file_progress fix

[libtorrent.git] / src / session_impl.cpp

/*

Copyright (c) 2006, Arvid Norberg, Magnus Jonsson
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/pch.hpp"

#include <ctime>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <iterator>
#include <algorithm>
#include <set>
#include <cctype>
#include <algorithm>

#ifdef _MSC_VER
#pragma warning(push, 1)
#endif

#include <boost/lexical_cast.hpp>
#include <boost/filesystem/convenience.hpp>
#include <boost/filesystem/exception.hpp>
#include <boost/limits.hpp>
#include <boost/bind.hpp>

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#include "libtorrent/peer_id.hpp"
#include "libtorrent/torrent_info.hpp"
#include "libtorrent/tracker_manager.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/hasher.hpp"
#include "libtorrent/entry.hpp"
#include "libtorrent/session.hpp"
#include "libtorrent/fingerprint.hpp"
#include "libtorrent/entry.hpp"
#include "libtorrent/alert_types.hpp"
#include "libtorrent/invariant_check.hpp"
#include "libtorrent/file.hpp"
#include "libtorrent/bt_peer_connection.hpp"
#include "libtorrent/ip_filter.hpp"
#include "libtorrent/socket.hpp"
#include "libtorrent/aux_/session_impl.hpp"
#include "libtorrent/kademlia/dht_tracker.hpp"
#include "libtorrent/enum_net.hpp"
#include "libtorrent/config.hpp"

#ifndef TORRENT_WINDOWS
#include <sys/resource.h>
#endif

#ifndef TORRENT_DISABLE_ENCRYPTION

#include <openssl/crypto.h>

namespace
{
        // openssl requires this to clean up internal
        // structures it allocates
        struct openssl_cleanup
        {
                ~openssl_cleanup() { CRYPTO_cleanup_all_ex_data(); }
        } openssl_global_destructor;
}

#endif
#ifdef _WIN32
// for ERROR_SEM_TIMEOUT
#include <winerror.h>
#endif

using boost::shared_ptr;
using boost::weak_ptr;
using boost::bind;
using boost::mutex;
using libtorrent::aux::session_impl;

namespace libtorrent {

namespace fs = boost::filesystem;

namespace detail
{

        std::string generate_auth_string(std::string const& user
                , std::string const& passwd)
        {
                if (user.empty()) return std::string();
                return user + ":" + passwd;
        }
        

}
namespace aux {

        struct seed_random_generator
        {
                seed_random_generator()
                {
                        std::srand(total_microseconds(time_now() - min_time()));
                }
        };

        session_impl::session_impl(
                std::pair<int, int> listen_port_range
                , fingerprint const& cl_fprint
                , char const* listen_interface
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
                , fs::path const& logpath
#endif
                )
                : 
#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
                m_send_buffers(send_buffer_size),
#endif
                  m_files(40)
                , m_io_service()
                , m_disk_thread(m_io_service)
                , m_half_open(m_io_service)
                , m_download_channel(m_io_service, peer_connection::download_channel)
#ifdef TORRENT_VERBOSE_BANDWIDTH_LIMIT
                , m_upload_channel(m_io_service, peer_connection::upload_channel, true)
#else
                , m_upload_channel(m_io_service, peer_connection::upload_channel)
#endif
                , m_tracker_manager(m_settings, m_tracker_proxy)
                , m_listen_port_retries(listen_port_range.second - listen_port_range.first)
                , m_listen_interface(address::from_string(listen_interface), listen_port_range.first)
                , m_abort(false)
                , m_paused(false)
                , m_max_uploads(8)
                , m_allowed_upload_slots(8)
                , m_max_connections(200)
                , m_num_unchoked(0)
                , m_unchoke_time_scaler(0)
                , m_auto_manage_time_scaler(0)
                , m_optimistic_unchoke_time_scaler(0)
                , m_disconnect_time_scaler(90)
                , m_auto_scrape_time_scaler(180)
                , m_incoming_connection(false)
                , m_last_tick(time_now())
#ifndef TORRENT_DISABLE_DHT
                , m_dht_same_port(true)
                , m_external_udp_port(0)
                , m_dht_socket(m_io_service, bind(&session_impl::on_receive_udp, this, _1, _2, _3, _4)
                        , m_half_open)
#endif
                , m_timer(m_io_service)
                , m_next_connect_torrent(0)
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
                , m_logpath(logpath)
#endif
#ifndef TORRENT_DISABLE_GEO_IP
                , m_asnum_db(0)
                , m_country_db(0)
#endif
                , m_total_failed_bytes(0)
                , m_total_redundant_bytes(0)
        {
                m_tcp_mapping[0] = -1;
                m_tcp_mapping[1] = -1;
                m_udp_mapping[0] = -1;
                m_udp_mapping[1] = -1;
#ifdef WIN32
                // windows XP has a limit on the number of
                // simultaneous half-open TCP connections
                DWORD windows_version = ::GetVersion();
                if ((windows_version & 0xff) >= 6)
                {
                        // on vista the limit is 5 (in home edition)
                        m_half_open.limit(4);
                }
                else
                {
                        // on XP SP2 it's 10    
                        m_half_open.limit(8);
                }
#endif

                m_bandwidth_manager[peer_connection::download_channel] = &m_download_channel;
                m_bandwidth_manager[peer_connection::upload_channel] = &m_upload_channel;

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
                m_logger = create_log("main_session", listen_port(), false);
                (*m_logger) << time_now_string() << "\n";

                (*m_logger) << "sizeof(torrent): " << sizeof(torrent) << "\n";
                (*m_logger) << "sizeof(peer_connection): " << sizeof(peer_connection) << "\n";
                (*m_logger) << "sizeof(bt_peer_connection): " << sizeof(bt_peer_connection) << "\n";
                (*m_logger) << "sizeof(policy::peer): " << sizeof(policy::peer) << "\n";
#endif

#ifdef TORRENT_STATS
                m_stats_logger.open("session_stats.log", std::ios::trunc);
                m_stats_logger <<
                        "1. second\n"
                        "2. upload rate\n"
                        "3. download rate\n"
                        "4. downloading torrents\n"
                        "5. seeding torrents\n"
                        "6. peers\n"
                        "7. connecting peers\n"
                        "8. disk block buffers\n"
                        "\n";
                m_buffer_usage_logger.open("buffer_stats.log", std::ios::trunc);
                m_second_counter = 0;
                m_buffer_allocations = 0;
#endif

                // ---- generate a peer id ----
                static seed_random_generator seeder;

                m_key = rand() + (rand() << 15) + (rand() << 30);
                std::string print = cl_fprint.to_string();
                TORRENT_ASSERT(print.length() <= 20);

                // the client's fingerprint
                std::copy(
                        print.begin()
                        , print.begin() + print.length()
                        , m_peer_id.begin());

                // http-accepted characters:
                static char const printable[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                        "abcdefghijklmnopqrstuvwxyz-_.!~*'()";

                // the random number
                for (unsigned char* i = m_peer_id.begin() + print.length();
                        i != m_peer_id.end(); ++i)
                {
                        *i = printable[rand() % (sizeof(printable)-1)];
                }

                error_code ec;
                m_timer.expires_from_now(seconds(1), ec);
                m_timer.async_wait(
                        bind(&session_impl::second_tick, this, _1));

                m_thread.reset(new boost::thread(boost::ref(*this)));
        }

#ifndef TORRENT_DISABLE_GEO_IP
        namespace
        {
                struct free_ptr
                {
                        void* ptr_;
                        free_ptr(void* p): ptr_(p) {}
                        ~free_ptr() { free(ptr_); }
                };
        }

        char const* session_impl::country_for_ip(address const& a)
        {
                if (!a.is_v4() || m_country_db == 0) return 0;
                return GeoIP_country_code_by_ipnum(m_country_db, a.to_v4().to_ulong());
        }

        int session_impl::as_for_ip(address const& a)
        {
                if (!a.is_v4() || m_asnum_db == 0) return 0;
                char* name = GeoIP_name_by_ipnum(m_asnum_db, a.to_v4().to_ulong());
                if (name == 0) return 0;
                free_ptr p(name);
                // GeoIP returns the name as AS??? where ? is the AS-number
                return atoi(name + 2);
        }

        std::string session_impl::as_name_for_ip(address const& a)
        {
                if (!a.is_v4() || m_asnum_db == 0) return std::string();
                char* name = GeoIP_name_by_ipnum(m_asnum_db, a.to_v4().to_ulong());
                if (name == 0) return std::string();
                free_ptr p(name);
                char* tmp = std::strchr(name, ' ');
                if (tmp == 0) return std::string();
                return tmp + 1;
        }

        std::pair<const int, int>* session_impl::lookup_as(int as)
        {
                std::map<int, int>::iterator i = m_as_peak.lower_bound(as);

                if (i == m_as_peak.end() || i->first != as)
                {
                        // we don't have any data for this AS, insert a new entry
                        i = m_as_peak.insert(i, std::pair<int, int>(as, 0));
                }
                return &(*i);
        }

        bool session_impl::load_asnum_db(char const* file)
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_asnum_db) GeoIP_delete(m_asnum_db);
                m_asnum_db = GeoIP_open(file, GEOIP_STANDARD);
                return m_asnum_db;
        }

        bool session_impl::load_country_db(char const* file)
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_country_db) GeoIP_delete(m_country_db);
                m_country_db = GeoIP_open(file, GEOIP_STANDARD);
                return m_country_db;
        }

