dcsctp: Add Retransmission Error Counter

This is just a simple SCTP variable, but wrapped in its own object
for convenience.

Bug: webrtc:12614
Change-Id: I0c45c356488d21b71c72a936e4ceeee5ed0ec96d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214047
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33827}

net/dcsctp/tx/BUILD.gn

@@ -30,6 +30,17 @@ rtc_library("fcfs_send_queue") {
   ]
 }
 
+rtc_library("retransmission_error_counter") {
+  deps = [
+    "../../../rtc_base:checks",
+    "../../../rtc_base:rtc_base_approved",
+  ]
+  sources = [
+    "retransmission_error_counter.cc",
+    "retransmission_error_counter.h",
+  ]
+}
+
 if (rtc_include_tests) {
   rtc_source_set("mock_send_queue") {
     testonly = true
@@ -42,12 +53,16 @@ if (rtc_include_tests) {
 
     deps = [
       ":fcfs_send_queue",
+      ":retransmission_error_counter",
       "../../../api:array_view",
       "../../../rtc_base:checks",
       "../../../rtc_base:gunit_helpers",
       "../../../rtc_base:rtc_base_approved",
       "../../../test:test_support",
     ]
-    sources = [ "fcfs_send_queue_test.cc" ]
+    sources = [
+      "fcfs_send_queue_test.cc",
+      "retransmission_error_counter_test.cc",
+    ]
   }
 }

net/dcsctp/tx/retransmission_error_counter.cc

@@ -0,0 +1,37 @@
+/*
+ *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "net/dcsctp/tx/retransmission_error_counter.h"
+
+#include "absl/strings/string_view.h"
+#include "rtc_base/logging.h"
+
+namespace dcsctp {
+bool RetransmissionErrorCounter::Increment(absl::string_view reason) {
+  ++counter_;
+  if (counter_ > limit_) {
+    RTC_DLOG(INFO) << log_prefix_ << reason
+                   << ", too many retransmissions, counter=" << counter_;
+    return false;
+  }
+
+  RTC_DLOG(LS_VERBOSE) << log_prefix_ << reason << ", new counter=" << counter_
+                       << ", max=" << limit_;
+  return true;
+}
+
+void RetransmissionErrorCounter::Clear() {
+  if (counter_ > 0) {
+    RTC_DLOG(LS_VERBOSE) << log_prefix_
+                         << "recovered from counter=" << counter_;
+    counter_ = 0;
+  }
+}
+
+}  // namespace dcsctp

net/dcsctp/tx/retransmission_error_counter.h

@@ -0,0 +1,51 @@
+/*
+ *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef NET_DCSCTP_TX_RETRANSMISSION_ERROR_COUNTER_H_
+#define NET_DCSCTP_TX_RETRANSMISSION_ERROR_COUNTER_H_
+
+#include <functional>
+#include <string>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+#include "net/dcsctp/public/dcsctp_options.h"
+
+namespace dcsctp {
+
+// The RetransmissionErrorCounter is a simple counter with a limit, and when
+// the limit is exceeded, the counter is exhausted and the connection will
+// be closed. It's incremented on retransmission errors, such as the T3-RTX
+// timer expiring, but also missing heartbeats and stream reset requests.
+class RetransmissionErrorCounter {
+ public:
+  RetransmissionErrorCounter(absl::string_view log_prefix,
+                             const DcSctpOptions& options)
+      : log_prefix_(std::string(log_prefix) + "rtx-errors: "),
+        limit_(options.max_retransmissions) {}
+
+  // Increments the retransmission timer. If the maximum error count has been
+  // reached, `false` will be returned.
+  bool Increment(absl::string_view reason);
+  bool IsExhausted() const { return counter_ > limit_; }
+
+  // Clears the retransmission errors.
+  void Clear();
+
+  // Returns its current value
+  int value() const { return counter_; }
+
+ private:
+  const std::string log_prefix_;
+  const int limit_;
+  int counter_ = 0;
+};
+}  // namespace dcsctp
+
+#endif  // NET_DCSCTP_TX_RETRANSMISSION_ERROR_COUNTER_H_

net/dcsctp/tx/retransmission_error_counter_test.cc

@@ -0,0 +1,76 @@
+/*
+ *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "net/dcsctp/tx/retransmission_error_counter.h"
+
+#include "net/dcsctp/public/dcsctp_options.h"
+#include "rtc_base/gunit.h"
+#include "test/gmock.h"
+
+namespace dcsctp {
+namespace {
+
+TEST(RetransmissionErrorCounterTest, HasInitialValue) {
+  DcSctpOptions options;
+  RetransmissionErrorCounter counter("log: ", options);
+  EXPECT_EQ(counter.value(), 0);
+}
+
+TEST(RetransmissionErrorCounterTest, ReturnsFalseAtMaximumValue) {
+  DcSctpOptions options;
+  options.max_retransmissions = 5;
+  RetransmissionErrorCounter counter("log: ", options);
+  EXPECT_TRUE(counter.Increment("test"));   // 1
+  EXPECT_TRUE(counter.Increment("test"));   // 2
+  EXPECT_TRUE(counter.Increment("test"));   // 3
+  EXPECT_TRUE(counter.Increment("test"));   // 4
+  EXPECT_TRUE(counter.Increment("test"));   // 5
+  EXPECT_FALSE(counter.Increment("test"));  // Too many retransmissions
+}
+
+TEST(RetransmissionErrorCounterTest, CanHandleZeroRetransmission) {
+  DcSctpOptions options;
+  options.max_retransmissions = 0;
+  RetransmissionErrorCounter counter("log: ", options);
+  EXPECT_FALSE(counter.Increment("test"));  // One is too many.
+}
+
+TEST(RetransmissionErrorCounterTest, IsExhaustedAtMaximum) {
+  DcSctpOptions options;
+  options.max_retransmissions = 3;
+  RetransmissionErrorCounter counter("log: ", options);
+  EXPECT_TRUE(counter.Increment("test"));  // 1
+  EXPECT_FALSE(counter.IsExhausted());
+  EXPECT_TRUE(counter.Increment("test"));  // 2
+  EXPECT_FALSE(counter.IsExhausted());
+  EXPECT_TRUE(counter.Increment("test"));  // 3
+  EXPECT_FALSE(counter.IsExhausted());
+  EXPECT_FALSE(counter.Increment("test"));  // Too many retransmissions
+  EXPECT_TRUE(counter.IsExhausted());
+  EXPECT_FALSE(counter.Increment("test"));  // One after too many
+  EXPECT_TRUE(counter.IsExhausted());
+}
+
+TEST(RetransmissionErrorCounterTest, ClearingCounter) {
+  DcSctpOptions options;
+  options.max_retransmissions = 3;
+  RetransmissionErrorCounter counter("log: ", options);
+  EXPECT_TRUE(counter.Increment("test"));  // 1
+  EXPECT_TRUE(counter.Increment("test"));  // 2
+  counter.Clear();
+  EXPECT_TRUE(counter.Increment("test"));  // 1
+  EXPECT_TRUE(counter.Increment("test"));  // 2
+  EXPECT_TRUE(counter.Increment("test"));  // 3
+  EXPECT_FALSE(counter.IsExhausted());
+  EXPECT_FALSE(counter.Increment("test"));  // Too many retransmissions
+  EXPECT_TRUE(counter.IsExhausted());
+}
+
+}  // namespace
+}  // namespace dcsctp