/*

Copyright (c) 2007-2012, 2014-2020, Arvid Norberg

Copyright (c) 2016-2017, Alden Torres

Copyright (c) 2016, Pavel Pimenov

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:

    * Redistributions of source code must retain the above copyright

      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright

      notice, this list of conditions and the following disclaimer in

      the documentation and/or other materials provided with the distribution.

    * Neither the name of the author nor the names of its

      contributors may be used to endorse or promote products derived

      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

#include <cstdlib>

#include <cstdarg>

#include <functional>

#include <cstdio> // for vsnprintf

#include "libtorrent/lsd.hpp"

#include "libtorrent/time.hpp"

#include "libtorrent/random.hpp"

#include "libtorrent/http_parser.hpp"

#include "libtorrent/socket_io.hpp" // for print_address

#include "libtorrent/debug.hpp"

#include "libtorrent/hex.hpp" // to_hex, from_hex

#include "libtorrent/aux_/numeric_cast.hpp"

#include "libtorrent/enum_net.hpp"

#include "libtorrent/aux_/scope_end.hpp"

#include "libtorrent/aux_/disable_warnings_push.hpp"

#include <boost/asio/ip/multicast.hpp>

#include "libtorrent/aux_/disable_warnings_pop.hpp"

using namespace std::placeholders;

namespace libtorrent {

namespace {

int render_lsd_packet(char* dst, int const len, int const listen_port

  , char const* info_hash_hex, std::uint32_t const cookie, char const* host)

{

  TORRENT_ASSERT(len > 0);

  return std::snprintf(dst, aux::numeric_cast<std::size_t>(len),

    "BT-SEARCH * HTTP/1.1\r\n"

    "Host: %s:6771\r\n"

    "Port: %d\r\n"

    "Infohash: %s\r\n"

    "cookie: %x\r\n"

    "\r\n\r\n", host, listen_port, info_hash_hex, cookie);

}

} // anonymous namespace

lsd::lsd(io_context& ios, aux::lsd_callback& cb

  , address const listen_address, address const netmask)

  : m_callback(cb)

  , m_listen_address(listen_address)

  , m_netmask(netmask)

  , m_socket(ios)

  , m_broadcast_timer(ios)

  , m_cookie((random(0x7fffffff) ^ std::uintptr_t(this)) & 0x7fffffff)

{

}

#ifndef TORRENT_DISABLE_LOGGING

bool lsd::should_log() const

{

  return m_callback.should_log_lsd();

}

TORRENT_FORMAT(2, 3)

void lsd::debug_log(char const* fmt, ...) const

{

  if (!should_log()) return;

  va_list v;

  va_start(v, fmt);

  char buf[1024];

  std::vsnprintf(buf, sizeof(buf), fmt, v);

  va_end(v);

  m_callback.log_lsd(buf);

}

#endif

namespace {

  address_v4 const lsd_multicast_addr4 = make_address_v4("239.192.152.143");

  address_v6 const lsd_multicast_addr6 = make_address_v6("ff15::efc0:988f");

  int const lsd_port = 6771;

}

void lsd::start(error_code& ec)

{

  using namespace boost::asio::ip::multicast;

  bool const v4 = m_listen_address.is_v4();

  m_socket.open(v4 ? udp::v4() : udp::v6(), ec);

  if (ec) return;

  m_socket.set_option(udp::socket::reuse_address(true), ec);

  if (ec) return;

  m_socket.bind(udp::endpoint(v4 ? address(address_v4::any()) : address(address_v6::any()), lsd_port), ec);

  if (ec) return;

  if (v4)

    m_socket.set_option(join_group(lsd_multicast_addr4, m_listen_address.to_v4()), ec);

  else

    m_socket.set_option(join_group(lsd_multicast_addr6, m_listen_address.to_v6().scope_id()), ec);

  if (ec) return;

  m_socket.set_option(hops(32), ec);

  if (ec) return;

  m_socket.set_option(enable_loopback(true), ec);

  if (ec) return;

  if (v4)

  {

    m_socket.set_option(outbound_interface(m_listen_address.to_v4()), ec);

    if (ec) return;

  }

  ADD_OUTSTANDING_ASYNC("lsd::on_announce");

  m_socket.async_receive_from(boost::asio::buffer(m_buffer), m_remote

    , std::bind(&lsd::on_announce, self(), _1, _2));

}

lsd::~lsd() = default;

void lsd::announce(sha1_hash const& ih, int listen_port)

{

  announce_impl(ih, listen_port, 0);

}

void lsd::announce_impl(sha1_hash const& ih, int const listen_port

  , int retry_count)

{

  if (m_disabled) return;

  char msg[200];

  error_code ec;

  if (!m_disabled)

  {

    bool const v4 = m_listen_address.is_v4();

    char const* v4_address = "239.192.152.143";

    char const* v6_address = "[ff15::efc0:988f]";

    int const msg_len = render_lsd_packet(msg, sizeof(msg), listen_port, aux::to_hex(ih).c_str()