#endif

        void session_impl::load_state(entry const& ses_state)
        {
                if (ses_state.type() != entry::dictionary_t) return;
                mutex_t::scoped_lock l(m_mutex);
#ifndef TORRENT_DISABLE_GEO_IP
                entry const* as_map = ses_state.find_key("AS map");
                if (as_map && as_map->type() == entry::dictionary_t)
                {
                        entry::dictionary_type const& as_peak = as_map->dict();
                        for (entry::dictionary_type::const_iterator i = as_peak.begin()
                                , end(as_peak.end()); i != end; ++i)
                        {
                                int as_num = atoi(i->first.c_str());
                                if (i->second.type() != entry::int_t || i->second.integer() == 0) continue;
                                int& peak = m_as_peak[as_num];
                                if (peak < i->second.integer()) peak = i->second.integer();
                        }
                }
#endif
        }

        entry session_impl::state() const
        {
                mutex_t::scoped_lock l(m_mutex);
                entry ret;
#ifndef TORRENT_DISABLE_GEO_IP
                entry::dictionary_type& as_map = ret["AS map"].dict();
                char buf[10];
                for (std::map<int, int>::const_iterator i = m_as_peak.begin()
                        , end(m_as_peak.end()); i != end; ++i)
                {
                        if (i->second == 0) continue;
                        sprintf(buf, "%05d", i->first);
                        as_map[buf] = i->second;
                }
#endif
                return ret;
        }

#ifndef TORRENT_DISABLE_EXTENSIONS
        void session_impl::add_extension(
                boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> ext)
        {
                m_extensions.push_back(ext);
        }
#endif

#ifndef TORRENT_DISABLE_DHT
        void session_impl::add_dht_node(udp::endpoint n)
        {
                if (m_dht) m_dht->add_node(n);
        }
#endif

        void session_impl::pause()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_paused) return;
                m_paused = true;
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        torrent& t = *i->second;
                        if (!t.is_torrent_paused()) t.do_pause();
                }
        }

        void session_impl::resume()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (!m_paused) return;
                m_paused = false;
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        torrent& t = *i->second;
                        t.do_resume();
                }
        }
        
        void session_impl::abort()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_abort) return;
#if defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " *** ABORT CALLED ***\n";
#endif
                // abort the main thread
                m_abort = true;
                m_queued_for_checking.clear();
                if (m_lsd) m_lsd->close();
                if (m_upnp) m_upnp->close();
                if (m_natpmp) m_natpmp->close();
#ifndef TORRENT_DISABLE_DHT
                if (m_dht) m_dht->stop();
                m_dht_socket.close();
#endif
                error_code ec;
                m_timer.cancel(ec);

                // close the listen sockets
                for (std::list<listen_socket_t>::iterator i = m_listen_sockets.begin()
                        , end(m_listen_sockets.end()); i != end; ++i)
                {
                        i->sock->close(ec);
                }

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " aborting all torrents (" << m_torrents.size() << ")\n";
#endif
                // abort all torrents
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        i->second->abort();
                }

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " aborting all tracker requests\n";
#endif
                m_tracker_manager.abort_all_requests();

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " sending event=stopped to trackers\n";
                int counter = 0;
#endif
                for (torrent_map::iterator i = m_torrents.begin();
                        i != m_torrents.end(); ++i)
                {
                        torrent& t = *i->second;
                        t.abort();
                }

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " sent " << counter << " tracker stop requests\n";
#endif

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " aborting all connections (" << m_connections.size() << ")\n";
#endif
                // abort all connections
                while (!m_connections.empty())
                {
#ifndef NDEBUG
                        int conn = m_connections.size();
#endif
                        (*m_connections.begin())->disconnect("stopping torrent");
                        TORRENT_ASSERT(conn == int(m_connections.size()) + 1);
                }

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " shutting down connection queue\n";
#endif
                m_half_open.close();

                m_download_channel.close();
                m_upload_channel.close();
        }

        void session_impl::set_port_filter(port_filter const& f)
        {
                mutex_t::scoped_lock l(m_mutex);
                m_port_filter = f;
        }

        void session_impl::set_ip_filter(ip_filter const& f)
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                m_ip_filter = f;

                // Close connections whose endpoint is filtered
                // by the new ip-filter
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                        i->second->ip_filter_updated();
        }

        void session_impl::set_settings(session_settings const& s)
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                TORRENT_ASSERT(s.file_pool_size > 0);

                // less than 5 seconds unchoke interval is insane
                TORRENT_ASSERT(s.unchoke_interval >= 5);
                if (m_settings.cache_size != s.cache_size)
                        m_disk_thread.set_cache_size(s.cache_size);
                if (m_settings.cache_expiry != s.cache_expiry)
                        m_disk_thread.set_cache_size(s.cache_expiry);
                // if queuing settings were changed, recalculate
                // queued torrents sooner
                if ((m_settings.active_downloads != s.active_downloads
                        || m_settings.active_seeds != s.active_seeds
                        || m_settings.active_limit != s.active_limit)
                        && m_auto_manage_time_scaler > 2)
                        m_auto_manage_time_scaler = 2;
                m_settings = s;
                if (m_settings.connection_speed <= 0) m_settings.connection_speed = 200;
 
                m_files.resize(m_settings.file_pool_size);
                if (!s.auto_upload_slots) m_allowed_upload_slots = m_max_uploads;
                // replace all occurances of '\n' with ' '.
                std::string::iterator i = m_settings.user_agent.begin();
                while ((i = std::find(i, m_settings.user_agent.end(), '\n'))
                        != m_settings.user_agent.end())
                        *i = ' ';
        }

        tcp::endpoint session_impl::get_ipv6_interface() const
        {
                return m_ipv6_interface;
        }

        session_impl::listen_socket_t session_impl::setup_listener(tcp::endpoint ep
                , int retries, bool v6_only)
        {
                error_code ec;
                listen_socket_t s;
                s.sock.reset(new socket_acceptor(m_io_service));
                s.sock->open(ep.protocol(), ec);
                s.sock->set_option(socket_acceptor::reuse_address(true), ec);
                if (ep.protocol() == tcp::v6()) s.sock->set_option(v6only(v6_only), ec);
                s.sock->bind(ep, ec);
                while (ec && retries > 0)
                {
                        ec = error_code();
                        TORRENT_ASSERT(!ec);
                        --retries;
                        ep.port(ep.port() + 1);
                        s.sock->bind(ep, ec);
                }
                if (ec)
                {
                        // instead of giving up, try
                        // let the OS pick a port
                        ep.port(0);
                        ec = error_code();
                        s.sock->bind(ep, ec);
                }
                if (ec)
                {
                        // not even that worked, give up
                        if (m_alerts.should_post<listen_failed_alert>())
                                m_alerts.post_alert(listen_failed_alert(ep, ec));
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        std::stringstream msg;
                        msg << "cannot bind to interface '";
                        print_endpoint(msg, ep) << "' " << ec.message();
                        (*m_logger) << msg.str() << "\n";
#endif
                        return listen_socket_t();
                }
                s.external_port = s.sock->local_endpoint(ec).port();
                s.sock->listen(0, ec);
                if (ec)
                {
                        if (m_alerts.should_post<listen_failed_alert>())
                                m_alerts.post_alert(listen_failed_alert(ep, ec));
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        std::stringstream msg;
                        msg << "cannot listen on interface '";
                        print_endpoint(msg, ep) << "' " << ec.message();
                        (*m_logger) << msg.str() << "\n";
#endif
                        return listen_socket_t();
                }

                if (m_alerts.should_post<listen_succeeded_alert>())
                        m_alerts.post_alert(listen_succeeded_alert(ep));

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << "listening on: " << ep
                        << " external port: " << s.external_port << "\n";
#endif
                return s;
        }
        
        void session_impl::open_listen_port()
        {
                // close the open listen sockets
                m_listen_sockets.clear();
                m_incoming_connection = false;

                if (is_any(m_listen_interface.address()))
                {
                        // this means we should open two listen sockets
                        // one for IPv4 and one for IPv6
                
                        listen_socket_t s = setup_listener(
                                tcp::endpoint(address_v4::any(), m_listen_interface.port())
                                , m_listen_port_retries);

                        if (s.sock)
                        {
                                m_listen_sockets.push_back(s);
                                async_accept(s.sock);
                        }

                        s = setup_listener(
                                tcp::endpoint(address_v6::any(), m_listen_interface.port())
                                , m_listen_port_retries, true);

                        if (s.sock)
                        {
                                m_listen_sockets.push_back(s);
                                async_accept(s.sock);
                        }
                }
                else
                {
                        // we should only open a single listen socket, that
                        // binds to the given interface

                        listen_socket_t s = setup_listener(
                                m_listen_interface, m_listen_port_retries);

                        if (s.sock)
                        {
                                m_listen_sockets.push_back(s);
                                async_accept(s.sock);
                        }
                }

                m_ipv6_interface = tcp::endpoint();

                for (std::list<listen_socket_t>::const_iterator i = m_listen_sockets.begin()
                        , end(m_listen_sockets.end()); i != end; ++i)
                {
                        error_code ec;
                        tcp::endpoint ep = i->sock->local_endpoint(ec);
                        if (ec || ep.address().is_v4()) continue;

