/*

Copyright (c) 2006, Daniel Wallin

Copyright (c) 2013-2020, Arvid Norberg

Copyright (c) 2015, Steven Siloti

Copyright (c) 2015, Thomas Yuan

Copyright (c) 2016-2017, Alden Torres

Copyright (c) 2016-2017, 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 <libtorrent/kademlia/get_peers.hpp>

#include <libtorrent/kademlia/node.hpp>

#include <libtorrent/kademlia/dht_observer.hpp>

#include <libtorrent/socket_io.hpp>

#include <libtorrent/performance_counters.hpp>

#include <libtorrent/aux_/ip_helpers.hpp> // for is_v4

#ifndef TORRENT_DISABLE_LOGGING

#include <libtorrent/hex.hpp> // to_hex

#endif

namespace libtorrent { namespace dht {

void get_peers_observer::reply(msg const& m)

{

  bdecode_node const r = m.message.dict_find_dict("r");

  if (!r)

  {

#ifndef TORRENT_DISABLE_LOGGING

    get_observer()->log(dht_logger::traversal, "[%u] missing response dict"

      , algorithm()->id());

#endif

    timeout();

    return;

  }

  // look for peers

  bdecode_node const n = r.dict_find_list("values");

  if (n)

  {

    std::vector<tcp::endpoint> peer_list;

    if (n.list_size() == 1 && n.list_at(0).type() == bdecode_node::string_t

      && aux::is_v4(m.addr))

    {

      // assume it's mainline format

      char const* peers = n.list_at(0).string_ptr();

      char const* end = peers + n.list_at(0).string_length();

#ifndef TORRENT_DISABLE_LOGGING

      log_peers(m, r, int((end - peers) / 6));

#endif

      while (end - peers >= 6)

        peer_list.push_back(aux::read_v4_endpoint<tcp::endpoint>(peers));

    }

    else

    {

      // assume it's uTorrent/libtorrent format

      peer_list = aux::read_endpoint_list<tcp::endpoint>(n);

#ifndef TORRENT_DISABLE_LOGGING

      log_peers(m, r, n.list_size());

#endif

    }

    static_cast<get_peers*>(algorithm())->got_peers(peer_list);

  }

  find_data_observer::reply(m);

}

#ifndef TORRENT_DISABLE_LOGGING

void get_peers_observer::log_peers(msg const& m, bdecode_node const& r, int const size) const

{

      auto logger = get_observer();

      if (logger != nullptr && logger->should_log(dht_logger::traversal))

      {

        bdecode_node const id = r.dict_find_string("id");

        if (id && id.string_length() == 20)

        {

          logger->log(dht_logger::traversal, "[%u] PEERS "

            "invoke-count: %d branch-factor: %d addr: %s id: %s distance: %d p: %d"

            , algorithm()->id()

            , algorithm()->invoke_count()

            , algorithm()->branch_factor()

            , print_endpoint(m.addr).c_str()

            , aux::to_hex({id.string_ptr(), id.string_length()}).c_str()

            , distance_exp(algorithm()->target(), node_id(id.string_ptr()))

            , size);

        }

      }

}

#endif

void get_peers::got_peers(std::vector<tcp::endpoint> const& peers)

{

  if (m_data_callback) m_data_callback(peers);

}

get_peers::get_peers(

  node& dht_node

  , node_id const& target

  , data_callback dcallback

  , nodes_callback ncallback

  , bool noseeds)

  : find_data(dht_node, target, std::move(ncallback))

  , m_data_callback(std::move(dcallback))

  , m_noseeds(noseeds)

{

}

char const* get_peers::name() const { return "get_peers"; }

bool get_peers::invoke(observer_ptr o)

{

  if (m_done) return false;

  entry e;

  e["y"] = "q";

  entry& a = e["a"];

  e["q"] = "get_peers";

  a["info_hash"] = target().to_string();

  if (m_noseeds) a["noseed"] = 1;

  if (m_node.observer() != nullptr)

  {

    m_node.observer()->outgoing_get_peers(target(), target(), o->target_ep());

  }

  m_node.stats_counters().inc_stats_counter(counters::dht_get_peers_out);

  return m_node.m_rpc.invoke(e, o->target_ep(), o);

}

observer_ptr get_peers::new_observer(udp::endpoint const& ep

  , node_id const& id)

{

  auto o = m_node.m_rpc.allocate_observer<get_peers_observer>(self(), ep, id);

