1 files changed, 196 insertions, 0 deletions
diff --git a/third_party/libwebrtc/net/dcsctp/socket/heartbeat_handler.cc b/third_party/libwebrtc/net/dcsctp/socket/heartbeat_handler.cc
new file mode 100644
index 0000000000..9588b85b59
--- /dev/null
+++ b/third_party/libwebrtc/net/dcsctp/socket/heartbeat_handler.cc
@@ -0,0 +1,196 @@
+/*
+ *  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/socket/heartbeat_handler.h"
+
+#include <stddef.h>
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/functional/bind_front.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "net/dcsctp/packet/bounded_byte_reader.h"
+#include "net/dcsctp/packet/bounded_byte_writer.h"
+#include "net/dcsctp/packet/chunk/heartbeat_ack_chunk.h"
+#include "net/dcsctp/packet/chunk/heartbeat_request_chunk.h"
+#include "net/dcsctp/packet/parameter/heartbeat_info_parameter.h"
+#include "net/dcsctp/packet/parameter/parameter.h"
+#include "net/dcsctp/packet/sctp_packet.h"
+#include "net/dcsctp/public/dcsctp_options.h"
+#include "net/dcsctp/public/dcsctp_socket.h"
+#include "net/dcsctp/socket/context.h"
+#include "net/dcsctp/timer/timer.h"
+#include "rtc_base/logging.h"
+
+namespace dcsctp {
+
+// This is stored (in serialized form) as HeartbeatInfoParameter sent in
+// HeartbeatRequestChunk and received back in HeartbeatAckChunk. It should be
+// well understood that this data may be modified by the peer, so it can't
+// be trusted.
+//
+// It currently only stores a timestamp, in millisecond precision, to allow for
+// RTT measurements. If that would be manipulated by the peer, it would just
+// result in incorrect RTT measurements, which isn't an issue.
+class HeartbeatInfo {
+ public:
+  static constexpr size_t kBufferSize = sizeof(uint64_t);
+  static_assert(kBufferSize == 8, "Unexpected buffer size");
+
+  explicit HeartbeatInfo(TimeMs created_at) : created_at_(created_at) {}
+
+  std::vector<uint8_t> Serialize() {
+    uint32_t high_bits = static_cast<uint32_t>(*created_at_ >> 32);
+    uint32_t low_bits = static_cast<uint32_t>(*created_at_);
+
+    std::vector<uint8_t> data(kBufferSize);
+    BoundedByteWriter<kBufferSize> writer(data);
+    writer.Store32<0>(high_bits);
+    writer.Store32<4>(low_bits);
+    return data;
+  }
+
+  static absl::optional<HeartbeatInfo> Deserialize(
+      rtc::ArrayView<const uint8_t> data) {
+    if (data.size() != kBufferSize) {
+      RTC_LOG(LS_WARNING) << "Invalid heartbeat info: " << data.size()
+                          << " bytes";
+      return absl::nullopt;
+    }
+
+    BoundedByteReader<kBufferSize> reader(data);
+    uint32_t high_bits = reader.Load32<0>();
+    uint32_t low_bits = reader.Load32<4>();
+
+    uint64_t created_at = static_cast<uint64_t>(high_bits) << 32 | low_bits;
+    return HeartbeatInfo(TimeMs(created_at));
+  }
+
+  TimeMs created_at() const { return created_at_; }
+
+ private:
+  const TimeMs created_at_;
+};
+
+HeartbeatHandler::HeartbeatHandler(absl::string_view log_prefix,
+                                   const DcSctpOptions& options,
+                                   Context* context,
+                                   TimerManager* timer_manager)
+    : log_prefix_(std::string(log_prefix) + "heartbeat: "),
+      ctx_(context),
+      timer_manager_(timer_manager),
+      interval_duration_(options.heartbeat_interval),
+      interval_duration_should_include_rtt_(
+          options.heartbeat_interval_include_rtt),
+      interval_timer_(timer_manager_->CreateTimer(
+          "heartbeat-interval",
+          absl::bind_front(&HeartbeatHandler::OnIntervalTimerExpiry, this),
+          TimerOptions(interval_duration_, TimerBackoffAlgorithm::kFixed))),
+      timeout_timer_(timer_manager_->CreateTimer(
+          "heartbeat-timeout",
+          absl::bind_front(&HeartbeatHandler::OnTimeoutTimerExpiry, this),
+          TimerOptions(options.rto_initial,
+                       TimerBackoffAlgorithm::kExponential,
+                       /*max_restarts=*/0))) {
+  // The interval timer must always be running as long as the association is up.