                        if (ep.address().to_v6() != address_v6::any())
                        {
                                // if we're listening on a specific address
                                // pick it
                                m_ipv6_interface = ep;
                        }
                        else
                        {
                                // if we're listening on any IPv6 address, enumerate them and
                                // pick the first non-local address
                                std::vector<ip_interface> const& ifs = enum_net_interfaces(m_io_service, ec);
                                for (std::vector<ip_interface>::const_iterator i = ifs.begin()
                                        , end(ifs.end()); i != end; ++i)
                                {
                                        if (i->interface_address.is_v4()
                                                || i->interface_address.to_v6().is_link_local()
                                                || i->interface_address.to_v6().is_loopback()) continue;
                                        m_ipv6_interface = tcp::endpoint(i->interface_address, ep.port());
                                        break;
                                }
                                break;
                        }
                }

                if (!m_listen_sockets.empty())
                {
                        error_code ec;
                        tcp::endpoint local = m_listen_sockets.front().sock->local_endpoint(ec);
                        if (!ec)
                        {
                                if (m_natpmp.get())
                                {
                                        if (m_tcp_mapping[0] != -1) m_natpmp->delete_mapping(m_tcp_mapping[0]);
                                        m_tcp_mapping[0] = m_natpmp->add_mapping(natpmp::tcp
                                                , local.port(), local.port());
                                }
                                if (m_upnp.get())
                                {
                                        if (m_tcp_mapping[1] != -1) m_upnp->delete_mapping(m_tcp_mapping[1]);
                                        m_tcp_mapping[1] = m_upnp->add_mapping(upnp::tcp
                                                , local.port(), local.port());
                                }
                        }
                }
        }

#ifndef TORRENT_DISABLE_DHT

        void session_impl::on_receive_udp(error_code const& e
                , udp::endpoint const& ep, char const* buf, int len)
        {
                if (e)
                {
                        if (e == asio::error::connection_refused
                                || e == asio::error::connection_reset
                                || e == asio::error::connection_aborted)
                                m_dht->on_unreachable(ep);

                        if (m_alerts.should_post<udp_error_alert>())
                                m_alerts.post_alert(udp_error_alert(ep, e));
                        return;
                }

                if (len > 20 && *buf == 'd' && m_dht)
                {
                        // this is probably a dht message
                        m_dht->on_receive(ep, buf, len);
                }
        }

#endif
        
        void session_impl::async_accept(boost::shared_ptr<socket_acceptor> const& listener)
        {
                shared_ptr<socket_type> c(new socket_type(m_io_service));
                c->instantiate<stream_socket>(m_io_service);
                listener->async_accept(c->get<stream_socket>()
                        , bind(&session_impl::on_incoming_connection, this, c
                        , boost::weak_ptr<socket_acceptor>(listener), _1));
        }

        void session_impl::on_incoming_connection(shared_ptr<socket_type> const& s
                , weak_ptr<socket_acceptor> listen_socket, error_code const& e)
        {
                boost::shared_ptr<socket_acceptor> listener = listen_socket.lock();
                if (!listener) return;
                
                if (e == asio::error::operation_aborted) return;

                mutex_t::scoped_lock l(m_mutex);
                if (m_abort) return;

                error_code ec;
                if (e)
                {
                        tcp::endpoint ep = listener->local_endpoint(ec);
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        std::string msg = "error accepting connection on '"
                                + boost::lexical_cast<std::string>(ep) + "' " + e.message();
                        (*m_logger) << msg << "\n";
#endif
#ifdef TORRENT_WINDOWS
                        // Windows sometimes generates this error. It seems to be
                        // non-fatal and we have to do another async_accept.
                        if (e.value() == ERROR_SEM_TIMEOUT)
                        {
                                async_accept(listener);
                                return;
                        }
#endif
#ifdef TORRENT_BSD
                        // Leopard sometimes generates an "invalid argument" error. It seems to be
                        // non-fatal and we have to do another async_accept.
                        if (e.value() == EINVAL)
                        {
                                async_accept(listener);
                                return;
                        }
#endif
                        if (m_alerts.should_post<listen_failed_alert>())
                                m_alerts.post_alert(listen_failed_alert(ep, e));
                        return;
                }
                async_accept(listener);

                // we got a connection request!
                tcp::endpoint endp = s->remote_endpoint(ec);

                if (ec)
                {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        (*m_logger) << endp << " <== INCOMING CONNECTION FAILED, could "
                                "not retrieve remote endpoint " << ec.message() << "\n";
#endif
                        return;
                }

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " <== INCOMING CONNECTION " << endp << "\n";
#endif

                // local addresses do not count, since it's likely
                // coming from our own client through local service discovery
                // and it does not reflect whether or not a router is open
                // for incoming connections or not.
                if (!is_local(endp.address()))
                        m_incoming_connection = true;

                if (m_ip_filter.access(endp.address()) & ip_filter::blocked)
                {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        (*m_logger) << "filtered blocked ip\n";
#endif
                        if (m_alerts.should_post<peer_blocked_alert>())
                                m_alerts.post_alert(peer_blocked_alert(endp.address()));
                        return;
                }

                // don't allow more connections than the max setting
                if (num_connections() >= max_connections())
                {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        (*m_logger) << "number of connections limit exceeded (conns: "
                                << num_connections() << ", limit: " << max_connections()
                                << "), connection rejected\n";
#endif
                        return;
                }

                // check if we have any active torrents
                // if we don't reject the connection
                if (m_torrents.empty())
                {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        (*m_logger) << " There are no torrents, disconnect\n";
#endif
                        return;
                }

                bool has_active_torrent = false;
                for (torrent_map::iterator i = m_torrents.begin()
                                , end(m_torrents.end()); i != end; ++i)
                {
                        if (!i->second->is_paused())
                        {
                                has_active_torrent = true;
                                break;
                        }
                }
                if (!has_active_torrent)
                {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                        (*m_logger) << " There are no _active_ torrents, disconnect\n";
#endif
                        return;
                }

                boost::intrusive_ptr<peer_connection> c(
                        new bt_peer_connection(*this, s, endp, 0));
#ifndef NDEBUG
                c->m_in_constructor = false;
#endif

                if (!c->is_disconnecting())
                {
                        m_connections.insert(c);
                        c->start();
                }
        }
        void session_impl::close_connection(peer_connection const* p
                , char const* message)
        {
                mutex_t::scoped_lock l(m_mutex);

// too expensive
//              INVARIANT_CHECK;

#ifndef NDEBUG
//              for (aux::session_impl::torrent_map::const_iterator i = m_torrents.begin()
//                      , end(m_torrents.end()); i != end; ++i)
//                      TORRENT_ASSERT(!i->second->has_peer((peer_connection*)p));
#endif

#if defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " CLOSING CONNECTION "
                        << p->remote() << " : " << message << "\n";
#endif

                TORRENT_ASSERT(p->is_disconnecting());

                if (!p->is_choked()) --m_num_unchoked;
//              connection_map::iterator i = std::lower_bound(m_connections.begin(), m_connections.end()
//                      , p, bind(&boost::intrusive_ptr<peer_connection>::get, _1) < p);
//              if (i->get() != p) i == m_connections.end();
                connection_map::iterator i = std::find_if(m_connections.begin(), m_connections.end()
                        , bind(&boost::intrusive_ptr<peer_connection>::get, _1) == p);
                if (i != m_connections.end()) m_connections.erase(i);
        }

        void session_impl::set_peer_id(peer_id const& id)
        {
                mutex_t::scoped_lock l(m_mutex);
                m_peer_id = id;
        }

        void session_impl::set_key(int key)
        {
                mutex_t::scoped_lock l(m_mutex);
                m_key = key;
        }

        int session_impl::next_port()
        {
                std::pair<int, int> const& out_ports = m_settings.outgoing_ports;
                if (m_next_port < out_ports.first || m_next_port > out_ports.second)
                        m_next_port = out_ports.first;
        
                int port = m_next_port;
                ++m_next_port;
                if (m_next_port > out_ports.second) m_next_port = out_ports.first;
#if defined TORRENT_LOGGING
                (*m_logger) << time_now_string() << " *** BINDING OUTGOING CONNECTION [ "
                        "port: " << port << " ]\n";
#endif
                return port;
        }

        void session_impl::second_tick(error_code const& e)
        {
                session_impl::mutex_t::scoped_lock l(m_mutex);

// too expensive
//              INVARIANT_CHECK;

                if (m_abort) return;

                if (e)
                {
#if defined TORRENT_LOGGING
                        (*m_logger) << "*** SECOND TIMER FAILED " << e.message() << "\n";
#endif
                        ::abort();
                        return;
                }

                float tick_interval = total_microseconds(time_now() - m_last_tick) / 1000000.f;
                m_last_tick = time_now();

                error_code ec;
                m_timer.expires_from_now(seconds(1), ec);
                m_timer.async_wait(
                        bind(&session_impl::second_tick, this, _1));

