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 <algorithm>
#include <set>
#include <cctype>
#include <algorithm>

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

#include <boost/limits.hpp>
#include <boost/bind.hpp>
#include <boost/function_equal.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"
#ifndef TORRENT_DISABLE_DHT
#include "libtorrent/kademlia/dht_tracker.hpp"
#endif
#include "libtorrent/enum_net.hpp"
#include "libtorrent/config.hpp"
#include "libtorrent/utf8.hpp"
#include "libtorrent/upnp.hpp"
#include "libtorrent/natpmp.hpp"
#include "libtorrent/lsd.hpp"
#include "libtorrent/instantiate_connection.hpp"
#include "libtorrent/peer_info.hpp"
#include "libtorrent/settings.hpp"
#include "libtorrent/build_config.hpp"
#include "libtorrent/extensions.hpp"
#include "libtorrent/random.hpp"

#if defined TORRENT_STATS && defined __MACH__
#include <mach/task.h>
#endif

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

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING

// for logging stat layout
#include "libtorrent/stat.hpp"
#include "libtorrent/struct_debug.hpp"

// for logging the size of DHT structures
#ifndef TORRENT_DISABLE_DHT
#include <libtorrent/kademlia/find_data.hpp>
#include <libtorrent/kademlia/refresh.hpp>
#include <libtorrent/kademlia/node.hpp>
#include <libtorrent/kademlia/observer.hpp>
#endif // TORRENT_DISABLE_DHT

#include "libtorrent/http_tracker_connection.hpp"
#include "libtorrent/udp_tracker_connection.hpp"

#include "libtorrent/debug.hpp"

#if TORRENT_USE_IOSTREAM
namespace libtorrent {
std::ofstream logger::log_file;
std::string logger::open_filename;
mutex logger::file_mutex;
}
#endif // TORRENT_USE_IOSTREAM

#endif

#ifdef TORRENT_USE_GCRYPT

extern "C" {
GCRY_THREAD_OPTION_PTHREAD_IMPL;
}

namespace
{
	// libgcrypt requires this to initialize the library
	struct gcrypt_setup
	{
		gcrypt_setup()
		{
			gcry_check_version(0);
			gcry_error_t e = gcry_control(GCRYCTL_SET_THREAD_CBS, &gcry_threads_pthread);
			if (e != 0) fprintf(stderr, "libcrypt ERROR: %s\n", gcry_strerror(e));
			e = gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
			if (e != 0) fprintf(stderr, "initialization finished error: %s\n", gcry_strerror(e));
		}
	} gcrypt_global_constructor;
}

#endif // TORRENT_USE_GCRYPT

#ifdef TORRENT_USE_OPENSSL

#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 // TORRENT_USE_OPENSSL

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

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

#ifdef BOOST_NO_EXCEPTIONS
namespace boost {
	void throw_exception(std::exception const& e) { ::abort(); }
}
#endif

namespace libtorrent {

#if defined TORRENT_ASIO_DEBUGGING
	std::map<std::string, async_t> _async_ops;
	int _async_ops_nthreads = 0;
	mutex _async_ops_mutex;
#endif

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 {

#ifdef TORRENT_STATS
	void get_vm_stats(vm_statistics_data_t* vm_stat)
	{
		memset(vm_stat, 0, sizeof(*vm_stat));
#if defined __MACH__
		mach_port_t host_port = mach_host_self();
		mach_msg_type_number_t host_count = HOST_VM_INFO_COUNT;
		kern_return_t error = host_statistics(host_port, HOST_VM_INFO,
			(host_info_t)vm_stat, &host_count);
#elif defined TORRENT_LINUX
		char buffer[4096];
		char string[1024];
		boost::uint32_t value;
		FILE* f = fopen("/proc/vmstat", "r");
		int ret = 0;
		while ((ret = fscanf(f, "%s %u\n", string, &value)) != EOF)
		{
			if (ret != 2) continue;
			if (strcmp(string, "nr_active_anon") == 0) vm_stat->active_count += value;
			else if (strcmp(string, "nr_active_file") == 0) vm_stat->active_count += value;
			else if (strcmp(string, "nr_inactive_anon") == 0) vm_stat->inactive_count += value;
			else if (strcmp(string, "nr_inactive_file") == 0) vm_stat->inactive_count += value;
			else if (strcmp(string, "nr_free_pages") == 0) vm_stat->free_count = value;
			else if (strcmp(string, "nr_unevictable") == 0) vm_stat->wire_count = value;
			else if (strcmp(string, "pswpin") == 0) vm_stat->pageins = value;
			else if (strcmp(string, "pswpout") == 0) vm_stat->pageouts = value;
			else if (strcmp(string, "pgfault") == 0) vm_stat->faults = value;
		}
		fclose(f);
#endif
// TOOD: windows?
	}

	void get_thread_cpu_usage(thread_cpu_usage* tu)
	{
#if defined __MACH__
		task_thread_times_info t_info;
		mach_msg_type_number_t t_info_count = TASK_THREAD_TIMES_INFO_COUNT;
		task_info(mach_task_self(), TASK_THREAD_TIMES_INFO, (task_info_t)&t_info, &t_info_count);

		tu->user_time = min_time()
			+ seconds(t_info.user_time.seconds)
			+ microsec(t_info.user_time.microseconds);
		tu->system_time = min_time()
			+ seconds(t_info.system_time.seconds)
			+ microsec(t_info.system_time.microseconds);
#elif defined TORRENT_LINUX
		struct rusage ru;
		getrusage(RUSAGE_THREAD, &ru);
		tu->user_time = min_time()
			+ seconds(ru.ru_utime.tv_sec)
			+ microsec(ru.ru_utime.tv_usec);
		tu->system_time = min_time()
			+ seconds(ru.ru_stime.tv_sec)
			+ microsec(ru.ru_stime.tv_usec);
#elif defined TORRENT_WINDOWS
		FILETIME system_time;
		FILETIME user_time;
		FILETIME creation_time;
		FILETIME exit_time;
		GetThreadTimes(GetCurrentThread(), &creation_time, &exit_time, &user_time, &system_time);

		boost::uint64_t utime = (boost::uint64_t(user_time.dwHighDateTime) << 32)
			+ user_time.dwLowDateTime;
		boost::uint64_t stime = (boost::uint64_t(system_time.dwHighDateTime) << 32)
			+ system_time.dwLowDateTime;

		tu->user_time = min_time() + microsec(utime / 10);
		tu->system_time = min_time() + microsec(stime / 10);
#endif
	}
#endif //TORRENT_STATS

	struct seed_random_generator
	{
		seed_random_generator()
		{
			random_seed((unsigned int)total_microseconds(time_now_hires() - min_time()));
		}
	};

#define TORRENT_SETTING(t, x) {#x, offsetof(session_settings,x), t},

	bencode_map_entry session_settings_map[] =
	{
		TORRENT_SETTING(std_string, user_agent)
		TORRENT_SETTING(integer, tracker_completion_timeout)
		TORRENT_SETTING(integer, tracker_receive_timeout)
		TORRENT_SETTING(integer, stop_tracker_timeout)
		TORRENT_SETTING(integer, tracker_maximum_response_length)
		TORRENT_SETTING(integer, piece_timeout)
		TORRENT_SETTING(integer, request_timeout)
		TORRENT_SETTING(integer, request_queue_time)
		TORRENT_SETTING(integer, max_allowed_in_request_queue)
		TORRENT_SETTING(integer, max_out_request_queue)
		TORRENT_SETTING(integer, whole_pieces_threshold)
		TORRENT_SETTING(integer, peer_timeout)
		TORRENT_SETTING(integer, urlseed_timeout)
		TORRENT_SETTING(integer, urlseed_pipeline_size)
		TORRENT_SETTING(integer, urlseed_wait_retry)
		TORRENT_SETTING(integer, file_pool_size)
		TORRENT_SETTING(boolean, allow_multiple_connections_per_ip)
		TORRENT_SETTING(integer, max_failcount)
		TORRENT_SETTING(integer, min_reconnect_time)
		TORRENT_SETTING(integer, peer_connect_timeout)
		TORRENT_SETTING(boolean, ignore_limits_on_local_network)
		TORRENT_SETTING(integer, connection_speed)
		TORRENT_SETTING(boolean, send_redundant_have)
		TORRENT_SETTING(boolean, lazy_bitfields)
		TORRENT_SETTING(integer, inactivity_timeout)
		TORRENT_SETTING(integer, unchoke_interval)
		TORRENT_SETTING(integer, optimistic_unchoke_interval)
		TORRENT_SETTING(std_string, announce_ip)
		TORRENT_SETTING(integer, num_want)
		TORRENT_SETTING(integer, initial_picker_threshold)
		TORRENT_SETTING(integer, allowed_fast_set_size)
		TORRENT_SETTING(integer, suggest_mode)
		TORRENT_SETTING(integer, max_queued_disk_bytes)
		TORRENT_SETTING(integer, max_queued_disk_bytes_low_watermark)
		TORRENT_SETTING(integer, handshake_timeout)
#ifndef TORRENT_DISABLE_DHT
		TORRENT_SETTING(boolean, use_dht_as_fallback)
#endif
		TORRENT_SETTING(boolean, free_torrent_hashes)
		TORRENT_SETTING(boolean, upnp_ignore_nonrouters)
 		TORRENT_SETTING(integer, send_buffer_watermark)
#ifndef TORRENT_NO_DEPRECATE
		TORRENT_SETTING(boolean, auto_upload_slots)
		TORRENT_SETTING(boolean, auto_upload_slots_rate_based)
#endif
		TORRENT_SETTING(integer, choking_algorithm)
		TORRENT_SETTING(integer, seed_choking_algorithm)
		TORRENT_SETTING(boolean, use_parole_mode)
		TORRENT_SETTING(integer, cache_size)
		TORRENT_SETTING(integer, cache_buffer_chunk_size)
		TORRENT_SETTING(integer, cache_expiry)
		TORRENT_SETTING(boolean, use_read_cache)
		TORRENT_SETTING(boolean, explicit_read_cache)
		TORRENT_SETTING(integer, disk_io_write_mode)
		TORRENT_SETTING(integer, disk_io_read_mode)
		TORRENT_SETTING(boolean, coalesce_reads)
		TORRENT_SETTING(boolean, coalesce_writes)
		TORRENT_SETTING(character, peer_tos)
		TORRENT_SETTING(integer, active_downloads)
		TORRENT_SETTING(integer, active_seeds)
		TORRENT_SETTING(integer, active_dht_limit)
		TORRENT_SETTING(integer, active_tracker_limit)
		TORRENT_SETTING(integer, active_lsd_limit)
		TORRENT_SETTING(integer, active_limit)
		TORRENT_SETTING(boolean, auto_manage_prefer_seeds)
		TORRENT_SETTING(boolean, dont_count_slow_torrents)
		TORRENT_SETTING(integer, auto_manage_interval)
		TORRENT_SETTING(floating_point, share_ratio_limit)
		TORRENT_SETTING(floating_point, seed_time_ratio_limit)
		TORRENT_SETTING(integer, seed_time_limit)
		TORRENT_SETTING(floating_point, peer_turnover)
		TORRENT_SETTING(floating_point, peer_turnover_cutoff)
		TORRENT_SETTING(boolean, close_redundant_connections)
		TORRENT_SETTING(integer, auto_scrape_interval)
		TORRENT_SETTING(integer, auto_scrape_min_interval)
		TORRENT_SETTING(integer, max_peerlist_size)
		TORRENT_SETTING(integer, max_paused_peerlist_size)
		TORRENT_SETTING(integer, min_announce_interval)
		TORRENT_SETTING(boolean, prioritize_partial_pieces)
		TORRENT_SETTING(integer, auto_manage_startup)
		TORRENT_SETTING(boolean, rate_limit_ip_overhead)
		TORRENT_SETTING(boolean, announce_to_all_trackers)
		TORRENT_SETTING(boolean, announce_to_all_tiers)
		TORRENT_SETTING(boolean, prefer_udp_trackers)
		TORRENT_SETTING(boolean, strict_super_seeding)
		TORRENT_SETTING(integer, seeding_piece_quota)
		TORRENT_SETTING(integer, max_sparse_regions)
#ifndef TORRENT_DISABLE_MLOCK
		TORRENT_SETTING(boolean, lock_disk_cache)
#endif
		TORRENT_SETTING(integer, max_rejects)
		TORRENT_SETTING(integer, recv_socket_buffer_size)
		TORRENT_SETTING(integer, send_socket_buffer_size)
		TORRENT_SETTING(boolean, optimize_hashing_for_speed)
		TORRENT_SETTING(integer, file_checks_delay_per_block)
		TORRENT_SETTING(integer, disk_cache_algorithm)
		TORRENT_SETTING(integer, read_cache_line_size)
		TORRENT_SETTING(integer, write_cache_line_size)
		TORRENT_SETTING(integer, optimistic_disk_retry)
		TORRENT_SETTING(boolean, disable_hash_checks)
		TORRENT_SETTING(boolean, allow_reordered_disk_operations)
		TORRENT_SETTING(boolean, allow_i2p_mixed)
		TORRENT_SETTING(integer, max_suggest_pieces)
		TORRENT_SETTING(boolean, drop_skipped_requests)
		TORRENT_SETTING(boolean, low_prio_disk)
		TORRENT_SETTING(integer, local_service_announce_interval)
		TORRENT_SETTING(integer, udp_tracker_token_expiry)
		TORRENT_SETTING(boolean, volatile_read_cache)
		TORRENT_SETTING(boolean, guided_read_cache)
		TORRENT_SETTING(integer, default_cache_min_age)
		TORRENT_SETTING(integer, num_optimistic_unchoke_slots)
		TORRENT_SETTING(boolean, no_atime_storage)
		TORRENT_SETTING(integer, default_est_reciprocation_rate)
		TORRENT_SETTING(integer, increase_est_reciprocation_rate)
		TORRENT_SETTING(integer, decrease_est_reciprocation_rate)
		TORRENT_SETTING(boolean, incoming_starts_queued_torrents)
		TORRENT_SETTING(boolean, report_true_downloaded)
		TORRENT_SETTING(boolean, strict_end_game_mode)
		TORRENT_SETTING(boolean, broadcast_lsd)
		TORRENT_SETTING(boolean, enable_outgoing_utp)
		TORRENT_SETTING(boolean, enable_incoming_utp)
		TORRENT_SETTING(boolean, enable_outgoing_tcp)
		TORRENT_SETTING(boolean, enable_incoming_tcp)
		TORRENT_SETTING(integer, max_pex_peers)
		TORRENT_SETTING(boolean, ignore_resume_timestamps)
		TORRENT_SETTING(boolean, no_recheck_incomplete_resume)
		TORRENT_SETTING(boolean, anonymous_mode)
		TORRENT_SETTING(integer, tick_interval)
		TORRENT_SETTING(integer, upload_rate_limit)
		TORRENT_SETTING(integer, download_rate_limit)
		TORRENT_SETTING(integer, local_upload_rate_limit)
		TORRENT_SETTING(integer, local_download_rate_limit)
		TORRENT_SETTING(integer, dht_upload_rate_limit)
		TORRENT_SETTING(integer, unchoke_slots_limit)
		TORRENT_SETTING(integer, half_open_limit)
		TORRENT_SETTING(integer, connections_limit)
		TORRENT_SETTING(integer, utp_target_delay)
		TORRENT_SETTING(integer, utp_gain_factor)
		TORRENT_SETTING(integer, utp_syn_resends)
		TORRENT_SETTING(integer, utp_fin_resends)
		TORRENT_SETTING(integer, utp_num_resends)
		TORRENT_SETTING(integer, utp_connect_timeout)
		TORRENT_SETTING(integer, utp_delayed_ack)
		TORRENT_SETTING(boolean, utp_dynamic_sock_buf)
		TORRENT_SETTING(integer, mixed_mode_algorithm)
		TORRENT_SETTING(boolean, rate_limit_utp)
		TORRENT_SETTING(integer, listen_queue_size)
		TORRENT_SETTING(boolean, announce_double_nat)
		TORRENT_SETTING(integer, torrent_connect_boost)
		TORRENT_SETTING(boolean, seeding_outgoing_connections)
		TORRENT_SETTING(boolean, no_connect_privileged_ports)
		TORRENT_SETTING(integer, alert_queue_size)
		TORRENT_SETTING(integer, max_metadata_size)
		TORRENT_SETTING(boolean, smooth_connects)
		TORRENT_SETTING(boolean, always_send_user_agent)
		TORRENT_SETTING(boolean, apply_ip_filter_to_trackers)
		TORRENT_SETTING(integer, read_job_every)
		TORRENT_SETTING(boolean, use_disk_read_ahead)
		TORRENT_SETTING(boolean, lock_files)
	};

#undef TORRENT_SETTING
#define TORRENT_SETTING(t, x) {#x, offsetof(proxy_settings,x), t},

	bencode_map_entry proxy_settings_map[] =
	{
		TORRENT_SETTING(std_string, hostname)
		TORRENT_SETTING(integer, port)
		TORRENT_SETTING(std_string, username)
		TORRENT_SETTING(std_string, password)
		TORRENT_SETTING(integer, type)
		TORRENT_SETTING(boolean, proxy_hostnames)
		TORRENT_SETTING(boolean, proxy_peer_connections)
	};
#undef TORRENT_SETTING

#ifndef TORRENT_DISABLE_DHT
#define TORRENT_SETTING(t, x) {#x, offsetof(dht_settings,x), t},
	bencode_map_entry dht_settings_map[] =
	{
		TORRENT_SETTING(integer, max_peers_reply)
		TORRENT_SETTING(integer, search_branching)
#ifndef TORRENT_NO_DEPRECATE
		TORRENT_SETTING(integer, service_port)
#endif
		TORRENT_SETTING(integer, max_fail_count)
		TORRENT_SETTING(integer, max_torrent_search_reply)
	};
#undef TORRENT_SETTING
#endif

#ifndef TORRENT_DISABLE_ENCRYPTION
#define TORRENT_SETTING(t, x) {#x, offsetof(pe_settings,x), t},
	bencode_map_entry pe_settings_map[] = 
	{
		TORRENT_SETTING(integer, out_enc_policy)
		TORRENT_SETTING(integer, in_enc_policy)
		TORRENT_SETTING(integer, allowed_enc_level)
		TORRENT_SETTING(boolean, prefer_rc4)
	};
#undef TORRENT_SETTING
#endif

	struct session_category
	{
		char const* name;
		bencode_map_entry const* map;
		int num_entries;
		int flag;
		int offset;
		int default_offset;
	};

	// the names in here need to match the names in session_impl
	// to make the macro simpler
	struct all_default_values
	{
		session_settings m_settings;
		proxy_settings m_proxy;
#ifndef TORRENT_DISABLE_ENCRYPTION
		pe_settings m_pe_settings;
#endif
#ifndef TORRENT_DISABLE_DHT
		dht_settings m_dht_settings;
#endif
	};

#define lenof(x) sizeof(x)/sizeof(x[0])
#define TORRENT_CATEGORY(name, flag, member, map) \
	{ name, map, lenof(map), session:: flag , offsetof(session_impl, member), offsetof(all_default_values, member) },

	session_category all_settings[] =
	{
		TORRENT_CATEGORY("settings", save_settings, m_settings, session_settings_map)
#ifndef TORRENT_DISABLE_DHT
		TORRENT_CATEGORY("dht", save_dht_settings, m_dht_settings, dht_settings_map)
#endif
		TORRENT_CATEGORY("proxy", save_proxy, m_proxy, proxy_settings_map)
#if TORRENT_USE_I2P
//		TORRENT_CATEGORY("i2p", save_i2p_proxy, m_i2p_proxy, proxy_settings_map)
#endif
#ifndef TORRENT_DISABLE_ENCRYPTION
		TORRENT_CATEGORY("encryption", save_encryption_settings, m_pe_settings, pe_settings_map)
#endif
	};

	std::pair<bencode_map_entry*, int> settings_map()
	{
		return std::make_pair(session_settings_map, lenof(session_settings_map));
	}
#undef lenof

#ifdef TORRENT_STATS
	int session_impl::logging_allocator::allocations = 0;
	int session_impl::logging_allocator::allocated_bytes = 0;
#endif

#ifdef TORRENT_USE_OPENSSL
	// when running bittorrent over SSL, the SNI (server name indication)
	// extension is used to know which torrent the incoming connection is
	// trying to connect to. The 40 first bytes in the name is expected to
	// be the hex encoded info-hash
	int servername_callback(SSL *s, int *ad, void *arg)
	{
		session_impl* ses = (session_impl*)arg;
		const char* servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
	
		if (!servername || strlen(servername) < 40)
			return SSL_TLSEXT_ERR_ALERT_FATAL;

		sha1_hash info_hash;
		bool valid = from_hex(servername, 40, (char*)&info_hash[0]);

		// the server name is not a valid hex-encoded info-hash
		if (!valid)
			return SSL_TLSEXT_ERR_ALERT_FATAL;

		// see if there is a torrent with this info-hash
		boost::shared_ptr<torrent> t = ses->find_torrent(info_hash).lock();

		// if there isn't, fail
		if (!t) return SSL_TLSEXT_ERR_ALERT_FATAL;

		// if the torrent we found isn't an SSL torrent, also fail.
		// the torrent doesn't have an SSL context and should not allow
		// incoming SSL connections
		if (!t->is_ssl_torrent()) return SSL_TLSEXT_ERR_ALERT_FATAL;