#if TORRENT_USE_ASSERTS

  if (o) o->m_in_constructor = false;

#endif

  return o;

}

obfuscated_get_peers::obfuscated_get_peers(

  node& dht_node

  , node_id const& target

  , data_callback dcallback

  , nodes_callback ncallback

  , bool noseeds)

  : get_peers(dht_node, target, std::move(dcallback), std::move(ncallback), noseeds)

  , m_obfuscated(true)

{

}

char const* obfuscated_get_peers::name() const

{ return !m_obfuscated ? get_peers::name() : "get_peers [obfuscated]"; }

observer_ptr obfuscated_get_peers::new_observer(udp::endpoint const& ep

  , node_id const& id)

{

  if (m_obfuscated)

  {

    auto o = m_node.m_rpc.allocate_observer<obfuscated_get_peers_observer>(self()

      , ep, id);

#if TORRENT_USE_ASSERTS

    if (o) o->m_in_constructor = false;

#endif

    return o;

  }

  else

  {

    auto o = m_node.m_rpc.allocate_observer<get_peers_observer>(self()

      , ep, id);

#if TORRENT_USE_ASSERTS

    if (o) o->m_in_constructor = false;

#endif

    return o;

  }

}

bool obfuscated_get_peers::invoke(observer_ptr o)

{

  if (!m_obfuscated) return get_peers::invoke(o);

  node_id const& id = o->id();

  int const shared_prefix = 160 - distance_exp(id, target());

  entry e;

  e["y"] = "q";

  e["q"] = "get_peers";

  entry& a = e["a"];

  // This logic will obfuscate the target info-hash

  // we're looking up, in order to preserve more privacy

  // on the DHT. This is done by only including enough

  // bits in the info-hash for the node we're querying to

  // give a good answer, but not more.

  // now, obfuscate the bits past shared_prefix + 3

  node_id mask = generate_prefix_mask(shared_prefix + 3);

  node_id obfuscated_target = generate_random_id() & ~mask;

  obfuscated_target |= target() & mask;

  a["info_hash"] = obfuscated_target.to_string();

  if (m_node.observer() != nullptr)

  {

    m_node.observer()->outgoing_get_peers(target(), obfuscated_target

      , o->target_ep());

  }

  m_node.stats_counters().inc_stats_counter(counters::dht_get_peers_out);

  return m_node.m_rpc.invoke(e, o->target_ep(), o);

}

void obfuscated_get_peers::done()

{

  if (!m_obfuscated) return get_peers::done();

  // oops, we failed to switch over to the non-obfuscated

  // mode early enough. do it now

  auto ta = std::make_shared<get_peers>(m_node, target()

    , m_data_callback, m_nodes_callback, m_noseeds);

  // don't call these when the obfuscated_get_peers

  // is done, we're passing them on to be called when

  // ta completes.

  m_data_callback = nullptr;

  m_nodes_callback = nullptr;

#ifndef TORRENT_DISABLE_LOGGING

    get_node().observer()->log(dht_logger::traversal, "[%u] obfuscated get_peers "

      "phase 1 done, spawning get_peers [ %u ]"

      , id(), ta->id());

#endif

  int num_added = 0;

  for (auto i = m_results.begin()

    , end(m_results.end()); i != end && num_added < 16; ++i)

  {

    observer_ptr o = *i;

    // only add nodes whose node ID we know and that

    // we know are alive

    if (o->flags & observer::flag_no_id) continue;

    if (!(o->flags & observer::flag_alive)) continue;

    ta->add_entry(o->id(), o->target_ep(), observer::flag_initial);

    ++num_added;

  }

  ta->start();

  get_peers::done();

}

void obfuscated_get_peers_observer::reply(msg const& m)

{

  bdecode_node const r = m.message.dict_find_dict("r");

  if (!r)

  {

#ifndef TORRENT_DISABLE_LOGGING

    get_observer()->log(dht_logger::traversal, "[%u] missing response dict"

      , algorithm()->id());

#endif

    timeout();

    return;

  }

  bdecode_node const id = r.dict_find_string("id");

  if (!id || id.string_length() != 20)

  {

#ifndef TORRENT_DISABLE_LOGGING

    get_observer()->log(dht_logger::traversal, "[%u] invalid id in response"

      , algorithm()->id());

#endif

    timeout();

    return;

  }

  traversal_observer::reply(m);

  done();

}

} } // namespace libtorrent::dht