premiere-libtorrent/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"

#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
		)
		: m_send_buffers(send_buffer_size)
		, 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_max_uploads(8)
		, m_allowed_upload_slots(8)
		, m_max_connections(200)
		, m_num_unchoked(0)
		, m_unchoke_time_scaler(0)
		, m_optimistic_unchoke_time_scaler(0)
		, m_disconnect_time_scaler(0)
		, 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
	{
#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";
#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)];
		}

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

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

#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::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;
		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
		m_timer.cancel();

		// 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();
		}

#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;

			if ((!t.is_paused() || t.should_request())
				&& !t.trackers().empty())
			{
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
				++counter;
#endif
				tracker_request req = t.generate_tracker_request();
				TORRENT_ASSERT(req.event == tracker_request::stopped);
				req.listen_port = 0;
				if (!m_listen_sockets.empty())
					req.listen_port = m_listen_sockets.front().external_port;
				req.key = m_key;
				std::string login = i->second->tracker_login();
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
				boost::shared_ptr<tracker_logger> tl(new tracker_logger(*this));
				m_tracker_loggers.push_back(tl);
				m_tracker_manager.queue_request(m_io_service, m_half_open, req, login
					, m_listen_interface.address(), tl);
#else
				m_tracker_manager.queue_request(m_io_service, m_half_open, req, login
					, m_listen_interface.address());
#endif
			}
		}
#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);
		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)
	{
		asio::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 = asio::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 = asio::error_code();
			s.sock->bind(ep, ec);
		}
		if (ec)
		{
			// not even that worked, give up
			if (m_alerts.should_post(alert::fatal))
			{
				std::stringstream msg;
				msg << "cannot bind to interface '";
				print_endpoint(msg, ep) << "' " << ec.message();
				m_alerts.post_alert(listen_failed_alert(ep, msg.str()));
			}
#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(alert::fatal))
			{
				std::stringstream msg;
				msg << "cannot listen on interface '";
				print_endpoint(msg, ep) << "' " << ec.message();
				m_alerts.post_alert(listen_failed_alert(ep, msg.str()));
			}
#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(alert::fatal))
		{
			std::string msg = "listening on interface "
				+ boost::lexical_cast<std::string>(ep);
			m_alerts.post_alert(listen_succeeded_alert(ep, msg));
		}

#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)
		{
			asio::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())
		{
			asio::error_code ec;
			tcp::endpoint local = m_listen_sockets.front().sock->local_endpoint(ec);
			if (!ec)
			{
				if (m_natpmp.get()) m_natpmp->set_mappings(local.port(), 0);
				if (m_upnp.get()) m_upnp->set_mappings(local.port(), 0);
			}
		}
	}

#ifndef TORRENT_DISABLE_DHT

	void session_impl::on_receive_udp(asio::error_code const& e
		, udp::endpoint const& ep, char const* buf, int len)
	{
		if (e)
		{
			if (m_alerts.should_post(alert::info))
			{
				std::string msg = "UDP socket error from '"
					+ boost::lexical_cast<std::string>(ep) + "' " + e.message();
				m_alerts.post_alert(udp_error_alert(ep, msg));
			}
			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, asio::error_code const& e) try
	{
		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;

		asio::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 _WIN32
			// 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
			if (m_alerts.should_post(alert::fatal))
			{
				std::string msg = "error accepting connection on '"
					+ boost::lexical_cast<std::string>(ep) + "' " + e.message();
				m_alerts.post_alert(listen_failed_alert(ep, msg));
			}
			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(alert::info))
			{
				m_alerts.post_alert(peer_blocked_alert(endp.address()
					, "incoming connection blocked by IP filter"));
			}
			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()) 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) return;

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

		if (!c->is_disconnecting())
		{
			m_connections.insert(c);
			c->start();
		}
	}
	catch (std::exception& exc)
	{
#ifndef NDEBUG
		std::string err = exc.what();
#endif
	};

	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(asio::error_code const& e) try
	{
		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();

		m_timer.expires_from_now(seconds(1));
		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

		// --------------------------------------------------------------
		// 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;

		// 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_finished())
			{
				++num_seeds;
			}
			else
			{
				++num_downloads;
				num_downloads_peers += t.num_peers();
			}

			if (t.should_request())
			{
				tracker_request req = t.generate_tracker_request();
				req.listen_port = 0;
				if (!m_listen_sockets.empty())
					req.listen_port = m_listen_sockets.front().external_port;
				req.key = m_key;
				m_tracker_manager.queue_request(m_io_service, m_half_open, req
					, t.tracker_login(), m_listen_interface.address(), i->second);

				if (m_alerts.should_post(alert::info))
				{
					m_alerts.post_alert(
						tracker_announce_alert(
							t.get_handle(), "tracker announce"));
				}
			}

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

		m_stat.second_tick(tick_interval);

	
		// --------------------------------------------------------------
		// 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;
			}
		}

