGURE
 
+rsource "abe/Kconfig"
 rsource "mock/Kconfig"
 rsource "quic/Kconfig"
 rsource "reno/Kconfig"

sys/congure/Makefile

@@ -1,3 +1,6 @@
+ifneq (,$(filter congure_abe,$(USEMODULE)))
+  DIRS += abe
+endif
 ifneq (,$(filter congure_quic,$(USEMODULE)))
   DIRS += quic
 endif

sys/congure/abe/Kconfig

@@ -0,0 +1,31 @@
+# Copyright (c) 2021 Freie Universität Berlin
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+if !TEST_KCONFIG
+
+menuconfig KCONFIG_USEMODULE_CONGURE_ABE
+    bool "Configure TCP-ABE-like congestion control"
+    depends on USEMODULE_CONGURE_ABE
+    help
+        Configure TCP-ABE-like congestion control via Kconfig.
+
+if KCONFIG_USEMODULE_CONGURE_ABE
+rsource "Kconfig.config"
+endif # KCONFIG_USEMODULE_CONGURE_ABE
+
+endif # !TEST_KCONFIG
+
+if TEST_KCONFIG
+menuconfig MODULE_CONGURE_ABE
+    bool "CongURE implementation of TCP ABE"
+    depends on MODULE_CONGURE
+    select MODULE_CONGURE_RENO_METHODS
+
+if MODULE_CONGURE_ABE
+rsource "Kconfig.config"
+endif # MODULE_CONGURE_ABE
+
+endif # TEST_KCONFIG

sys/congure/abe/Kconfig.config

@@ -0,0 +1,28 @@
+# Copyright (c) 2021 Freie Universität
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+#
+
+# XXX This file only is required since there is no easy way to use these config
+# options with both the final MODULE_CONGURE_ABE (used with TEST_KCONFIG=1) and
+# KCONFIG_USEMODULE_CONGURE_ABE (used with TEST_KCONFIG=0) in a # nicely looking
+# and easy to migrate way. After migration, the content of this file can be folded
+# back into `sys/congure/abe/Kconfig`
+
+config CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT
+    int "Default numerator of the ABE multiplier"
+    default 4
+    help
+        RFC 8511, section 3.1 defines the ABE multiplier to be 0.8 = 4/5, so
+        assuming CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT is 5, this should be
+        4.
+
+config CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT
+    int "Default denominator of the ABE multiplier"
+    default 5
+    help
+        RFC 8511, section 3.1 defines the ABE multiplier to be 0.8 = 4/5, so
+        assuming CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT is 4, this should be
+        5.

sys/congure/abe/Makefile

@@ -0,0 +1,3 @@
+MODULE := congure_abe
+
+include $(RIOTBASE)/Makefile.base

sys/congure/abe/congure_abe.c

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#include <stdint.h>
+
+#include "clist.h"
+#include "seq.h"
+
+#include "congure/abe.h"
+#include "congure/reno.h"
+
+static void _snd_report_ecn_ce(congure_snd_t *cong, ztimer_now_t time);
+
+static const congure_snd_driver_t _driver = {
+    .init = congure_reno_snd_init,
+    .inter_msg_interval = congure_reno_snd_inter_msg_interval,
+    .report_msg_sent = congure_reno_snd_report_msg_sent,
+    .report_msg_discarded = congure_reno_snd_report_msg_discarded,
+    .report_msgs_timeout = congure_reno_snd_report_msgs_timeout,
+    .report_msgs_lost = congure_reno_snd_report_msgs_lost,
+    .report_msg_acked = congure_reno_snd_report_msg_acked,
+    .report_ecn_ce = _snd_report_ecn_ce,
+};
+
+static void _snd_report_ecn_ce(congure_snd_t *cong, ztimer_now_t time)
+{
+    congure_abe_snd_t *c = (congure_abe_snd_t *)cong;
+    const congure_abe_snd_consts_t *consts =
+        container_of(c->consts, congure_abe_snd_consts_t, reno);
+    unsigned abe_product = (c->in_flight_size * consts->abe_multiplier_numerator)
+                           / consts->abe_multiplier_denominator;
+
+    (void)time;
+    c->ssthresh = (abe_product > (c->mss * 2)) ? abe_product : (c->mss * 2);
+    c->super.cwnd = c->ssthresh;
+}
+
+void congure_abe_snd_setup(congure_abe_snd_t *c,
+                           const congure_abe_snd_consts_t *consts)
+{
+    c->super.driver = &_driver;
+    c->consts = &consts->reno;
+}
+
+/** @} */