		// use this torrent's certificate
		SSL_set_SSL_CTX(s, t->ssl_ctx()->native_handle());

		return SSL_TLSEXT_ERR_OK;
	}
#endif

	session_impl::session_impl(
		std::pair<int, int> listen_port_range
		, fingerprint const& cl_fprint
		, char const* listen_interface
		, boost::uint32_t alert_mask
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		, std::string const& logpath
#endif
		)
		: m_ipv4_peer_pool(500)
#if TORRENT_USE_IPV6
		, m_ipv6_peer_pool(500)
#endif
#ifndef TORRENT_DISABLE_POOL_ALLOCATOR
		, m_send_buffers(send_buffer_size)
#endif
		, m_files(40)
		, m_io_service()
#ifdef TORRENT_USE_OPENSSL
		, m_ssl_ctx(m_io_service, asio::ssl::context::sslv23)
#endif
		, m_alerts(m_io_service, m_settings.alert_queue_size, alert_mask)
		, m_disk_thread(m_io_service, boost::bind(&session_impl::on_disk_queue, this), m_files)
		, m_half_open(m_io_service)
		, m_download_rate(peer_connection::download_channel)
#ifdef TORRENT_VERBOSE_BANDWIDTH_LIMIT
		, m_upload_rate(peer_connection::upload_channel, true)
#else
		, m_upload_rate(peer_connection::upload_channel)
#endif
		, m_tracker_manager(*this, m_proxy)
		, m_listen_port_retries(listen_port_range.second - listen_port_range.first)
#if TORRENT_USE_I2P
		, m_i2p_conn(m_io_service)
#endif
		, m_abort(false)
		, m_paused(false)
		, m_allowed_upload_slots(8)
		, 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_next_explicit_cache_torrent(0)
		, m_cache_rotation_timer(0)
		, m_peak_up_rate(0)
		, m_peak_down_rate(0)
		, m_incoming_connection(false)
		, m_created(time_now_hires())
		, m_last_tick(m_created)
		, m_last_second_tick(m_created - milliseconds(900))
		, m_last_disk_performance_warning(min_time())
		, m_last_disk_queue_performance_warning(min_time())
		, m_last_choke(m_created)
		, m_next_rss_update(min_time())
#ifndef TORRENT_DISABLE_DHT
		, m_dht_announce_timer(m_io_service)
#endif
		, m_external_udp_port(0)
		, m_udp_socket(m_io_service
			, boost::bind(&session_impl::on_receive_udp, this, _1, _2, _3, _4)
			, boost::bind(&session_impl::on_receive_udp_hostname, this, _1, _2, _3, _4)
			, m_half_open)
		, m_utp_socket_manager(m_settings, m_udp_socket
			, boost::bind(&session_impl::incoming_connection, this, _1))
		, m_boost_connections(0)
		, m_timer(m_io_service)
		, m_lsd_announce_timer(m_io_service)
		, m_host_resolver(m_io_service)
		, m_tick_residual(0)
		, m_non_filtered_torrents(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)
#if (defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS) && defined BOOST_HAS_PTHREADS
		, m_network_thread(0)
#endif
	{
		memset(m_redundant_bytes, 0, sizeof(m_redundant_bytes));
		m_udp_socket.set_rate_limit(m_settings.dht_upload_rate_limit);

		m_disk_queues[0] = 0;
		m_disk_queues[1] = 0;

#ifdef TORRENT_REQUEST_LOGGING
		char log_filename[200];
		snprintf(log_filename, sizeof(log_filename), "requests-%d.log", getpid());
		m_request_log = fopen(log_filename, "w+");
		if (m_request_log == 0)
		{
			fprintf(stderr, "failed to open request log file: (%d) %s\n", errno, strerror(errno));
		}
#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

		error_code ec;
#ifdef TORRENT_USE_OPENSSL
		m_ssl_ctx.set_verify_mode(asio::ssl::context::verify_none, ec);
		SSL_CTX_set_tlsext_servername_callback(m_ssl_ctx.native_handle(), servername_callback);
		SSL_CTX_set_tlsext_servername_arg(m_ssl_ctx.native_handle(), this);
#endif

#ifndef TORRENT_DISABLE_DHT
		m_next_dht_torrent = m_torrents.begin();
#endif
		m_next_lsd_torrent = m_torrents.begin();
		m_next_connect_torrent = m_torrents.begin();
		m_next_disk_peer = m_connections.begin();

		if (!listen_interface) listen_interface = "0.0.0.0";
		m_listen_interface = tcp::endpoint(address::from_string(listen_interface, ec), listen_port_range.first);
		TORRENT_ASSERT_VAL(!ec, ec);

		m_tcp_mapping[0] = -1;
		m_tcp_mapping[1] = -1;
		m_udp_mapping[0] = -1;
		m_udp_mapping[1] = -1;
#ifdef TORRENT_USE_OPENSSL
		m_ssl_mapping[0] = -1;
		m_ssl_mapping[1] = -1;
#endif
#ifdef WIN32
		// windows XP has a limit on the number of
		// simultaneous half-open TCP connections
		// here's a table:

		// windows version       half-open connections limit
		// --------------------- ---------------------------
		// XP sp1 and earlier    infinite
		// earlier than vista    8
		// vista sp1 and earlier 5
		// vista sp2 and later   infinite

		// windows release                     version number
		// ----------------------------------- --------------
		// Windows 7                           6.1
		// Windows Server 2008 R2              6.1
		// Windows Server 2008                 6.0
		// Windows Vista                       6.0
		// Windows Server 2003 R2              5.2
		// Windows Home Server                 5.2
		// Windows Server 2003                 5.2
		// Windows XP Professional x64 Edition 5.2
		// Windows XP                          5.1
		// Windows 2000                        5.0

 		OSVERSIONINFOEX osv;
		memset(&osv, 0, sizeof(osv));
		osv.dwOSVersionInfoSize = sizeof(osv);
		GetVersionEx((OSVERSIONINFO*)&osv);

		// the low two bytes of windows_version is the actual
		// version.
		boost::uint32_t windows_version
			= ((osv.dwMajorVersion & 0xff) << 16)
			| ((osv.dwMinorVersion & 0xff) << 8)
			| (osv.wServicePackMajor & 0xff);

		// this is the format of windows_version
		// xx xx xx
		// |  |  |
		// |  |  + service pack version
		// |  + minor version
		// + major version

		// the least significant byte is the major version
		// and the most significant one is the minor version
		if (windows_version >= 0x060100)
		{
			// windows 7 and up doesn't have a half-open limit
			m_half_open.limit(0);
		}
		else if (windows_version >= 0x060002)
		{
			// on vista SP 2 and up, there's no limit
			m_half_open.limit(0);
		}
		else if (windows_version >= 0x060000)
		{
			// on vista the limit is 5 (in home edition)
			m_half_open.limit(4);
		}
		else if (windows_version >= 0x050102)
		{
			// on XP SP2 the limit is 10	
			m_half_open.limit(9);
		}
		else
		{
			// before XP SP2, there was no limit
			m_half_open.limit(0);
		}
		m_settings.half_open_limit = m_half_open.limit();
#endif

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

#ifdef TORRENT_UPNP_LOGGING
		m_upnp_log.open("upnp.log", std::ios::in | std::ios::out | std::ios::trunc);
#endif

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING

		char tmp[300];
		snprintf(tmp, sizeof(tmp), "libtorrent configuration: %s\n"
			"libtorrent version: %s\n"
			"libtorrent revision: %s\n\n"
		  	, TORRENT_CFG_STRING
			, LIBTORRENT_VERSION
			, LIBTORRENT_REVISION);
		(*m_logger) << tmp;

		logger& l = *m_logger;

		int temp = 0;
		int prev_size = 0;

		PRINT_SIZEOF(announce_entry)
		PRINT_OFFSETOF(announce_entry, url)
		PRINT_OFFSETOF(announce_entry, trackerid)
		PRINT_OFFSETOF(announce_entry, message)
		PRINT_OFFSETOF(announce_entry, last_error)
		PRINT_OFFSETOF(announce_entry, next_announce)
		PRINT_OFFSETOF(announce_entry, min_announce)
		PRINT_OFFSETOF(announce_entry, tier)
		PRINT_OFFSETOF(announce_entry, fail_limit)
		PRINT_OFFSETOF_END(announce_entry)

		PRINT_SIZEOF(torrent_info)
		PRINT_OFFSETOF(torrent_info, m_refs)
		PRINT_OFFSETOF(torrent_info, m_merkle_first_leaf)
		PRINT_OFFSETOF(torrent_info, m_files)
		PRINT_OFFSETOF(torrent_info, m_orig_files)
		PRINT_OFFSETOF(torrent_info, m_urls)
		PRINT_OFFSETOF(torrent_info, m_web_seeds)
		PRINT_OFFSETOF(torrent_info, m_nodes)
		PRINT_OFFSETOF(torrent_info, m_merkle_tree)
		PRINT_OFFSETOF(torrent_info, m_info_section)
		PRINT_OFFSETOF(torrent_info, m_piece_hashes)
		PRINT_OFFSETOF(torrent_info, m_comment)
		PRINT_OFFSETOF(torrent_info, m_created_by)
#ifdef TORRENT_USE_OPENSSL
		PRINT_OFFSETOF(torrent_info, m_ssl_root_cert)
		PRINT_OFFSETOF(torrent_info, m_aes_key)
#endif
		PRINT_OFFSETOF(torrent_info, m_info_dict)
		PRINT_OFFSETOF(torrent_info, m_creation_date)
		PRINT_OFFSETOF(torrent_info, m_info_hash)
		PRINT_OFFSETOF_END(torrent_info)

		PRINT_SIZEOF(union_endpoint)
		PRINT_SIZEOF(request_callback)
		PRINT_SIZEOF(stat)
		PRINT_SIZEOF(bandwidth_channel)
		PRINT_SIZEOF(policy)
		(*m_logger) << "sizeof(utp_socket_impl): " << socket_impl_size() << "\n";

		PRINT_SIZEOF(file_entry)
		PRINT_SIZEOF(internal_file_entry)
		PRINT_OFFSETOF(internal_file_entry, name)
		PRINT_OFFSETOF(internal_file_entry, path_index)
		PRINT_OFFSETOF_END(internal_file_entry)

		PRINT_SIZEOF(file_storage)
		PRINT_OFFSETOF(file_storage, m_files)
		PRINT_OFFSETOF(file_storage, m_file_hashes)
		PRINT_OFFSETOF(file_storage, m_symlinks)
		PRINT_OFFSETOF(file_storage, m_mtime)
		PRINT_OFFSETOF(file_storage, m_file_base)
		PRINT_OFFSETOF(file_storage, m_paths)
		PRINT_OFFSETOF(file_storage, m_name)
		PRINT_OFFSETOF(file_storage, m_total_size)
		PRINT_OFFSETOF(file_storage, m_num_pieces)
		PRINT_OFFSETOF(file_storage, m_piece_length)
		PRINT_OFFSETOF_END(file_storage)

//		PRINT_SIZEOF(stat_channel)
//		PRINT_OFFSETOF(stat_channel, m_counter)
//		PRINT_OFFSETOF(stat_channel, m_average)
//		PRINT_OFFSETOF(stat_channel, m_total_counter)

		torrent::print_size(*m_logger);

		PRINT_SIZEOF(peer_connection)
		PRINT_SIZEOF(bt_peer_connection)
		PRINT_SIZEOF(address)
		PRINT_SIZEOF(address_v4)
		PRINT_SIZEOF(address_v4::bytes_type)
#if TORRENT_USE_IPV6
		PRINT_SIZEOF(address_v6)
		PRINT_SIZEOF(address_v6::bytes_type)
#endif
		PRINT_SIZEOF(void*)
#ifndef TORRENT_DISABLE_DHT
		PRINT_SIZEOF(dht::node_entry)
#endif

		PRINT_SIZEOF(policy::peer)
		PRINT_OFFSETOF(policy::peer, prev_amount_upload)
		PRINT_OFFSETOF(policy::peer, prev_amount_download)
		PRINT_OFFSETOF(policy::peer, connection)
#ifndef TORRENT_DISABLE_GEO_IP
#ifdef TORRENT_DEBUG
		PRINT_OFFSETOF(policy::peer, inet_as_num)
#endif
		PRINT_OFFSETOF(policy::peer, inet_as)
#endif
		PRINT_OFFSETOF(policy::peer, last_optimistically_unchoked)
		PRINT_OFFSETOF(policy::peer, last_connected)
		PRINT_OFFSETOF(policy::peer, port)
		PRINT_OFFSETOF(policy::peer, upload_rate_limit)
		PRINT_OFFSETOF(policy::peer, download_rate_limit)
		PRINT_OFFSETOF(policy::peer, hashfails)
		PRINT_OFFSETOF_END(policy::peer)

		PRINT_SIZEOF(policy::ipv4_peer)
#if TORRENT_USE_IPV6
		PRINT_SIZEOF(policy::ipv6_peer)
#endif

		PRINT_SIZEOF(udp_socket)
		PRINT_OFFSETOF(udp_socket, m_callback)
		PRINT_OFFSETOF(udp_socket, m_callback2)
		PRINT_OFFSETOF(udp_socket, m_ipv4_sock)
		PRINT_OFFSETOF(udp_socket, m_v4_ep)
		PRINT_OFFSETOF(udp_socket, m_v4_buf)
		PRINT_OFFSETOF(udp_socket, m_reallocate_buffer4)
#if TORRENT_USE_IPV6
		PRINT_OFFSETOF(udp_socket, m_ipv6_sock)
		PRINT_OFFSETOF(udp_socket, m_v6_ep)
		PRINT_OFFSETOF(udp_socket, m_v6_buf)
		PRINT_OFFSETOF(udp_socket, m_reallocate_buffer6)
#endif
		PRINT_OFFSETOF(udp_socket, m_bind_port)
		PRINT_OFFSETOF(udp_socket, m_v4_outstanding)
#if TORRENT_USE_IPV6
		PRINT_OFFSETOF(udp_socket, m_v6_outstanding)
#endif
		PRINT_OFFSETOF(udp_socket, m_socks5_sock)
		PRINT_OFFSETOF(udp_socket, m_connection_ticket)
		PRINT_OFFSETOF(udp_socket, m_proxy_settings)
#ifndef _MSC_VER
		PRINT_OFFSETOF(udp_socket, m_cc)
#endif
		PRINT_OFFSETOF(udp_socket, m_resolver)
		PRINT_OFFSETOF(udp_socket, m_tmp_buf)
		PRINT_OFFSETOF(udp_socket, m_queue_packets)
		PRINT_OFFSETOF(udp_socket, m_tunnel_packets)
		PRINT_OFFSETOF(udp_socket, m_abort)
		PRINT_OFFSETOF(udp_socket, m_proxy_addr)
		PRINT_OFFSETOF(udp_socket, m_queue)
		PRINT_OFFSETOF(udp_socket, m_outstanding_ops)
#ifdef TORRENT_DEBUG
		PRINT_OFFSETOF(udp_socket, m_started)
		PRINT_OFFSETOF(udp_socket, m_magic)
		PRINT_OFFSETOF(udp_socket, m_outstanding_when_aborted)
#endif
		PRINT_OFFSETOF_END(udp_socket)

		PRINT_SIZEOF(tracker_connection)
		PRINT_SIZEOF(http_tracker_connection)

		PRINT_SIZEOF(udp_tracker_connection)
		PRINT_OFFSETOF(udp_tracker_connection, m_refs)

		PRINT_OFFSETOF(udp_tracker_connection, m_start_time)
		PRINT_OFFSETOF(udp_tracker_connection, m_read_time)
		PRINT_OFFSETOF(udp_tracker_connection, m_timeout)
		PRINT_OFFSETOF(udp_tracker_connection, m_completion_timeout)
		PRINT_OFFSETOF(udp_tracker_connection, m_read_timeout)
		PRINT_OFFSETOF(udp_tracker_connection, m_mutex)
		PRINT_OFFSETOF(udp_tracker_connection, timeout_handler::m_abort)
		PRINT_OFFSETOF(udp_tracker_connection, m_requester)
#ifndef _MSC_VER
		PRINT_OFFSETOF(udp_tracker_connection, m_man)
#endif

		PRINT_OFFSETOF(udp_tracker_connection, m_req)

		PRINT_OFFSETOF(udp_tracker_connection, m_abort)
		PRINT_OFFSETOF(udp_tracker_connection, m_hostname)
		PRINT_OFFSETOF(udp_tracker_connection, m_target)
		PRINT_OFFSETOF(udp_tracker_connection, m_endpoints)
		PRINT_OFFSETOF(udp_tracker_connection, m_transaction_id)
#ifndef _MSC_VER
		PRINT_OFFSETOF(udp_tracker_connection, m_ses)
#endif
		PRINT_OFFSETOF(udp_tracker_connection, m_attempts)
		PRINT_OFFSETOF(udp_tracker_connection, m_state)
		PRINT_OFFSETOF(udp_tracker_connection, m_proxy)
		PRINT_OFFSETOF_END(udp_tracker_connection)

#ifndef TORRENT_DISABLE_DHT
		PRINT_SIZEOF(dht::find_data_observer)
		PRINT_SIZEOF(dht::announce_observer)
		PRINT_SIZEOF(dht::null_observer)
#endif
#undef PRINT_OFFSETOF_END
#undef PRINT_OFFSETOF
#undef PRINT_SIZEOF

#endif

#ifdef TORRENT_STATS

		m_stats_logger = 0;
		m_log_seq = 0;
		m_stats_logging_enabled = true;

		memset(&m_last_cache_status, 0, sizeof(m_last_cache_status));
		get_vm_stats(&m_last_vm_stat);

		m_last_failed = 0;
		m_last_redundant = 0;
		m_last_uploaded = 0;
		m_last_downloaded = 0;
		get_thread_cpu_usage(&m_network_thread_cpu_usage);

		reset_stat_counters();
		rotate_stats_log();
#endif
#ifdef TORRENT_DISK_STATS
		m_buffer_usage_logger.open("buffer_stats.log", std::ios::trunc);
		m_buffer_allocations = 0;
#endif

#if defined TORRENT_BSD || defined TORRENT_LINUX
		// ---- auto-cap open files ----

		struct rlimit rl;
		if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
		{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			(*m_logger) << time_now_string() << " max number of open files: " << rl.rlim_cur << "\n";
#endif

			// deduct some margin for epoll/kqueue, log files,
			// futexes, shared objects etc.
			rl.rlim_cur -= 20;

			// 80% of the available file descriptors should go
			m_settings.connections_limit = (std::min)(m_settings.connections_limit
				, int(rl.rlim_cur * 8 / 10));
			// 20% goes towards regular files
			m_files.resize((std::min)(m_files.size_limit(), int(rl.rlim_cur * 2 / 10)));
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			(*m_logger) << time_now_string() << "   max connections: " << m_settings.connections_limit << "\n";
			(*m_logger) << time_now_string() << "   max files: " << m_files.size_limit() << "\n";
#endif
		}
#endif // TORRENT_BSD || TORRENT_LINUX


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

		m_key = random() + (random() << 15) + (random() << 30);
		std::string print = cl_fprint.to_string();
		TORRENT_ASSERT_VAL(print.length() <= 20, print.length());

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

		url_random((char*)&m_peer_id[print.length()], (char*)&m_peer_id[0] + 20);

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		(*m_logger) << time_now_string() << " generated peer ID: " << m_peer_id.to_string() << "\n";
#endif

		update_rate_settings();
		update_connections_limit();
		update_unchoke_limit();
	}

#ifdef TORRENT_STATS
	void session_impl::rotate_stats_log()
	{
		if (m_stats_logger)
		{
			++m_log_seq;
			fclose(m_stats_logger);
		}

		error_code ec;
		char filename[100];
		create_directory("session_stats", ec);
		snprintf(filename, sizeof(filename), "session_stats/%d.%04d.log", int(getpid()), m_log_seq);
		m_stats_logger = fopen(filename, "w+");
		if (m_stats_logger == 0)
		{
			fprintf(stderr, "Failed to create session stats log file \"%s\": (%d) %s\n"
				, filename, errno, strerror(errno));
			return;
		}
		m_last_log_rotation = time_now();
			
		fputs("second:uploaded bytes:downloaded bytes:downloading torrents:seeding torrents"
			":peers:connecting peers:disk block buffers:num list peers"
			":peer allocations:peer storage bytes"
			":checking torrents:stopped torrents:upload-only torrents"
			":peers bw-up:peers bw-down:peers disk-up:peers disk-down"
			":upload rate:download rate:disk write queued bytes"
			":peers down 0:peers down 0-2:peers down 2-5:peers down 5-10:peers down 10-50"
			":peers down 50-100:peers down 100-"
			":peers up 0:peers up 0-2:peers up 2-5:peers up 5-10:peers up 10-50:peers up 50-100"
			":peers up 100-:error peers"
			":peers down interesting:peers down unchoked:peers down requests"
			":peers up interested:peers up unchoked:peers up requests"
			":peer disconnects:peers eof:peers connection reset"
			":outstanding requests:outstanding end-game requests"
			":outstanding writing blocks"
			":end game piece picker blocks"
			":piece picker blocks"
			":piece picks"
			":reject piece picks"
			":unchoke piece picks"
			":incoming redundant piece picks"
			":incoming piece picks"
			":end game piece picks"
			":snubbed piece picks"
			":connect timeouts"
			":uninteresting peers disconnect"
			":timeout peers"
			":% failed payload bytes"
			":% wasted payload bytes"
			":% protocol bytes"
			":disk read time"
			":disk write time"
			":disk queue time"
			":disk queue size"
			":disk queued bytes"
			":read cache hits"
			":disk block read"
			":disk block written"
			":failed bytes"
			":redundant bytes"
			":error torrents"
			":read disk cache size"
			":disk cache size"
			":disk buffer allocations"
			":disk hash time"
			":disk job time"
			":disk sort time"
			":connection attempts"
			":banned peers"
			":banned for hash failure"
			":cache size"
			":max connections"
			":connect candidates"
			":disk queue limit"
			":disk queue low watermark"
			":% read time"
			":% write time"
			":% hash time"
			":% sort time"
			":disk read back"
			":% read back"
			":disk read queue size"
			":tick interval"
			":tick residual"
			":max unchoked"
			":read job queue size limit"
			":smooth upload rate"
			":smooth download rate"
			":num end-game peers"
			":TCP up rate"
			":TCP down rate"
			":TCP up limit"
			":TCP down limit"
			":uTP up rate"
			":uTP down rate"
			":uTP peak send delay"
			":uTP avg send delay"
			":uTP peak recv delay"
			":uTP avg recv delay"
			":read ops/s"
			":write ops/s"
			":active resident pages"
			":inactive resident pages"
			":pinned resident pages"
			":free pages"
			":pageins"
			":pageouts"
			":page faults"
			":smooth read ops/s"
			":smooth write ops/s"
			":pending reading bytes"
			":read_counter"
			":write_counter"
			":tick_counter"
			":lsd_counter"
			":lsd_peer_counter"
			":udp_counter"
			":accept_counter"
			":disk_queue_counter"
			":disk_read_counter"
			":disk_write_counter"
			":up 8:up 16:up 32:up 64:up 128:up 256:up 512:up 1024:up 2048:up 4096:up 8192:up 16384:up 32768:up 65536:up 131072:up 262144:up 524288:up 1048576"
			":down 8:down 16:down 32:down 64:down 128:down 256:down 512:down 1024:down 2048:down 4096:down 8192:down 16384:down 32768:down 65536:down 131072:down 262144:down 524288:down 1048576"
			":network thread system time"
			":network thread user+system time"