		// do the second_tick() on each connection
		// this will update their statistics (download and upload speeds)
		// also purge sockets that have timed out
		// and keep sockets open by keeping them alive.
		for (connection_map::iterator i = m_connections.begin();
			i != m_connections.end();)
		{
			// we need to do like this because j->second->disconnect() will
			// erase the connection from the map we're iterating
			connection_map::iterator j = i;
			++i;
			// if this socket has timed out
			// close it.
			peer_connection& c = *j->get();
			if (c.has_timed_out())
			{
				if (m_alerts.should_post(alert::debug))
				{
					m_alerts.post_alert(
						peer_error_alert(
							c.remote()
							, c.pid()
							, "connection timed out"));
				}
#if defined(TORRENT_VERBOSE_LOGGING)
				(*c.m_logger) << "*** CONNECTION TIMED OUT\n";
#endif

				c.set_failed();
				c.disconnect("timed out");
				continue;
			}

			c.keep_alive();
		}

		// --------------------------------------------------------------
		// 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;

			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;
				}
			}
		}

		// --------------------------------------------------------------
		// disconnect peers when we have too many
		// --------------------------------------------------------------
		--m_disconnect_time_scaler;
		if (m_disconnect_time_scaler <= 0)
		{
			m_disconnect_time_scaler = 60;

			// every 60 seconds, disconnect the worst peer
			// if we have reached the connection limit
			if (num_connections() >= max_connections() && !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());
				i->second->get_policy().disconnect_one_peer();
			}
		}
	}
	catch (std::exception& exc)
	{
#ifndef NDEBUG
		std::cerr << exc.what() << std::endl;
		TORRENT_ASSERT(false);
#endif
	}; // msvc 7.1 seems to require this

	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
		{
			try
			{
				m_io_service.run();
				TORRENT_ASSERT(m_abort == true);
			}
			catch (std::exception& e)
			{
#ifndef NDEBUG
				std::cerr << e.what() << "\n";
				std::string err = e.what();
#endif
				TORRENT_ASSERT(false);
			}
		}
		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(this, i->first));
		}
		return ret;
	}

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

	torrent_handle session_impl::add_torrent(
		boost::intrusive_ptr<torrent_info> ti
		, fs::path const& save_path
		, entry const& resume_data
		, storage_mode_t storage_mode
		, storage_constructor_type sc
		, bool paused
		, void* userdata)
	{
		TORRENT_ASSERT(!save_path.empty());

		if (ti->begin_files() == ti->end_files())
			throw std::runtime_error("no files in torrent");

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

//		INVARIANT_CHECK;

		if (is_aborted())
			throw std::runtime_error("session is closing");
		
		// is the torrent already active?
		if (!find_torrent(ti->info_hash()).expired())
			throw duplicate_torrent();

		// create the torrent and the data associated with
		// the checker thread and store it before starting
		// the thread
		boost::shared_ptr<torrent> torrent_ptr(
			new torrent(*this, ti, save_path
				, m_listen_interface, storage_mode, 16 * 1024
				, sc, paused, resume_data));
		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(), userdata));
			if (tp) torrent_ptr->add_extension(tp);
		}
#endif

#ifndef TORRENT_DISABLE_DHT
		if (m_dht)
		{
			torrent_info::nodes_t const& nodes = 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(ti->info_hash(), torrent_ptr));

		return torrent_handle(this, ti->info_hash());
	}

	void session_impl::check_torrent(boost::shared_ptr<torrent> const& t)
	{
		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)
	{
		TORRENT_ASSERT(m_queued_for_checking.front() == t);
		m_queued_for_checking.pop_front();
		if (!m_queued_for_checking.empty())
			m_queued_for_checking.front()->start_checking();
	}

	torrent_handle session_impl::add_torrent(
		char const* tracker_url
		, sha1_hash const& info_hash
		, char const* name
		, fs::path const& save_path
		, entry const& resume_data
		, storage_mode_t storage_mode
		, storage_constructor_type sc
		, bool paused
		, void* userdata)
	{
	
		// TODO: support resume data in this case
		TORRENT_ASSERT(!save_path.empty());

		// lock the session
		session_impl::mutex_t::scoped_lock l(m_mutex);

//		INVARIANT_CHECK;

		// is the torrent already active?
		if (!find_torrent(info_hash).expired())
#ifndef BOOST_NO_EXCEPTIONS
			throw duplicate_torrent();
#else
			return torrent_handle();
#endif

		// you cannot add new torrents to a session that is closing down
		TORRENT_ASSERT(!is_aborted());

		// create the torrent and the data associated with
		// the checker thread and store it before starting
		// the thread
		boost::shared_ptr<torrent> torrent_ptr(
			new torrent(*this, tracker_url, info_hash, name
			, save_path, m_listen_interface, storage_mode, 16 * 1024
			, sc, paused, resume_data));
		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(), userdata));
			if (tp) torrent_ptr->add_extension(tp);
		}
#endif

		m_torrents.insert(std::make_pair(info_hash, torrent_ptr));

		return torrent_handle(this, info_hash);
	}

	void session_impl::remove_torrent(const torrent_handle& h, int options)
	{
		if (h.m_ses != this) return;
		TORRENT_ASSERT(h.m_ses != 0);

		mutex_t::scoped_lock l(m_mutex);