sys/include/congure/abe.h

@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    sys_congure_abe CongURE implementation of TCP ABE
+ * @ingroup     sys_congure
+ * @brief       Implementation of the TCP Alternative Backoff with ECN (ABE)
+ *              congestion control mechanism for the CongURE framework.
+ *
+ * @see [RFC 8511](https://tools.ietf.org/html/rfc8511)
+ * @{
+ *
+ * @file
+ * @brief
+ *
+ * @author  Martine S. Lenders <m.lenders@fu-berlin.de>
+ */
+#ifndef CONGURE_ABE_H
+#define CONGURE_ABE_H
+
+#include <stdint.h>
+
+#include "congure/config.h"
+#include "congure/reno.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Alias of CongURE Reno state object for CongURE ABE.
+ *
+ * @extends congure_reno_snd_t
+ */
+typedef congure_reno_snd_t congure_abe_snd_t;
+
+/**
+ * @brief   Constants for the congestion control.
+ *
+ * @extends congure_reno_snd_consts_t
+ */
+typedef struct {
+    congure_reno_snd_consts_t reno;     /**< TCP Reno constants */
+    /**
+     * @brief   numerator for the `beta_{ecn} `factor used to set the slow start
+     *          threshold on an ECN CE.
+     *
+     * Use @ref CONFIG_CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT for a default
+     * value
+     */
+    uint8_t abe_multiplier_numerator;
+    /**
+     * @brief   numerator for the `beta_{ecn} `factor used to set the slow start
+     *          threshold on an ECN CE.
+     *
+     * Use @ref CONFIG_CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT for a default
+     * value
+     */
+    uint8_t abe_multiplier_denominator;
+} congure_abe_snd_consts_t;
+
+/**
+ * @brief   Set's up the driver for a CongURE ABE object
+ *
+ * @param[in] c         A CongURE ABE object.
+ * @param[in] consts    The constants to use for @p c
+ */
+void congure_abe_snd_setup(congure_abe_snd_t *c,
+                           const congure_abe_snd_consts_t *consts);
+
+/**
+ * @brief   Set sender maximum segment size.
+ *
+ * @attention   This resets congure_reno_snd_t::cwnd to the new initial window
+ *              size based on @p mss. So use with care.
+ *
+ * @param[in] c     A CongURE state object
+ * @param[in] mss   Maximum segment size of the sender in caller-defined units
+ */
+static inline void congure_abe_set_mss(congure_abe_snd_t *c, unsigned mss)
+{
+    congure_reno_set_mss((congure_reno_snd_t *)c, mss);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CONGURE_ABE_H */
+/** @} */

sys/include/congure/config.h

@@ -24,6 +24,26 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Default numerator of the ABE multiplier (0.8)
+ *
+ * @note Use with @ref sys_congure_abe
+ * @see [RFC 8511, section 3.1](https://tools.ietf.org/html/rfc8511#section-3.1)
+ */
+#ifndef CONFIG_CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT
+#define CONFIG_CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT     (4U)
+#endif
+
+/**
+ * @brief   Default denominator of the ABE multiplier (0.8)
+ *
+ * @note Use with @ref sys_congure_abe
+ * @see [RFC 8511, section 3.1](https://tools.ietf.org/html/rfc8511#section-3.1)
+ */
+#ifndef CONFIG_CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT
+#define CONFIG_CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT   (5U)
+#endif
+
 #ifdef __cplusplus
 }
 #endif