+  RestartTimer();
+}
+
+void HeartbeatHandler::RestartTimer() {
+  if (interval_duration_ == DurationMs(0)) {
+    // Heartbeating has been disabled.
+    return;
+  }
+
+  if (interval_duration_should_include_rtt_) {
+    // The RTT should be used, but it's not easy accessible. The RTO will
+    // suffice.
+    interval_timer_->set_duration(interval_duration_ + ctx_->current_rto());
+  } else {
+    interval_timer_->set_duration(interval_duration_);
+  }
+
+  interval_timer_->Start();
+}
+
+void HeartbeatHandler::HandleHeartbeatRequest(HeartbeatRequestChunk chunk) {
+  // https://tools.ietf.org/html/rfc4960#section-8.3
+  // "The receiver of the HEARTBEAT should immediately respond with a
+  // HEARTBEAT ACK that contains the Heartbeat Information TLV, together with
+  // any other received TLVs, copied unchanged from the received HEARTBEAT
+  // chunk."
+  ctx_->Send(ctx_->PacketBuilder().Add(
+      HeartbeatAckChunk(std::move(chunk).extract_parameters())));
+}
+
+void HeartbeatHandler::HandleHeartbeatAck(HeartbeatAckChunk chunk) {
+  timeout_timer_->Stop();
+  absl::optional<HeartbeatInfoParameter> info_param = chunk.info();
+  if (!info_param.has_value()) {
+    ctx_->callbacks().OnError(
+        ErrorKind::kParseFailed,
+        "Failed to parse HEARTBEAT-ACK; No Heartbeat Info parameter");
+    return;
+  }
+  absl::optional<HeartbeatInfo> info =
+      HeartbeatInfo::Deserialize(info_param->info());
+  if (!info.has_value()) {
+    ctx_->callbacks().OnError(ErrorKind::kParseFailed,
+                              "Failed to parse HEARTBEAT-ACK; Failed to "
+                              "deserialized Heartbeat info parameter");
+    return;
+  }
+
+  TimeMs now = ctx_->callbacks().TimeMillis();
+  if (info->created_at() > TimeMs(0) && info->created_at() <= now) {
+    ctx_->ObserveRTT(now - info->created_at());
+  }
+
+  // https://tools.ietf.org/html/rfc4960#section-8.1
+  // "The counter shall be reset each time ... a HEARTBEAT ACK is received from
+  // the peer endpoint."
+  ctx_->ClearTxErrorCounter();
+}
+
+absl::optional<DurationMs> HeartbeatHandler::OnIntervalTimerExpiry() {
+  if (ctx_->is_connection_established()) {
+    HeartbeatInfo info(ctx_->callbacks().TimeMillis());
+    timeout_timer_->set_duration(ctx_->current_rto());
+    timeout_timer_->Start();
+    RTC_DLOG(LS_INFO) << log_prefix_ << "Sending HEARTBEAT with timeout "
+                      << *timeout_timer_->duration();
+
+    Parameters parameters = Parameters::Builder()
+                                .Add(HeartbeatInfoParameter(info.Serialize()))
+                                .Build();
+
+    ctx_->Send(ctx_->PacketBuilder().Add(
+        HeartbeatRequestChunk(std::move(parameters))));
+  } else {
+    RTC_DLOG(LS_VERBOSE)
+        << log_prefix_
+        << "Will not send HEARTBEAT when connection not established";
+  }
+  return absl::nullopt;
+}
+
+absl::optional<DurationMs> HeartbeatHandler::OnTimeoutTimerExpiry() {
+  // Note that the timeout timer is not restarted. It will be started again when
+  // the interval timer expires.
+  RTC_DCHECK(!timeout_timer_->is_running());
+  ctx_->IncrementTxErrorCounter("HEARTBEAT timeout");
+  return absl::nullopt;
+}
+}  // namespace dcsctp