// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/quic/quic_chromium_packet_reader.h"

#include "base/functional/bind.h"
#include "base/location.h"
#include "base/metrics/histogram_macros.h"
#include "base/task/single_thread_task_runner.h"
#include "net/base/features.h"
#include "net/base/net_errors.h"
#include "net/quic/address_utils.h"
#include "net/third_party/quiche/src/quiche/quic/core/quic_clock.h"
#include "net/third_party/quiche/src/quiche/quic/core/quic_types.h"

namespace net {

namespace {
// Add 1 because some of our UDP socket implementations do not read successfully
// when the packet length is equal to the read buffer size.
const size_t kReadBufferSize =
    static_cast<size_t>(quic::kMaxIncomingPacketSize + 1);
}  // namespace

QuicChromiumPacketReader::QuicChromiumPacketReader(
    std::unique_ptr<DatagramClientSocket> socket,
    const quic::QuicClock* clock,
    Visitor* visitor,
    int yield_after_packets,
    quic::QuicTime::Delta yield_after_duration,
    const NetLogWithSource& net_log)
    : socket_(std::move(socket)),
      visitor_(visitor),
      clock_(clock),
      yield_after_packets_(yield_after_packets),
      yield_after_duration_(yield_after_duration),
      yield_after_(quic::QuicTime::Infinite()),
      read_buffer_(base::MakeRefCounted<IOBufferWithSize>(kReadBufferSize)),
      net_log_(net_log),
      report_ecn_(base::FeatureList::IsEnabled(net::features::kReceiveEcn)) {}

QuicChromiumPacketReader::~QuicChromiumPacketReader() = default;

void QuicChromiumPacketReader::StartReading() {
  for (;;) {
    if (read_pending_)
      return;

    if (num_packets_read_ == 0)
      yield_after_ = clock_->Now() + yield_after_duration_;

    CHECK(socket_);
    read_pending_ = true;
    int rv =
        socket_->Read(read_buffer_.get(), read_buffer_->size(),
                      base::BindOnce(&QuicChromiumPacketReader::OnReadComplete,
                                     weak_factory_.GetWeakPtr()));
    UMA_HISTOGRAM_BOOLEAN("Net.QuicSession.AsyncRead", rv == ERR_IO_PENDING);
    if (rv == ERR_IO_PENDING) {
      num_packets_read_ = 0;
      return;
    }

    if (++num_packets_read_ > yield_after_packets_ ||
        clock_->Now() > yield_after_) {
      num_packets_read_ = 0;
      // Data was read, process it.
      // Schedule the work through the message loop to 1) prevent infinite
      // recursion and 2) avoid blocking the thread for too long.
      base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
          FROM_HERE, base::BindOnce(&QuicChromiumPacketReader::OnReadComplete,
                                    weak_factory_.GetWeakPtr(), rv));
    } else {
      if (!ProcessReadResult(rv)) {
        return;
      }
    }
  }
}

void QuicChromiumPacketReader::CloseSocket() {
  socket_->Close();
}

static_assert(static_cast<EcnCodePoint>(quic::ECN_NOT_ECT) == ECN_NOT_ECT &&
                  static_cast<EcnCodePoint>(quic::ECN_ECT1) == ECN_ECT1 &&
                  static_cast<EcnCodePoint>(quic::ECN_ECT0) == ECN_ECT0 &&
                  static_cast<EcnCodePoint>(quic::ECN_CE) == ECN_CE,
              "Mismatch ECN codepoint values");
bool QuicChromiumPacketReader::ProcessReadResult(int result) {
  read_pending_ = false;
  if (result <= 0 && net_log_.IsCapturing()) {
    net_log_.AddEventWithIntParams(NetLogEventType::QUIC_READ_ERROR,
                                   "net_error", result);
  }
  if (result == 0) {
    // 0-length UDP packets are legal but useless, ignore them.
    return true;
  }
  if (result == ERR_MSG_TOO_BIG) {
    // This indicates that we received a UDP packet larger than our receive
    // buffer, ignore it.
    return true;
  }
  if (result < 0) {
    // Report all other errors to the visitor.
    return visitor_->OnReadError(result, socket_.get());
  }

  quic::QuicEcnCodepoint ecn = quic::ECN_NOT_ECT;
  if (report_ecn_) {
    DscpAndEcn tos = socket_->GetLastTos();
    ecn = static_cast<quic::QuicEcnCodepoint>(tos.ecn);
  }
  quic::QuicReceivedPacket packet(read_buffer_->data(), result, clock_->Now(),
                                  /*owns_buffer=*/false, /*ttl=*/0,
                                  /*ttl_valid=*/true,
                                  /*packet_headers=*/nullptr,
                                  /*headers_length=*/0,
                                  /*owns_header_buffer=*/false, ecn);
  IPEndPoint local_address;
  IPEndPoint peer_address;
  socket_->GetLocalAddress(&local_address);
  socket_->GetPeerAddress(&peer_address);
  auto self = weak_factory_.GetWeakPtr();
  // Notifies the visitor that |this| reader gets a new packet, which may delete
  // |this| if |this| is a connectivity probing reader.
  return visitor_->OnPacket(packet, ToQuicSocketAddress(local_address),
                            ToQuicSocketAddress(peer_address)) &&
         self;
}

void QuicChromiumPacketReader::OnReadComplete(int result) {
  if (ProcessReadResult(result)) {
    StartReading();
  }
}

}  // namespace net