		INVARIANT_CHECK;

		session_impl::torrent_map::iterator i =
			m_torrents.find(h.m_info_hash);
		if (i != m_torrents.end())
		{
			torrent& t = *i->second;
			if (options & session::delete_files)
				t.delete_files();
			t.abort();

			if ((!t.is_paused() || t.should_request())
				&& !t.trackers().empty())
			{
				tracker_request req = t.generate_tracker_request();
				TORRENT_ASSERT(req.event == tracker_request::stopped);
				req.listen_port = 0;
				if (!m_listen_sockets.empty())
					req.listen_port = m_listen_sockets.front().external_port;
				req.key = m_key;

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
				boost::shared_ptr<tracker_logger> tl(new tracker_logger(*this));
				m_tracker_loggers.push_back(tl);
				m_tracker_manager.queue_request(m_io_service, m_half_open, req
					, t.tracker_login(), m_listen_interface.address(), tl);
#else
				m_tracker_manager.queue_request(m_io_service, m_half_open, req
					, t.tracker_login(), m_listen_interface.address());
#endif

				if (m_alerts.should_post(alert::info))
				{
					m_alerts.post_alert(
						tracker_announce_alert(
							t.get_handle(), "tracker announce, event=stopped"));
				}
			}
#ifndef NDEBUG
			sha1_hash i_hash = t.torrent_file().info_hash();
#endif
			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())
				m_natpmp->set_mappings(0, m_dht_settings.service_port);
			if (m_upnp.get())
				m_upnp->set_mappings(0, 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 tcp_port, int udp_port
		, std::string const& errmsg)
	{
#ifndef TORRENT_DISABLE_DHT
		if (udp_port != 0)
		{
			m_external_udp_port = udp_port;
			m_dht_settings.service_port = udp_port;
			if (m_alerts.should_post(alert::info))
			{
				std::stringstream msg;
				msg << "successfully mapped UDP port " << udp_port;
				m_alerts.post_alert(portmap_alert(msg.str()));
			}
		}
#endif

		if (tcp_port != 0)
		{
			if (!m_listen_sockets.empty())
				m_listen_sockets.front().external_port = tcp_port;
			if (m_alerts.should_post(alert::info))
			{
				std::stringstream msg;
				msg << "successfully mapped TCP port " << tcp_port;
				m_alerts.post_alert(portmap_alert(msg.str()));
			}
		}

		if (!errmsg.empty())
		{
			if (m_alerts.should_post(alert::warning))
			{
				std::stringstream msg;
				msg << "Error while mapping ports on NAT router: " << errmsg;
				m_alerts.post_alert(portmap_error_alert(msg.str()));
			}
		}
	}

	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.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_natpmp->set_mappings(0, m_dht_settings.service_port);
		if (m_upnp.get())
			m_upnp->set_mappings(0, 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())
				m_natpmp->set_mappings(0, m_dht_settings.service_port);
			if (m_upnp.get())
				m_upnp->set_mappings(0, 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();

#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)();
		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_severity_level(alert::severity_t s)
	{
		mutex_t::scoped_lock l(m_mutex);
		m_alerts.set_severity(s);
	}

	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));
	}
	
	void session_impl::start_natpmp()
	{
		mutex_t::scoped_lock l(m_mutex);

		INVARIANT_CHECK;

		if (m_natpmp) return;

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

		m_natpmp->set_mappings(m_listen_interface.port(),
#ifndef TORRENT_DISABLE_DHT
			m_dht ? m_dht_settings.service_port : 
#endif
			0);
	}

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

		INVARIANT_CHECK;

		if (m_upnp) return;

		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)
			, m_settings.upnp_ignore_nonrouters);

		m_upnp->discover_device();
		m_upnp->set_mappings(m_listen_interface.port(), 
#ifndef TORRENT_DISABLE_DHT
			m_dht ? m_dht_settings.service_port : 
#endif
			0);
	}

	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_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(alert::info))
		{
			std::stringstream msg;
			msg << "external address is '";
			print_address(msg, ip) << "'";
			m_alerts.post_alert(external_ip_alert(ip, msg.str()));
		}
	}

	void session_impl::free_disk_buffer(char* buf)
	{
		m_disk_thread.free_buffer(buf);
	}
	
	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
		return std::make_pair((char*)m_send_buffers.ordered_malloc(num_buffers)
			, num_buffers * send_buffer_size);
	}

	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
		m_send_buffers.ordered_free(buf, num_buffers);
	}	

#ifndef NDEBUG
	void session_impl::check_invariant() const
	{
		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

}}