tests/congure_abe/Makefile

@@ -0,0 +1,18 @@
+include ../Makefile.tests_common
+
+USEMODULE += congure_abe
+USEMODULE += congure_test
+USEMODULE += fmt
+USEMODULE += shell
+
+INCLUDES += -I$(CURDIR)
+
+include $(RIOTBASE)/Makefile.include
+
+ifndef CONFIG_SHELL_NO_ECHO
+  CFLAGS += -DCONFIG_SHELL_NO_ECHO=1
+endif
+
+ifndef CONFIG_CONGURE_TEST_LOST_MSG_POOL_SIZE
+  CFLAGS += -DCONFIG_CONGURE_TEST_LOST_MSG_POOL_SIZE=6
+endif

tests/congure_abe/Makefile.ci

@@ -0,0 +1,8 @@
+BOARD_INSUFFICIENT_MEMORY := \
+    arduino-duemilanove \
+    arduino-leonardo \
+    arduino-nano \
+    arduino-uno \
+    atmega328p \
+    atmega328p-xplained-mini \
+    #

tests/congure_abe/README.md

@@ -0,0 +1,30 @@
+Tests for the CongURE TCP ABE implementation
+=============================================
+
+This test tests the `congure_abe` implementation.
+
+Usage
+-----
+
+The test requires an up-to-date version of `riotctrl` with `rapidjson` support:
+
+```console
+$ pip install --upgrade riotctrl[rapidjson]
+```
+
+Then simply run the application using:
+
+```console
+$ BOARD="<board>" make flash test
+```
+
+It can also executed with pytest:
+
+```console
+$ pytest tests/01-run.py
+```
+
+Expected result
+---------------
+
+The application's test script passes without error code.

tests/congure_abe/app.config

@@ -0,0 +1,4 @@
+CONFIG_KCONFIG_USEMODULE_CONGURE_TEST=y
+CONFIG_KCONFIG_USEMODULE_SHELL=y
+CONFIG_CONGURE_TEST_LOST_MSG_POOL_SIZE=6
+CONFIG_SHELL_NO_ECHO=y

tests/congure_abe/app.config.test

@@ -0,0 +1,9 @@
+CONFIG_MODULE_CONGURE=y
+CONFIG_MODULE_CONGURE_ABE=y
+CONFIG_MODULE_CONGURE_TEST=y
+CONFIG_MODULE_FMT=y
+CONFIG_MODULE_SEQ=y
+CONFIG_MODULE_SHELL=y
+
+CONFIG_CONGURE_TEST_LOST_MSG_POOL_SIZE=6
+CONFIG_SHELL_NO_ECHO=y

tests/congure_abe/congure_impl.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#include <stdbool.h>
+#include "kernel_defines.h"
+
+#include "congure_impl.h"
+
+static unsigned _fr_calls;
+static bool _same_wnd_adv_res;
+
+static void _fr(congure_abe_snd_t *c);
+static bool _same_wnd_adv(congure_abe_snd_t *c, congure_snd_ack_t *ack);
+
+static const congure_abe_snd_consts_t _consts[] = {
+    {
+        .reno = {
+            .fr = _fr,
+            .same_wnd_adv = _same_wnd_adv,
+            .init_mss = 1460,
+            .cwnd_lower = 1095,
+            .cwnd_upper = 2190,
+            .init_ssthresh = CONGURE_WND_SIZE_MAX,
+            .frthresh = 3,
+        },
+        .abe_multiplier_numerator = CONFIG_CONGURE_ABE_MULTIPLIER_NUMERATOR_DEFAULT,
+        .abe_multiplier_denominator = CONFIG_CONGURE_ABE_MULTIPLIER_DENOMINATOR_DEFAULT,
+    }
+};
+
+int congure_test_snd_setup(congure_test_snd_t *c, unsigned id)
+{
+    if (id >= ARRAY_SIZE(_consts)) {
+        return -1;
+    }
+    _fr_calls = 0;
+    congure_abe_snd_setup(c, &_consts[id]);
+    return 0;
+}
+
+unsigned congure_abe_test_get_fr_calls(void)
+{
+    return _fr_calls;
+}
+
+void congure_abe_test_set_same_wnd_adv_res(bool value)
+{
+    _same_wnd_adv_res = value;
+}
+
+static void _fr(congure_abe_snd_t *c)
+{
+    (void)c;
+    _fr_calls++;
+}
+
+static bool _same_wnd_adv(congure_abe_snd_t *c, congure_snd_ack_t *ack)
+{
+    (void)c;
+    (void)ack;
+    return _same_wnd_adv_res;
+}
+
+/** @} */

