// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "quic/core/http/quic_server_session_base.h"

#include <string>

#include "quic/core/proto/cached_network_parameters_proto.h"
#include "quic/core/quic_connection.h"
#include "quic/core/quic_stream.h"
#include "quic/core/quic_tag.h"
#include "quic/core/quic_utils.h"
#include "quic/platform/api/quic_bug_tracker.h"
#include "quic/platform/api/quic_flag_utils.h"
#include "quic/platform/api/quic_flags.h"
#include "quic/platform/api/quic_logging.h"

namespace quic {

QuicServerSessionBase::QuicServerSessionBase(
    const QuicConfig& config,
    const ParsedQuicVersionVector& supported_versions,
    QuicConnection* connection,
    Visitor* visitor,
    QuicCryptoServerStreamBase::Helper* helper,
    const QuicCryptoServerConfig* crypto_config,
    QuicCompressedCertsCache* compressed_certs_cache)
    : QuicSpdySession(connection, visitor, config, supported_versions),
      crypto_config_(crypto_config),
      compressed_certs_cache_(compressed_certs_cache),
      helper_(helper),
      bandwidth_resumption_enabled_(false),
      bandwidth_estimate_sent_to_client_(QuicBandwidth::Zero()),
      last_scup_time_(QuicTime::Zero()) {}

QuicServerSessionBase::~QuicServerSessionBase() {}

void QuicServerSessionBase::Initialize() {
  crypto_stream_ =
      CreateQuicCryptoServerStream(crypto_config_, compressed_certs_cache_);
  QuicSpdySession::Initialize();
  SendSettingsToCryptoStream();
}

void QuicServerSessionBase::OnConfigNegotiated() {
  QuicSpdySession::OnConfigNegotiated();

  if (!config()->HasReceivedConnectionOptions()) {
    return;
  }

  // Disable server push if peer sends the corresponding connection option.
  if (!version().UsesHttp3() &&
      ContainsQuicTag(config()->ReceivedConnectionOptions(), kQNSP)) {
    OnSetting(spdy::SETTINGS_ENABLE_PUSH, 0);
  }

  // Enable bandwidth resumption if peer sent correct connection options.
  const bool last_bandwidth_resumption =
      ContainsQuicTag(config()->ReceivedConnectionOptions(), kBWRE);
  const bool max_bandwidth_resumption =
      ContainsQuicTag(config()->ReceivedConnectionOptions(), kBWMX);
  bandwidth_resumption_enabled_ =
      last_bandwidth_resumption || max_bandwidth_resumption;

  // If the client has provided a bandwidth estimate from the same serving
  // region as this server, then decide whether to use the data for bandwidth
  // resumption.
  const CachedNetworkParameters* cached_network_params =
      crypto_stream_->PreviousCachedNetworkParams();
  if (cached_network_params != nullptr &&
      cached_network_params->serving_region() == serving_region_) {
    // Log the received connection parameters, regardless of how they
    // get used for bandwidth resumption.
    connection()->OnReceiveConnectionState(*cached_network_params);

    if (bandwidth_resumption_enabled_) {
      // Only do bandwidth resumption if estimate is recent enough.
      const uint64_t seconds_since_estimate =
          connection()->clock()->WallNow().ToUNIXSeconds() -
          cached_network_params->timestamp();
      if (seconds_since_estimate <= kNumSecondsPerHour) {
        connection()->ResumeConnectionState(*cached_network_params,
                                            max_bandwidth_resumption);
      }
    }
  }
}

void QuicServerSessionBase::OnConnectionClosed(
    const QuicConnectionCloseFrame& frame,
    ConnectionCloseSource source) {
  QuicSession::OnConnectionClosed(frame, source);
  // In the unlikely event we get a connection close while doing an asynchronous
  // crypto event, make sure we cancel the callback.
  if (crypto_stream_ != nullptr) {
    crypto_stream_->CancelOutstandingCallbacks();
  }
}

void QuicServerSessionBase::OnCongestionWindowChange(QuicTime now) {
  if (!bandwidth_resumption_enabled_) {
    return;
  }
  // Only send updates when the application has no data to write.
  if (HasDataToWrite()) {
    return;
  }