#ifdef TORRENT_STATS
                ++m_second_counter;
                int downloading_torrents = 0;
                int seeding_torrents = 0;
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        if (i->second->is_seed())
                                ++seeding_torrents;
                        else
                                ++downloading_torrents;
                }
                int num_complete_connections = 0;
                int num_half_open = 0;
                for (connection_map::iterator i = m_connections.begin()
                        , end(m_connections.end()); i != end; ++i)
                {
                        if ((*i)->is_connecting())
                                ++num_half_open;
                        else
                                ++num_complete_connections;
                }
                
                m_stats_logger
                        << m_second_counter << "\t"
                        << m_stat.upload_rate() << "\t"
                        << m_stat.download_rate() << "\t"
                        << downloading_torrents << "\t"
                        << seeding_torrents << "\t"
                        << num_complete_connections << "\t"
                        << num_half_open << "\t"
                        << m_disk_thread.disk_allocations() << "\t"
                        << std::endl;
#endif

                // --------------------------------------------------------------
                // check for incoming connections that might have timed out
                // --------------------------------------------------------------

                for (connection_map::iterator i = m_connections.begin();
                        i != m_connections.end();)
                {
                        peer_connection* p = (*i).get();
                        ++i;
                        // ignore connections that already have a torrent, since they
                        // are ticket through the torrents' second_ticket
                        if (!p->associated_torrent().expired()) continue;
                        if (m_last_tick - p->connected_time() > seconds(m_settings.handshake_timeout))
                                p->disconnect("timeout: incoming connection");
                }

                // --------------------------------------------------------------
                // second_tick every torrent
                // --------------------------------------------------------------

                int congested_torrents = 0;
                int uncongested_torrents = 0;

                // count the number of seeding torrents vs. downloading
                // torrents we are running
                int num_seeds = 0;
                int num_downloads = 0;

                // count the number of peers of downloading torrents
                int num_downloads_peers = 0;

                torrent_map::iterator least_recently_scraped = m_torrents.begin();
                int num_paused_auto_managed = 0;

                // check each torrent for tracker updates
                // TODO: do this in a timer-event in each torrent instead
                for (torrent_map::iterator i = m_torrents.begin();
                        i != m_torrents.end();)
                {
                        torrent& t = *i->second;
                        TORRENT_ASSERT(!t.is_aborted());
                        if (t.bandwidth_queue_size(peer_connection::upload_channel))
                                ++congested_torrents;
                        else
                                ++uncongested_torrents;

                        if (t.is_auto_managed() && t.is_paused() && !t.has_error())
                        {
                                ++num_paused_auto_managed;
                                if (!least_recently_scraped->second->is_auto_managed()
                                        || !least_recently_scraped->second->is_paused()
                                        || least_recently_scraped->second->last_scrape() > t.last_scrape())
                                {
                                        least_recently_scraped = i;
                                }
                        }

                        if (t.is_finished())
                        {
                                ++num_seeds;
                        }
                        else
                        {
                                ++num_downloads;
                                num_downloads_peers += t.num_peers();
                        }

                        t.second_tick(m_stat, tick_interval);
                        ++i;
                }

                // drain the IP overhead from the bandwidth limiters
                m_download_channel.drain(m_stat.download_ip_overhead());
                m_upload_channel.drain(m_stat.upload_ip_overhead());

                m_stat.second_tick(tick_interval);

                // --------------------------------------------------------------
                // scrape paused torrents that are auto managed
                // --------------------------------------------------------------
                --m_auto_scrape_time_scaler;
                if (m_auto_scrape_time_scaler <= 0)
                {
                        m_auto_scrape_time_scaler = m_settings.auto_scrape_interval
                                / (std::max)(1, num_paused_auto_managed);
                        if (m_auto_scrape_time_scaler < m_settings.auto_scrape_min_interval)
                                m_auto_scrape_time_scaler = m_settings.auto_scrape_min_interval;

                        if (least_recently_scraped != m_torrents.end())
                        {
                                least_recently_scraped->second->scrape_tracker();
                        }
                }

                // --------------------------------------------------------------
                // connect new peers
                // --------------------------------------------------------------

                // let torrents connect to peers if they want to
                // if there are any torrents and any free slots

                // this loop will "hand out" max(connection_speed
                // , half_open.free_slots()) to the torrents, in a
                // round robin fashion, so that every torrent is
                // equallt likely to connect to a peer

                int free_slots = m_half_open.free_slots();
                if (!m_torrents.empty()
                        && free_slots > -m_half_open.limit()
                        && num_connections() < m_max_connections)
                {
                        // this is the maximum number of connections we will
                        // attempt this tick
                        int max_connections = m_settings.connection_speed;
                        int average_peers = 0;
                        if (num_downloads > 0)
                                average_peers = num_downloads_peers / num_downloads;

                        torrent_map::iterator i = m_torrents.begin();
                        if (m_next_connect_torrent < int(m_torrents.size()))
                                std::advance(i, m_next_connect_torrent);
                        else
                                m_next_connect_torrent = 0;
                        int steps_since_last_connect = 0;
                        int num_torrents = int(m_torrents.size());
                        for (;;)
                        {
                                torrent& t = *i->second;
                                if (t.want_more_peers())
                                {
                                        int connect_points = 100;
                                        // have a bias against torrents with more peers
                                        // than average
                                        if (!t.is_seed() && t.num_peers() > average_peers)
                                                connect_points /= 2;
                                        // if this is a seed and there is a torrent that
                                        // is downloading, lower the rate at which this
                                        // torrent gets connections.
                                        // dividing by num_seeds will have the effect
                                        // that all seed will get as many connections
                                        // together, as a single downloading torrent.
                                        if (t.is_seed() && num_downloads > 0)
                                                connect_points /= num_seeds + 1;
                                        if (connect_points <= 0) connect_points = 1;
                                        t.give_connect_points(connect_points);
                                        try
                                        {
                                                if (t.try_connect_peer())
                                                {
                                                        --max_connections;
                                                        --free_slots;
                                                        steps_since_last_connect = 0;
                                                }
                                        }
                                        catch (std::bad_alloc&)
                                        {
                                                // we ran out of memory trying to connect to a peer
                                                // lower the global limit to the number of peers
                                                // we already have
                                                m_max_connections = num_connections();
                                                if (m_max_connections < 2) m_max_connections = 2;
                                        }
                                }
                                ++m_next_connect_torrent;
                                ++steps_since_last_connect;
                                ++i;
                                if (i == m_torrents.end())
                                {
                                        TORRENT_ASSERT(m_next_connect_torrent == num_torrents);
                                        i = m_torrents.begin();
                                        m_next_connect_torrent = 0;
                                }
                                // if we have gone two whole loops without
                                // handing out a single connection, break
                                if (steps_since_last_connect > num_torrents * 2) break;
                                // if there are no more free connection slots, abort
                                if (free_slots <= -m_half_open.limit()) break;
                                // if we should not make any more connections
                                // attempts this tick, abort
                                if (max_connections == 0) break;
                                // maintain the global limit on number of connections
                                if (num_connections() >= m_max_connections) break;
                        }
                }

                // --------------------------------------------------------------
                // auto managed torrent
                // --------------------------------------------------------------
                m_auto_manage_time_scaler--;
                if (m_auto_manage_time_scaler <= 0)
                {
                        m_auto_manage_time_scaler = settings().auto_manage_interval;
                        recalculate_auto_managed_torrents();
                }

                // --------------------------------------------------------------
                // unchoke set and optimistic unchoke calculations
                // --------------------------------------------------------------
                m_unchoke_time_scaler--;
                if (m_unchoke_time_scaler <= 0 && !m_connections.empty())
                {
                        m_unchoke_time_scaler = settings().unchoke_interval;
                        recalculate_unchoke_slots(congested_torrents
                                , uncongested_torrents);
                }

                // --------------------------------------------------------------
                // disconnect peers when we have too many
                // --------------------------------------------------------------
                --m_disconnect_time_scaler;
                if (m_disconnect_time_scaler <= 0)
                {
                        m_disconnect_time_scaler = 90;

                        // every 90 seconds, disconnect the worst peers
                        // if we have reached the connection limit
                        if (num_connections() >= max_connections() * m_settings.peer_turnover_cutoff
                                && !m_torrents.empty())
                        {
                                torrent_map::iterator i = std::max_element(m_torrents.begin(), m_torrents.end()
                                        , bind(&torrent::num_peers, bind(&torrent_map::value_type::second, _1))
                                        < bind(&torrent::num_peers, bind(&torrent_map::value_type::second, _2)));
                        
                                TORRENT_ASSERT(i != m_torrents.end());
                                int peers_to_disconnect = (std::min)((std::max)(int(i->second->num_peers()
                                        * m_settings.peer_turnover), 1)
                                        , i->second->get_policy().num_connect_candidates());
                                i->second->disconnect_peers(peers_to_disconnect);
                        }
                        else
                        {
                                // if we haven't reached the global max. see if any torrent
                                // has reached its local limit
                                for (torrent_map::iterator i = m_torrents.begin()
                                        , end(m_torrents.end()); i != end; ++i)
                                {
                                        boost::shared_ptr<torrent> t = i->second;
                                        if (t->num_peers() < t->max_connections() * m_settings.peer_turnover_cutoff)
                                                continue;