tests/congure_abe/congure_impl.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ *
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+#ifndef CONGURE_IMPL_H
+#define CONGURE_IMPL_H
+
+#include "congure/abe.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef congure_abe_snd_t congure_test_snd_t;
+
+int congure_test_snd_setup(congure_test_snd_t *c, unsigned id);
+unsigned congure_abe_test_get_fr_calls(void);
+void congure_abe_test_set_same_wnd_adv_res(bool value);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CONGURE_IMPL_H */
+/** @} */

tests/congure_abe/main.c

@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Martine S. Lenders <m.lenders@fu-berlin.de>
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "clist.h"
+#include "congure/test.h"
+#include "fmt.h"
+#include "shell.h"
+
+#include "congure_impl.h"
+
+static int _json_statham(int argc, char **argv);
+static int _set_cwnd(int argc, char **argv);
+static int _get_fr_calls(int argc, char **argv);
+static int _set_same_wnd_adv_res(int argc, char **argv);
+
+static congure_abe_snd_t _congure_state;
+static const shell_command_t shell_commands[] = {
+    { "state", "Prints current CongURE state object as JSON", _json_statham },
+    { "set_cwnd", "Set cwnd member for CongURE state object", _set_cwnd },
+    { "get_ff_calls",
+      "Get the number of calls to fast_retransmit callback of CongURE state "
+      "object", _get_fr_calls },
+    { "set_same_wnd_adv",
+      "Set the result for the same_window_advertised callback of CongURE state "
+      "object", _set_same_wnd_adv_res },
+    { NULL, NULL, NULL }
+};
+
+int main(void)
+{
+    char line_buf[SHELL_DEFAULT_BUFSIZE];
+    shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE);
+    return 0;
+}
+
+congure_test_snd_t *congure_test_get_state(void)
+{
+    return &_congure_state;
+}
+
+#define PRINT_FIELD_PTR(obj_ptr, field) \
+    print_str("\"" #field "\":\"0x"); \
+    print_u32_hex((intptr_t)((obj_ptr)->field)); \
+    print_str("\",")
+
+#define PRINT_FIELD_UINT(obj, field) \
+    print_str("\"" #field "\":"); \
+    print_u32_dec((obj).field); \
+    print_str(",")
+
+static void _print_congure_abe_consts(const congure_abe_snd_consts_t *consts)
+{
+    print_str("\"consts\":");
+
+    if (consts) {
+        print_str("{");
+        PRINT_FIELD_PTR(&consts->reno, fr);
+        PRINT_FIELD_PTR(&consts->reno, same_wnd_adv);
+        PRINT_FIELD_PTR(&consts->reno, ss_cwnd_inc);
+        PRINT_FIELD_PTR(&consts->reno, ca_cwnd_inc);
+        PRINT_FIELD_PTR(&consts->reno, fr_cwnd_dec);
+        PRINT_FIELD_UINT(consts->reno, init_mss);
+        PRINT_FIELD_UINT(consts->reno, cwnd_upper);
+        PRINT_FIELD_UINT(consts->reno, cwnd_lower);
+        PRINT_FIELD_UINT(consts->reno, init_ssthresh);
+        PRINT_FIELD_UINT(consts->reno, frthresh);
+        PRINT_FIELD_UINT(*consts, abe_multiplier_numerator);
+        PRINT_FIELD_UINT(*consts, abe_multiplier_denominator);
+        print_str("},");
+    }
+    else {
+        print_str("null,");
+    }
+}
+
+static int _json_statham(int argc, char **argv)
+{
+    (void)argc;
+    (void)argv;
+    print_str("{");
+
+    PRINT_FIELD_UINT(_congure_state.super, cwnd);
+    _print_congure_abe_consts(
+        (congure_abe_snd_consts_t *)_congure_state.consts
+    );
+    PRINT_FIELD_UINT(_congure_state, mss);
+    PRINT_FIELD_UINT(_congure_state, last_ack);
+    PRINT_FIELD_UINT(_congure_state, ssthresh);
+    PRINT_FIELD_UINT(_congure_state, in_flight_size);
+    PRINT_FIELD_UINT(_congure_state, dup_acks);
+
+    print_str("}\n");
+    return 0;
+}
+
+static int _set_cwnd(int argc, char **argv)
+{
+    uint32_t tmp;
+
+    if (argc < 2) {
+        print_str("{\"error\":\"`cwnd` argument expected\"}");
+        return 1;
+    }
+    tmp = scn_u32_dec(argv[1], strlen(argv[1]));
+    if (tmp > CONGURE_WND_SIZE_MAX) {
+        print_str("{\"error\":\"`ssthresh` not 16 bit wide\"}\n");
+    }
+    _congure_state.super.cwnd = (congure_wnd_size_t)tmp;
+    return 0;
+}
+
+static int _get_fr_calls(int argc, char **argv)
+{
+    (void)argc;
+    (void)argv;
+
+    print_str("{\"fr_calls\":");
+    print_u32_dec(congure_abe_test_get_fr_calls());
+    print_str("}\n");
+    return 0;
+}
+
+static int _set_same_wnd_adv_res(int argc, char **argv)
+{
+    if (argc < 2) {
+        print_str("{\"error\":\"`value` argument expected\"}");
+        return 1;
+    }
+    congure_abe_test_set_same_wnd_adv_res(
+        (bool)scn_u32_dec(argv[1], strlen(argv[1]))
+    );
+    return 0;
+}
+
+/** @} */