			":redundant timed-out"
			":redundant cancelled"
			":redundant unknown"
			":redundant seed"
			":redundant end-game"
			":redundant closing"
			":no memory peer errors"
			":too many peers"
			":transport timeout peers"
			"\n\n", m_stats_logger);
	}
#endif

	void session_impl::start_session()
	{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		(*m_logger) << time_now_string() << " spawning network thread\n";
#endif
		m_thread.reset(new thread(boost::bind(&session_impl::main_thread, this)));
	}

	void session_impl::init()
	{
#if defined TORRENT_LOGGING || defined TORRENT_VERBOSE_LOGGING
		(*m_logger) << time_now_string() << " *** session thread init\n";
#endif

		// this is where we should set up all async operations. This
		// is called from within the network thread as opposed to the
		// constructor which is called from the main thread

#if defined TORRENT_ASIO_DEBUGGING
		async_inc_threads();
		add_outstanding_async("session_impl::on_tick");
#endif
		error_code ec;
		m_io_service.post(boost::bind(&session_impl::on_tick, this, ec));

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_lsd_announce");
#endif
		int delay = (std::max)(m_settings.local_service_announce_interval
			/ (std::max)(int(m_torrents.size()), 1), 1);
		m_lsd_announce_timer.expires_from_now(seconds(delay), ec);
		m_lsd_announce_timer.async_wait(
			boost::bind(&session_impl::on_lsd_announce, this, _1));
		TORRENT_ASSERT(!ec);

#ifndef TORRENT_DISABLE_DHT

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_dht_announce");
#endif
		delay = (std::max)(m_settings.dht_announce_interval
			/ (std::max)(int(m_torrents.size()), 1), 1);
		m_dht_announce_timer.expires_from_now(seconds(delay), ec);
		m_dht_announce_timer.async_wait(
			boost::bind(&session_impl::on_dht_announce, this, _1));
		TORRENT_ASSERT(!ec);
#endif

#if defined TORRENT_LOGGING || defined TORRENT_VERBOSE_LOGGING
		(*m_logger) << time_now_string() << " open listen port\n";
#endif
		// no reuse_address and allow system defined port
		open_listen_port(0, ec);
#if defined TORRENT_LOGGING || defined TORRENT_VERBOSE_LOGGING
		(*m_logger) << time_now_string() << " done starting session\n";
#endif
	}

	void session_impl::save_state(entry* eptr, boost::uint32_t flags) const
	{
		TORRENT_ASSERT(is_network_thread());

		entry& e = *eptr;

		all_default_values def;

		for (int i = 0; i < int(sizeof(all_settings)/sizeof(all_settings[0])); ++i)
		{
			session_category const& c = all_settings[i];
			if ((flags & c.flag) == 0) continue;
			save_struct(e[c.name], reinterpret_cast<char const*>(this) + c.offset
				, c.map, c.num_entries, reinterpret_cast<char const*>(&def) + c.default_offset);
		}
#ifndef TORRENT_DISABLE_DHT
		if (m_dht && (flags & session::save_dht_state))
		{
			e["dht state"] = m_dht->state();
		}
#endif

#if TORRENT_USE_I2P
		if (flags & session::save_i2p_proxy)
		{
			save_struct(e["i2p"], &i2p_proxy(), proxy_settings_map
				, sizeof(proxy_settings_map)/sizeof(proxy_settings_map[0])
				, &def.m_proxy);
		}
#endif
#ifndef TORRENT_DISABLE_GEO_IP
		if (flags & session::save_as_map)
		{
			entry::dictionary_type& as_map = e["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

		if (flags & session::save_feeds)
		{
			entry::list_type& feeds = e["feeds"].list();
			for (std::vector<boost::shared_ptr<feed> >::const_iterator i =
				m_feeds.begin(), end(m_feeds.end()); i != end; ++i)
			{
				feeds.push_back(entry());
				(*i)->save_state(feeds.back());
			}
		}

#ifndef TORRENT_DISABLE_EXTENSIONS
		for (ses_extension_list_t::const_iterator i = m_ses_extensions.begin()
			, end(m_ses_extensions.end()); i != end; ++i)
		{
			TORRENT_TRY {
				(*i)->save_state(*eptr);
			} TORRENT_CATCH(std::exception&) {}
		}
#endif
	}
	
	void session_impl::set_proxy(proxy_settings const& s)
	{
		TORRENT_ASSERT(is_network_thread());

		m_proxy = s;
		// in case we just set a socks proxy, we might have to
		// open the socks incoming connection
		if (!m_socks_listen_socket) open_new_incoming_socks_connection();
		m_udp_socket.set_proxy_settings(m_proxy);
	}

	void session_impl::load_state(lazy_entry const* e)
	{
		TORRENT_ASSERT(is_network_thread());

		lazy_entry const* settings;
	  
		if (e->type() != lazy_entry::dict_t) return;

		for (int i = 0; i < int(sizeof(all_settings)/sizeof(all_settings[0])); ++i)
		{
			session_category const& c = all_settings[i];
			settings = e->dict_find_dict(c.name);
			if (!settings) continue;
			load_struct(*settings, reinterpret_cast<char*>(this) + c.offset, c.map, c.num_entries);
		}
		
		update_rate_settings();
		update_connections_limit();
		update_unchoke_limit();
		m_alerts.set_alert_queue_size_limit(m_settings.alert_queue_size);

		// in case we just set a socks proxy, we might have to
		// open the socks incoming connection
		if (!m_socks_listen_socket) open_new_incoming_socks_connection();
		m_udp_socket.set_proxy_settings(m_proxy);

#ifndef TORRENT_DISABLE_DHT
		settings = e->dict_find_dict("dht state");
		if (settings)
		{
			m_dht_state = *settings;
		}
#endif

#if TORRENT_USE_I2P
		settings = e->dict_find_dict("i2p");
		if (settings)
		{
			proxy_settings s;
			load_struct(*settings, &s, proxy_settings_map
				, sizeof(proxy_settings_map)/sizeof(proxy_settings_map[0]));
			set_i2p_proxy(s);
		}
#endif
#ifndef TORRENT_DISABLE_GEO_IP
		settings  = e->dict_find_dict("AS map");
		if (settings)
		{
			for (int i = 0; i < settings->dict_size(); ++i)
			{
				std::pair<std::string, lazy_entry const*> item = settings->dict_at(i);
				int as_num = atoi(item.first.c_str());
				if (item.second->type() != lazy_entry::int_t || item.second->int_value() == 0) continue;
				int& peak = m_as_peak[as_num];
				if (peak < item.second->int_value()) peak = item.second->int_value();
			}
		}
#endif

 		if (m_settings.connection_speed < 0) m_settings.connection_speed = 200;

		update_disk_thread_settings();

		settings = e->dict_find_list("feeds");
		if (settings)
		{
			m_feeds.reserve(settings->list_size());
			for (int i = 0; i < settings->list_size(); ++i)
			{
				boost::shared_ptr<feed> f(new_feed(*this, feed_settings()));
				if (settings->list_at(i)->type() != lazy_entry::dict_t) continue;
				f->load_state(*settings->list_at(i));
				f->update_feed();
				m_feeds.push_back(f);
			}
			update_rss_feeds();
		}

#ifndef TORRENT_DISABLE_EXTENSIONS
		for (ses_extension_list_t::iterator i = m_ses_extensions.begin()
			, end(m_ses_extensions.end()); i != end; ++i)
		{
			TORRENT_TRY {
				(*i)->load_state(*e);
			} TORRENT_CATCH(std::exception&) {}
		}
#endif
	}

#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)
	{
		TORRENT_ASSERT(is_network_thread());

		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)
	{
		TORRENT_ASSERT(is_network_thread());

		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)
	{
		TORRENT_ASSERT(is_network_thread());

		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)
	{
		TORRENT_ASSERT(is_network_thread());

		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);
	}

	void session_impl::load_asnum_db(std::string file)
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_asnum_db) GeoIP_delete(m_asnum_db);
		m_asnum_db = GeoIP_open(file.c_str(), GEOIP_STANDARD);
//		return m_asnum_db;
	}

#if TORRENT_USE_WSTRING
	void session_impl::load_asnum_dbw(std::wstring file)
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_asnum_db) GeoIP_delete(m_asnum_db);
		std::string utf8;
		wchar_utf8(file, utf8);
		m_asnum_db = GeoIP_open(utf8.c_str(), GEOIP_STANDARD);
//		return m_asnum_db;
	}

	void session_impl::load_country_dbw(std::wstring file)
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_country_db) GeoIP_delete(m_country_db);
		std::string utf8;
		wchar_utf8(file, utf8);
		m_country_db = GeoIP_open(utf8.c_str(), GEOIP_STANDARD);
//		return m_country_db;
	}
#endif // TORRENT_USE_WSTRING

	void session_impl::load_country_db(std::string file)
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_country_db) GeoIP_delete(m_country_db);
		m_country_db = GeoIP_open(file.c_str(), GEOIP_STANDARD);
//		return m_country_db;
	}

#endif // TORRENT_DISABLE_GEO_IP

#ifndef TORRENT_DISABLE_EXTENSIONS
	void session_impl::add_extension(
		boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> ext)
	{
		TORRENT_ASSERT(is_network_thread());
		TORRENT_ASSERT_VAL(ext, ext);

		typedef boost::shared_ptr<torrent_plugin>(*function_t)(torrent*, void*);
		function_t const* f = ext.target<function_t>();

		if (f)
		{
			for (extension_list_t::iterator i = m_extensions.begin(); i != m_extensions.end(); ++i)
				if (function_equal(*i, *f)) return;
		}

		m_extensions.push_back(ext);
	}

	void session_impl::add_ses_extension(boost::shared_ptr<plugin> ext)
	{
		TORRENT_ASSERT(is_network_thread());
		TORRENT_ASSERT_VAL(ext, ext);

		m_ses_extensions.push_back(ext);
		m_alerts.add_extension(ext);
		ext->added(shared_from_this());
	}
#endif

#ifndef TORRENT_DISABLE_DHT
	void session_impl::add_dht_node(udp::endpoint n)
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_dht) m_dht->add_node(n);
	}
#endif

	feed_handle session_impl::add_feed(feed_settings const& sett)
	{
		TORRENT_ASSERT(is_network_thread());

		// look for duplicates. If we already have a feed with this
		// URL, return a handle to the existing one
		for (std::vector<boost::shared_ptr<feed> >::const_iterator i
			= m_feeds.begin(), end(m_feeds.end()); i != end; ++i)
		{
			if (sett.url != (*i)->m_settings.url) continue;
			return feed_handle(*i);
		}

		boost::shared_ptr<feed> f(new_feed(*this, sett));
		m_feeds.push_back(f);
		update_rss_feeds();
		return feed_handle(f);
	}

	void session_impl::remove_feed(feed_handle h)
	{
		TORRENT_ASSERT(is_network_thread());

		boost::shared_ptr<feed> f = h.m_feed_ptr.lock();
		if (!f) return;

		std::vector<boost::shared_ptr<feed> >::iterator i
			= std::find(m_feeds.begin(), m_feeds.end(), f);

		if (i == m_feeds.end()) return;

		m_feeds.erase(i);
	}

	void session_impl::get_feeds(std::vector<feed_handle>* ret) const
	{
		TORRENT_ASSERT(is_network_thread());

		ret->clear();
		ret->reserve(m_feeds.size());
		for (std::vector<boost::shared_ptr<feed> >::const_iterator i = m_feeds.begin()
			, end(m_feeds.end()); i != end; ++i)
			ret->push_back(feed_handle(*i));
	}

	void session_impl::pause()
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_paused) return;
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING
		(*m_logger) << time_now_string() << " *** session paused ***\n";
#endif
		m_paused = true;
		for (torrent_map::iterator i = m_torrents.begin()
			, end(m_torrents.end()); i != end; ++i)
		{
			torrent& t = *i->second;
			t.do_pause();
		}
	}

	void session_impl::resume()
	{
		TORRENT_ASSERT(is_network_thread());

		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();
			if (t.should_check_files()) t.queue_torrent_check();
		}
	}
	
	void session_impl::abort()
	{
		TORRENT_ASSERT(is_network_thread());

		if (m_abort) return;
#if defined TORRENT_LOGGING
		(*m_logger) << time_now_string() << " *** ABORT CALLED ***\n";
#endif
		// abort the main thread
		m_abort = true;
		error_code ec;
#if TORRENT_USE_I2P
		m_i2p_conn.close(ec);
#endif
		m_queued_for_checking.clear();
		stop_lsd();
		stop_upnp();
		stop_natpmp();
#ifndef TORRENT_DISABLE_DHT
		if (m_dht)
		{
			m_dht->stop();
			m_dht = 0;
		}
		m_dht_announce_timer.cancel(ec);
#endif
		m_timer.cancel(ec);
		m_lsd_announce_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);
			TORRENT_ASSERT(!ec);
		}
		m_listen_sockets.clear();

#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";
#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() << " aborting all connections (" << m_connections.size() << ")\n";
#endif
		// closing all the connections needs to be done from a callback,
		// when the session mutex is not held
		m_io_service.post(boost::bind(&connection_queue::close, &m_half_open));

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

		// abort all connections
		while (!m_connections.empty())
		{
#if defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS
			int conn = m_connections.size();
#endif
			(*m_connections.begin())->disconnect(errors::stopping_torrent);
			TORRENT_ASSERT_VAL(conn == int(m_connections.size()) + 1, conn);
		}

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

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

		m_download_rate.close();
		m_upload_rate.close();

		// #error closing the udp socket here means that
		// the uTP connections cannot be closed gracefully
		m_udp_socket.close();
		m_external_udp_port = 0;

#ifndef TORRENT_DISABLE_GEO_IP
		if (m_asnum_db) GeoIP_delete(m_asnum_db);
		if (m_country_db) GeoIP_delete(m_country_db);
		m_asnum_db = 0;
		m_country_db = 0;
#endif

		m_disk_thread.abort();
	}

	void session_impl::set_port_filter(port_filter const& f)
	{
		m_port_filter = f;
		// TODO: recalculate all connect candidates for all torrents
	}

	void session_impl::set_ip_filter(ip_filter const& f)
	{
		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();
	}

	ip_filter const& session_impl::get_ip_filter() const
	{
		return m_ip_filter;
	}

	void session_impl::update_disk_thread_settings()
	{
		disk_io_job j;
		j.buffer = (char*)&m_settings;
		j.action = disk_io_job::update_settings;
		m_disk_thread.add_job(j);
	}

	void session_impl::set_settings(session_settings const& s)
	{
		INVARIANT_CHECK;
		TORRENT_ASSERT(is_network_thread());

		TORRENT_ASSERT_VAL(s.file_pool_size > 0, s.file_pool_size);

		// less than 5 seconds unchoke interval is insane
		TORRENT_ASSERT_VAL(s.unchoke_interval >= 5, s.unchoke_interval);

		// if disk io thread settings were changed
		// post a notification to that thread
		bool update_disk_io_thread = false;
		if (m_settings.cache_size != s.cache_size
			|| m_settings.cache_expiry != s.cache_expiry
			|| m_settings.optimize_hashing_for_speed != s.optimize_hashing_for_speed
			|| m_settings.file_checks_delay_per_block != s.file_checks_delay_per_block
			|| m_settings.disk_cache_algorithm != s.disk_cache_algorithm
			|| m_settings.read_cache_line_size != s.read_cache_line_size
			|| m_settings.write_cache_line_size != s.write_cache_line_size
			|| m_settings.coalesce_writes != s.coalesce_writes
			|| m_settings.coalesce_reads != s.coalesce_reads
			|| m_settings.max_queued_disk_bytes != s.max_queued_disk_bytes
			|| m_settings.max_queued_disk_bytes_low_watermark != s.max_queued_disk_bytes_low_watermark
			|| m_settings.disable_hash_checks != s.disable_hash_checks
			|| m_settings.explicit_read_cache != s.explicit_read_cache
#ifndef TORRENT_DISABLE_MLOCK
			|| m_settings.lock_disk_cache != s.lock_disk_cache
#endif
			|| m_settings.use_read_cache != s.use_read_cache
			|| m_settings.disk_io_write_mode != s.disk_io_write_mode
			|| m_settings.disk_io_read_mode != s.disk_io_read_mode
			|| m_settings.allow_reordered_disk_operations != s.allow_reordered_disk_operations
			|| m_settings.file_pool_size != s.file_pool_size
			|| m_settings.volatile_read_cache != s.volatile_read_cache
			|| m_settings.no_atime_storage!= s.no_atime_storage
			|| m_settings.ignore_resume_timestamps != s.ignore_resume_timestamps
			|| m_settings.no_recheck_incomplete_resume != s.no_recheck_incomplete_resume
			|| m_settings.low_prio_disk != s.low_prio_disk
			|| m_settings.lock_files != s.lock_files)
			update_disk_io_thread = true;

		bool connections_limit_changed = m_settings.connections_limit != s.connections_limit;
		bool unchoke_limit_changed = m_settings.unchoke_slots_limit != s.unchoke_slots_limit;

#ifndef TORRENT_NO_DEPRECATE
		// support deprecated choker settings
		if (s.choking_algorithm == session_settings::rate_based_choker)
		{
			if (s.auto_upload_slots && !s.auto_upload_slots_rate_based)
				m_settings.choking_algorithm = session_settings::auto_expand_choker;
			else if (!s.auto_upload_slots)
				m_settings.choking_algorithm = session_settings::fixed_slots_choker;
		}
#endif

		// safety check
		if (m_settings.volatile_read_cache
			&& (m_settings.suggest_mode == session_settings::suggest_read_cache
				|| m_settings.explicit_read_cache))
		{
			// If you hit this assert, you're trying to set your cache to be
			// volatile and to suggest pieces out of it (or to make the cache
			// explicit) at the same time this is a bad configuration, don't do it
			TORRENT_ASSERT(false);
			m_settings.volatile_read_cache = false;
		}

		if (m_settings.choking_algorithm != s.choking_algorithm)
		{
			// trigger recalculation of the unchoked peers
			m_unchoke_time_scaler = 0;
		}

#ifndef TORRENT_DISABLE_DHT
		if (m_settings.dht_announce_interval != s.dht_announce_interval)
		{
#if defined TORRENT_ASIO_DEBUGGING
			add_outstanding_async("session_impl::on_dht_announce");
#endif
			error_code ec;
			int delay = (std::max)(s.dht_announce_interval
				/ (std::max)(int(m_torrents.size()), 1), 1);
			m_dht_announce_timer.expires_from_now(seconds(delay), ec);
			m_dht_announce_timer.async_wait(
				boost::bind(&session_impl::on_dht_announce, this, _1));
		}
#endif

		if (m_settings.local_service_announce_interval != s.local_service_announce_interval)
		{
#if defined TORRENT_ASIO_DEBUGGING
			add_outstanding_async("session_impl::on_lsd_announce");
#endif
			error_code ec;
			int delay = (std::max)(s.local_service_announce_interval
				/ (std::max)(int(m_torrents.size()), 1), 1);
			m_lsd_announce_timer.expires_from_now(seconds(delay), ec);
			m_lsd_announce_timer.async_wait(
				boost::bind(&session_impl::on_lsd_announce, this, _1));
		}

		// 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;

		// if anonymous mode was enabled, clear out the peer ID
		bool anonymous = (m_settings.anonymous_mode != s.anonymous_mode && s.anonymous_mode);

		if (m_settings.report_web_seed_downloads != s.report_web_seed_downloads)
		{
			// if this flag changed, update all web seed connections
			for (connection_map::iterator i = m_connections.begin()
				, end(m_connections.end()); i != end; ++i)
			{
				int type = (*i)->type();
				if (type == peer_connection::url_seed_connection
					|| type == peer_connection::http_seed_connection)
					(*i)->ignore_stats(!s.report_web_seed_downloads);
			}
		}

		if (m_settings.alert_queue_size != s.alert_queue_size)
			m_alerts.set_alert_queue_size_limit(s.alert_queue_size);

		if (m_settings.dht_upload_rate_limit != s.dht_upload_rate_limit)
			m_udp_socket.set_rate_limit(s.dht_upload_rate_limit);

		m_settings = s;

		if (m_settings.cache_buffer_chunk_size <= 0)
			m_settings.cache_buffer_chunk_size = 1;

		update_rate_settings();

		if (connections_limit_changed) update_connections_limit();
		if (unchoke_limit_changed) update_unchoke_limit();
	
		// enable anonymous mode. We don't want to accept any incoming
		// connections, except through a proxy.
		if (anonymous)
		{
			m_settings.user_agent.clear();
			url_random((char*)&m_peer_id[0], (char*)&m_peer_id[0] + 20);
			stop_lsd();
			stop_upnp();
			stop_natpmp();
#ifndef TORRENT_DISABLE_DHT
			stop_dht();
#endif
			// close the listen sockets
			error_code ec;
			for (std::list<listen_socket_t>::iterator i = m_listen_sockets.begin()
				, end(m_listen_sockets.end()); i != end; ++i)
				i->sock->close(ec);
			m_listen_sockets.clear();
		}
 		if (m_settings.connection_speed < 0) m_settings.connection_speed = 200;
 
		if (update_disk_io_thread)
			update_disk_thread_settings();

		if (m_settings.num_optimistic_unchoke_slots >= m_allowed_upload_slots / 2)
		{
			if (m_alerts.should_post<performance_alert>())
				m_alerts.post_alert(performance_alert(torrent_handle()
					, performance_alert::too_many_optimistic_unchoke_slots));
		}

		if (s.choking_algorithm == session_settings::fixed_slots_choker)
			m_allowed_upload_slots = m_settings.unchoke_slots_limit;
		else if (s.choking_algorithm == session_settings::auto_expand_choker
			&& m_allowed_upload_slots < m_settings.unchoke_slots_limit)
			m_allowed_upload_slots = m_settings.unchoke_slots_limit;