                                        int peers_to_disconnect = (std::min)((std::max)(int(i->second->num_peers()
                                                * m_settings.peer_turnover), 1)
                                                , i->second->get_policy().num_connect_candidates());
                                        t->disconnect_peers(peers_to_disconnect);
                                }
                        }
                }
        }

        namespace
        {
                bool is_active(torrent* t, session_settings const& s)
                {
                        return !(s.dont_count_slow_torrents
                                && t->statistics().upload_payload_rate() == 0.f
                                && t->statistics().download_payload_rate() == 0.f);
                }
        }

        void session_impl::recalculate_auto_managed_torrents()
        {
                // these vectors are filled with auto managed torrents
                std::vector<torrent*> downloaders;
                downloaders.reserve(m_torrents.size());
                std::vector<torrent*> seeds;
                seeds.reserve(m_torrents.size());

                // these counters are set to the number of torrents
                // of each kind we're allowed to have active
                int num_downloaders = settings().active_downloads;
                int num_seeds = settings().active_seeds;
                int hard_limit = settings().active_limit;

        if (num_downloaders == -1)
            num_downloaders = (std::numeric_limits<int>::max)();
        if (num_seeds == -1)
            num_seeds = (std::numeric_limits<int>::max)();
        if (hard_limit == -1)
            hard_limit = (std::numeric_limits<int>::max)();
            
                for (torrent_map::iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        torrent* t = i->second.get();
                        TORRENT_ASSERT(t);
                        if (t->is_auto_managed() && !t->has_error())
                        {
                                // this torrent is auto managed, add it to
                                // the list (depending on if it's a seed or not)
                                if (t->is_finished())
                                        seeds.push_back(t);
                                else
                                        downloaders.push_back(t);
                        }
                        else if (!t->is_paused())
                        {
                                --hard_limit;
                                if (is_active(t, settings()))
                                {
                                        // this is not an auto managed torrent,
                                        // if it's running and active, decrease the
                                        // counters.
                                        --num_downloaders;
                                        --num_seeds;
                                }
                        }
                }

                bool handled_by_extension = false;

#ifndef TORRENT_DISABLE_EXTENSIONS
                // TODO: allow extensions to sort torrents for queuing
#endif

                if (!handled_by_extension)
                {
                        std::sort(downloaders.begin(), downloaders.end()
                                , bind(&torrent::sequence_number, _1) < bind(&torrent::sequence_number, _2));

                        std::sort(seeds.begin(), seeds.end()
                                , bind(&torrent::seed_rank, _1, boost::ref(m_settings))
                                > bind(&torrent::seed_rank, _2, boost::ref(m_settings)));
                }

                for (std::vector<torrent*>::iterator i = downloaders.begin()
                        , end(downloaders.end()); i != end; ++i)
                {
                        torrent* t = *i;
                        if (!t->is_paused() && !is_active(t, settings()) && hard_limit > 0)
                        {
                                --hard_limit;
                                continue;
                        }

                        if (num_downloaders > 0 && hard_limit > 0)
                        {
                                --hard_limit;
                                if (t->state() != torrent_status::queued_for_checking
                                        && t->state() != torrent_status::checking_files)
                                {
                                        --num_downloaders;
                                        if (t->is_paused()) t->resume();
                                }
                        }
                        else
                        {
                                if (!t->is_paused()) t->pause();
                        }
                }

                for (std::vector<torrent*>::iterator i = seeds.begin()
                        , end(seeds.end()); i != end; ++i)
                {
                        torrent* t = *i;
                        if (!t->is_paused() && !is_active(t, settings()) && hard_limit > 0)
                        {
                                --hard_limit;
                                continue;
                        }

                        if (num_seeds > 0 && hard_limit > 0)
                        {
                                --hard_limit;
                                --num_seeds;
                                if (t->is_paused()) t->resume();
                        }
                        else
                        {
                                if (!t->is_paused()) t->pause();
                        }
                }
        }

        void session_impl::recalculate_unchoke_slots(int congested_torrents
                , int uncongested_torrents)
        {
                std::vector<peer_connection*> peers;
                for (connection_map::iterator i = m_connections.begin()
                        , end(m_connections.end()); i != end; ++i)
                {
                        peer_connection* p = i->get();
                        torrent* t = p->associated_torrent().lock().get();
                        if (!p->peer_info_struct()
                                || t == 0
                                || !p->is_peer_interested()
                                || p->is_disconnecting()
                                || p->is_connecting()
                                || (p->share_diff() < -free_upload_amount
                                        && !t->is_seed()))
                        {
                                if (!(*i)->is_choked() && t)
                                {
                                        policy::peer* pi = p->peer_info_struct();
                                        if (pi && pi->optimistically_unchoked)
                                        {
                                                pi->optimistically_unchoked = false;
                                                // force a new optimistic unchoke
                                                m_optimistic_unchoke_time_scaler = 0;
                                        }
                                        t->choke_peer(*(*i));
                                }
                                continue;
                        }
                        peers.push_back(i->get());
                }

                // sorts the peers that are eligible for unchoke by download rate and secondary
                // by total upload. The reason for this is, if all torrents are being seeded,
                // the download rate will be 0, and the peers we have sent the least to should
                // be unchoked
                std::sort(peers.begin(), peers.end()
                        , bind(&peer_connection::unchoke_compare, _1, _2));

                std::for_each(m_connections.begin(), m_connections.end()
                        , bind(&peer_connection::reset_choke_counters, _1));

                // auto unchoke
                int upload_limit = m_bandwidth_manager[peer_connection::upload_channel]->throttle();
                if (m_settings.auto_upload_slots && upload_limit != bandwidth_limit::inf)
                {
                        // if our current upload rate is less than 90% of our 
                        // limit AND most torrents are not "congested", i.e.
                        // they are not holding back because of a per-torrent
                        // limit
                        if (m_stat.upload_rate() < upload_limit * 0.9f
                                && m_allowed_upload_slots <= m_num_unchoked + 1
                                && congested_torrents < uncongested_torrents)
                        {
                                ++m_allowed_upload_slots;
                        }
                        else if (m_upload_channel.queue_size() > 1
                                && m_allowed_upload_slots > m_max_uploads)
                        {
                                --m_allowed_upload_slots;
                        }
                }

                // reserve one upload slot for optimistic unchokes
                int unchoke_set_size = m_allowed_upload_slots - 1;

                m_num_unchoked = 0;
                // go through all the peers and unchoke the first ones and choke
                // all the other ones.
                for (std::vector<peer_connection*>::iterator i = peers.begin()
                        , end(peers.end()); i != end; ++i)
                {
                        peer_connection* p = *i;
                        TORRENT_ASSERT(p);
                        torrent* t = p->associated_torrent().lock().get();
                        TORRENT_ASSERT(t);
                        if (unchoke_set_size > 0)
                        {
                                if (p->is_choked())
                                {
                                        if (!t->unchoke_peer(*p))
                                                continue;
                                }

                                --unchoke_set_size;
                                ++m_num_unchoked;

                                TORRENT_ASSERT(p->peer_info_struct());
                                if (p->peer_info_struct()->optimistically_unchoked)
                                {
                                        // force a new optimistic unchoke
                                        m_optimistic_unchoke_time_scaler = 0;
                                        p->peer_info_struct()->optimistically_unchoked = false;
                                }
                        }
                        else
                        {
                                TORRENT_ASSERT(p->peer_info_struct());
                                if (!p->is_choked() && !p->peer_info_struct()->optimistically_unchoked)
                                        t->choke_peer(*p);
                                if (!p->is_choked())
                                        ++m_num_unchoked;
                        }
                }

                m_optimistic_unchoke_time_scaler--;
                if (m_optimistic_unchoke_time_scaler <= 0)
                {
                        m_optimistic_unchoke_time_scaler
                                = settings().optimistic_unchoke_multiplier;

                        // find the peer that has been waiting the longest to be optimistically
                        // unchoked
                        connection_map::iterator current_optimistic_unchoke = m_connections.end();
                        connection_map::iterator optimistic_unchoke_candidate = m_connections.end();
                        ptime last_unchoke = max_time();

                        for (connection_map::iterator i = m_connections.begin()
                                , end(m_connections.end()); i != end; ++i)
                        {
                                peer_connection* p = i->get();
                                TORRENT_ASSERT(p);
                                policy::peer* pi = p->peer_info_struct();
                                if (!pi) continue;
                                torrent* t = p->associated_torrent().lock().get();
                                if (!t) continue;

                                if (pi->optimistically_unchoked)
                                {
                                        TORRENT_ASSERT(!p->is_choked());
                                        TORRENT_ASSERT(current_optimistic_unchoke == m_connections.end());
                                        current_optimistic_unchoke = i;
                                }

                                if (pi->last_optimistically_unchoked < last_unchoke
                                        && !p->is_connecting()
                                        && !p->is_disconnecting()
                                        && p->is_peer_interested()
                                        && t->free_upload_slots()
                                        && p->is_choked())
                                {
                                        last_unchoke = pi->last_optimistically_unchoked;
                                        optimistic_unchoke_candidate = i;
                                }
                        }

                        if (optimistic_unchoke_candidate != m_connections.end()
                                && optimistic_unchoke_candidate != current_optimistic_unchoke)
                        {
                                if (current_optimistic_unchoke != m_connections.end())
                                {
                                        torrent* t = (*current_optimistic_unchoke)->associated_torrent().lock().get();
                                        TORRENT_ASSERT(t);
                                        (*current_optimistic_unchoke)->peer_info_struct()->optimistically_unchoked = false;
                                        t->choke_peer(*current_optimistic_unchoke->get());
                                }
                                else
                                {
                                        ++m_num_unchoked;
                                }

