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/*
* 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 <optional>
#include <string>
#include <utility>
#include <vector>
#include "absl/functional/bind_front.h"
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/units/time_delta.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 {
using ::webrtc::TimeDelta;
using ::webrtc::Timestamp;
// 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(Timestamp created_at) : created_at_(created_at) {}
std::vector<uint8_t> Serialize() {
uint32_t high_bits = static_cast<uint32_t>(created_at_.ms() >> 32);
uint32_t low_bits = static_cast<uint32_t>(created_at_.ms());
std::vector<uint8_t> data(kBufferSize);
BoundedByteWriter<kBufferSize> writer(data);
writer.Store32<0>(high_bits);
writer.Store32<4>(low_bits);
return data;
}
static std::optional<HeartbeatInfo> Deserialize(
webrtc::ArrayView<const uint8_t> data) {
if (data.size() != kBufferSize) {
RTC_LOG(LS_WARNING) << "Invalid heartbeat info: " << data.size()
<< " bytes";
return std::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(Timestamp::Millis(created_at));
}
Timestamp created_at() const { return created_at_; }
private:
const Timestamp created_at_;
};
HeartbeatHandler::HeartbeatHandler(absl::string_view log_prefix,
const DcSctpOptions& options,
Context* context,
TimerManager* timer_manager)
: log_prefix_(log_prefix),
ctx_(context),
timer_manager_(timer_manager),
interval_duration_(options.heartbeat_interval.ToTimeDelta()),
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.ToTimeDelta(),
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_.IsZero()) {
// 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();
std::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;
}
std::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;
}
Timestamp now = ctx_->callbacks().Now();
if (info->created_at() > Timestamp::Zero() && 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();
}
TimeDelta HeartbeatHandler::OnIntervalTimerExpiry() {
if (ctx_->is_connection_established()) {
HeartbeatInfo info(ctx_->callbacks().Now());
timeout_timer_->set_duration(ctx_->current_rto());
timeout_timer_->Start();
RTC_DLOG(LS_INFO) << log_prefix_ << "Sending HEARTBEAT with timeout "
<< webrtc::ToString(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 TimeDelta::Zero();
}
TimeDelta 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 TimeDelta::Zero();
}
} // namespace dcsctp
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