		// 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;
	}

	tcp::endpoint session_impl::get_ipv4_interface() const
	{
		return m_ipv4_interface;
	}

	void session_impl::setup_listener(listen_socket_t* s, tcp::endpoint ep
		, int retries, bool v6_only, int flags, error_code& ec)
	{
		s->sock.reset(new socket_acceptor(m_io_service));
		s->sock->open(ep.protocol(), ec);
		if (ec)
		{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			(*m_logger) << "failed to open socket: " << print_endpoint(ep)
				<< ": " << ec.message() << "\n" << "\n";
#endif
			return;
		}
		if (flags & session::listen_reuse_address)
		{
			error_code err; // ignore errors here
			s->sock->set_option(socket_acceptor::reuse_address(true), err);
		}
#if TORRENT_USE_IPV6
		if (ep.protocol() == tcp::v6())
		{
			error_code err; // ignore errors here
			s->sock->set_option(v6only(v6_only), err);
#ifdef TORRENT_WINDOWS

#ifndef PROTECTION_LEVEL_UNRESTRICTED
#define PROTECTION_LEVEL_UNRESTRICTED 10
#endif
			// enable Teredo on windows
			s->sock->set_option(v6_protection_level(PROTECTION_LEVEL_UNRESTRICTED), err);
#endif
		}
#endif
		s->sock->bind(ep, ec);
		while (ec && retries > 0)
		{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			char msg[200];
			snprintf(msg, 200, "failed to bind to interface \"%s\": %s"
				, print_endpoint(ep).c_str(), ec.message().c_str());
			(*m_logger) << time_now_string() << " " << msg << "\n";
#endif
			ec.clear();
			TORRENT_ASSERT_VAL(!ec, ec);
			--retries;
			ep.port(ep.port() + 1);
			s->sock->bind(ep, ec);
		}
		if (ec && !(flags & session::listen_no_system_port))
		{
			// instead of giving up, trying
			// 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 || defined TORRENT_ERROR_LOGGING
			char msg[200];
			snprintf(msg, 200, "cannot bind to interface \"%s\": %s"
				, print_endpoint(ep).c_str(), ec.message().c_str());
			(*m_logger) << time_now_string() << msg << "\n";
#endif
			return;
		}
		s->external_port = s->sock->local_endpoint(ec).port();
		if (!ec) s->sock->listen(m_settings.listen_queue_size, 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 || defined TORRENT_ERROR_LOGGING
			char msg[200];
			snprintf(msg, 200, "cannot listen on interface \"%s\": %s"
				, print_endpoint(ep).c_str(), ec.message().c_str());
			(*m_logger) << time_now_string() << msg << "\n";
#endif
			return;
		}

		// if we asked the system to listen on port 0, which
		// socket did it end up choosing?
		if (ep.port() == 0)
			ep.port(s->sock->local_endpoint().port());

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

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		(*m_logger) << time_now_string() << " listening on: " << ep
			<< " external port: " << s->external_port << "\n";
#endif
	}
	
	void session_impl::open_listen_port(int flags, error_code& ec)
	{
		TORRENT_ASSERT(is_network_thread());

		// close the open listen sockets
		m_listen_sockets.clear();
		m_incoming_connection = false;

		m_ipv6_interface = tcp::endpoint();
		m_ipv4_interface = tcp::endpoint();

#ifdef TORRENT_USE_OPENSSL
		tcp::endpoint ssl_interface = m_listen_interface;
		ssl_interface.port(m_settings.ssl_listen);
#endif
	
		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(&s, tcp::endpoint(address_v4::any(), m_listen_interface.port())
				, m_listen_port_retries, false, flags, ec);

			if (s.sock)
			{
				// update the listen_interface member with the
				// actual port we ended up listening on, so that the other
				// sockets can be bound to the same one
				m_listen_interface.port(s.external_port);

				m_listen_sockets.push_back(s);
				async_accept(s.sock, s.ssl);
			}

#ifdef TORRENT_USE_OPENSSL
			if (m_settings.ssl_listen)
			{
				listen_socket_t s;
				s.ssl = true;
				setup_listener(&s, ssl_interface, 10, false, flags, ec);

				if (s.sock)
				{
					m_listen_sockets.push_back(s);
					async_accept(s.sock, s.ssl);
				}
			}
#endif

#if TORRENT_USE_IPV6
			// only try to open the IPv6 port if IPv6 is installed
			if (supports_ipv6())
			{
				setup_listener(&s, tcp::endpoint(address_v6::any(), m_listen_interface.port())
					, m_listen_port_retries, true, flags, ec);

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

#ifdef TORRENT_USE_OPENSSL
				if (m_settings.ssl_listen)
				{
					listen_socket_t s;
					s.ssl = true;
					setup_listener(&s, tcp::endpoint(address_v6::any(), ssl_interface.port())
						, 10, false, flags, ec);

					if (s.sock)
					{
						m_listen_sockets.push_back(s);
						async_accept(s.sock, s.ssl);
					}
				}
#endif // TORRENT_USE_OPENSSL
			}
#endif // TORRENT_USE_IPV6

			// set our main IPv4 and IPv6 interfaces
			// used to send to the tracker
			std::vector<ip_interface> ifs = enum_net_interfaces(m_io_service, ec);
			for (std::vector<ip_interface>::const_iterator i = ifs.begin()
					, end(ifs.end()); i != end; ++i)
			{
				address const& addr = i->interface_address;
				if (addr.is_v6() && !is_local(addr) && !is_loopback(addr))
					m_ipv6_interface = tcp::endpoint(addr, m_listen_interface.port());
				else if (addr.is_v4() && !is_local(addr) && !is_loopback(addr))
					m_ipv4_interface = tcp::endpoint(addr, m_listen_interface.port());
			}
		}
		else
		{
			// we should only open a single listen socket, that
			// binds to the given interface

			listen_socket_t s;
			setup_listener(&s, m_listen_interface, m_listen_port_retries, false, flags, ec);

			if (s.sock)
			{
				m_listen_sockets.push_back(s);
				async_accept(s.sock, s.ssl);

				if (m_listen_interface.address().is_v6())
					m_ipv6_interface = m_listen_interface;
				else
					m_ipv4_interface = m_listen_interface;
			}

#ifdef TORRENT_USE_OPENSSL
			if (m_settings.ssl_listen)
			{
				listen_socket_t s;
				s.ssl = true;
				setup_listener(&s, ssl_interface, 10, false, flags, ec);

				if (s.sock)
				{
					m_listen_sockets.push_back(s);
					async_accept(s.sock, s.ssl);
				}
			}
#endif
		}

		m_udp_socket.bind(udp::endpoint(m_listen_interface.address(), m_listen_interface.port()), ec);
		if (ec)
		{
			if (m_alerts.should_post<listen_failed_alert>())
				m_alerts.post_alert(listen_failed_alert(m_listen_interface, ec));
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			char msg[200];
			snprintf(msg, sizeof(msg), "cannot bind to UDP interface \"%s\": %s"
				, print_endpoint(m_listen_interface).c_str(), ec.message().c_str());
			(*m_logger) << msg << "\n";
#endif
		}
		else
		{
			m_external_udp_port = m_udp_socket.local_port();
			maybe_update_udp_mapping(0, m_listen_interface.port(), m_listen_interface.port());
			maybe_update_udp_mapping(1, m_listen_interface.port(), m_listen_interface.port());
		}

		open_new_incoming_socks_connection();
#if TORRENT_USE_I2P
		open_new_incoming_i2p_connection();
#endif

		if (!m_listen_sockets.empty())
		{
			tcp::endpoint local = m_listen_sockets.front().sock->local_endpoint(ec);
			if (!ec) remap_tcp_ports(3, local.port(), ssl_listen_port());
		}

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		m_logger = create_log("main_session", listen_port(), false);
#endif
	}

	void session_impl::remap_tcp_ports(boost::uint32_t mask, int tcp_port, int ssl_port)
	{
		if ((mask & 1) && 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, tcp_port, tcp_port);
#ifdef TORRENT_USE_OPENSSL
			if (m_ssl_mapping[0] != -1) m_natpmp->delete_mapping(m_ssl_mapping[0]);
			m_ssl_mapping[0] = m_natpmp->add_mapping(natpmp::tcp, ssl_port, ssl_port);
#endif
		}
		if ((mask & 2) && 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, tcp_port, tcp_port);
#ifdef TORRENT_USE_OPENSSL
			if (m_ssl_mapping[1] != -1) m_upnp->delete_mapping(m_ssl_mapping[1]);
			m_ssl_mapping[1] = m_upnp->add_mapping(upnp::tcp, ssl_port, ssl_port);
#endif
		}
	}

	void session_impl::open_new_incoming_socks_connection()
	{
		if (m_proxy.type != proxy_settings::socks5
			&& m_proxy.type != proxy_settings::socks5_pw
			&& m_proxy.type != proxy_settings::socks4)
			return;
		
		if (m_socks_listen_socket) return;

		m_socks_listen_socket = boost::shared_ptr<socket_type>(new socket_type(m_io_service));
		bool ret = instantiate_connection(m_io_service, m_proxy
			, *m_socks_listen_socket);
		TORRENT_ASSERT_VAL(ret, ret);

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_socks_accept");
#endif
		socks5_stream& s = *m_socks_listen_socket->get<socks5_stream>();
		s.set_command(2); // 2 means BIND (as opposed to CONNECT)
		m_socks_listen_port = m_listen_interface.port();
		if (m_socks_listen_port == 0) m_socks_listen_port = 2000 + random() % 60000;
		s.async_connect(tcp::endpoint(address_v4::any(), m_socks_listen_port)
			, boost::bind(&session_impl::on_socks_accept, this, m_socks_listen_socket, _1));
	}

#if TORRENT_USE_I2P
	void session_impl::on_i2p_open(error_code const& ec)
	{
		open_new_incoming_i2p_connection();
	}

	void session_impl::open_new_incoming_i2p_connection()
	{
		if (!m_i2p_conn.is_open()) return;

		if (m_i2p_listen_socket) return;

		m_i2p_listen_socket = boost::shared_ptr<socket_type>(new socket_type(m_io_service));
		bool ret = instantiate_connection(m_io_service, m_i2p_conn.proxy()
			, *m_i2p_listen_socket);
		TORRENT_ASSERT_VAL(ret, ret);

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_i2p_accept");
#endif
		i2p_stream& s = *m_i2p_listen_socket->get<i2p_stream>();
		s.set_command(i2p_stream::cmd_accept);
		s.set_session_id(m_i2p_conn.session_id());
		s.async_connect(tcp::endpoint(address_v4::any(), m_listen_interface.port())
			, boost::bind(&session_impl::on_i2p_accept, this, m_i2p_listen_socket, _1));
	}

	void session_impl::on_i2p_accept(boost::shared_ptr<socket_type> const& s
		, error_code const& e)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_i2p_accept");
#endif
		m_i2p_listen_socket.reset();
		if (e == asio::error::operation_aborted) return;
		if (e)
		{
			if (m_alerts.should_post<listen_failed_alert>())
				m_alerts.post_alert(listen_failed_alert(tcp::endpoint(
					address_v4::any(), m_listen_interface.port()), e));
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
			char msg[200];
			snprintf(msg, sizeof(msg), "cannot bind to port %d: %s"
				, m_listen_interface.port(), e.message().c_str());
			(*m_logger) << msg << "\n";
#endif
			return;
		}
		open_new_incoming_i2p_connection();
		incoming_connection(s);
	}
#endif

	void session_impl::on_receive_udp(error_code const& e
		, udp::endpoint const& ep, char const* buf, int len)
	{
#ifdef TORRENT_STATS
		++m_num_messages[on_udp_counter];
#endif
		if (e)
		{
			if (e == asio::error::connection_refused
				|| e == asio::error::connection_reset
				|| e == asio::error::connection_aborted)
			{
#ifndef TORRENT_DISABLE_DHT
				if (m_dht) m_dht->on_unreachable(ep);
#endif
				if (m_tracker_manager.incoming_udp(e, ep, buf, len))
					m_stat.received_tracker_bytes(len + 28);
			}

			// don't bubble up operation aborted errors to the user
			if (e != asio::error::operation_aborted
				&& m_alerts.should_post<udp_error_alert>())
				m_alerts.post_alert(udp_error_alert(ep, e));
			return;
		}

#ifndef TORRENT_DISABLE_DHT
		if (len > 20 && *buf == 'd' && buf[len-1] == 'e' && m_dht)
		{
			// this is probably a dht message
			m_dht->on_receive(ep, buf, len);
			return;
		}
#endif
		
		if (m_utp_socket_manager.incoming_packet(buf, len, ep))
			return;

		// maybe it's a udp tracker response
		if (m_tracker_manager.incoming_udp(e, ep, buf, len))
			m_stat.received_tracker_bytes(len + 28);
	}

	void session_impl::on_receive_udp_hostname(error_code const& e
		, char const* hostname, char const* buf, int len)
	{
		// it's probably a udp tracker response
		if (m_tracker_manager.incoming_udp(e, hostname, buf, len))
		{
			m_stat.received_tracker_bytes(len + 28);
		}
	}

	void session_impl::async_accept(boost::shared_ptr<socket_acceptor> const& listener, bool ssl)
	{
		TORRENT_ASSERT(!m_abort);
		shared_ptr<socket_type> c(new socket_type(m_io_service));
		stream_socket* str = 0;

#ifdef TORRENT_USE_OPENSSL
		if (ssl)
		{
			// accept connections initializing the SSL connection to
			// use the generic m_ssl_ctx context. However, since it has
			// the servername callback set on it, we will switch away from
			// this context into a specific torrent once we start handshaking
			c->instantiate<ssl_stream<stream_socket> >(m_io_service, &m_ssl_ctx);
			str = &c->get<ssl_stream<stream_socket> >()->next_layer();
		}
		else
#endif
		{
			c->instantiate<stream_socket>(m_io_service);
			str = c->get<stream_socket>();
		}


#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_accept_connection");
#endif
		listener->async_accept(*str
			, boost::bind(&session_impl::on_accept_connection, this, c
			, boost::weak_ptr<socket_acceptor>(listener), _1, ssl));
	}

	void session_impl::on_accept_connection(shared_ptr<socket_type> const& s
		, weak_ptr<socket_acceptor> listen_socket, error_code const& e, bool ssl)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_accept_connection");
#endif
#ifdef TORRENT_STATS
		++m_num_messages[on_accept_counter];
#endif
		TORRENT_ASSERT(is_network_thread());
		boost::shared_ptr<socket_acceptor> listener = listen_socket.lock();
		if (!listener) return;
		
		if (e == asio::error::operation_aborted) return;

		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 '"
				+ print_endpoint(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, ssl);
				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, ssl);
				return;
			}
#endif
			if (e == boost::system::errc::too_many_files_open)
			{
				// if we failed to accept an incoming connection
				// because we have too many files open, try again
				// and lower the number of file descriptors used
				// elsewere.
				if (m_settings.connections_limit > 10)
				{
					// now, disconnect a random peer
					torrent_map::iterator i = std::max_element(m_torrents.begin()
						, m_torrents.end(), boost::bind(&torrent::num_peers
							, boost::bind(&torrent_map::value_type::second, _1)));

					if (i != m_torrents.end())
					{
						error_code ec;
						i->second->disconnect_peers(1, ec);
					}

					m_settings.connections_limit = m_connections.size();
				}
				// try again, but still alert the user of the problem
				async_accept(listener, ssl);
			}
			if (m_alerts.should_post<listen_failed_alert>())
				m_alerts.post_alert(listen_failed_alert(ep, e));
			return;
		}
		async_accept(listener, ssl);

#ifdef TORRENT_USE_OPENSSL
		if (ssl)
		{
			// for SSL connections, incoming_connection() is called
			// after the handshake is done
			s->get<ssl_stream<stream_socket> >()->async_accept_handshake(
				boost::bind(&session_impl::ssl_handshake, this, _1, s));
		}
		else
#endif
		{
			incoming_connection(s);
		}
	}

#ifdef TORRENT_USE_OPENSSL

	// to test SSL connections, one can use this openssl command template:
	// 
	// openssl s_client -cert <client-cert>.pem -key <client-private-key>.pem \ 
	//   -CAfile <torrent-cert>.pem  -debug -connect 127.0.0.1:4433 -tls1 \ 
	//   -servername <hex-encoded-info-hash>

	void session_impl::ssl_handshake(error_code const& ec, boost::shared_ptr<socket_type> s)
	{
		error_code e;
		tcp::endpoint endp = s->remote_endpoint(e);
		if (e) return;

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
		(*m_logger) << time_now_string() << " *** peer SSL handshake done [ ip: "
			<< endp << " ec: " << ec.message() << " socket: " << s->type_name() << "]\n";
#endif

		if (ec)
		{
			if (m_alerts.should_post<peer_error_alert>())
			{
				m_alerts.post_alert(peer_error_alert(torrent_handle(), endp
					, peer_id(), ec));
			}
			return;
		}

		incoming_connection(s);
	}

#endif // TORRENT_USE_OPENSSL

	void session_impl::incoming_connection(boost::shared_ptr<socket_type> const& s)
	{
		TORRENT_ASSERT(is_network_thread());

#ifdef TORRENT_USE_OPENSSL
		// add the current time to the PRNG, to add more unpredictability
		boost::uint64_t now = total_microseconds(time_now_hires() - min_time());
		// assume 12 bits of entropy (i.e. about 8 milliseconds)
		RAND_add(&now, 8, 1.5);
#endif

		if (m_paused)
		{
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
			(*m_logger) << time_now_string() << " <== INCOMING CONNECTION [ ignored, paused ]\n";
#endif
			return;
		}

		error_code ec;
		// 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;
		}

		TORRENT_ASSERT(endp.address() != address_v4::any());

#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
		(*m_logger) << time_now_string() << " <== INCOMING CONNECTION " << endp
			<< " type: " << s->type_name() << "\n";
#endif

		if (m_alerts.should_post<incoming_connection_alert>())
		{
			m_alerts.post_alert(incoming_connection_alert(s->type(), endp));
		}

		if (!m_settings.enable_incoming_utp
			&& s->get<utp_stream>())
		{
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
			(*m_logger) << "    rejected uTP connection\n";
#endif
			if (m_alerts.should_post<peer_blocked_alert>())
				m_alerts.post_alert(peer_blocked_alert(torrent_handle(), endp.address()));
			return;
		}

		if (!m_settings.enable_incoming_tcp
			&& s->get<stream_socket>())
		{
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
			(*m_logger) << "    rejected TCP connection\n";
#endif
			if (m_alerts.should_post<peer_blocked_alert>())
				m_alerts.post_alert(peer_blocked_alert(torrent_handle(), endp.address()));
			return;
		}

		// 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;

		// this filter is ignored if a single torrent
		// is set to ignore the filter, since this peer might be
		// for that torrent
		if (m_non_filtered_torrents == 0
			&& (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(torrent_handle(), endp.address()));
			return;
		}

		// don't allow more connections than the max setting
		bool reject = false;
		if (m_settings.ignore_limits_on_local_network && is_local(endp.address()))
			reject = m_settings.connections_limit < INT_MAX / 12
				&& num_connections() >= m_settings.connections_limit * 12 / 10;
		else
			reject = num_connections() >= m_settings.connections_limit;

		if (reject)
		{
			if (m_alerts.should_post<peer_disconnected_alert>())
			{
				m_alerts.post_alert(
					peer_disconnected_alert(torrent_handle(), endp, peer_id()
						, error_code(errors::too_many_connections, get_libtorrent_category())));
			}
#if defined(TORRENT_VERBOSE_LOGGING) || defined(TORRENT_LOGGING)
			(*m_logger) << "number of connections limit exceeded (conns: "
				<< num_connections() << ", limit: " << m_settings.connections_limit
				<< "), 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;
		}

		// if we don't have any active torrents, there's no
		// point in accepting this connection. If, however,
		// the setting to start up queued torrents when they
		// get an incoming connection is enabled, we cannot
		// perform this check.
		if (!m_settings.incoming_starts_queued_torrents)
		{
			bool has_active_torrent = false;
			for (torrent_map::iterator i = m_torrents.begin()
				, end(m_torrents.end()); i != end; ++i)
			{
				if (i->second->allows_peers())
				{
					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;
			}
		}

		setup_socket_buffers(*s);

		boost::intrusive_ptr<peer_connection> c(
			new bt_peer_connection(*this, s, endp, 0));
#if defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS
		c->m_in_constructor = false;
#endif

		if (!c->is_disconnecting())
		{
			m_connections.insert(c);
			c->start();
			// update the next disk peer round-robin cursor
			if (m_next_disk_peer == m_connections.end()) m_next_disk_peer = m_connections.begin();
		}
	}

	void session_impl::setup_socket_buffers(socket_type& s)
	{
		error_code ec;
		if (m_settings.send_socket_buffer_size)
		{
			stream_socket::send_buffer_size option(
				m_settings.send_socket_buffer_size);
			s.set_option(option, ec);
		}
		if (m_settings.recv_socket_buffer_size)
		{
			stream_socket::receive_buffer_size option(
				m_settings.recv_socket_buffer_size);
			s.set_option(option, ec);
		}
	}

	void session_impl::on_socks_accept(boost::shared_ptr<socket_type> const& s
		, error_code const& e)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_socks_accept");
#endif
		m_socks_listen_socket.reset();
		if (e == asio::error::operation_aborted) return;
		if (e)
		{
			if (m_alerts.should_post<listen_failed_alert>())
				m_alerts.post_alert(listen_failed_alert(tcp::endpoint(
					address_v4::any(), m_listen_interface.port()), e));
			return;
		}
		open_new_incoming_socks_connection();
		incoming_connection(s);
	}

	void session_impl::close_connection(peer_connection const* p
		, error_code const& ec)
	{
		TORRENT_ASSERT(is_network_thread());

// too expensive
//		INVARIANT_CHECK;

#ifdef TORRENT_DEBUG
//		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() << " : " << ec.message() << "\n";
#endif