                                torrent* t = (*optimistic_unchoke_candidate)->associated_torrent().lock().get();
                                TORRENT_ASSERT(t);
                                bool ret = t->unchoke_peer(*optimistic_unchoke_candidate->get());
                                TORRENT_ASSERT(ret);
                                (*optimistic_unchoke_candidate)->peer_info_struct()->optimistically_unchoked = true;
                        }
                }
        }

        void session_impl::operator()()
        {
                eh_initializer();

                {
                        session_impl::mutex_t::scoped_lock l(m_mutex);
                        if (m_listen_interface.port() != 0) open_listen_port();
                }

                ptime timer = time_now();

                do
                {
#ifndef BOOST_NO_EXCEPTIONS
                        try
                        {
#endif
                                m_io_service.run();
                                TORRENT_ASSERT(m_abort == true);
#ifndef BOOST_NO_EXCEPTIONS
                        }
                        catch (std::exception& e)
                        {
#ifndef NDEBUG
                                std::cerr << e.what() << "\n";
                                std::string err = e.what();
#endif
                                TORRENT_ASSERT(false);
                        }
#endif
                }
                while (!m_abort);

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " locking mutex\n";
#endif

                session_impl::mutex_t::scoped_lock l(m_mutex);
/*
#ifndef NDEBUG
                for (torrent_map::iterator i = m_torrents.begin();
                        i != m_torrents.end(); ++i)
                {
                        TORRENT_ASSERT(i->second->num_peers() == 0);
                }
#endif
*/
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " cleaning up torrents\n";
#endif
                m_torrents.clear();

                TORRENT_ASSERT(m_torrents.empty());
                TORRENT_ASSERT(m_connections.empty());
        }


        // the return value from this function is valid only as long as the
        // session is locked!
        boost::weak_ptr<torrent> session_impl::find_torrent(sha1_hash const& info_hash)
        {
                std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator i
                        = m_torrents.find(info_hash);
#ifndef NDEBUG
                for (std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator j
                        = m_torrents.begin(); j != m_torrents.end(); ++j)
                {
                        torrent* p = boost::get_pointer(j->second);
                        TORRENT_ASSERT(p);
                }
#endif
                if (i != m_torrents.end()) return i->second;
                return boost::weak_ptr<torrent>();
        }

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
        boost::shared_ptr<logger> session_impl::create_log(std::string const& name
                , int instance, bool append)
        {
                // current options are file_logger, cout_logger and null_logger
                return boost::shared_ptr<logger>(new logger(m_logpath, name + ".log", instance, append));
        }
#endif

        std::vector<torrent_handle> session_impl::get_torrents()
        {
                mutex_t::scoped_lock l(m_mutex);
                std::vector<torrent_handle> ret;

                for (session_impl::torrent_map::iterator i
                        = m_torrents.begin(), end(m_torrents.end());
                        i != end; ++i)
                {
                        if (i->second->is_aborted()) continue;
                        ret.push_back(torrent_handle(i->second));
                }
                return ret;
        }

        torrent_handle session_impl::find_torrent_handle(sha1_hash const& info_hash)
        {
                return torrent_handle(find_torrent(info_hash));
        }

        torrent_handle session_impl::add_torrent(add_torrent_params const& params)
        {
                TORRENT_ASSERT(!params.save_path.empty());

                if (params.ti && params.ti->files().num_files() == 0)
                {
#ifndef BOOST_NO_EXCEPTIONS
                        throw std::runtime_error("no files in torrent");
#else
                        return torrent_handle();
#endif
                }

                // lock the session and the checker thread (the order is important!)
                mutex_t::scoped_lock l(m_mutex);

//              INVARIANT_CHECK;

                if (is_aborted())
                {
#ifndef BOOST_NO_EXCEPTIONS
                        throw std::runtime_error("session is closing");
#else
                        return torrent_handle();
#endif
                }
                
                // figure out the info hash of the torrent
                sha1_hash const* ih = 0;
                if (params.ti) ih = &params.ti->info_hash();
                else ih = &params.info_hash;

                // is the torrent already active?
                boost::shared_ptr<torrent> torrent_ptr = find_torrent(*ih).lock();
                if (torrent_ptr)
                {
                        if (!params.duplicate_is_error)
                                return torrent_handle(torrent_ptr);

#ifndef BOOST_NO_EXCEPTIONS
                        throw duplicate_torrent();
#else
                        return torrent_handle();
#endif
                }

                int queue_pos = 0;
                for (torrent_map::const_iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        int pos = i->second->queue_position();
                        if (pos >= queue_pos) queue_pos = pos + 1;
                }

                // create the torrent and the data associated with
                // the checker thread and store it before starting
                // the thread
                if (params.ti)
                {
                        torrent_ptr.reset(new torrent(*this, params.ti, params.save_path
                                , m_listen_interface, params.storage_mode, 16 * 1024
                                , params.storage, params.paused, params.resume_data
                                , queue_pos, params.auto_managed));
                }
                else
                {
                        torrent_ptr.reset(new torrent(*this, params.tracker_url, *ih, params.name
                                , params.save_path, m_listen_interface, params.storage_mode, 16 * 1024
                                , params.storage, params.paused, params.resume_data
                                , queue_pos, params.auto_managed));
                }
                torrent_ptr->start();

#ifndef TORRENT_DISABLE_EXTENSIONS
                for (extension_list_t::iterator i = m_extensions.begin()
                        , end(m_extensions.end()); i != end; ++i)
                {
                        boost::shared_ptr<torrent_plugin> tp((*i)(torrent_ptr.get(), params.userdata));
                        if (tp) torrent_ptr->add_extension(tp);
                }
#endif

#ifndef TORRENT_DISABLE_DHT
                if (m_dht && params.ti)
                {
                        torrent_info::nodes_t const& nodes = params.ti->nodes();
                        std::for_each(nodes.begin(), nodes.end(), bind(
                                (void(dht::dht_tracker::*)(std::pair<std::string, int> const&))
                                &dht::dht_tracker::add_node
                                , boost::ref(m_dht), _1));
                }
#endif

                m_torrents.insert(std::make_pair(*ih, torrent_ptr));

                // if this is an auto managed torrent, force a recalculation
                // of which torrents to have active
                if (params.auto_managed && m_auto_manage_time_scaler > 2)
                        m_auto_manage_time_scaler = 2;

                return torrent_handle(torrent_ptr);
        }

        void session_impl::check_torrent(boost::shared_ptr<torrent> const& t)
        {
                if (m_abort) return;
                if (m_queued_for_checking.empty()) t->start_checking();
                m_queued_for_checking.push_back(t);
        }

        void session_impl::done_checking(boost::shared_ptr<torrent> const& t)
        {
                if (m_queued_for_checking.empty()) return;
                check_queue_t::iterator next_check = m_queued_for_checking.begin();
                check_queue_t::iterator done = m_queued_for_checking.end();
                for (check_queue_t::iterator i = m_queued_for_checking.begin()
                        , end(m_queued_for_checking.end()); i != end; ++i)
                {
                        if (*i == t) done = i;
                        if (next_check == done || (*next_check)->queue_position() > (*i)->queue_position())
                                next_check = i;
                }
                if (next_check != done) (*next_check)->start_checking();
                m_queued_for_checking.erase(done);
        }

        void session_impl::remove_torrent(const torrent_handle& h, int options)
        {
                boost::shared_ptr<torrent> tptr = h.m_torrent.lock();
                if (!tptr)
#ifdef BOOST_NO_EXCEPTIONS
                        return;
#else
                        throw invalid_handle();
#endif

                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                session_impl::torrent_map::iterator i =
                        m_torrents.find(tptr->torrent_file().info_hash());

                if (i != m_torrents.end())
                {
                        torrent& t = *i->second;
                        if (options & session::delete_files)
                                t.delete_files();
                        t.abort();

#ifndef NDEBUG
                        sha1_hash i_hash = t.torrent_file().info_hash();
#endif
                        i->second->set_queue_position(-1);
                        m_torrents.erase(i);
                        TORRENT_ASSERT(m_torrents.find(i_hash) == m_torrents.end());
                        return;
                }
        }

        bool session_impl::listen_on(
                std::pair<int, int> const& port_range
                , const char* net_interface)
        {
                session_impl::mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                tcp::endpoint new_interface;
                if (net_interface && std::strlen(net_interface) > 0)
                        new_interface = tcp::endpoint(address::from_string(net_interface), port_range.first);
                else
                        new_interface = tcp::endpoint(address_v4::any(), port_range.first);

                m_listen_port_retries = port_range.second - port_range.first;

                // if the interface is the same and the socket is open
                // don't do anything
                if (new_interface == m_listen_interface
                        && !m_listen_sockets.empty()) return true;

                m_listen_interface = new_interface;

                open_listen_port();

                bool new_listen_address = m_listen_interface.address() != new_interface.address();