  // If not enough time has passed since the last time we sent an update to the
  // client, or not enough packets have been sent, then return early.
  const QuicSentPacketManager& sent_packet_manager =
      connection()->sent_packet_manager();
  int64_t srtt_ms =
      sent_packet_manager.GetRttStats()->smoothed_rtt().ToMilliseconds();
  int64_t now_ms = (now - last_scup_time_).ToMilliseconds();
  int64_t packets_since_last_scup = 0;
  const QuicPacketNumber largest_sent_packet =
      connection()->sent_packet_manager().GetLargestSentPacket();
  if (largest_sent_packet.IsInitialized()) {
    packets_since_last_scup =
        last_scup_packet_number_.IsInitialized()
            ? largest_sent_packet - last_scup_packet_number_
            : largest_sent_packet.ToUint64();
  }
  if (now_ms < (kMinIntervalBetweenServerConfigUpdatesRTTs * srtt_ms) ||
      now_ms < kMinIntervalBetweenServerConfigUpdatesMs ||
      packets_since_last_scup < kMinPacketsBetweenServerConfigUpdates) {
    return;
  }

  // If the bandwidth recorder does not have a valid estimate, return early.
  const QuicSustainedBandwidthRecorder* bandwidth_recorder =
      sent_packet_manager.SustainedBandwidthRecorder();
  if (bandwidth_recorder == nullptr || !bandwidth_recorder->HasEstimate()) {
    return;
  }

  // The bandwidth recorder has recorded at least one sustained bandwidth
  // estimate. Check that it's substantially different from the last one that
  // we sent to the client, and if so, send the new one.
  QuicBandwidth new_bandwidth_estimate =
      bandwidth_recorder->BandwidthEstimate();

  int64_t bandwidth_delta =
      std::abs(new_bandwidth_estimate.ToBitsPerSecond() -
               bandwidth_estimate_sent_to_client_.ToBitsPerSecond());

  // Define "substantial" difference as a 50% increase or decrease from the
  // last estimate.
  bool substantial_difference =
      bandwidth_delta >
      0.5 * bandwidth_estimate_sent_to_client_.ToBitsPerSecond();
  if (!substantial_difference) {
    return;
  }

  bandwidth_estimate_sent_to_client_ = new_bandwidth_estimate;
  QUIC_DVLOG(1) << "Server: sending new bandwidth estimate (KBytes/s): "
                << bandwidth_estimate_sent_to_client_.ToKBytesPerSecond();

  // Include max bandwidth in the update.
  QuicBandwidth max_bandwidth_estimate =
      bandwidth_recorder->MaxBandwidthEstimate();
  int32_t max_bandwidth_timestamp = bandwidth_recorder->MaxBandwidthTimestamp();

  // Fill the proto before passing it to the crypto stream to send.
  const int32_t bw_estimate_bytes_per_second =
      BandwidthToCachedParameterBytesPerSecond(
          bandwidth_estimate_sent_to_client_);
  const int32_t max_bw_estimate_bytes_per_second =
      BandwidthToCachedParameterBytesPerSecond(max_bandwidth_estimate);
  QUIC_BUG_IF(max_bw_estimate_bytes_per_second < 0)
      << max_bw_estimate_bytes_per_second;
  QUIC_BUG_IF(bw_estimate_bytes_per_second < 0) << bw_estimate_bytes_per_second;