tests/congure_abe/tests/01-run.py

@@ -0,0 +1,332 @@
+#! /usr/bin/env python3
+
+# Copyright (C) 2021 Freie Universität Berlin
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import logging
+import sys
+import unittest
+
+from riotctrl.ctrl import RIOTCtrl
+from riotctrl.shell.json import RapidJSONShellInteractionParser, rapidjson
+
+from riotctrl_shell.congure_test import CongureTest
+
+
+class TestCongUREBase(unittest.TestCase):
+    # pylint: disable=too-many-public-methods
+    # it's just one more ...
+    DEBUG = False
+
+    @classmethod
+    def setUpClass(cls):
+        cls.ctrl = RIOTCtrl()
+        cls.ctrl.start_term()
+        if cls.DEBUG:
+            cls.ctrl.term.logfile = sys.stdout
+        cls.ctrl.reset()
+        cls.shell = CongureTest(cls.ctrl)
+        cls.json_parser = RapidJSONShellInteractionParser()
+        cls.json_parser.set_parser_args(
+            parse_mode=rapidjson.PM_TRAILING_COMMAS
+        )
+        cls.logger = logging.getLogger(cls.__name__)
+        if cls.DEBUG:
+            cls.logger.setLevel(logging.DEBUG)
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.ctrl.stop_term()
+
+    def setUp(self):
+        self.shell.clear()
+
+    def tearDown(self):
+        self.shell.msgs_reset()
+
+    def _parse(self, res):
+        self.logger.debug(res)
+        if res.strip():
+            return self.json_parser.parse(res)
+        return None
+
+    def exec_cmd(self, cmd, timeout=-1, async_=False):
+        res = self.shell.cmd(cmd, timeout, async_)
+        return self._parse(res)
+
+    def assertSlowStart(self, state):
+        # pylint: disable=invalid-name
+        # trying to be in line with `unittest`
+        """
+        > The slow start algorithm is used when cwnd < ssthresh, while the
+        > congestion avoidance algorithm is used when cwnd > ssthresh.  When
+        > cwnd and ssthresh are equal, the sender may use either slow start or
+        > congestion avoidance.
+        """
+        self.assertLess(state['cwnd'], state['ssthresh'])
+
+    def assertInFastRetransmit(self, state):
+        # pylint: disable=invalid-name
+        # trying to be in line with `unittest`
+        """
+        > The TCP sender SHOULD use the "fast retransmit" algorithm to detect
+        > and repair loss, based on incoming duplicate ACKs.  The fast
+        > retransmit algorithm uses the arrival of 3 duplicate ACKs [...] as
+        > an indication that a segment has been lost.
+        """
+        self.assertGreaterEqual(state['dup_acks'], state['consts']['frthresh'])
+
+    def assertNotInFastRetransmit(self, state):
+        # pylint: disable=invalid-name
+        # trying to be in line with `unittest`
+        """Reverse of self.assertInFastRetransmit()"""
+        self.assertLess(state['dup_acks'], state['consts']['frthresh'])
+
+    def get_ff_calls(self):
+        res = self.exec_cmd('get_ff_calls')
+        return res['fr_calls']
+
+    def set_same_wnd_adv(self, value):
+        self.exec_cmd(f'set_same_wnd_adv {value:d}')
+
+    def set_cwnd(self, cwnd):
+        self.exec_cmd(f'set_cwnd {cwnd}')
+
+    def cong_state(self):
+        return self.exec_cmd('state')
+
+    def cong_init(self, ctx=0):
+        res = self.shell.init(ctx)