#ifndef TORRENT_DISABLE_DHT
                if ((new_listen_address || m_dht_same_port) && m_dht)
                {
                        if (m_dht_same_port)
                                m_dht_settings.service_port = new_interface.port();
                        // the listen interface changed, rebind the dht listen socket as well
                        m_dht_socket.bind(m_dht_settings.service_port);
                        if (m_natpmp.get())
                        {
                                if (m_udp_mapping[0] != -1) m_natpmp->delete_mapping(m_udp_mapping[0]);
                                m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::tcp
                                        , m_dht_settings.service_port
                                        , m_dht_settings.service_port);
                        }
                        if (m_upnp.get())
                        {
                                if (m_udp_mapping[1] != -1) m_upnp->delete_mapping(m_udp_mapping[1]);
                                m_udp_mapping[1] = m_upnp->add_mapping(upnp::tcp
                                        , m_dht_settings.service_port
                                        , m_dht_settings.service_port);
                        }
                }
#endif

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
                m_logger = create_log("main_session", listen_port(), false);
                (*m_logger) << time_now_string() << "\n";
#endif

                return !m_listen_sockets.empty();
        }

        unsigned short session_impl::listen_port() const
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_listen_sockets.empty()) return 0;
                return m_listen_sockets.front().external_port;;
        }

        void session_impl::announce_lsd(sha1_hash const& ih)
        {
                mutex_t::scoped_lock l(m_mutex);
                // use internal listen port for local peers
                if (m_lsd.get())
                        m_lsd->announce(ih, m_listen_interface.port());
        }

        void session_impl::on_lsd_peer(tcp::endpoint peer, sha1_hash const& ih)
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                boost::shared_ptr<torrent> t = find_torrent(ih).lock();
                if (!t) return;
                // don't add peers from lsd to private torrents
                if (t->torrent_file().priv()) return;

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string()
                        << ": added peer from local discovery: " << peer << "\n";
#endif
                t->get_policy().peer_from_tracker(peer, peer_id(0), peer_info::lsd, 0);
        }

        void session_impl::on_port_mapping(int mapping, int port
                , std::string const& errmsg, int map_transport)
        {
#ifndef TORRENT_DISABLE_DHT
                if (mapping == m_udp_mapping[map_transport] && port != 0)
                {
                        m_external_udp_port = port;
                        m_dht_settings.service_port = port;
                        if (m_alerts.should_post<portmap_alert>())
                                m_alerts.post_alert(portmap_alert(mapping, port
                                        , map_transport));
                        return;
                }
#endif

                if (mapping == m_tcp_mapping[map_transport] && port != 0)
                {
                        if (!m_listen_sockets.empty())
                                m_listen_sockets.front().external_port = port;
                        if (m_alerts.should_post<portmap_alert>())
                                m_alerts.post_alert(portmap_alert(mapping, port
                                        , map_transport));
                        return;
                }

                if (!errmsg.empty())
                {
                        if (m_alerts.should_post<portmap_error_alert>())
                                m_alerts.post_alert(portmap_error_alert(mapping
                                        , map_transport, errmsg));
                }
                else
                {
                        if (m_alerts.should_post<portmap_alert>())
                                m_alerts.post_alert(portmap_alert(mapping, port
                                        , map_transport));
                }
        }

        session_status session_impl::status() const
        {
                mutex_t::scoped_lock l(m_mutex);

//              INVARIANT_CHECK;

                session_status s;

                s.num_peers = (int)m_connections.size();
                s.num_unchoked = m_num_unchoked;
                s.allowed_upload_slots = m_allowed_upload_slots;

                s.total_redundant_bytes = m_total_redundant_bytes;
                s.total_failed_bytes = m_total_failed_bytes;

                s.up_bandwidth_queue = m_upload_channel.queue_size();
                s.down_bandwidth_queue = m_download_channel.queue_size();

                s.has_incoming_connections = m_incoming_connection;

                s.download_rate = m_stat.download_rate();
                s.upload_rate = m_stat.upload_rate();

                s.payload_download_rate = m_stat.download_payload_rate();
                s.payload_upload_rate = m_stat.upload_payload_rate();

                s.total_download = m_stat.total_protocol_download()
                        + m_stat.total_payload_download();

                s.total_upload = m_stat.total_protocol_upload()
                        + m_stat.total_payload_upload();

                s.total_payload_download = m_stat.total_payload_download();
                s.total_payload_upload = m_stat.total_payload_upload();

#ifndef TORRENT_DISABLE_DHT
                if (m_dht)
                {
                        m_dht->dht_status(s);
                }
                else
                {
                        s.dht_nodes = 0;
                        s.dht_node_cache = 0;
                        s.dht_torrents = 0;
                        s.dht_global_nodes = 0;
                }
#endif

                return s;
        }

#ifndef TORRENT_DISABLE_DHT

        void session_impl::start_dht(entry const& startup_state)
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (m_dht)
                {
                        m_dht->stop();
                        m_dht = 0;
                }
                if (m_dht_settings.service_port == 0
                        || m_dht_same_port)
                {
                        m_dht_same_port = true;
                        // if you hit this assert you are trying to start the
                        // DHT with the same port as the tcp listen port
                        // (which is default) _before_ you have opened the
                        // tcp listen port (so there is no configured port to use)
                        // basically, make sure you call listen_on() before
                        // start_dht(). See documentation for listen_on() for
                        // more information.
                        TORRENT_ASSERT(m_listen_interface.port() > 0);
                        m_dht_settings.service_port = m_listen_interface.port();
                }
                m_external_udp_port = m_dht_settings.service_port;
                if (m_natpmp.get() && m_udp_mapping[0] == -1)
                {
                        m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
                                , m_dht_settings.service_port
                                , m_dht_settings.service_port);
                }
                if (m_upnp.get() && m_udp_mapping[1] == -1)
                {
                        m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
                                , m_dht_settings.service_port
                                , m_dht_settings.service_port);
                }
                m_dht = new dht::dht_tracker(m_dht_socket, m_dht_settings, startup_state);
                if (!m_dht_socket.is_open() || m_dht_socket.local_port() != m_dht_settings.service_port)
                {
                        m_dht_socket.bind(m_dht_settings.service_port);
                }
        }

        void session_impl::stop_dht()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (!m_dht) return;
                m_dht->stop();
                m_dht = 0;
        }

        void session_impl::set_dht_settings(dht_settings const& settings)
        {
                mutex_t::scoped_lock l(m_mutex);
                // only change the dht listen port in case the settings
                // contains a vaiid port, and if it is different from
                // the current setting
                if (settings.service_port != 0)
                        m_dht_same_port = false;
                else
                        m_dht_same_port = true;
                if (!m_dht_same_port
                        && settings.service_port != m_dht_settings.service_port
                        && m_dht)
                {
                        m_dht_socket.bind(settings.service_port);

                        if (m_natpmp.get())
                        {
                                if (m_udp_mapping[0] != -1) m_upnp->delete_mapping(m_udp_mapping[0]);
                                m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
                                        , m_dht_settings.service_port
                                        , m_dht_settings.service_port);
                        }
                        if (m_upnp.get())
                        {
                                if (m_udp_mapping[1] != -1) m_upnp->delete_mapping(m_udp_mapping[1]);
                                m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
                                        , m_dht_settings.service_port
                                        , m_dht_settings.service_port);
                        }
                        m_external_udp_port = settings.service_port;
                }
                m_dht_settings = settings;
                if (m_dht_same_port)
                        m_dht_settings.service_port = m_listen_interface.port();
        }

        entry session_impl::dht_state() const
        {
                mutex_t::scoped_lock l(m_mutex);
                if (!m_dht) return entry();
                return m_dht->state();
        }

        void session_impl::add_dht_node(std::pair<std::string, int> const& node)
        {
                TORRENT_ASSERT(m_dht);
                mutex_t::scoped_lock l(m_mutex);
                m_dht->add_node(node);
        }

        void session_impl::add_dht_router(std::pair<std::string, int> const& node)
        {
                TORRENT_ASSERT(m_dht);
                mutex_t::scoped_lock l(m_mutex);
                m_dht->add_router_node(node);
        }

#endif

#ifndef TORRENT_DISABLE_ENCRYPTION
        void session_impl::set_pe_settings(pe_settings const& settings)
        {
                mutex_t::scoped_lock l(m_mutex);
                m_pe_settings = settings;
        }
#endif

        bool session_impl::is_listening() const
        {
                mutex_t::scoped_lock l(m_mutex);
                return !m_listen_sockets.empty();
        }

        session_impl::~session_impl()
        {
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << "\n\n *** shutting down session *** \n\n";
#endif
                abort();

#ifndef TORRENT_DISABLE_GEO_IP
                if (m_asnum_db) GeoIP_delete(m_asnum_db);
                if (m_country_db) GeoIP_delete(m_country_db);
#endif
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " waiting for main thread\n";
#endif
                m_thread->join();

                TORRENT_ASSERT(m_torrents.empty());

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " waiting for disk io thread\n";
#endif
                m_disk_thread.join();