      , m_cookie, v4 ? v4_address : v6_address);

    udp::endpoint const to(v4 ? address(lsd_multicast_addr4) : address(lsd_multicast_addr6)

      , lsd_port);

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("==> LSD: ih: %s port: %d [iface: %s]", aux::to_hex(ih).c_str()

      , listen_port, m_listen_address.to_string().c_str());

#endif

    m_socket.send_to(boost::asio::buffer(msg, static_cast<std::size_t>(msg_len))

      , to, {}, ec);

    if (ec)

    {

      m_disabled = true;

#ifndef TORRENT_DISABLE_LOGGING

      if (should_log())

      {

        debug_log("*** LSD: failed to send message: (%d) %s", ec.value()

          , ec.message().c_str());

      }

#endif

    }

  }

  ++retry_count;

  if (retry_count >= 3) return;

  if (m_disabled) return;

  ADD_OUTSTANDING_ASYNC("lsd::resend_announce");

  m_broadcast_timer.expires_after(seconds(2 * retry_count));

  m_broadcast_timer.async_wait(std::bind(&lsd::resend_announce, self(), _1

    , ih, listen_port, retry_count));

}

void lsd::resend_announce(error_code const& e, sha1_hash const& info_hash

  , int listen_port, int retry_count)

{

  COMPLETE_ASYNC("lsd::resend_announce");

  if (e) return;

  announce_impl(info_hash, listen_port, retry_count);

}

void lsd::on_announce(error_code const& ec, std::size_t len)

{

  COMPLETE_ASYNC("lsd::on_announce");

  if (ec)

  {

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: receive error: %s", ec.message().c_str());

#endif

    return;

  }

  udp::endpoint const from = m_remote;

  // reissue the async receive as we exit the function. We can't do this

  // earlier because we still need to use m_buffer

  auto reissue_receive = aux::scope_end([&] {

    ADD_OUTSTANDING_ASYNC("lsd::on_announce");

    m_socket.async_receive_from(boost::asio::buffer(m_buffer), m_remote

      , std::bind(&lsd::on_announce, self(), _1, _2));

  });

  if (!match_addr_mask(from.address(), m_listen_address, m_netmask))

  {

    // we don't care about this network. Ignore this packet

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: receive from out of network: %s"

      , from.address().to_string().c_str());

#endif

    return;

  }

  http_parser p;

  bool error = false;

  p.incoming(span<char const>{m_buffer.data(), std::ptrdiff_t(len)}, error);

  if (!p.header_finished() || error)

  {

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: incomplete HTTP message");

#endif

    return;

  }

  if (p.method() != "bt-search")

  {

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: invalid HTTP method: %s", p.method().c_str());

#endif

    return;

  }

  std::string const& port_str = p.header("port");

  if (port_str.empty())

  {

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: invalid BT-SEARCH, missing port");

#endif

    return;

  }

  long const port = std::strtol(port_str.c_str(), nullptr, 10);

  if (port <= 0 || port >= int(std::numeric_limits<std::uint16_t>::max()))

  {

#ifndef TORRENT_DISABLE_LOGGING

    debug_log("<== LSD: invalid BT-SEARCH port value: %s", port_str.c_str());

#endif

    return;

  }

  auto const& headers = p.headers();

  auto const cookie_iter = headers.find("cookie");

  if (cookie_iter != headers.end())

  {

    // we expect it to be hexadecimal

    // if it isn't, it's not our cookie anyway

    unsigned long const cookie = std::strtoul(cookie_iter->second.c_str(), nullptr, 16);

    if (cookie == m_cookie)

    {

#ifndef TORRENT_DISABLE_LOGGING

      debug_log("<== LSD: ignoring packet (cookie matched our own): %x"

        , m_cookie);

#endif

      return;

    }

  }

  auto const ihs = headers.equal_range("infohash");

  for (auto i = ihs.first; i != ihs.second; ++i)

  {

    std::string const& ih_str = i->second;

    if (ih_str.size() != 40)

    {

#ifndef TORRENT_DISABLE_LOGGING

      debug_log("<== LSD: invalid BT-SEARCH, invalid infohash: %s"

        , ih_str.c_str());

#endif

      continue;

    }

    sha1_hash ih;

    aux::from_hex(ih_str, ih.data());

    if (!ih.is_all_zeros())

    {

#ifndef TORRENT_DISABLE_LOGGING

      if (should_log())

      {

        debug_log("<== LSD: %s:%d ih: %s"

          , print_address(from.address()).c_str()

          , int(port), ih_str.c_str());

      }

#endif

      // we got an announce, pass it on through the callback

      m_callback.on_lsd_peer(tcp::endpoint(from.address(), std::uint16_t(port)), ih);

    }

  }

}

void lsd::close()

{

  error_code ec;

  m_socket.close(ec);

  m_broadcast_timer.cancel();

  m_disabled = true;

}

} // libtorrent namespace