+        return self._parse(res)
+
+    def cong_report_msg_sent(self, msg_size):
+        res = self.shell.report_msg_sent(msg_size)
+        return self._parse(res)
+
+    def cong_report_msg_acked(self, msg, ack):
+        res = self.shell.report_msg_acked(msg, ack)
+        return self._parse(res)
+
+    def cong_report_ecn_ce(self, time):
+        res = self.shell.report_ecn_ce(time)
+        return self._parse(res)
+
+
+class TestCongUREABEWithoutSetup(TestCongUREBase):
+    def test_no_setup(self):
+        state = self.exec_cmd('state')
+        self.assertEqual(state, {
+            'cwnd': 0,
+            'consts': None,
+            'mss': 0,
+            'last_ack': 0,
+            'ssthresh': 0,
+            'in_flight_size': 0,
+            'dup_acks': 0,
+        })
+
+
+class TestCongUREABEDefaultInitTests(TestCongUREBase):
+    def setUp(self):
+        super().setUp()
+        res = self.shell.setup(0)
+        self.assertIn('success', res)
+
+    def test_setup(self):
+        state = self.cong_state()
+        self.assertIsNotNone(state['consts'])
+        # fast_retransmit and same_window_advertised need to be set to a
+        # function pointer
+        self.assertNotEqual(int(state['consts']['fr'], base=16), 0)
+        self.assertNotEqual(int(state['consts']['same_wnd_adv'], base=16), 0)
+        # ss_cwnd_inc, ca_cwnd_inc, fr_cwnd_dec are optional and setup 0 need
+        # to be set to a function pointer
+        self.assertEqual(int(state['consts']['ss_cwnd_inc'], base=16), 0)
+        self.assertEqual(int(state['consts']['ca_cwnd_inc'], base=16), 0)
+        self.assertEqual(int(state['consts']['fr_cwnd_dec'], base=16), 0)
+        self.assertEqual(state['consts']['init_mss'], 1460)
+        self.assertEqual(state['consts']['cwnd_lower'], 1095)
+        self.assertEqual(state['consts']['cwnd_upper'], 2190)
+        self.assertEqual(state['consts']['init_ssthresh'], 0xffff)
+        self.assertEqual(state['consts']['frthresh'], 3)
+        # https://tools.ietf.org/html/rfc8511#section-3.1
+        beta_ecn = (state['consts']['abe_multiplier_numerator'] /
+                    state['consts']['abe_multiplier_denominator'])
+        self.assertAlmostEqual(beta_ecn, 0.8)
+        self.assertEqual(state['consts']['frthresh'], 3)
+
+    def test_init(self):
+        """
+        This is inherited from `congure_reno`, so it should be the same as
+        in `tests/congure_reno`.
+
+        https://tools.ietf.org/html/rfc5681#section-3.1
+
+        > IW, the initial value of cwnd, MUST be set using the following
+        > guidelines as an upper bound.
+        >
+        > If SMSS > 2190 bytes:
+        >     IW = 2 * SMSS bytes and MUST NOT be more than 2 segments
+        > If (SMSS > 1095 bytes) and (SMSS <= 2190 bytes):
+        >     IW = 3 * SMSS bytes and MUST NOT be more than 3 segments
+        > if SMSS <= 1095 bytes:
+        >     IW = 4 * SMSS bytes and MUST NOT be more than 4 segments
+        """
+        res = self.cong_init()
+        self.assertIn('success', res)
+        state = self.cong_state()
+        self.assertEqual(state['consts']['init_mss'], state['mss'])
+        # (SMSS > 1095 bytes)
+        self.assertGreater(state['mss'], state['consts']['cwnd_lower'])
+        # (SMSS <= 2190 bytes)