  CachedNetworkParameters cached_network_params;
  cached_network_params.set_bandwidth_estimate_bytes_per_second(
      bw_estimate_bytes_per_second);
  cached_network_params.set_max_bandwidth_estimate_bytes_per_second(
      max_bw_estimate_bytes_per_second);
  cached_network_params.set_max_bandwidth_timestamp_seconds(
      max_bandwidth_timestamp);
  cached_network_params.set_min_rtt_ms(
      sent_packet_manager.GetRttStats()->min_rtt().ToMilliseconds());
  cached_network_params.set_previous_connection_state(
      bandwidth_recorder->EstimateRecordedDuringSlowStart()
          ? CachedNetworkParameters::SLOW_START
          : CachedNetworkParameters::CONGESTION_AVOIDANCE);
  cached_network_params.set_timestamp(
      connection()->clock()->WallNow().ToUNIXSeconds());
  if (!serving_region_.empty()) {
    cached_network_params.set_serving_region(serving_region_);
  }

  crypto_stream_->SendServerConfigUpdate(&cached_network_params);

  connection()->OnSendConnectionState(cached_network_params);

  last_scup_time_ = now;
  last_scup_packet_number_ =
      connection()->sent_packet_manager().GetLargestSentPacket();
}

bool QuicServerSessionBase::ShouldCreateIncomingStream(QuicStreamId id) {
  if (!connection()->connected()) {
    QUIC_BUG << "ShouldCreateIncomingStream called when disconnected";
    return false;
  }

  if (QuicUtils::IsServerInitiatedStreamId(transport_version(), id)) {
    QUIC_BUG << "ShouldCreateIncomingStream called with server initiated "
                "stream ID.";
    return false;
  }

  if (QuicUtils::IsServerInitiatedStreamId(transport_version(), id)) {
    QUIC_DLOG(INFO) << "Invalid incoming even stream_id:" << id;
    connection()->CloseConnection(
        QUIC_INVALID_STREAM_ID, "Client created even numbered stream",
        ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET);
    return false;
  }
  return true;
}

bool QuicServerSessionBase::ShouldCreateOutgoingBidirectionalStream() {
  if (!connection()->connected()) {
    QUIC_BUG
        << "ShouldCreateOutgoingBidirectionalStream called when disconnected";
    return false;
  }
  if (!crypto_stream_->encryption_established()) {
    QUIC_BUG << "Encryption not established so no outgoing stream created.";
    return false;
  }

  return CanOpenNextOutgoingBidirectionalStream();
}

bool QuicServerSessionBase::ShouldCreateOutgoingUnidirectionalStream() {
  if (!connection()->connected()) {
    QUIC_BUG
        << "ShouldCreateOutgoingUnidirectionalStream called when disconnected";
    return false;
  }
  if (!crypto_stream_->encryption_established()) {
    QUIC_BUG << "Encryption not established so no outgoing stream created.";
    return false;
  }

  return CanOpenNextOutgoingUnidirectionalStream();
}

QuicCryptoServerStreamBase* QuicServerSessionBase::GetMutableCryptoStream() {
  return crypto_stream_.get();
}

const QuicCryptoServerStreamBase* QuicServerSessionBase::GetCryptoStream()
    const {
  return crypto_stream_.get();
}

int32_t QuicServerSessionBase::BandwidthToCachedParameterBytesPerSecond(
    const QuicBandwidth& bandwidth) {
  return static_cast<int32_t>(std::min<int64_t>(
      bandwidth.ToBytesPerSecond(), std::numeric_limits<uint32_t>::max()));
}

void QuicServerSessionBase::SendSettingsToCryptoStream() {
  if (!version().UsesTls()) {
    return;
  }
  std::unique_ptr<char[]> buffer;
  QuicByteCount buffer_size =
      HttpEncoder::SerializeSettingsFrame(settings(), &buffer);

  std::unique_ptr<ApplicationState> serialized_settings =
      std::make_unique<ApplicationState>(buffer.get(),
                                         buffer.get() + buffer_size);
  GetMutableCryptoStream()->SetServerApplicationStateForResumption(
      std::move(serialized_settings));
}

}  // namespace quic