		TORRENT_ASSERT(p->is_disconnecting());

		if (!p->is_choked() && !p->ignore_unchoke_slots()) --m_num_unchoked;
		TORRENT_ASSERT(p->refcount() > 0);

		boost::intrusive_ptr<peer_connection> sp((peer_connection*)p);
		connection_map::iterator i = m_connections.find(sp);
		// make sure the next disk peer round-robin cursor stays valid
		if (m_next_disk_peer == i) ++m_next_disk_peer;
		if (i != m_connections.end()) m_connections.erase(i);
		if (m_next_disk_peer == m_connections.end()) m_next_disk_peer = m_connections.begin();
	}

	void session_impl::set_peer_id(peer_id const& id)
	{
		m_peer_id = id;
	}

	void session_impl::set_key(int key)
	{
		m_key = key;
	}

	void session_impl::unchoke_peer(peer_connection& c)
	{
		TORRENT_ASSERT(!c.ignore_unchoke_slots());
		torrent* t = c.associated_torrent().lock().get();
		TORRENT_ASSERT(t);
		if (t->unchoke_peer(c))
			++m_num_unchoked;
	}

	void session_impl::choke_peer(peer_connection& c)
	{
		TORRENT_ASSERT(!c.ignore_unchoke_slots());
		torrent* t = c.associated_torrent().lock().get();
		TORRENT_ASSERT(t);
		if (t->choke_peer(c))
			--m_num_unchoked;
	}

	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;
	}

	// this function is called from the disk-io thread
	// when the disk queue is low enough to post new
	// write jobs to it. It will go through all peer
	// connections that are blocked on the disk and
	// wake them up
	void session_impl::on_disk_queue()
	{
#ifdef TORRENT_STATS
		++m_num_messages[on_disk_queue_counter];
#endif
		TORRENT_ASSERT(is_network_thread());

		// just to play it safe
		if (m_next_disk_peer == m_connections.end()) m_next_disk_peer = m_connections.begin();

		// never loop more times than there are connections
		// keep in mind that connections may disconnect
		// while we're looping, that's why this is a reliable
		// way of limiting it
		int limit = m_connections.size();

		while (m_next_disk_peer != m_connections.end() && limit > 0 && can_write_to_disk())
		{
			--limit;
			peer_connection* p = m_next_disk_peer->get();
			++m_next_disk_peer;
			if (m_next_disk_peer == m_connections.end()) m_next_disk_peer = m_connections.begin();
			if ((p->m_channel_state[peer_connection::download_channel]
				& peer_info::bw_disk) == 0) continue;
			p->on_disk();
		}

	}

	// used to cache the current time
	// every 100 ms. This is cheaper
	// than a system call and can be
	// used where more accurate time
	// is not necessary
	extern ptime g_current_time;

	initialize_timer::initialize_timer()
	{
		g_current_time = time_now_hires();
	}

	void session_impl::on_tick(error_code const& e)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_tick");
#endif
#ifdef TORRENT_STATS
		++m_num_messages[on_tick_counter];
#endif

		TORRENT_ASSERT(is_network_thread());

		ptime now = time_now_hires();
		aux::g_current_time = now;
// too expensive
//		INVARIANT_CHECK;

#if defined TORRENT_VERBOSE_LOGGING
//		(*m_logger) << time_now_string() << " session_impl::on_tick\n";
#endif
		if (m_abort) return;

		if (e == asio::error::operation_aborted) return;

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

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_tick");
#endif
		error_code ec;
		m_timer.expires_at(now + milliseconds(m_settings.tick_interval), ec);
		m_timer.async_wait(bind(&session_impl::on_tick, this, _1));

		m_download_rate.update_quotas(now - m_last_tick);
		m_upload_rate.update_quotas(now - m_last_tick);

		m_last_tick = now;

		m_utp_socket_manager.tick(now);

		// only tick the following once per second
		if (now - m_last_second_tick < seconds(1)) return;

		int tick_interval_ms = total_milliseconds(now - m_last_second_tick);
		m_last_second_tick = now;
		m_tick_residual += tick_interval_ms - 1000;

		int session_time = total_seconds(now - m_created);
		if (session_time > 65000)
		{
			// we're getting close to the point where our timestamps
			// in policy::peer are wrapping. We need to step all counters back
			// four hours. This means that any timestamp that refers to a time
			// more than 18.2 - 4 = 14.2 hours ago, will be incremented to refer to
			// 14.2 hours ago.

			m_created += hours(4);

			const int four_hours = 60 * 60 * 4;
			for (torrent_map::iterator i = m_torrents.begin()
				, end(m_torrents.end()); i != end; ++i)
			{
				policy& p = i->second->get_policy();
				for (policy::iterator j = p.begin_peer()
					, end(p.end_peer()); j != end; ++j)
				{
					policy::peer* pe = *j;

					if (pe->last_optimistically_unchoked < four_hours)
						pe->last_optimistically_unchoked = 0;
					else
						pe->last_optimistically_unchoked -= four_hours;

					if (pe->last_connected < four_hours)
						pe->last_connected = 0;
					else
						pe->last_connected -= four_hours;
				}
			}
		}

#ifndef TORRENT_DISABLE_EXTENSIONS
		for (ses_extension_list_t::const_iterator i = m_ses_extensions.begin()
			, end(m_ses_extensions.end()); i != end; ++i)
		{
			TORRENT_TRY {
				(*i)->on_tick();
			} TORRENT_CATCH(std::exception&) {}
		}
#endif

		// --------------------------------------------------------------
		// RSS feeds
		// --------------------------------------------------------------
		if (now > m_next_rss_update)
			update_rss_feeds();

		switch (m_settings.mixed_mode_algorithm)
		{
			case session_settings::prefer_tcp:
				m_tcp_upload_channel.throttle(0);
				m_tcp_download_channel.throttle(0);
				break;
			case session_settings::peer_proportional:
				{
					int num_peers[2][2] = {{0, 0}, {0, 0}};
					for (connection_map::iterator i = m_connections.begin()
						, end(m_connections.end());i != end; ++i)
					{
						peer_connection& p = *(*i);
						if (p.in_handshake()) continue;
						int protocol = 0;
						if (p.get_socket()->get<utp_stream>()) protocol = 1;

						if (p.download_queue().size() + p.request_queue().size() > 0)
							++num_peers[protocol][peer_connection::download_channel];
						if (p.upload_queue().size() > 0)
							++num_peers[protocol][peer_connection::upload_channel];
					}

					bandwidth_channel* tcp_channel[] = { &m_tcp_upload_channel, &m_tcp_download_channel };
					int stat_rate[] = {m_stat.upload_rate(), m_stat.download_rate() };
					// never throttle below this
					int lower_limit[] = {5000, 30000};

					for (int i = 0; i < 2; ++i)
					{
						// if there are no uploading uTP peers, don't throttle TCP up
						if (num_peers[1][i] == 0)
						{
							tcp_channel[i]->throttle(0);
						}
						else
						{
							if (num_peers[0][i] == 0) num_peers[0][i] = 1;
							int total_peers = num_peers[0][i] + num_peers[1][i];
							// this are 64 bits since it's multiplied by the number
							// of peers, which otherwise might overflow an int
							boost::uint64_t rate = (std::max)(stat_rate[i], lower_limit[i]);
							tcp_channel[i]->throttle(int(rate * num_peers[0][i] / total_peers));
						}
					}
				}
				break;
		}

		// --------------------------------------------------------------
		// auto managed torrent
		// --------------------------------------------------------------
		if (!m_paused) 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();
		}

		// --------------------------------------------------------------
		// 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 ticked through the torrents' second_tick
			if (!p->associated_torrent().expired()) continue;
			if (m_last_tick - p->connected_time() > seconds(m_settings.handshake_timeout))
				p->disconnect(errors::timed_out);
		}

		// --------------------------------------------------------------
		// 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.end();
		int num_paused_auto_managed = 0;

		int num_checking = 0;
		int num_queued = 0;
		for (torrent_map::iterator i = m_torrents.begin();
			i != m_torrents.end();)
		{
			torrent& t = *i->second;
			TORRENT_ASSERT(!t.is_aborted());
			if (t.statistics().upload_rate() * 11 / 10 > t.upload_limit())
				++congested_torrents;
			else
				++uncongested_torrents;

			if (t.state() == torrent_status::checking_files) ++num_checking;
			else if (t.state() == torrent_status::queued_for_checking && !t.is_paused()) ++num_queued;

			if (t.is_auto_managed() && t.is_paused() && !t.has_error())
			{
				++num_paused_auto_managed;
				if (least_recently_scraped == m_torrents.end()
					|| least_recently_scraped->second->seconds_since_last_scrape()
						< t.seconds_since_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_ms);
			++i;
		}

		// some people claim that there sometimes can be cases where
		// there is no torrent being checked, but there are torrents
		// waiting to be checked. I have never seen this, and I can't 
		// see a way for it to happen. But, if it does, start one of
		// the queued torrents
		if (num_checking == 0 && num_queued > 0 && !m_paused)
		{
			TORRENT_ASSERT(false);
			check_queue_t::iterator i = std::min_element(m_queued_for_checking.begin()
				, m_queued_for_checking.end(), boost::bind(&torrent::queue_position, _1)
				< boost::bind(&torrent::queue_position, _2));
			if (i != m_queued_for_checking.end())
			{
				(*i)->start_checking();
			}
		}

#ifndef TORRENT_DISABLE_DHT
		if (m_dht)
		{
			int dht_down;
			int dht_up;
			m_dht->network_stats(dht_up, dht_down);
			m_stat.sent_dht_bytes(dht_up);
			m_stat.received_dht_bytes(dht_down);
		}
#endif

		if (m_settings.rate_limit_ip_overhead)
		{
			m_download_channel.use_quota(
#ifndef TORRENT_DISABLE_DHT
				m_stat.download_dht() +
#endif
				m_stat.download_tracker());

			m_upload_channel.use_quota(
#ifndef TORRENT_DISABLE_DHT
				m_stat.upload_dht() +
#endif
				m_stat.upload_tracker());

			int up_limit = m_upload_channel.throttle();
			int down_limit = m_download_channel.throttle();

			if (down_limit > 0
				&& m_stat.download_ip_overhead() >= down_limit
				&& m_alerts.should_post<performance_alert>())
			{
				m_alerts.post_alert(performance_alert(torrent_handle()
					, performance_alert::download_limit_too_low));
			}

			if (up_limit > 0
				&& m_stat.upload_ip_overhead() >= up_limit
				&& m_alerts.should_post<performance_alert>())
			{
				m_alerts.post_alert(performance_alert(torrent_handle()
					, performance_alert::upload_limit_too_low));
			}
		}

		m_peak_up_rate = (std::max)(m_stat.upload_rate(), m_peak_up_rate);
		m_peak_down_rate = (std::max)(m_stat.download_rate(), m_peak_down_rate);
	
		m_stat.second_tick(tick_interval_ms);

		TORRENT_ASSERT(least_recently_scraped == m_torrents.end()
			|| (least_recently_scraped->second->is_paused()
			&& least_recently_scraped->second->is_auto_managed()));

#ifdef TORRENT_STATS

		if (m_stats_logging_enabled)
		{
			print_log_line(tick_interval_ms, now);
		}
#endif

		// --------------------------------------------------------------
		// scrape paused torrents that are auto managed
		// (unless the session is paused)
		// --------------------------------------------------------------
		if (!is_paused())
		{
			--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();
				}
			}
		}

		// --------------------------------------------------------------
		// refresh explicit disk read cache
		// --------------------------------------------------------------
		--m_cache_rotation_timer;
		if (m_settings.explicit_read_cache
			&& m_cache_rotation_timer <= 0)
		{
			m_cache_rotation_timer = m_settings.explicit_cache_interval;

			torrent_map::iterator least_recently_refreshed = m_torrents.begin();
			if (m_next_explicit_cache_torrent >= int(m_torrents.size()))
				m_next_explicit_cache_torrent = 0;

			std::advance(least_recently_refreshed, m_next_explicit_cache_torrent);

			// how many blocks does this torrent get?
			int cache_size = (std::max)(0, m_settings.cache_size * 9 / 10);

			if (m_connections.empty())
			{
				// if we don't have any connections at all, split the
				// cache evenly across all torrents
				cache_size = cache_size / (std::max)(int(m_torrents.size()), 1);
			}
			else
			{
				cache_size = cache_size * least_recently_refreshed->second->num_peers()
					/ m_connections.size();
			}

			if (least_recently_refreshed != m_torrents.end())
				least_recently_refreshed->second->refresh_explicit_cache(cache_size);
			++m_next_explicit_cache_torrent;
		}

		// --------------------------------------------------------------
		// 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
		// equally likely to connect to a peer

		int free_slots = m_half_open.free_slots();
		int max_connections = m_settings.connection_speed;
		// boost connections are connections made by torrent connection
		// boost, which are done immediately on a tracker response. These
		// connections needs to be deducted from this second
		if (m_boost_connections > 0)
		{
			if (m_boost_connections > max_connections)
			{
				m_boost_connections -= max_connections;
				max_connections = 0;
			}
			else
			{
				max_connections -= m_boost_connections;
				m_boost_connections = 0;
			}
		}

		// this logic is here to smooth out the number of new connection
		// attempts over time, to prevent connecting a large number of
		// sockets, wait 10 seconds, and then try again
		int limit = (std::min)(m_settings.connections_limit - num_connections(), free_slots);
		if (m_settings.smooth_connects && max_connections > (limit+1) / 2)
			max_connections = (limit+1) / 2;

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

			if (m_next_connect_torrent == m_torrents.end())
				m_next_connect_torrent = m_torrents.begin();

			int steps_since_last_connect = 0;
			int num_torrents = int(m_torrents.size());
			for (;;)
			{
				torrent& t = *m_next_connect_torrent->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);
					TORRENT_TRY
					{
						if (t.try_connect_peer())
						{
							--max_connections;
							--free_slots;
							steps_since_last_connect = 0;
#ifdef TORRENT_STATS
							++m_connection_attempts;
#endif
						}
					}
					TORRENT_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_settings.connections_limit = num_connections();
						if (m_settings.connections_limit < 2) m_settings.connections_limit = 2;
					}
				}

				++m_next_connect_torrent;
				++steps_since_last_connect;
				if (m_next_connect_torrent == m_torrents.end())
					m_next_connect_torrent = m_torrents.begin();

				// if we have gone a whole loop without
				// handing out a single connection, break
				if (steps_since_last_connect > num_torrents + 1) 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_settings.connections_limit) break;
			}
		}

		// --------------------------------------------------------------
		// unchoke set 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);
		}

		// --------------------------------------------------------------
		// optimistic unchoke calculation
		// --------------------------------------------------------------
		m_optimistic_unchoke_time_scaler--;
		if (m_optimistic_unchoke_time_scaler <= 0)
		{
			m_optimistic_unchoke_time_scaler
				= settings().optimistic_unchoke_interval;
			recalculate_optimistic_unchoke_slots();
		}

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

			if (num_connections() >= m_settings.connections_limit * m_settings.peer_turnover_cutoff
				&& !m_torrents.empty())
			{
				// every 90 seconds, disconnect the worst peers
				// if we have reached the connection limit
				torrent_map::iterator i = std::max_element(m_torrents.begin(), m_torrents.end()
					, boost::bind(&torrent::num_peers, boost::bind(&torrent_map::value_type::second, _1))
					< boost::bind(&torrent::num_peers, boost::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
					, error_code(errors::optimistic_disconnect, get_libtorrent_category()));
			}
			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
						, error_code(errors::optimistic_disconnect, get_libtorrent_category()));
				}
			}
		}

		while (m_tick_residual >= 1000) m_tick_residual -= 1000;
//		m_peer_pool.release_memory();
	}

#ifdef TORRENT_STATS
		
	void session_impl::enable_stats_logging(bool s)
	{
		if (m_stats_logging_enabled == s) return;

		m_stats_logging_enabled = s;

		reset_stat_counters();
		if (!s)
		{
			if (m_stats_logger) fclose(m_stats_logger);
			m_stats_logger = 0;
		}
		else
		{
			rotate_stats_log();
			get_thread_cpu_usage(&m_network_thread_cpu_usage);
		}
	}

	void session_impl::reset_stat_counters()
	{
		m_error_peers = 0;
		m_disconnected_peers = 0;
		m_eof_peers = 0;
		m_connreset_peers = 0;
		m_end_game_piece_picker_blocks = 0;
		m_piece_picker_blocks = 0;
		m_piece_picks = 0;
		m_reject_piece_picks = 0;
		m_unchoke_piece_picks = 0;
		m_incoming_redundant_piece_picks = 0;
		m_incoming_piece_picks = 0;
		m_end_game_piece_picks = 0;
		m_snubbed_piece_picks = 0;
		m_connect_timeouts = 0;
		m_uninteresting_peers = 0;
		m_transport_timeout_peers = 0;
		m_timeout_peers = 0;
		m_no_memory_peers = 0;
		m_too_many_peers = 0;
		m_connection_attempts = 0;
		m_num_banned_peers = 0;
		m_banned_for_hash_failure = 0;

		memset(m_num_messages, 0, sizeof(m_num_messages));
		memset(m_send_buffer_sizes, 0, sizeof(m_send_buffer_sizes));
		memset(m_recv_buffer_sizes, 0, sizeof(m_recv_buffer_sizes));
	}

	void session_impl::print_log_line(int tick_interval_ms, ptime now)
	{
		int connect_candidates = 0;
		int downloading_torrents = 0;
		int seeding_torrents = 0;
		int checking_torrents = 0;
		int stopped_torrents = 0;
		int error_torrents = 0;
		int upload_only_torrents = 0;
		int num_peers = 0;
		int peer_dl_rate_buckets[7];
		int peer_ul_rate_buckets[7];
		memset(peer_dl_rate_buckets, 0, sizeof(peer_dl_rate_buckets));
		memset(peer_ul_rate_buckets, 0, sizeof(peer_ul_rate_buckets));
		int outstanding_requests = 0;
		int outstanding_end_game_requests = 0;
		int outstanding_write_blocks = 0;

		int peers_up_interested = 0;
		int peers_down_interesting = 0;
		int peers_up_requests = 0;
		int peers_down_requests = 0;

		std::vector<partial_piece_info> dq;
		for (torrent_map::iterator i = m_torrents.begin()
			, end(m_torrents.end()); i != end; ++i)
		{
			int connection_slots = (std::max)(i->second->max_connections() - i->second->num_peers(), 0);
			int candidates = i->second->get_policy().num_connect_candidates();
			connect_candidates += (std::min)(candidates, connection_slots);
			num_peers += i->second->get_policy().num_peers();
			if (i->second->is_seed())
				++seeding_torrents;
			else
				++downloading_torrents;
			if (i->second->state() == torrent_status::checking_files
				|| i->second->state() == torrent_status::queued_for_checking)
				++checking_torrents;
			if (i->second->is_paused())
				++stopped_torrents;
			if (i->second->is_upload_only())
				++upload_only_torrents;
			if (i->second->has_error())
				++error_torrents;

			dq.clear();
			i->second->get_download_queue(&dq);
			for (std::vector<partial_piece_info>::iterator j = dq.begin()
				, end(dq.end()); j != end; ++j)
			{
				for (int k = 0; k < j->blocks_in_piece; ++k)
				{
					block_info& bi = j->blocks[k];
					if (bi.state == block_info::requested)
					{
						++outstanding_requests;
						if (bi.num_peers > 1) ++outstanding_end_game_requests;
					}
					else if (bi.state == block_info::writing)
						++outstanding_write_blocks;
				}
			}
		}
		int tcp_up_rate = 0;
		int tcp_down_rate = 0;
		int utp_up_rate = 0;
		int utp_down_rate = 0;
		int utp_peak_send_delay = 0;
		int utp_peak_recv_delay = 0;
		boost::uint64_t utp_send_delay_sum = 0;
		boost::uint64_t utp_recv_delay_sum = 0;
		int utp_num_delay_sockets = 0;
		int utp_num_recv_delay_sockets = 0;
		int num_complete_connections = 0;
		int num_half_open = 0;
		int peers_down_unchoked = 0;
		int peers_up_unchoked = 0;
		int num_end_game_peers = 0;
		int reading_bytes = 0;
		for (connection_map::iterator i = m_connections.begin()
			, end(m_connections.end()); i != end; ++i)
		{
			peer_connection* p = i->get();
			if (p->is_connecting())
			{
				++num_half_open;
				continue;
			}

			++num_complete_connections;
			if (!p->is_choked()) ++peers_up_unchoked;
			if (!p->has_peer_choked()) ++peers_down_unchoked;
			if (!p->download_queue().empty()) ++peers_down_requests;
			if (p->is_peer_interested()) ++peers_up_interested;
			if (p->is_interesting()) ++peers_down_interesting;
			if (p->send_buffer_size() > 100 || !p->upload_queue().empty())
				++peers_up_requests;
			if (p->endgame()) ++num_end_game_peers;
			reading_bytes += p->num_reading_bytes();

			int dl_bucket = 0;
			int dl_rate = p->statistics().download_payload_rate();
			if (dl_rate == 0) dl_bucket = 0;
			else if (dl_rate < 2000) dl_bucket = 1;
			else if (dl_rate < 5000) dl_bucket = 2;
			else if (dl_rate < 10000) dl_bucket = 3;
			else if (dl_rate < 50000) dl_bucket = 4;
			else if (dl_rate < 100000) dl_bucket = 5;
			else dl_bucket = 6;

			int ul_rate = p->statistics().upload_payload_rate();
			int ul_bucket = 0;
			if (ul_rate == 0) ul_bucket = 0;
			else if (ul_rate < 2000) ul_bucket = 1;
			else if (ul_rate < 5000) ul_bucket = 2;
			else if (ul_rate < 10000) ul_bucket = 3;
			else if (ul_rate < 50000) ul_bucket = 4;
			else if (ul_rate < 100000) ul_bucket = 5;
			else ul_bucket = 6;

			++peer_dl_rate_buckets[dl_bucket];
			++peer_ul_rate_buckets[ul_bucket];

			utp_stream* utp_socket = p->get_socket()->get<utp_stream>();
			if (utp_socket)
			{
				utp_up_rate += ul_rate;
				utp_down_rate += dl_rate;
				int send_delay = utp_socket->send_delay();
				int recv_delay = utp_socket->recv_delay();
				utp_peak_send_delay = (std::max)(utp_peak_send_delay, send_delay);
				utp_peak_recv_delay = (std::max)(utp_peak_recv_delay, recv_delay);
				if (send_delay > 0)
				{
					utp_send_delay_sum += send_delay;
					++utp_num_delay_sockets;
				}
				if (recv_delay > 0)
				{
					utp_recv_delay_sum += recv_delay;
					++utp_num_recv_delay_sockets;
				}
			}
			else
			{
				tcp_up_rate += ul_rate;
				tcp_down_rate += dl_rate;
			}