+        self.assertLessEqual(state['mss'], state['consts']['cwnd_upper'])
+        # as such, IW = 3 * SMSS bytes
+        self.assertEqual(state['cwnd'], 3 * state['mss'])
+        # We start with slow start
+        self.assertSlowStart(state)
+        self.assertNotInFastRetransmit(state)
+
+
+class TestCongUREABE(TestCongUREBase):
+    """
+    Most functionality should be the same as for `congure_reno`, except
+    for the behavior of `report_ecn_ce`. So only test some basics from
+    `tests/congure_reno` and focus testing on `report_ecn_ce`
+    """
+    def setUp(self):
+        super().setUp()
+        res = self.shell.setup(0)
+        self.assertIn('success', res)
+        res = self.cong_init()
+        self.assertIn('success', res)
+
+    def _send_msg_and_recv_ack(self, msg_size, msg_resends=0,
+                               ack_id=15, ack_size=None, ack_clean=True):
+        # pylint: disable=too-many-arguments
+        # already reduced number of arguments, cong_report_msg_acked would
+        # need...
+        if ack_size is None:
+            # set ack_size to arbitrary value
+            ack_size = msg_size
+        res = self.cong_report_msg_sent(msg_size=msg_size)
+        self.assertIn('success', res)
+        state = self.cong_state()
+        self.assertEqual(state['in_flight_size'], msg_size)
+        res = self.cong_report_msg_acked(
+            msg={'send_time': 1000, 'size': msg_size, 'resends': msg_resends},
+            ack={'recv_time': 1100, 'id': ack_id, 'size': ack_size,
+                 'clean': ack_clean, 'wnd': 1234, 'delay': 0},
+        )
+        self.assertIn('success', res)
+
+    def test_slow_start_increase(self):
+        # pylint: disable=invalid-name
+        # name chosen to be in line with RFC
+        """
+        See test_slow_start_increase_large_N() from `tests/congure_reno`
+        """
+        state = self.cong_state()
+        init_cwnd = state['cwnd']
+        init_mss = state['mss']
+        init_ssthresh = state['ssthresh']
+        self.assertEqual(state['in_flight_size'], 0)
+        # pylint: disable=invalid-name
+        # name chosen to be in line with RFC
+        # set N to larger than SMSS
+        N = state['mss'] + 1337
+        self._send_msg_and_recv_ack(N)
+        state = self.cong_state()
+        # MSS did not change
+        self.assertEqual(state['mss'], init_mss)
+        self.assertEqual(state['cwnd'], init_cwnd + state['mss'])
+        self.assertEqual(state['in_flight_size'], 0)
+        self.assertEqual(state['ssthresh'], init_ssthresh)
+        self.assertNotInFastRetransmit(state)
+
+    def test_enter_fast_retransmit(self):
+        """
+        See self.test_enter_fast_retransmit_all_check_true() from
+        `tests/congure_reno`
+        """
+        state = self.cong_state()
+        self.assertEqual(0, self.get_ff_calls())
+        self.assertNotInFastRetransmit(state)
+        self.assertEqual(state['in_flight_size'], 0)
+        self._send_msg_and_recv_ack(42, ack_id=15, ack_size=0, ack_clean=True)
+        # make condition (a) true
+        self.cong_report_msg_sent(52)
+        state = self.cong_state()
+        self.assertEqual(state['in_flight_size'], 52)
+        # make condition (e) not true
