/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2014-2015,  Regents of the University of California,
 *                           Arizona Board of Regents,
 *                           Colorado State University,
 *                           University Pierre & Marie Curie, Sorbonne University,
 *                           Washington University in St. Louis,
 *                           Beijing Institute of Technology,
 *                           The University of Memphis.
 *
 * This file is part of NFD (Named Data Networking Forwarding Daemon).
 * See AUTHORS.md for complete list of NFD authors and contributors.
 *
 * NFD is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "udp-face.hpp"
// #include "core/global-io.hpp" // for #1718 manual test below

#ifdef __linux__
#include <cerrno>       // for errno
#include <cstring>      // for std::strerror()
#include <netinet/in.h> // for IP_MTU_DISCOVER and IP_PMTUDISC_DONT
#include <sys/socket.h> // for setsockopt()
#endif

namespace nfd {

NFD_LOG_INCLASS_TEMPLATE_SPECIALIZATION_DEFINE(DatagramFace, UdpFace::protocol, "UdpFace");

UdpFace::UdpFace(const FaceUri& remoteUri, const FaceUri& localUri,
                 protocol::socket socket, bool isOnDemand,
                 const time::seconds& idleTimeout)
  : DatagramFace(remoteUri, localUri, std::move(socket))
  , m_idleTimeout(idleTimeout)
  , m_lastIdleCheck(time::steady_clock::now())
{
  this->setOnDemand(isOnDemand);

#ifdef __linux__
  //
  // By default, Linux does path MTU discovery on IPv4 sockets,
  // and sets the DF (Don't Fragment) flag on datagrams smaller
  // than the interface MTU. However this does not work for us,
  // because we cannot properly respond to ICMP "packet too big"
  // messages by fragmenting the packet at the application level,
  // since we want to rely on IP for fragmentation and reassembly.
  //
  // Therefore, we disable PMTU discovery, which prevents the kernel
  // from setting the DF flag on outgoing datagrams, and thus allows
  // routers along the path to perform fragmentation as needed.
  //
  const int value = IP_PMTUDISC_DONT;
  if (::setsockopt(m_socket.native_handle(), IPPROTO_IP,
                   IP_MTU_DISCOVER, &value, sizeof(value)) < 0) {
    NFD_LOG_FACE_WARN("Failed to disable path MTU discovery: " << std::strerror(errno));
  }
#endif

  if (this->isOnDemand() && m_idleTimeout > time::seconds::zero()) {
    m_closeIfIdleEvent = scheduler::schedule(m_idleTimeout, bind(&UdpFace::closeIfIdle, this));
  }
}

ndn::nfd::FaceStatus
UdpFace::getFaceStatus() const
{
  auto status = DatagramFace::getFaceStatus();

  if (isOnDemand()) {
    time::milliseconds left = m_idleTimeout;
    left -= time::duration_cast<time::milliseconds>(time::steady_clock::now() - m_lastIdleCheck);

    if (left < time::milliseconds::zero())
      left = time::milliseconds::zero();

    if (hasBeenUsedRecently())
      left += m_idleTimeout;

    status.setExpirationPeriod(left);
  }

  return status;
}

void
UdpFace::closeIfIdle()
{
  // Face can be switched from on-demand to non-on-demand mode
  // (non-on-demand -> on-demand transition is not allowed)
  if (isOnDemand()) {
    if (!hasBeenUsedRecently()) {
      NFD_LOG_FACE_INFO("Closing for inactivity");
      close();

      // #1718 manual test: uncomment, run NFD in valgrind, send in a UDP packet
      //                    expect read-after-free error and crash
      // getGlobalIoService().post([this] {
      //   NFD_LOG_FACE_ERROR("Remaining references: " << this->shared_from_this().use_count());
      // });
    }
    else {
      resetRecentUsage();

      m_lastIdleCheck = time::steady_clock::now();
      m_closeIfIdleEvent = scheduler::schedule(m_idleTimeout, bind(&UdpFace::closeIfIdle, this));
    }
  }
  // else do nothing and do not reschedule the event
}

} // namespace nfd