		}

		int low_watermark = m_settings.max_queued_disk_bytes_low_watermark == 0
			|| m_settings.max_queued_disk_bytes_low_watermark >= m_settings.max_queued_disk_bytes
			? size_type(m_settings.max_queued_disk_bytes) * 7 / 8
			: m_settings.max_queued_disk_bytes_low_watermark;

		if (now - m_last_log_rotation > hours(1))
			rotate_stats_log();

		// system memory stats
		vm_statistics_data_t vm_stat;
		get_vm_stats(&vm_stat);
		thread_cpu_usage cur_cpu_usage;
		get_thread_cpu_usage(&cur_cpu_usage);

		if (m_stats_logger)
		{
			cache_status cs = m_disk_thread.status();

			m_read_ops.add_sample((cs.reads - m_last_cache_status.reads) * 1000.0 / float(tick_interval_ms));
			m_write_ops.add_sample((cs.writes - m_last_cache_status.writes) * 1000.0 / float(tick_interval_ms));

			int total_job_time = cs.cumulative_job_time == 0 ? 1 : cs.cumulative_job_time;

#define STAT_LOG(type, val) fprintf(m_stats_logger, "%" #type "\t", val)

			STAT_LOG(f, total_milliseconds(now - m_last_log_rotation) / 1000.f);
			size_type uploaded = m_stat.total_upload() - m_last_uploaded;
			STAT_LOG(d, int(uploaded));
			size_type downloaded = m_stat.total_download() - m_last_downloaded;
			STAT_LOG(d, int(downloaded));
			STAT_LOG(d, downloading_torrents);
			STAT_LOG(d, seeding_torrents);
			STAT_LOG(d, num_complete_connections);
			STAT_LOG(d, num_half_open);
			STAT_LOG(d, m_disk_thread.disk_allocations());
			STAT_LOG(d, num_peers);
			STAT_LOG(d, logging_allocator::allocations);
			STAT_LOG(d, logging_allocator::allocated_bytes);
			STAT_LOG(d, checking_torrents);
			STAT_LOG(d, stopped_torrents);
			STAT_LOG(d, upload_only_torrents);
			STAT_LOG(d, m_upload_rate.queue_size());
			STAT_LOG(d, m_download_rate.queue_size());
			STAT_LOG(d, m_disk_queues[peer_connection::upload_channel]);
			STAT_LOG(d, m_disk_queues[peer_connection::download_channel]);
			STAT_LOG(d, m_stat.upload_rate());
			STAT_LOG(d, m_stat.download_rate());
			STAT_LOG(d, int(m_disk_thread.queue_buffer_size()));
			STAT_LOG(d, peer_dl_rate_buckets[0]);
			STAT_LOG(d, peer_dl_rate_buckets[1]);
			STAT_LOG(d, peer_dl_rate_buckets[2]);
			STAT_LOG(d, peer_dl_rate_buckets[3]);
			STAT_LOG(d, peer_dl_rate_buckets[4]);
			STAT_LOG(d, peer_dl_rate_buckets[5]);
			STAT_LOG(d, peer_dl_rate_buckets[6]);
			STAT_LOG(d, peer_ul_rate_buckets[0]);
			STAT_LOG(d, peer_ul_rate_buckets[1]);
			STAT_LOG(d, peer_ul_rate_buckets[2]);
			STAT_LOG(d, peer_ul_rate_buckets[3]);
			STAT_LOG(d, peer_ul_rate_buckets[4]);
			STAT_LOG(d, peer_ul_rate_buckets[5]);
			STAT_LOG(d, peer_ul_rate_buckets[6]);
			STAT_LOG(d, m_error_peers);
			STAT_LOG(d, peers_down_interesting);
			STAT_LOG(d, peers_down_unchoked);
			STAT_LOG(d, peers_down_requests);
			STAT_LOG(d, peers_up_interested);
			STAT_LOG(d, peers_up_unchoked);
			STAT_LOG(d, peers_up_requests);
			STAT_LOG(d, m_disconnected_peers);
			STAT_LOG(d, m_eof_peers);
			STAT_LOG(d, m_connreset_peers);
			STAT_LOG(d, outstanding_requests);
			STAT_LOG(d, outstanding_end_game_requests);
			STAT_LOG(d, outstanding_write_blocks);
			STAT_LOG(d, m_end_game_piece_picker_blocks);
			STAT_LOG(d, m_piece_picker_blocks);
			STAT_LOG(d, m_piece_picks);
			STAT_LOG(d, m_reject_piece_picks);
			STAT_LOG(d, m_unchoke_piece_picks);
			STAT_LOG(d, m_incoming_redundant_piece_picks);
			STAT_LOG(d, m_incoming_piece_picks);
			STAT_LOG(d, m_end_game_piece_picks);
			STAT_LOG(d, m_snubbed_piece_picks);
			STAT_LOG(d, m_connect_timeouts);
			STAT_LOG(d, m_uninteresting_peers);
			STAT_LOG(d, m_timeout_peers);
			STAT_LOG(f, (float(m_total_failed_bytes) * 100.f / m_stat.total_payload_download()));
			STAT_LOG(f, (float(m_total_redundant_bytes) * 100.f / m_stat.total_payload_download()));
			STAT_LOG(f, (float(m_stat.total_protocol_download()) * 100.f / m_stat.total_download()));
			STAT_LOG(f, float(cs.average_read_time) / 1000000.f);
			STAT_LOG(f, float(cs.average_write_time) / 1000000.f);
			STAT_LOG(f, float(cs.average_queue_time) / 1000000.f);
			STAT_LOG(d, int(cs.job_queue_length));
			STAT_LOG(d, int(cs.queued_bytes));
			STAT_LOG(d, int(cs.blocks_read_hit - m_last_cache_status.blocks_read_hit));
			STAT_LOG(d, int(cs.blocks_read - m_last_cache_status.blocks_read));
			STAT_LOG(d, int(cs.blocks_written - m_last_cache_status.blocks_written));
			STAT_LOG(d, int(m_total_failed_bytes - m_last_failed));
			STAT_LOG(d, int(m_total_redundant_bytes - m_last_redundant));
			STAT_LOG(d, error_torrents);
			STAT_LOG(d, cs.read_cache_size);
			STAT_LOG(d, cs.cache_size);
			STAT_LOG(d, cs.total_used_buffers);
			STAT_LOG(f, float(cs.average_hash_time) / 1000000.f);
			STAT_LOG(f, float(cs.average_job_time) / 1000000.f);
			STAT_LOG(f, float(cs.average_sort_time) / 1000000.f);
			STAT_LOG(d, m_connection_attempts);
			STAT_LOG(d, m_num_banned_peers);
			STAT_LOG(d, m_banned_for_hash_failure);
			STAT_LOG(d, m_settings.cache_size);
			STAT_LOG(d, m_settings.connections_limit);
			STAT_LOG(d, connect_candidates);
			STAT_LOG(d, int(m_settings.max_queued_disk_bytes));
			STAT_LOG(d, low_watermark);
			STAT_LOG(f, float(cs.cumulative_read_time * 100.f / total_job_time));
			STAT_LOG(f, float(cs.cumulative_write_time * 100.f / total_job_time));
			STAT_LOG(f, float(cs.cumulative_hash_time * 100.f / total_job_time));
			STAT_LOG(f, float(cs.cumulative_sort_time * 100.f / total_job_time));
			STAT_LOG(d, int(cs.total_read_back - m_last_cache_status.total_read_back));
			STAT_LOG(f, float(cs.total_read_back * 100.f / (cs.blocks_written == 0 ? 1: cs.blocks_written)));
			STAT_LOG(d, cs.read_queue_size);
			STAT_LOG(f, float(tick_interval_ms) / 1000.f);
			STAT_LOG(f, float(m_tick_residual) / 1000.f);
			STAT_LOG(d, m_allowed_upload_slots);
			STAT_LOG(d, m_settings.unchoke_slots_limit * 2);
			STAT_LOG(d, m_stat.low_pass_upload_rate());
			STAT_LOG(d, m_stat.low_pass_download_rate());
			STAT_LOG(d, num_end_game_peers);
			STAT_LOG(d, tcp_up_rate);
			STAT_LOG(d, tcp_down_rate);
			STAT_LOG(d, int(m_tcp_upload_channel.throttle()));
			STAT_LOG(d, int(m_tcp_download_channel.throttle()));
			STAT_LOG(d, utp_up_rate);
			STAT_LOG(d, utp_down_rate);
			STAT_LOG(f, float(utp_peak_send_delay) / 1000000.f);
			STAT_LOG(f, float(utp_num_delay_sockets ? float(utp_send_delay_sum) / float(utp_num_delay_sockets) : 0) / 1000000.f);
			STAT_LOG(f, float(utp_peak_recv_delay) / 1000000.f);
			STAT_LOG(f, float(utp_num_recv_delay_sockets ? float(utp_recv_delay_sum) / float(utp_num_recv_delay_sockets) : 0) / 1000000.f);
			STAT_LOG(f, float(cs.reads - m_last_cache_status.reads) * 1000.0 / float(tick_interval_ms));
			STAT_LOG(f, float(cs.writes - m_last_cache_status.writes) * 1000.0 / float(tick_interval_ms));

			STAT_LOG(d, int(vm_stat.active_count));
			STAT_LOG(d, int(vm_stat.inactive_count));
			STAT_LOG(d, int(vm_stat.wire_count));
			STAT_LOG(d, int(vm_stat.free_count));
			STAT_LOG(d, int(vm_stat.pageins - m_last_vm_stat.pageins));
			STAT_LOG(d, int(vm_stat.pageouts - m_last_vm_stat.pageouts));
			STAT_LOG(d, int(vm_stat.faults - m_last_vm_stat.faults));

			STAT_LOG(d, m_read_ops.mean());
			STAT_LOG(d, m_write_ops.mean());

			STAT_LOG(d, reading_bytes);

			for (int i = 0; i < max_messages; ++i)
				STAT_LOG(d, m_num_messages[i]);
			int num_max = sizeof(m_send_buffer_sizes)/sizeof(m_send_buffer_sizes[0]);
			for (int i = 0; i < num_max; ++i)
				STAT_LOG(d, m_send_buffer_sizes[i]);
			num_max = sizeof(m_recv_buffer_sizes)/sizeof(m_recv_buffer_sizes[0]);
			for (int i = 0; i < num_max; ++i)
				STAT_LOG(d, m_recv_buffer_sizes[i]);

			STAT_LOG(f, total_milliseconds(cur_cpu_usage.user_time
				- m_network_thread_cpu_usage.user_time) * 100.0 / double(tick_interval_ms));
			STAT_LOG(f, (total_milliseconds(cur_cpu_usage.system_time
					- m_network_thread_cpu_usage.system_time)
				+ total_milliseconds(cur_cpu_usage.user_time
					- m_network_thread_cpu_usage.user_time)) * 100.0
				/ double(tick_interval_ms));

			for (int i = 0; i < torrent::waste_reason_max; ++i)
				STAT_LOG(f, (m_redundant_bytes[i] * 100.) / double(m_total_redundant_bytes));

			STAT_LOG(d, m_no_memory_peers);
			STAT_LOG(d, m_too_many_peers);
			STAT_LOG(d, m_transport_timeout_peers);

			fprintf(m_stats_logger, "\n");

#undef STAT_LOG

			m_last_cache_status = cs;
			m_last_vm_stat = vm_stat;
			m_network_thread_cpu_usage = cur_cpu_usage;
			m_last_failed = m_total_failed_bytes;
			m_last_redundant = m_total_redundant_bytes;
			m_last_uploaded = m_stat.total_upload();
			m_last_downloaded = m_stat.total_download();
		}

		reset_stat_counters();
	}
#endif // TORRENT_STATS

	void session_impl::update_rss_feeds()
	{
		time_t now_posix = time(0);
		ptime min_update = max_time();
		ptime now = time_now();
		for (std::vector<boost::shared_ptr<feed> >::iterator i
			= m_feeds.begin(), end(m_feeds.end()); i != end; ++i)
		{
			feed& f = **i;
			int delta = f.next_update(now_posix);
			if (delta <= 0)
			{
				f.update_feed();
				continue;
			}
			ptime next_update = now + seconds(delta);
			if (next_update < min_update) min_update = next_update;
		}
		m_next_rss_update = min_update;
	}

#ifndef TORRENT_DISABLE_DHT

	void session_impl::on_dht_announce(error_code const& e)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_dht_announce");
#endif
		TORRENT_ASSERT(is_network_thread());
		if (e) return;

		if (m_abort) return;

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_dht_announce");
#endif
		// announce to DHT every 15 minutes
		int delay = (std::max)(m_settings.dht_announce_interval
			/ (std::max)(int(m_torrents.size()), 1), 1);
		error_code ec;
		m_dht_announce_timer.expires_from_now(seconds(delay), ec);
		m_dht_announce_timer.async_wait(
			bind(&session_impl::on_dht_announce, this, _1));

		if (m_torrents.empty()) return;

		if (m_next_dht_torrent == m_torrents.end())
			m_next_dht_torrent = m_torrents.begin();
		m_next_dht_torrent->second->dht_announce();
		++m_next_dht_torrent;
		if (m_next_dht_torrent == m_torrents.end())
			m_next_dht_torrent = m_torrents.begin();
  	}
#endif

	void session_impl::on_lsd_announce(error_code const& e)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_lsd_announce");
#endif
#ifdef TORRENT_STATS
		++m_num_messages[on_lsd_counter];
#endif
		TORRENT_ASSERT(is_network_thread());
		if (e) return;

		if (m_abort) return;

#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_lsd_announce");
#endif
		// announce on local network every 5 minutes
		int delay = (std::max)(m_settings.local_service_announce_interval
			/ (std::max)(int(m_torrents.size()), 1), 1);
		error_code ec;
		m_lsd_announce_timer.expires_from_now(seconds(delay), ec);
		m_lsd_announce_timer.async_wait(
			bind(&session_impl::on_lsd_announce, this, _1));

		if (m_torrents.empty()) return;

		if (m_next_lsd_torrent == m_torrents.end())
			m_next_lsd_torrent = m_torrents.begin();
		m_next_lsd_torrent->second->lsd_announce();
		++m_next_lsd_torrent;
		if (m_next_lsd_torrent == m_torrents.end())
			m_next_lsd_torrent = m_torrents.begin();
	}

	namespace
	{
		bool is_active(torrent* t, session_settings const& s)
		{
			// if we count slow torrents, every torrent
			// is considered active
			if (!s.dont_count_slow_torrents) return true;
			
			// if the torrent started less than 2 minutes
			// ago (default), let it count as active since
			// the rates are probably not accurate yet
			if (time_now() - t->started() < seconds(s.auto_manage_startup)) return true;

			return t->statistics().upload_payload_rate() != 0.f
				|| t->statistics().download_payload_rate() != 0.f;
		}
	}
	
	void session_impl::auto_manage_torrents(std::vector<torrent*>& list
		, int& dht_limit, int& tracker_limit, int& lsd_limit
		, int& hard_limit, int type_limit)
	{
		for (std::vector<torrent*>::iterator i = list.begin()
			, end(list.end()); i != end; ++i)
		{
			torrent* t = *i;

			if ((t->state() == torrent_status::checking_files
				|| t->state() == torrent_status::queued_for_checking))
				continue;

			--dht_limit;
			--lsd_limit;
			--tracker_limit;
			t->set_announce_to_dht(dht_limit >= 0);
			t->set_announce_to_trackers(tracker_limit >= 0);
			t->set_announce_to_lsd(lsd_limit >= 0);

			if (!t->is_paused() && !is_active(t, settings())
				&& hard_limit > 0)
			{
				--hard_limit;
				continue;
			}

			if (type_limit > 0 && hard_limit > 0)
			{
				--hard_limit;
				--type_limit;
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING || defined TORRENT_LOGGING
				t->log_to_all_peers(("AUTO MANAGER STARTING TORRENT: " + t->torrent_file().name()).c_str());
#endif
				t->set_allow_peers(true);
			}
			else
			{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING || defined TORRENT_LOGGING
				t->log_to_all_peers(("AUTO MANAGER PAUSING TORRENT: " + t->torrent_file().name()).c_str());
#endif
				// use graceful pause for auto-managed torrents
				t->set_allow_peers(false, true);
			}
		}
	}

	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 dht_limit = settings().active_dht_limit;
		int tracker_limit = settings().active_tracker_limit;
		int lsd_limit = settings().active_lsd_limit;
		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);

			// checking torrents are not subject to auto-management
			if (t->state() == torrent_status::checking_files
				|| t->state() == torrent_status::queued_for_checking)
			{
				if (t->is_auto_managed() && t->is_paused()) t->resume();
				continue;
			}
			if (t->is_auto_managed() && !t->has_error())
			{
				TORRENT_ASSERT(t->m_resume_data_loaded || !t->valid_metadata());
				// 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())
			{
				TORRENT_ASSERT(t->m_resume_data_loaded || !t->valid_metadata());
				--hard_limit;
			  	if (is_active(t, settings()))
				{
					// this is not an auto managed torrent,
					// if it's running and active, decrease the
					// counters.
					if (t->is_finished())
						--num_seeds;
					else
						--num_downloaders;
				}
			}
		}

		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()
				, boost::bind(&torrent::sequence_number, _1) < boost::bind(&torrent::sequence_number, _2));

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

		if (settings().auto_manage_prefer_seeds)
		{
			auto_manage_torrents(seeds, dht_limit, tracker_limit, lsd_limit
				, hard_limit, num_seeds);
			auto_manage_torrents(downloaders, dht_limit, tracker_limit, lsd_limit
				, hard_limit, num_downloaders);
		}
		else
		{
			auto_manage_torrents(downloaders, dht_limit, tracker_limit, lsd_limit
				, hard_limit, num_downloaders);
			auto_manage_torrents(seeds, dht_limit, tracker_limit, lsd_limit
				, hard_limit, num_seeds);
		}
            
	}

	void session_impl::recalculate_optimistic_unchoke_slots()
	{
		TORRENT_ASSERT(is_network_thread());
		if (m_allowed_upload_slots == 0) return;
	
		std::vector<policy::peer*> opt_unchoke;

		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 (t->is_paused()) continue;

			if (pi->optimistically_unchoked)
			{
				TORRENT_ASSERT(!p->is_choked());
				opt_unchoke.push_back(pi);
			}

			if (!p->is_connecting()
				&& !p->is_disconnecting()
				&& p->is_peer_interested()
				&& t->free_upload_slots()
				&& p->is_choked()
				&& !p->ignore_unchoke_slots()
				&& t->valid_metadata())
			{
				opt_unchoke.push_back(pi);
			}
		}

		// find the peers that has been waiting the longest to be optimistically
		// unchoked

		// avoid having a bias towards peers that happen to be sorted first
		std::random_shuffle(opt_unchoke.begin(), opt_unchoke.end());

		// sort all candidates based on when they were last optimistically
		// unchoked.
		std::sort(opt_unchoke.begin(), opt_unchoke.end()
			, boost::bind(&policy::peer::last_optimistically_unchoked, _1)
			< boost::bind(&policy::peer::last_optimistically_unchoked, _2));

		int num_opt_unchoke = m_settings.num_optimistic_unchoke_slots;
		if (num_opt_unchoke == 0) num_opt_unchoke = (std::max)(1, m_allowed_upload_slots / 5);

		// unchoke the first num_opt_unchoke peers in the candidate set
		// and make sure that the others are choked
		for (std::vector<policy::peer*>::iterator i = opt_unchoke.begin()
			, end(opt_unchoke.end()); i != end; ++i)
		{
			policy::peer* pi = *i;
			if (num_opt_unchoke > 0)
			{
				--num_opt_unchoke;
				if (!pi->optimistically_unchoked)
				{
					torrent* t = pi->connection->associated_torrent().lock().get();
					bool ret = t->unchoke_peer(*pi->connection, true);
					if (ret)
					{
						pi->optimistically_unchoked = true;
						++m_num_unchoked;
						pi->last_optimistically_unchoked = session_time();
					}
					else
					{
						// we failed to unchoke it, increment the count again
						++num_opt_unchoke;
					}
				}
			}
			else
			{
				if (pi->optimistically_unchoked)
				{
					torrent* t = pi->connection->associated_torrent().lock().get();
					pi->optimistically_unchoked = false;
					t->choke_peer(*pi->connection);
					--m_num_unchoked;
				}	
			}
		}
	}

	void session_impl::recalculate_unchoke_slots(int congested_torrents
		, int uncongested_torrents)
	{
		TORRENT_ASSERT(is_network_thread());
		INVARIANT_CHECK;

		ptime now = time_now();
		time_duration unchoke_interval = now - m_last_choke;
		m_last_choke = now;

		// build list of all peers that are
		// unchokable.
		std::vector<peer_connection*> peers;
		for (connection_map::iterator i = m_connections.begin();
			i != m_connections.end();)
		{
			boost::intrusive_ptr<peer_connection> p = *i;
			TORRENT_ASSERT(p);
			++i;
			torrent* t = p->associated_torrent().lock().get();
			policy::peer* pi = p->peer_info_struct();

			if (p->ignore_unchoke_slots() || t == 0 || pi == 0 || t->is_paused()) continue;

			if (m_settings.choking_algorithm == session_settings::bittyrant_choker)
			{
				if (!p->is_choked() && p->is_interesting())
				{
					if (!p->has_peer_choked())
					{
						// we're unchoked, we may want to lower our estimated
						// reciprocation rate
						p->decrease_est_reciprocation_rate();
					}
					else
					{
						// we've unchoked this peer, and it hasn't reciprocated
						// we may want to increase our estimated reciprocation rate
						p->increase_est_reciprocation_rate();
					}
				}
			}

			if (!p->is_peer_interested()
				|| p->is_disconnecting()
				|| p->is_connecting()
				|| (p->share_diff() < -free_upload_amount
					&& !t->is_seed()))
			{
				// this peer is not unchokable. So, if it's unchoked
				// already, make sure to choke it.
				if (p->is_choked()) continue;
				if (pi && pi->optimistically_unchoked)
				{
					pi->optimistically_unchoked = false;
					// force a new optimistic unchoke
					m_optimistic_unchoke_time_scaler = 0;
				}
				t->choke_peer(*p);
				continue;
			}
			peers.push_back(p.get());
		}

		if (m_settings.choking_algorithm == session_settings::rate_based_choker)
		{
			m_allowed_upload_slots = 0;
			std::sort(peers.begin(), peers.end()
				, boost::bind(&peer_connection::upload_rate_compare, _1, _2));