+        self.set_same_wnd_adv(True)
+        # condition (b) ack['size'] == 0, (c) ack['clean'] == True,
+        # (d) ack['id'] == 15
+        for _ in range(3):
+            res = self.cong_report_msg_acked(
+                msg={'send_time': 1000, 'size': 42, 'resends': 0},
+                ack={'recv_time': 1100, 'id': 15, 'size': 0,
+                     'clean': True, 'wnd': 1234, 'delay': 0},
+            )
+            self.assertIn('success', res)
+        self.assertEqual(1, self.get_ff_calls())
+        self.assertInFastRetransmit(self.cong_state())
+
+    def test_ecn_ce_small_flight_size(self):
+        """
+        https://tools.ietf.org/html/rfc8511#section-3
+
+        > As permitted by RFC 8311, this document specifies a sender-side
+        > change to TCP where receipt of a packet with the ECN-Echo flag SHOULD
+        > trigger the TCP source to set the slow start threshold (ssthresh) to
+        > 0.8 times the FlightSize, with a lower bound of 2 * SMSS applied to
+        > the result (where SMSS stands for Sender Maximum Segment Size)).  As
+        > in [RFC5681], the TCP sender also reduces the cwnd value to no more
+        > than the new ssthresh value.  Section 6.1.2 of RFC 3168 provides
+        > guidance on setting a cwnd less than 2 * SMSS.
+        """
+        state = self.cong_state()
+        beta_ecn = (state['consts']['abe_multiplier_numerator'] /
+                    state['consts']['abe_multiplier_denominator'])
+        self.assertAlmostEqual(beta_ecn, 0.8)
+        flight_size = 150
+        # put some bytes in the air
+        self.cong_report_msg_sent(flight_size)
+        self.cong_report_ecn_ce(1204)
+        state = self.cong_state()
+        # [...] set the slow start threshold (ssthresh) to 0.8 times the
+        # FlightSize, with a lower bound of 2 * SMSS applied to the result
+        self.assertEqual(state['ssthresh'], 2 * state['mss'])
+        # the TCP sender also reduces the cwnd value to no more
+        # than the new ssthresh value
+        self.assertLessEqual(state['cwnd'], state['ssthresh'])
+
+    def test_ecn_ce_large_flight_size(self):
+        """
+        Same as test_ecn_ce_small_flight_size, but with flight size
+        larger than (2 * SMSS / 0.8)
+        """
+        state = self.cong_state()
+        beta_ecn = (state['consts']['abe_multiplier_numerator'] /
+                    state['consts']['abe_multiplier_denominator'])
+        self.assertAlmostEqual(beta_ecn, 0.8)
+        flight_size = 3 * state['mss']
+        # increase congestion window large enough to send all those bytes
+        self.set_cwnd(flight_size)
+        # put some bytes in the air
+        for _ in range(3):
+            self.cong_report_msg_sent(state['mss'])
+        self.cong_report_ecn_ce(1204)
+        state = self.cong_state()
+        # [...] set the slow start threshold (ssthresh) to 0.8 times the
+        # FlightSize, with a lower bound of 2 * SMSS applied to the result
+        self.assertEqual(state['ssthresh'], beta_ecn * flight_size)
+        # the TCP sender also reduces the cwnd value to no more
+        # than the new ssthresh value
+        self.assertLessEqual(state['cwnd'], state['ssthresh'])
+
+
+if __name__ == '__main__':
+    unittest.main()