                TORRENT_ASSERT(m_torrents.empty());
                TORRENT_ASSERT(m_connections.empty());
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
                (*m_logger) << time_now_string() << " shutdown complete!\n";
#endif
        }

        void session_impl::set_max_uploads(int limit)
        {
                TORRENT_ASSERT(limit > 0 || limit == -1);
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (limit <= 0) limit = (std::numeric_limits<int>::max)();
                if (m_max_uploads == limit) return;
                m_max_uploads = limit;
                m_allowed_upload_slots = limit;
        }

        void session_impl::set_max_connections(int limit)
        {
                TORRENT_ASSERT(limit > 0 || limit == -1);
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (limit <= 0)
                {
                        limit = (std::numeric_limits<int>::max)();
#ifndef TORRENT_WINDOWS
                        rlimit l;
                        if (getrlimit(RLIMIT_NOFILE, &l) == 0
                                && l.rlim_cur != RLIM_INFINITY)
                        {
                                limit = l.rlim_cur - m_settings.file_pool_size;
                                if (limit < 5) limit = 5;
                        }
#endif
                }
                m_max_connections = limit;
        }

        void session_impl::set_max_half_open_connections(int limit)
        {
                TORRENT_ASSERT(limit > 0 || limit == -1);
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (limit <= 0) limit = (std::numeric_limits<int>::max)();
                m_half_open.limit(limit);
        }

        void session_impl::set_download_rate_limit(int bytes_per_second)
        {
                TORRENT_ASSERT(bytes_per_second > 0 || bytes_per_second == -1);
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (bytes_per_second <= 0) bytes_per_second = bandwidth_limit::inf;
                m_bandwidth_manager[peer_connection::download_channel]->throttle(bytes_per_second);
        }

        void session_impl::set_upload_rate_limit(int bytes_per_second)
        {
                TORRENT_ASSERT(bytes_per_second > 0 || bytes_per_second == -1);
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (bytes_per_second <= 0) bytes_per_second = bandwidth_limit::inf;
                m_bandwidth_manager[peer_connection::upload_channel]->throttle(bytes_per_second);
        }

        std::auto_ptr<alert> session_impl::pop_alert()
        {
                mutex_t::scoped_lock l(m_mutex);

// too expensive
//              INVARIANT_CHECK;

                if (m_alerts.pending())
                        return m_alerts.get();
                return std::auto_ptr<alert>(0);
        }
        
        alert const* session_impl::wait_for_alert(time_duration max_wait)
        {
                return m_alerts.wait_for_alert(max_wait);
        }

        void session_impl::set_alert_mask(int m)
        {
                mutex_t::scoped_lock l(m_mutex);
                m_alerts.set_alert_mask(m);
        }

        int session_impl::upload_rate_limit() const
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                int ret = m_bandwidth_manager[peer_connection::upload_channel]->throttle();
                return ret == (std::numeric_limits<int>::max)() ? -1 : ret;
        }

        int session_impl::download_rate_limit() const
        {
                mutex_t::scoped_lock l(m_mutex);
                int ret = m_bandwidth_manager[peer_connection::download_channel]->throttle();
                return ret == (std::numeric_limits<int>::max)() ? -1 : ret;
        }

        void session_impl::start_lsd()
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (m_lsd) return;

                m_lsd = new lsd(m_io_service
                        , m_listen_interface.address()
                        , bind(&session_impl::on_lsd_peer, this, _1, _2));
        }
        
        natpmp* session_impl::start_natpmp()
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (m_natpmp) return m_natpmp.get();

                m_natpmp = new natpmp(m_io_service
                        , m_listen_interface.address()
                        , bind(&session_impl::on_port_mapping
                                , this, _1, _2, _3, 0));

                if (m_listen_interface.port() > 0)
                {
                        m_tcp_mapping[0] = m_natpmp->add_mapping(natpmp::tcp
                                , m_listen_interface.port(), m_listen_interface.port());
                }
#ifndef TORRENT_DISABLE_DHT
                if (m_dht)
                        m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
                                , m_dht_settings.service_port 
                                , m_dht_settings.service_port);
#endif
                return m_natpmp.get();
        }

        upnp* session_impl::start_upnp()
        {
                mutex_t::scoped_lock l(m_mutex);

                INVARIANT_CHECK;

                if (m_upnp) return m_upnp.get();

                m_upnp = new upnp(m_io_service, m_half_open
                        , m_listen_interface.address()
                        , m_settings.user_agent
                        , bind(&session_impl::on_port_mapping
                                , this, _1, _2, _3, 1)
                        , m_settings.upnp_ignore_nonrouters);

                m_upnp->discover_device();
                if (m_listen_interface.port() > 0)
                {
                        m_tcp_mapping[1] = m_upnp->add_mapping(upnp::tcp
                                , m_listen_interface.port(), m_listen_interface.port());
                }
#ifndef TORRENT_DISABLE_DHT
                if (m_dht)
                        m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
                                , m_dht_settings.service_port 
                                , m_dht_settings.service_port);
#endif
                return m_upnp.get();
        }

        void session_impl::stop_lsd()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_lsd.get())
                        m_lsd->close();
                m_lsd = 0;
        }
        
        void session_impl::stop_natpmp()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_natpmp.get())
                        m_natpmp->close();
                m_natpmp = 0;
        }
        
        void session_impl::stop_upnp()
        {
                mutex_t::scoped_lock l(m_mutex);
                if (m_upnp.get())
                {
                        m_upnp->close();
                        m_udp_mapping[1] = -1;
                        m_tcp_mapping[1] = -1;
                }
                m_upnp = 0;
        }
        
        void session_impl::set_external_address(address const& ip)
        {
                TORRENT_ASSERT(ip != address());

                if (m_external_address == ip) return;

                m_external_address = ip;
                if (m_alerts.should_post<external_ip_alert>())
                        m_alerts.post_alert(external_ip_alert(ip));
        }

        void session_impl::free_disk_buffer(char* buf)
        {
                m_disk_thread.free_buffer(buf);
        }

        char* session_impl::allocate_disk_buffer()
        {
                return m_disk_thread.allocate_buffer();
        }
        
        std::pair<char*, int> session_impl::allocate_buffer(int size)
        {
                TORRENT_ASSERT(size > 0);
                int num_buffers = (size + send_buffer_size - 1) / send_buffer_size;
                TORRENT_ASSERT(num_buffers > 0);

                boost::mutex::scoped_lock l(m_send_buffer_mutex);
#ifdef TORRENT_STATS
                TORRENT_ASSERT(m_buffer_allocations >= 0);
                m_buffer_allocations += num_buffers;
                m_buffer_usage_logger << log_time() << " protocol_buffer: "
                        << (m_buffer_allocations * send_buffer_size) << std::endl;
#endif
#ifdef TORRENT_DISABLE_POOL_ALLOCATOR
                int num_bytes = num_buffers * send_buffer_size;
                return std::make_pair((char*)malloc(num_bytes), num_bytes);
#else
                return std::make_pair((char*)m_send_buffers.ordered_malloc(num_buffers)
                        , num_buffers * send_buffer_size);
#endif
        }

        void session_impl::free_buffer(char* buf, int size)
        {
                TORRENT_ASSERT(size > 0);
                TORRENT_ASSERT(size % send_buffer_size == 0);
                int num_buffers = size / send_buffer_size;
                TORRENT_ASSERT(num_buffers > 0);

                boost::mutex::scoped_lock l(m_send_buffer_mutex);
#ifdef TORRENT_STATS
                m_buffer_allocations -= num_buffers;
                TORRENT_ASSERT(m_buffer_allocations >= 0);
                m_buffer_usage_logger << log_time() << " protocol_buffer: "
                        << (m_buffer_allocations * send_buffer_size) << std::endl;
#endif
#ifdef TORRENT_DISABLE_POOL_ALLOCATOR
                free(buf);
#else
                m_send_buffers.ordered_free(buf, num_buffers);
#endif
        }       

#ifndef NDEBUG
        void session_impl::check_invariant() const
        {
                std::set<int> unique;
                int total_downloaders = 0;
                for (torrent_map::const_iterator i = m_torrents.begin()
                        , end(m_torrents.end()); i != end; ++i)
                {
                        int pos = i->second->queue_position();
                        if (pos < 0)
                        {
                                TORRENT_ASSERT(pos == -1);
                                continue;
                        }
                        ++total_downloaders;
                        unique.insert(i->second->queue_position());
                }
                TORRENT_ASSERT(unique.size() == total_downloaders);

                TORRENT_ASSERT(m_max_connections > 0);
                TORRENT_ASSERT(m_max_uploads > 0);
                TORRENT_ASSERT(m_allowed_upload_slots >= m_max_uploads);
                int unchokes = 0;
                int num_optimistic = 0;
                for (connection_map::const_iterator i = m_connections.begin();
                        i != m_connections.end(); ++i)
                {
                        TORRENT_ASSERT(*i);
                        boost::shared_ptr<torrent> t = (*i)->associated_torrent().lock();

                        peer_connection* p = i->get();
                        TORRENT_ASSERT(!p->is_disconnecting());
                        if (!p->is_choked()) ++unchokes;
                        if (p->peer_info_struct()
                                && p->peer_info_struct()->optimistically_unchoked)
                        {
                                ++num_optimistic;
                                TORRENT_ASSERT(!p->is_choked());
                        }
                        if (t && p->peer_info_struct())
                        {
                                TORRENT_ASSERT(t->get_policy().has_connection(p));
                        }
                }
                TORRENT_ASSERT(num_optimistic == 0 || num_optimistic == 1);
                if (m_num_unchoked != unchokes)
                {
                        TORRENT_ASSERT(false);
                }
                for (std::map<sha1_hash, boost::shared_ptr<torrent> >::const_iterator j
                        = m_torrents.begin(); j != m_torrents.end(); ++j)
                {
                        TORRENT_ASSERT(boost::get_pointer(j->second));
                }
        }
#endif

}}