#ifdef TORRENT_DEBUG
			for (std::vector<peer_connection*>::const_iterator i = peers.begin()
				, end(peers.end()), prev(peers.end()); i != end; ++i)
			{
				if (prev != end)
				{
					boost::shared_ptr<torrent> t1 = (*prev)->associated_torrent().lock();
					TORRENT_ASSERT(t1);
					boost::shared_ptr<torrent> t2 = (*i)->associated_torrent().lock();
					TORRENT_ASSERT(t2);
					TORRENT_ASSERT((*prev)->uploaded_since_unchoke() * 1000
						* (1 + t1->priority()) / total_milliseconds(unchoke_interval)
						>= (*i)->uploaded_since_unchoke() * 1000
						* (1 + t2->priority()) / total_milliseconds(unchoke_interval));
				}
				prev = i;
			}
#endif

			// TODO: make configurable
			int rate_threshold = 1024;

			for (std::vector<peer_connection*>::const_iterator i = peers.begin()
				, end(peers.end()); i != end; ++i)
			{
				peer_connection const& p = **i;
				int rate = int(p.uploaded_since_unchoke()
					* 1000 / total_milliseconds(unchoke_interval));

				if (rate < rate_threshold) break;

				++m_allowed_upload_slots;

				// TODO: make configurable
				rate_threshold += 1024;
			}
			// allow one optimistic unchoke
			++m_allowed_upload_slots;
		}

		if (m_settings.choking_algorithm == session_settings::bittyrant_choker)
		{
			// if we're using the bittyrant choker, sort peers by their return
			// on investment. i.e. download rate / upload rate
			std::sort(peers.begin(), peers.end()
				, boost::bind(&peer_connection::bittyrant_unchoke_compare, _1, _2));
		}
		else
		{
			// 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()
				, boost::bind(&peer_connection::unchoke_compare, _1, _2));
		}

		// auto unchoke
		int upload_limit = m_bandwidth_channel[peer_connection::upload_channel]->throttle();
		if (m_settings.choking_algorithm == session_settings::auto_expand_choker
			&& upload_limit > 0)
		{
			// 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_upload_rate.queue_size() < 2)
			{
				++m_allowed_upload_slots;
			}
			else if (m_upload_rate.queue_size() > 1
				&& m_allowed_upload_slots > m_settings.unchoke_slots_limit
				&& m_settings.unchoke_slots_limit >= 0)
			{
				--m_allowed_upload_slots;
			}
		}

		int num_opt_unchoke = m_settings.num_optimistic_unchoke_slots;
		if (num_opt_unchoke == 0) num_opt_unchoke = (std::max)(1, m_allowed_upload_slots / 5);

		// reserve some upload slots for optimistic unchokes
		int unchoke_set_size = m_allowed_upload_slots - num_opt_unchoke;

		int upload_capacity_left = 0;
		if (m_settings.choking_algorithm == session_settings::bittyrant_choker)
		{
			upload_capacity_left = m_upload_channel.throttle();
			if (upload_capacity_left == 0)
			{
				// we don't know at what rate we can upload. If we have a
				// measurement of the peak, use that + 10kB/s, otherwise
				// assume 20 kB/s
				upload_capacity_left = (std::max)(20000, m_peak_up_rate + 10000);
				if (m_alerts.should_post<performance_alert>())
					m_alerts.post_alert(performance_alert(torrent_handle()
						, performance_alert::bittyrant_with_no_uplimit));
			}
		}

		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_ASSERT(!p->ignore_unchoke_slots());

			// this will update the m_uploaded_at_last_unchoke
			// #error this should be called for all peers!
			p->reset_choke_counters();

			torrent* t = p->associated_torrent().lock().get();
			TORRENT_ASSERT(t);

			// if this peer should be unchoked depends on different things
			// in different unchoked schemes
			bool unchoke = false;
			if (m_settings.choking_algorithm == session_settings::bittyrant_choker)
			{
				unchoke = p->est_reciprocation_rate() <= upload_capacity_left;
			}
			else
			{
				unchoke = unchoke_set_size > 0;
			}

			if (unchoke)
			{
				upload_capacity_left -= p->est_reciprocation_rate();

				// yes, this peer should be unchoked
				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
					// since this one just got promoted into the
					// proper unchoke set
					m_optimistic_unchoke_time_scaler = 0;
					p->peer_info_struct()->optimistically_unchoked = false;
				}
			}
			else
			{
				// no, this peer should be shoked
				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;
			}
		}
	}

	void session_impl::main_thread()
	{
#if (defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS) && defined BOOST_HAS_PTHREADS
		m_network_thread = pthread_self();
#endif
		TORRENT_ASSERT(is_network_thread());
		eh_initializer();

		// initialize async operations
		init();

		bool stop_loop = false;
		while (!stop_loop)
		{
			error_code ec;
			m_io_service.run(ec);
			if (ec)
			{
#ifdef TORRENT_DEBUG
				fprintf(stderr, "%s\n", ec.message().c_str());
				std::string err = ec.message();
#endif
				TORRENT_ASSERT(false);
			}
			m_io_service.reset();

			stop_loop = m_abort;
		}

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

/*
#ifdef TORRENT_DEBUG
		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());

#if (defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS) && defined BOOST_HAS_PTHREADS
		m_network_thread = 0;
#endif
	}


	// 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)
	{
		TORRENT_ASSERT(is_network_thread());

		torrent_map::iterator i = m_torrents.find(info_hash);
#ifdef TORRENT_DEBUG
		for (torrent_map::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>();
	}

	boost::weak_ptr<torrent> session_impl::find_torrent(std::string const& uuid)
	{
		TORRENT_ASSERT(is_network_thread());

		std::map<std::string, boost::shared_ptr<torrent> >::iterator i
			= m_uuids.find(uuid);
		if (i != m_uuids.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

	void session_impl::get_torrent_status(std::vector<torrent_status>* ret
		, boost::function<bool(torrent_status const&)> const& pred
		, boost::uint32_t flags) const
	{
		for (torrent_map::const_iterator i
			= m_torrents.begin(), end(m_torrents.end());
			i != end; ++i)
		{
			if (i->second->is_aborted()) continue;
			torrent_status st;
			i->second->status(&st, flags);
			if (!pred(st)) continue;
			ret->push_back(st);
		}
	}

	void session_impl::refresh_torrent_status(std::vector<torrent_status>* ret
		, boost::uint32_t flags) const
	{
		for (std::vector<torrent_status>::iterator i
			= ret->begin(), end(ret->end()); i != end; ++i)
		{
			boost::shared_ptr<torrent> t = i->handle.m_torrent.lock();
			if (!t) continue;
			t->status(&*i, flags);
		}
	}
	
	void session_impl::post_torrent_updates()
	{
		std::auto_ptr<state_update_alert> alert(new state_update_alert());
		alert->status.reserve(m_state_updates.size());

		for (std::vector<boost::weak_ptr<torrent> >::iterator i = m_state_updates.begin()
			, end(m_state_updates.end()); i != end; ++i)
		{
			boost::shared_ptr<torrent> t = i->lock();
			if (!t) continue;
			alert->status.push_back(torrent_status());
			t->clear_in_state_update();
			t->status(&alert->status.back(), 0xffffffff);
		}
		m_state_updates.clear();

		m_alerts.post_alert_ptr(alert.release());
	}

	std::vector<torrent_handle> session_impl::get_torrents() const
	{
		std::vector<torrent_handle> ret;

		for (torrent_map::const_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));
	}

	void session_impl::async_add_torrent(add_torrent_params* params)
	{
		error_code ec;
		torrent_handle handle = add_torrent(*params, ec);
		m_alerts.post_alert(add_torrent_alert(handle, *params, ec));
		delete params->resume_data;
		free((char*)params->tracker_url);
		free((char*)params->name);
		delete params;
	}

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

#ifndef TORRENT_NO_DEPRECATE
		params.update_flags();
#endif

		if (params.ti && params.ti->is_valid() && params.ti->num_files() == 0)
		{
			ec = errors::no_files_in_torrent;
			return torrent_handle();
		}

//		INVARIANT_CHECK;

		if (is_aborted())
		{
			ec = errors::session_is_closing;
			return torrent_handle();
		}
		
		// figure out the info hash of the torrent
		sha1_hash const* ih = 0;
		sha1_hash tmp;
		if (params.ti) ih = &params.ti->info_hash();
		else if (!params.url.empty())
		{
			// in order to avoid info-hash collisions, for
			// torrents where we don't have an info-hash, but
			// just a URL, set the temporary info-hash to the
			// hash of the URL. This will be changed once we
			// have the actual .torrent file
			tmp = hasher(&params.url[0], params.url.size()).final();
			ih = &tmp;
		}
		else ih = &params.info_hash;

		// is the torrent already active?
		boost::shared_ptr<torrent> torrent_ptr = find_torrent(*ih).lock();
		if (!torrent_ptr && !params.uuid.empty()) torrent_ptr = find_torrent(params.uuid).lock();
		// TODO: find by url?

		if (torrent_ptr)
		{
			if ((params.flags & add_torrent_params::flag_duplicate_is_error) == 0)
			{
				if (!params.uuid.empty() && torrent_ptr->uuid().empty())
					torrent_ptr->set_uuid(params.uuid);
				if (!params.url.empty() && torrent_ptr->url().empty())
					torrent_ptr->set_url(params.url);
				if (!params.source_feed_url.empty() && torrent_ptr->source_feed_url().empty())
					torrent_ptr->set_source_feed_url(params.source_feed_url);
				return torrent_handle(torrent_ptr);
			}

			ec = errors::duplicate_torrent;
			return torrent_handle();
		}

		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;
		}

		torrent_ptr.reset(new torrent(*this, m_listen_interface
			, 16 * 1024, queue_pos, params, *ih));
		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);
		}

		for (ses_extension_list_t::iterator i = m_ses_extensions.begin()
			, end(m_ses_extensions.end()); i != end; ++i)
		{
			boost::shared_ptr<torrent_plugin> tp((*i)->new_torrent(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(), boost::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 (!params.uuid.empty() || !params.url.empty())
			m_uuids.insert(std::make_pair(params.uuid.empty()
				? params.url : params.uuid, torrent_ptr));

		if (m_alerts.should_post<torrent_added_alert>())
			m_alerts.post_alert(torrent_added_alert(torrent_ptr->get_handle()));

		// recalculate auto-managed torrents sooner (or put it off)
		// if another torrent will be added within one second from now
		// we want to put it off again anyway. So that while we're adding
		// a boat load of torrents, we postpone the recalculation until
		// we're done adding them all (since it's kind of an expensive operation)
		if (params.flags & add_torrent_params::flag_auto_managed)
			m_auto_manage_time_scaler = 2;

		return torrent_handle(torrent_ptr);
	}

	void session_impl::queue_check_torrent(boost::shared_ptr<torrent> const& t)
	{
		if (m_abort) return;
		TORRENT_ASSERT(t->should_check_files());
		TORRENT_ASSERT(t->state() != torrent_status::checking_files);
		if (m_queued_for_checking.empty()) t->start_checking();
		else t->set_state(torrent_status::queued_for_checking);
		TORRENT_ASSERT(std::find(m_queued_for_checking.begin()
			, m_queued_for_checking.end(), t) == m_queued_for_checking.end());
		m_queued_for_checking.push_back(t);
	}

	void session_impl::dequeue_check_torrent(boost::shared_ptr<torrent> const& t)
	{
		INVARIANT_CHECK;
		TORRENT_ASSERT(t->state() == torrent_status::checking_files
			|| t->state() == torrent_status::queued_for_checking);

		if (m_queued_for_checking.empty()) return;

		boost::shared_ptr<torrent> 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)
		{
			// the reason m_paused is in there is because when the session
			// is paused, all torrents  that are queued ar all of a sudden
			// not supposed to be queued anymore. The first torrent that gets
			// removed from the queue will hence trigger this assert, without
			// the m_paused exception
			TORRENT_ASSERT(*i == t || (*i)->should_check_files() || m_paused);
			if (*i == t) done = i;
			else if (next_check == t || next_check->queue_position() > (*i)->queue_position())
				next_check = *i;
		}
		TORRENT_ASSERT(next_check != t || m_queued_for_checking.size() == 1);
		// only start a new one if we removed the one that is checking
		TORRENT_ASSERT(done != m_queued_for_checking.end());
		if (done == m_queued_for_checking.end()) return;

		if (next_check != t
			&& t->state() == torrent_status::checking_files
			&& !m_paused)
		{
			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) return;

		remove_torrent_impl(tptr, options);

		if (m_alerts.should_post<torrent_removed_alert>())
			m_alerts.post_alert(torrent_removed_alert(tptr->get_handle(), tptr->info_hash()));

		tptr->abort();
		tptr->set_queue_position(-1);
	}

	void session_impl::remove_torrent_impl(boost::shared_ptr<torrent> tptr, int options)
	{
		INVARIANT_CHECK;

		// remove from uuid list
		if (!tptr->uuid().empty())
		{
			std::map<std::string, boost::shared_ptr<torrent> >::iterator j
				= m_uuids.find(tptr->uuid());
			if (j != m_uuids.end()) m_uuids.erase(j);
		}

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

		// this torrent might be filed under the URL-hash
		if (i == m_torrents.end() && !tptr->url().empty())
		{
			std::string const& url = tptr->url();
			sha1_hash urlhash = hasher(&url[0], url.size()).final();
			i = m_torrents.find(urlhash);
		}

		if (i == m_torrents.end()) return;

		torrent& t = *i->second;
		if (options & session::delete_files)
			t.delete_files();

#if defined TORRENT_DEBUG || TORRENT_RELEASE_ASSERTS
		sha1_hash i_hash = t.torrent_file().info_hash();
#endif
#ifndef TORRENT_DISABLE_DHT
		if (i == m_next_dht_torrent)
			++m_next_dht_torrent;
#endif
		if (i == m_next_lsd_torrent)
			++m_next_lsd_torrent;
		if (i == m_next_connect_torrent)
			++m_next_connect_torrent;

		m_torrents.erase(i);

#ifndef TORRENT_DISABLE_DHT
		if (m_next_dht_torrent == m_torrents.end())
			m_next_dht_torrent = m_torrents.begin();
#endif
		if (m_next_lsd_torrent == m_torrents.end())
			m_next_lsd_torrent = m_torrents.begin();
		if (m_next_connect_torrent == m_torrents.end())
			m_next_connect_torrent = m_torrents.begin();

		std::list<boost::shared_ptr<torrent> >::iterator k
			= std::find(m_queued_for_checking.begin(), m_queued_for_checking.end(), tptr);
		if (k != m_queued_for_checking.end()) m_queued_for_checking.erase(k);
		TORRENT_ASSERT(m_torrents.find(i_hash) == m_torrents.end());
	}

	void session_impl::listen_on(
		std::pair<int, int> const& port_range
		, error_code& ec
		, const char* net_interface, int flags)
	{
		INVARIANT_CHECK;

		tcp::endpoint new_interface;
		if (net_interface && std::strlen(net_interface) > 0)
		{
			new_interface = tcp::endpoint(address::from_string(net_interface, ec), port_range.first);
			if (ec)
			{
#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
				(*m_logger) << time_now_string() << "listen_on: " << net_interface
					<< " failed: " << ec.message() << "\n";
#endif
				return;
			}
		}
		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;

		m_listen_interface = new_interface;

		open_listen_port(flags, ec);

#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
	}

	address session_impl::listen_address() const
	{
		for (std::list<listen_socket_t>::const_iterator i = m_listen_sockets.begin()
			, end(m_listen_sockets.end()); i != end; ++i)
		{
			if (i->external_address != address()) return i->external_address;
		}
		return address();
	}

	boost::uint16_t session_impl::listen_port() const
	{
		// if peer connections are set up to be received over a socks
		// proxy, and it's the same one as we're using for the tracker
		// just tell the tracker the socks5 port we're listening on
		if (m_socks_listen_socket && m_socks_listen_socket->is_open()
			&& m_proxy.hostname == m_proxy.hostname)
			return m_socks_listen_port;

		// if not, don't tell the tracker anything if we're in anonymous
		// mode. We don't want to leak our listen port since it can
		// potentially identify us if it is leaked elsewere
		if (m_settings.anonymous_mode) return 0;
		if (m_listen_sockets.empty()) return 0;
		return m_listen_sockets.front().external_port;
	}

	boost::uint16_t session_impl::ssl_listen_port() const
	{
#ifdef TORRENT_USE_OPENSSL
		// if peer connections are set up to be received over a socks
		// proxy, and it's the same one as we're using for the tracker
		// just tell the tracker the socks5 port we're listening on
		if (m_socks_listen_socket && m_socks_listen_socket->is_open()
			&& m_proxy.hostname == m_proxy.hostname)
			return m_socks_listen_port;

		// if not, don't tell the tracker anything if we're in anonymous
		// mode. We don't want to leak our listen port since it can
		// potentially identify us if it is leaked elsewere
		if (m_settings.anonymous_mode) return 0;
		if (m_listen_sockets.empty()) return 0;
		for (std::list<listen_socket_t>::const_iterator i = m_listen_sockets.begin()
			, end(m_listen_sockets.end()); i != end; ++i)
		{
			if (i->ssl) return i->external_port;
		}
#endif
		return 0;
	}

	void session_impl::announce_lsd(sha1_hash const& ih, int port, bool broadcast)
	{
		// use internal listen port for local peers
		if (m_lsd.get())
			m_lsd->announce(ih, port, broadcast);
	}

	void session_impl::on_lsd_peer(tcp::endpoint peer, sha1_hash const& ih)
	{
#ifdef TORRENT_STATS
		++m_num_messages[on_lsd_peer_counter];
#endif
		TORRENT_ASSERT(is_network_thread());

		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() || (t->torrent_file().is_i2p()
			&& !m_settings.allow_i2p_mixed)) 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().add_peer(peer, peer_id(0), peer_info::lsd, 0);
		if (m_alerts.should_post<lsd_peer_alert>())
			m_alerts.post_alert(lsd_peer_alert(t->get_handle(), peer));
	}

	void session_impl::on_port_map_log(
		char const* msg, int map_transport)
	{
		TORRENT_ASSERT(map_transport >= 0 && map_transport <= 1);
		// log message
#ifdef TORRENT_UPNP_LOGGING
		char const* transport_names[] = {"NAT-PMP", "UPnP"};
		m_upnp_log << time_now_string() << " "
			<< transport_names[map_transport] << ": " << msg;
#endif
		if (m_alerts.should_post<portmap_log_alert>())
			m_alerts.post_alert(portmap_log_alert(map_transport, msg));
	}

	void session_impl::on_port_mapping(int mapping, address const& ip, int port
		, error_code const& ec, int map_transport)
	{
		TORRENT_ASSERT(is_network_thread());

		TORRENT_ASSERT(map_transport >= 0 && map_transport <= 1);

		if (mapping == m_udp_mapping[map_transport] && port != 0)
		{
			m_external_udp_port = port;
			if (m_alerts.should_post<portmap_alert>())
				m_alerts.post_alert(portmap_alert(mapping, port
					, map_transport));
			return;
		}

		if (mapping == m_tcp_mapping[map_transport] && port != 0)
		{
			// TODO: report the proper address of the router
			if (ip != address()) set_external_address(ip, source_router
				, address());

			if (!m_listen_sockets.empty()) {
				m_listen_sockets.front().external_address = ip;
				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 (ec)
		{
			if (m_alerts.should_post<portmap_error_alert>())
				m_alerts.post_alert(portmap_error_alert(mapping
					, map_transport, ec));
		}
		else
		{
			if (m_alerts.should_post<portmap_alert>())
				m_alerts.post_alert(portmap_alert(mapping, port
					, map_transport));
		}
	}

	session_status session_impl::status() const
	{
//		INVARIANT_CHECK;
		TORRENT_ASSERT(is_network_thread());

		session_status s;

		s.optimistic_unchoke_counter = m_optimistic_unchoke_time_scaler;
		s.unchoke_counter = m_unchoke_time_scaler;

		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_rate.queue_size();
		s.down_bandwidth_queue = m_download_rate.queue_size();

		s.up_bandwidth_bytes_queue = m_upload_rate.queued_bytes();
		s.down_bandwidth_bytes_queue = m_download_rate.queued_bytes();

		s.disk_write_queue = m_disk_queues[peer_connection::download_channel];
		s.disk_read_queue = m_disk_queues[peer_connection::upload_channel];

		s.has_incoming_connections = m_incoming_connection;

		// total
		s.download_rate = m_stat.download_rate();
		s.total_upload = m_stat.total_upload();
		s.upload_rate = m_stat.upload_rate();
		s.total_download = m_stat.total_download();

		// payload
		s.payload_download_rate = m_stat.transfer_rate(stat::download_payload);
		s.total_payload_download = m_stat.total_transfer(stat::download_payload);
		s.payload_upload_rate = m_stat.transfer_rate(stat::upload_payload);
		s.total_payload_upload = m_stat.total_transfer(stat::upload_payload);

#ifndef TORRENT_DISABLE_FULL_STATS
		// IP-overhead
		s.ip_overhead_download_rate = m_stat.transfer_rate(stat::download_ip_protocol);
		s.total_ip_overhead_download = m_stat.total_transfer(stat::download_ip_protocol);
		s.ip_overhead_upload_rate = m_stat.transfer_rate(stat::upload_ip_protocol);
		s.total_ip_overhead_upload = m_stat.total_transfer(stat::upload_ip_protocol);

#ifndef TORRENT_DISABLE_DHT
		// DHT protocol
		s.dht_download_rate = m_stat.transfer_rate(stat::download_dht_protocol);
		s.total_dht_download = m_stat.total_transfer(stat::download_dht_protocol);
		s.dht_upload_rate = m_stat.transfer_rate(stat::upload_dht_protocol);
		s.total_dht_upload = m_stat.total_transfer(stat::upload_dht_protocol);
#endif

		// tracker
		s.tracker_download_rate = m_stat.transfer_rate(stat::download_tracker_protocol);
		s.total_tracker_download = m_stat.total_transfer(stat::download_tracker_protocol);
		s.tracker_upload_rate = m_stat.transfer_rate(stat::upload_tracker_protocol);
		s.total_tracker_upload = m_stat.total_transfer(stat::upload_tracker_protocol);
#else
		// IP-overhead
		s.ip_overhead_download_rate = 0;
		s.total_ip_overhead_download = 0;
		s.ip_overhead_upload_rate = 0;
		s.total_ip_overhead_upload = 0;

		// DHT protocol
		s.dht_download_rate = 0;
		s.total_dht_download = 0;
		s.dht_upload_rate = 0;
		s.total_dht_upload = 0;

		// tracker
		s.tracker_download_rate = 0;
		s.total_tracker_download = 0;
		s.tracker_upload_rate = 0;
		s.total_tracker_upload = 0;
#endif

#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;
			s.dht_total_allocations = 0;
		}
#endif

		m_utp_socket_manager.get_status(s.utp_stats);

		int peerlist_size = 0;
		for (torrent_map::const_iterator i = m_torrents.begin()
			, end(m_torrents.end()); i != end; ++i)
		{
			peerlist_size += i->second->get_policy().num_peers();
		}

		s.peerlist_size = peerlist_size;

		return s;
	}

#ifndef TORRENT_DISABLE_DHT

	void session_impl::start_dht()
	{ start_dht(m_dht_state); }

	void session_impl::start_dht(entry const& startup_state)
	{
		INVARIANT_CHECK;

		if (m_dht)
		{
			m_dht->stop();
			m_dht = 0;
		}
		m_dht = new dht::dht_tracker(*this, m_udp_socket, m_dht_settings, &startup_state);

		for (std::list<udp::endpoint>::iterator i = m_dht_router_nodes.begin()
			, end(m_dht_router_nodes.end()); i != end; ++i)
		{
			m_dht->add_router_node(*i);
		}

		m_dht->start(startup_state);

		// announce all torrents we have to the DHT
		for (torrent_map::const_iterator i = m_torrents.begin()
			, end(m_torrents.end()); i != end; ++i)
		{
			i->second->dht_announce();
		}
	}

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

	void session_impl::set_dht_settings(dht_settings const& settings)
	{
		m_dht_settings = settings;
	}

#ifndef TORRENT_NO_DEPRECATE
	entry session_impl::dht_state() const
	{
		if (!m_dht) return entry();
		return m_dht->state();
	}
#endif

	void session_impl::add_dht_node_name(std::pair<std::string, int> const& node)
	{
		if (m_dht) m_dht->add_node(node);
	}

	void session_impl::add_dht_router(std::pair<std::string, int> const& node)
	{
#if defined TORRENT_ASIO_DEBUGGING
		add_outstanding_async("session_impl::on_dht_router_name_lookup");
#endif
		char port[7];
		snprintf(port, sizeof(port), "%d", node.second);
		tcp::resolver::query q(node.first, port);
		m_host_resolver.async_resolve(q,
			boost::bind(&session_impl::on_dht_router_name_lookup, this, _1, _2));
	}

	void session_impl::on_dht_router_name_lookup(error_code const& e
		, tcp::resolver::iterator host)
	{
#if defined TORRENT_ASIO_DEBUGGING
		complete_async("session_impl::on_dht_router_name_lookup");
#endif
		// TODO: report errors as alerts
		if (e) return;
		while (host != tcp::resolver::iterator())
		{
			// router nodes should be added before the DHT is started (and bootstrapped)
			udp::endpoint ep(host->endpoint().address(), host->endpoint().port());
			if (m_dht) m_dht->add_router_node(ep);
			m_dht_router_nodes.push_back(ep);
			++host;
		}
	}
#endif

	void session_impl::maybe_update_udp_mapping(int nat, int local_port, int external_port)
	{
		int local, external, protocol;
		if (nat == 0 && m_natpmp.get())
		{
			if (m_udp_mapping[nat] != -1)
			{
				if (m_natpmp->get_mapping(m_udp_mapping[nat], local, external, protocol))
				{
					// we already have a mapping. If it's the same, don't do anything
					if (local == local_port && external == external_port && protocol == natpmp::udp)
						return;
				}
				m_natpmp->delete_mapping(m_udp_mapping[nat]);
			}
			m_udp_mapping[nat] = m_natpmp->add_mapping(natpmp::udp
				, local_port, external_port);
			return;
		}
		else if (nat == 1 && m_upnp.get())
		{
			if (m_udp_mapping[nat] != -1)
			{
				if (m_upnp->get_mapping(m_udp_mapping[nat], local, external, protocol))
				{
					// we already have a mapping. If it's the same, don't do anything
					if (local == local_port && external == external_port && protocol == natpmp::udp)
						return;
				}
				m_upnp->delete_mapping(m_udp_mapping[nat]);
			}
			m_udp_mapping[nat] = m_upnp->add_mapping(upnp::udp
				, local_port, external_port);
			return;
		}
	}

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

	bool session_impl::is_listening() const
	{
		return !m_listen_sockets.empty();
	}

	session_impl::~session_impl()
	{
		m_io_service.post(boost::bind(&session_impl::abort, this));

		// we need to wait for the disk-io thread to
		// die first, to make sure it won't post any
		// more messages to the io_service containing references
		// to disk_io_pool inside the disk_io_thread. Once
		// the main thread has handled all the outstanding requests
		// we know it's safe to destruct the disk thread.
		m_disk_thread.join();

#if defined TORRENT_ASIO_DEBUGGING
		int counter = 0;
		while (log_async())
		{
			sleep(1000);
			++counter;
			printf("\n==== Waiting to shut down: %d ==== \n\n", counter);
		}
		async_dec_threads();
#endif

		if (m_thread) m_thread->join();

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

#ifdef TORRENT_REQUEST_LOGGING
		if (m_request_log) fclose(m_request_log);
#endif

#ifdef TORRENT_STATS
		if (m_stats_logger) fclose(m_stats_logger);
#endif
	}

#ifndef TORRENT_NO_DEPRECATE
	int session_impl::max_connections() const
	{
		return m_settings.connections_limit;
	}

	int session_impl::max_uploads() const
	{
		return m_settings.unchoke_slots_limit;
	}

	int session_impl::max_half_open_connections() const
	{
		return m_settings.half_open_limit;
	}

	void session_impl::set_local_download_rate_limit(int bytes_per_second)
	{
		session_settings s = m_settings;
		s.local_download_rate_limit = bytes_per_second;
		set_settings(s);
	}

	void session_impl::set_local_upload_rate_limit(int bytes_per_second)
	{
		session_settings s = m_settings;
		s.local_upload_rate_limit = bytes_per_second;
		set_settings(s);
	}

	void session_impl::set_download_rate_limit(int bytes_per_second)
	{
		session_settings s = m_settings;
		s.download_rate_limit = bytes_per_second;
		set_settings(s);
	}

	void session_impl::set_upload_rate_limit(int bytes_per_second)
	{
		session_settings s = m_settings;
		s.upload_rate_limit = bytes_per_second;
		set_settings(s);
	}

	void session_impl::set_max_half_open_connections(int limit)
	{
		session_settings s = m_settings;
		s.half_open_limit = limit;
		set_settings(s);
	}

	void session_impl::set_max_connections(int limit)
	{
		session_settings s = m_settings;
		s.connections_limit = limit;
		set_settings(s);
	}

	void session_impl::set_max_uploads(int limit)
	{
		session_settings s = m_settings;
		s.unchoke_slots_limit = limit;
		set_settings(s);
	}

	int session_impl::local_upload_rate_limit() const
	{
		return m_local_upload_channel.throttle();
	}

	int session_impl::local_download_rate_limit() const
	{
		return m_local_download_channel.throttle();
	}

	int session_impl::upload_rate_limit() const
	{
		return m_upload_channel.throttle();
	}

	int session_impl::download_rate_limit() const
	{
		return m_download_channel.throttle();
	}
#endif

	void session_impl::update_unchoke_limit()
	{
		m_allowed_upload_slots = m_settings.unchoke_slots_limit;
		if (m_allowed_upload_slots < 0)
			m_allowed_upload_slots = (std::numeric_limits<int>::max)();

		if (m_settings.num_optimistic_unchoke_slots >= m_allowed_upload_slots / 2)
		{
			if (m_alerts.should_post<performance_alert>())
				m_alerts.post_alert(performance_alert(torrent_handle()
					, performance_alert::too_many_optimistic_unchoke_slots));
		}
	}

	void session_impl::update_rate_settings()
	{
		if (m_settings.half_open_limit <= 0) m_settings.half_open_limit
			= (std::numeric_limits<int>::max)();
		m_half_open.limit(m_settings.half_open_limit);

		if (m_settings.local_download_rate_limit < 0)
			m_settings.local_download_rate_limit = 0;
		m_local_download_channel.throttle(m_settings.local_download_rate_limit);

		if (m_settings.local_upload_rate_limit < 0)
			m_settings.local_upload_rate_limit = 0;
		m_local_upload_channel.throttle(m_settings.local_upload_rate_limit);

		if (m_settings.download_rate_limit < 0)
			m_settings.download_rate_limit = 0;
		m_download_channel.throttle(m_settings.download_rate_limit);

		if (m_settings.upload_rate_limit < 0)
			m_settings.upload_rate_limit = 0;
		m_upload_channel.throttle(m_settings.upload_rate_limit);
	}

	void session_impl::update_connections_limit()
	{
		if (m_settings.connections_limit <= 0)
		{
			m_settings.connections_limit = (std::numeric_limits<int>::max)();
#if TORRENT_USE_RLIMIT
			rlimit l;
			if (getrlimit(RLIMIT_NOFILE, &l) == 0
				&& l.rlim_cur != RLIM_INFINITY)
			{
				m_settings.connections_limit = l.rlim_cur - m_settings.file_pool_size;
				if (m_settings.connections_limit < 5) m_settings.connections_limit = 5;
			}
#endif
		}

		if (num_connections() > m_settings.connections_limit && !m_torrents.empty())
		{
			// if we have more connections that we're allowed, disconnect
			// peers from the torrents so that they are all as even as possible

			int to_disconnect = num_connections() - m_settings.connections_limit;

			int last_average = 0;
			int average = m_settings.connections_limit / m_torrents.size();
	
			// the number of slots that are unused by torrents
			int extra = m_settings.connections_limit % m_torrents.size();
	
			// run 3 iterations of this, then we're probably close enough
			for (int iter = 0; iter < 4; ++iter)
			{
				// the number of torrents that are above average
				int num_above = 0;
				for (torrent_map::iterator i = m_torrents.begin()
					, end(m_torrents.end()); i != end; ++i)
				{
					int num = i->second->num_peers();
					if (num <= last_average) continue;
					if (num > average) ++num_above;
					if (num < average) extra += average - num;
				}

				// distribute extra among the torrents that are above average
				if (num_above == 0) num_above = 1;
				last_average = average;
				average += extra / num_above;
				if (extra == 0) break;
				// save the remainder for the next iteration
				extra = extra % num_above;
			}

			for (torrent_map::iterator i = m_torrents.begin()
				, end(m_torrents.end()); i != end; ++i)
			{
				int num = i->second->num_peers();
				if (num <= average) continue;

				// distribute the remainder
				int my_average = average;
				if (extra > 0)
				{
					++my_average;
					--extra;
				}

				int disconnect = (std::min)(to_disconnect, num - my_average);
				to_disconnect -= disconnect;
				i->second->disconnect_peers(disconnect
					, error_code(errors::too_many_connections, get_libtorrent_category()));
			}
		}
	}

	void session_impl::set_alert_dispatch(boost::function<void(std::auto_ptr<alert>)> const& fun)
	{
		m_alerts.set_dispatch_function(fun);
	}

	std::auto_ptr<alert> session_impl::pop_alert()
	{
		return m_alerts.get();
	}
	
	void session_impl::pop_alerts(std::deque<alert*>* alerts)
	{
		m_alerts.get_all(alerts);
	}

	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(boost::uint32_t m)
	{
		m_alerts.set_alert_mask(m);
	}

#ifndef TORRENT_NO_DEPRECATE
	size_t session_impl::set_alert_queue_size_limit(size_t queue_size_limit_)
	{
		m_settings.alert_queue_size = queue_size_limit_;
		return m_alerts.set_alert_queue_size_limit(queue_size_limit_);
	}
#endif

	void session_impl::start_lsd()
	{
		INVARIANT_CHECK;

		if (m_lsd) return;

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

		if (m_natpmp) return m_natpmp.get();

		// the natpmp constructor may fail and call the callbacks
		// into the session_impl.
		natpmp* n = new (std::nothrow) natpmp(m_io_service
			, m_listen_interface.address()
			, boost::bind(&session_impl::on_port_mapping
				, this, _1, _2, _3, _4, 0)
			, boost::bind(&session_impl::on_port_map_log
				, this, _1, 0));
		if (n == 0) return 0;

		m_natpmp = n;

		if (m_listen_interface.port() > 0)
		{
			remap_tcp_ports(1, m_listen_interface.port(), ssl_listen_port());
		}
		if (m_udp_socket.is_open())
		{
			m_udp_mapping[0] = m_natpmp->add_mapping(natpmp::udp
				, m_listen_interface.port(), m_listen_interface.port());
		}
		return n;
	}

	upnp* session_impl::start_upnp()
	{
		INVARIANT_CHECK;

		if (m_upnp) return m_upnp.get();

		// the upnp constructor may fail and call the callbacks
		upnp* u = new (std::nothrow) upnp(m_io_service
			, m_half_open
			, m_listen_interface.address()
			, m_settings.user_agent
			, boost::bind(&session_impl::on_port_mapping
				, this, _1, _2, _3, _4, 1)
			, boost::bind(&session_impl::on_port_map_log
				, this, _1, 1)
			, m_settings.upnp_ignore_nonrouters);

		if (u == 0) return 0;

		m_upnp = u;

		m_upnp->discover_device();
		if (m_listen_interface.port() > 0 || ssl_listen_port() > 0)
		{
			remap_tcp_ports(2, m_listen_interface.port(), ssl_listen_port());
		}
		if (m_udp_socket.is_open())
		{
			m_udp_mapping[1] = m_upnp->add_mapping(upnp::udp
				, m_listen_interface.port(), m_listen_interface.port());
		}
		return u;
	}

	void session_impl::stop_lsd()
	{
		if (m_lsd.get())
			m_lsd->close();
		m_lsd = 0;
	}
	
	void session_impl::stop_natpmp()
	{
		if (m_natpmp.get())
			m_natpmp->close();
		m_natpmp = 0;
	}
	
	void session_impl::stop_upnp()
	{
		if (m_upnp.get())
		{
			m_upnp->close();
			m_udp_mapping[1] = -1;
			m_tcp_mapping[1] = -1;
#ifdef TORRENT_USE_OPENSSL
			m_ssl_mapping[1] = -1;
#endif
		}
		m_upnp = 0;
	}
	
	bool session_impl::external_ip_t::add_vote(sha1_hash const& k, int type)
	{
		sources |= type;
		if (voters.find(k)) return false;
		voters.set(k);
		++num_votes;
		return true;
	}

	void session_impl::set_external_address(address const& ip
		, int source_type, address const& source)
	{
		if (is_any(ip)) return;
		if (is_local(ip)) return;
		if (is_loopback(ip)) return;

#if defined TORRENT_VERBOSE_LOGGING
		(*m_logger) << time_now_string() << ": set_external_address(" << print_address(ip)
			<< ", " << source_type << ", " << print_address(source) << ")\n";
#endif
		// this is the key to use for the bloom filters
		// it represents the identity of the voter
		sha1_hash k;
		hash_address(source, k);

		// do we already have an entry for this external IP?
		std::vector<external_ip_t>::iterator i = std::find_if(m_external_addresses.begin()
			, m_external_addresses.end(), boost::bind(&external_ip_t::addr, _1) == ip);

		if (i == m_external_addresses.end())
		{
			// each IP only gets to add a new IP once
			if (m_external_address_voters.find(k)) return;
		
			if (m_external_addresses.size() > 20)
			{
				if (random() < UINT_MAX / 2)
				{
#if defined TORRENT_VERBOSE_LOGGING
					(*m_logger) << time_now_string() << ": More than 20 slots, dopped\n";
#endif
					return;
				}
				// use stable sort here to maintain the fifo-order
				// of the entries with the same number of votes
				// this will sort in ascending order, i.e. the lowest
				// votes first. Also, the oldest are first, so this
				// is a sort of weighted LRU.
				std::stable_sort(m_external_addresses.begin(), m_external_addresses.end());
				// erase the first element, since this is the
				// oldest entry and the one with lowst number
				// of votes. This makes sense because the oldest
				// entry has had the longest time to receive more
				// votes to be bumped up
#if defined TORRENT_VERBOSE_LOGGING
				(*m_logger) << "  More than 20 slots, dopping "
					<< print_address(m_external_addresses.front().addr)
					<< " (" << m_external_addresses.front().num_votes << ")\n";
#endif
				m_external_addresses.erase(m_external_addresses.begin());
			}
			m_external_addresses.push_back(external_ip_t());
			i = m_external_addresses.end() - 1;
			i->addr = ip;
		}
		// add one more vote to this external IP
		if (!i->add_vote(k, source_type)) return;
		
		i = std::max_element(m_external_addresses.begin(), m_external_addresses.end());
		TORRENT_ASSERT(i != m_external_addresses.end());

#if defined TORRENT_VERBOSE_LOGGING
		for (std::vector<external_ip_t>::iterator j = m_external_addresses.begin()
			, end(m_external_addresses.end()); j != end; ++j)
		{
			(*m_logger) << ((j == i)?"-->":"   ")
				<< print_address(j->addr) << " votes: "
				<< j->num_votes << "\n";
		}
#endif
		if (i->addr == m_external_address) return;

#if defined TORRENT_VERBOSE_LOGGING
		(*m_logger) << "  external IP updated\n";
#endif
		m_external_address = i->addr;
		m_external_address_voters.clear();

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

		// since we have a new external IP now, we need to
		// restart the DHT with a new node ID
#ifndef TORRENT_DISABLE_DHT
		if (m_dht)
		{
			entry s = m_dht->state();
			int cur_state = 0;
			int prev_state = 0;
			entry* nodes1 = s.find_key("nodes");
			if (nodes1 && nodes1->type() == entry::list_t) cur_state = nodes1->list().size();
			entry* nodes2 = m_dht_state.find_key("nodes");
			if (nodes2 && nodes2->type() == entry::list_t) prev_state = nodes2->list().size();
			if (cur_state > prev_state) m_dht_state = s;
			start_dht(m_dht_state);
		}
#endif
	}

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

	char* session_impl::allocate_disk_buffer(char const* category)
	{
		return m_disk_thread.allocate_buffer(category);
	}
	
	char* session_impl::allocate_buffer()
	{
		TORRENT_ASSERT(is_network_thread());

#ifdef TORRENT_DISK_STATS
		TORRENT_ASSERT(m_buffer_allocations >= 0);
		m_buffer_allocations++;
		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 = send_buffer_size;
		return (char*)malloc(num_bytes);
#else
		return (char*)m_send_buffers.malloc();
#endif
	}

#ifdef TORRENT_DISK_STATS
	void session_impl::log_buffer_usage()
	{
		TORRENT_ASSERT(is_network_thread());

		int send_buffer_capacity = 0;
		int used_send_buffer = 0;
		for (connection_map::const_iterator i = m_connections.begin()
			, end(m_connections.end()); i != end; ++i)
		{
			send_buffer_capacity += (*i)->send_buffer_capacity();
			used_send_buffer += (*i)->send_buffer_size();
		}
		TORRENT_ASSERT(send_buffer_capacity >= used_send_buffer);
		m_buffer_usage_logger << log_time() << " send_buffer_size: " << send_buffer_capacity << std::endl;
		m_buffer_usage_logger << log_time() << " used_send_buffer: " << used_send_buffer << std::endl;
		m_buffer_usage_logger << log_time() << " send_buffer_utilization: "
			<< (used_send_buffer * 100.f / send_buffer_capacity) << std::endl;
	}
#endif

	void session_impl::free_buffer(char* buf)
	{
		TORRENT_ASSERT(is_network_thread());

#ifdef TORRENT_DISK_STATS
		m_buffer_allocations--;
		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.free(buf);
#endif
	}	

#ifdef TORRENT_DEBUG
	void session_impl::check_invariant() const
	{
		TORRENT_ASSERT(is_network_thread());

		int num_checking = 0;
		int num_queued_for_checking = 0;
		for (check_queue_t::const_iterator i = m_queued_for_checking.begin()
			, end(m_queued_for_checking.end()); i != end; ++i)
		{
			if ((*i)->state() == torrent_status::checking_files) ++num_checking;
			else if ((*i)->state() == torrent_status::queued_for_checking)
			{
				++num_queued_for_checking;
			}
		}

		// the queue is either empty, or it has exactly one checking torrent in it
		TORRENT_ASSERT(m_queued_for_checking.empty() || num_checking == 1 || (m_paused && num_checking == 0));
//		TORRENT_ASSERT(m_queued_for_checking.size() == num_queued_for_checking);

		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(int(unique.size()) == total_downloaders);

		std::set<peer_connection*> unique_peers;
		TORRENT_ASSERT(m_settings.connections_limit > 0);
		if (m_settings.choking_algorithm == session_settings::auto_expand_choker)
			TORRENT_ASSERT(m_allowed_upload_slots >= m_settings.unchoke_slots_limit);
		int unchokes = 0;
		int num_optimistic = 0;
		int disk_queue[2] = {0, 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();
			TORRENT_ASSERT(unique_peers.find(i->get()) == unique_peers.end());
			unique_peers.insert(i->get());

			if ((*i)->m_channel_state[0] & peer_info::bw_disk) ++disk_queue[0];
			if ((*i)->m_channel_state[1] & peer_info::bw_disk) ++disk_queue[1];

			peer_connection* p = i->get();
			TORRENT_ASSERT(!p->is_disconnecting());
			if (p->ignore_unchoke_slots()) continue;
			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(disk_queue[0] == m_disk_queues[0]);
		TORRENT_ASSERT(disk_queue[1] == m_disk_queues[1]);

		if (m_settings.num_optimistic_unchoke_slots)
		{
			TORRENT_ASSERT(num_optimistic <= m_settings.num_optimistic_unchoke_slots);
		}

		if (m_num_unchoked != unchokes)
		{
			TORRENT_ASSERT(false);
		}
		for (torrent_map::const_iterator j
			= m_torrents.begin(); j != m_torrents.end(); ++j)
		{
			TORRENT_ASSERT(boost::get_pointer(j->second));
		}
	}
#endif

}}