text: /*
  
  Copyright (c) 2006-2016, MassaRoddel, Arvid Norberg
  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/config.hpp"
  #include "libtorrent/bt_peer_connection.hpp"
  #include "libtorrent/peer_connection_handle.hpp"
  #include "libtorrent/bencode.hpp"
  #include "libtorrent/torrent.hpp"
  #include "libtorrent/extensions.hpp"
  #include "libtorrent/broadcast_socket.hpp"
  #include "libtorrent/socket_io.hpp"
  #include "libtorrent/peer_info.hpp"
  #include "libtorrent/socket_type.hpp" // for is_utp
  #include "libtorrent/performance_counters.hpp" // for counters
  #include "libtorrent/extensions/ut_pex.hpp"
  #include "libtorrent/aux_/time.hpp"
  
  #ifndef TORRENT_DISABLE_EXTENSIONS
  
  namespace libtorrent { namespace
  {
  	const char extension_name[] = "ut_pex";
  
  	enum
  	{
  		extension_index = 1,
  		max_peer_entries = 100
  	};
  
  	bool send_peer(peer_connection const& p)
  	{
  		// don't send out those peers that we haven't connected to
  		// (that have connected to us) and that aren't sharing their
  		// listening port
  		if (!p.is_outgoing() && !p.received_listen_port()) return false;
  		// don't send out peers that we haven't successfully connected to
  		if (p.is_connecting()) return false;
  		if (p.in_handshake()) return false;
  		return true;
  	}
  
  	struct ut_pex_plugin final
  		: torrent_plugin
  	{
  		// randomize when we rebuild the pex message
  		// to evenly spread it out across all torrents
  		// the more torrents we have, the longer we can
  		// delay the rebuilding
  		explicit ut_pex_plugin(torrent& t)
  			: m_torrent(t)
  			, m_last_msg(min_time())
  			, m_peers_in_message(0) {}
  
  		std::shared_ptr<peer_plugin> new_connection(
  			peer_connection_handle const& pc) override;
  
  		std::vector<char>& get_ut_pex_msg()
  		{
  			return m_ut_pex_msg;
  		}
  
  		int peers_in_msg() const
  		{
  			return m_peers_in_message;
  		}
  
  		// the second tick of the torrent
  		// each minute the new lists of "added" + "added.f" and "dropped"
  		// are calculated here and the pex message is created
  		// each peer connection will use this message
  		// max_peer_entries limits the packet size
  		void tick() override
  		{
  			time_point now = aux::time_now();
  			if (now - seconds(60) < m_last_msg) return;
  			m_last_msg = now;
  
  			int num_peers = m_torrent.num_peers();
  			if (num_peers == 0) return;
  
  			entry pex;
  			std::string& pla = pex["added"].string();
  			std::string& pld = pex["dropped"].string();
  			std::string& plf = pex["added.f"].string();
  			std::back_insert_iterator<std::string> pla_out(pla);
  			std::back_insert_iterator<std::string> pld_out(pld);
  			std::back_insert_iterator<std::string> plf_out(plf);
  #if TORRENT_USE_IPV6
  			std::string& pla6 = pex["added6"].string();
  			std::string& pld6 = pex["dropped6"].string();
  			std::string& plf6 = pex["added6.f"].string();
  			std::back_insert_iterator<std::string> pla6_out(pla6);
  			std::back_insert_iterator<std::string> pld6_out(pld6);
  			std::back_insert_iterator<std::string> plf6_out(plf6);
  #endif
  
  			std::set<tcp::endpoint> dropped;
  			m_old_peers.swap(dropped);
  
  			m_peers_in_message = 0;
  			int num_added = 0;
  			for (torrent::peer_iterator i = m_torrent.begin()
  				, end(m_torrent.end()); i != end; ++i)
  			{
  				peer_connection* peer = *i;
  				if (!send_peer(*peer)) continue;
  
  				tcp::endpoint remote = peer->remote();
  				m_old_peers.insert(remote);
  
  				std::set<tcp::endpoint>::iterator di = dropped.find(remote);
  				if (di == dropped.end())
  				{
  					// don't write too big of a package
  					if (num_added >= max_peer_entries) break;
  
  					// only send proper bittorrent peers
  					if (peer->type() != connection_type::bittorrent)
  						continue;
  
  					bt_peer_connection* p = static_cast<bt_peer_connection*>(peer);
  
  					// if the peer has told us which port its listening on,
  					// use that port. But only if we didn't connect to the peer.
  					// if we connected to it, use the port we know works
  					if (!p->is_outgoing())
  					{
  						torrent_peer const* const pi = peer->peer_info_struct();
  						if (pi != nullptr && pi->port > 0)
  							remote.port(pi->port);
  					}
  
  					// no supported flags to set yet
  					// 0x01 - peer supports encryption
  					// 0x02 - peer is a seed
  					// 0x04 - supports uTP. This is only a positive flags
  					//        passing 0 doesn't mean the peer doesn't
  					//        support uTP
  					// 0x08 - supports holepunching protocol. If this
  					//        flag is received from a peer, it can be
  					//        used as a rendezvous point in case direct
  					//        connections to the peer fail
  					int flags = p->is_seed() ? 2 : 0;
  #if !defined(TORRENT_DISABLE_ENCRYPTION) && !defined(TORRENT_DISABLE_EXTENSIONS)
  					flags |= p->supports_encryption() ? 1 : 0;
  #endif
  					flags |= is_utp(*p->get_socket()) ? 4 :  0;
  					flags |= p->supports_holepunch() ? 8 : 0;
  
  					// i->first was added since the last time
  					if (remote.address().is_v4())
  					{
  						detail::write_endpoint(remote, pla_out);
  						detail::write_uint8(flags, plf_out);
  					}
  #if TORRENT_USE_IPV6
  					else
  					{
  						detail::write_endpoint(remote, pla6_out);
  						detail::write_uint8(flags, plf6_out);
  					}
  #endif
  					++num_added;
  					++m_peers_in_message;
  				}
  				else
  				{
  					// this was in the previous message
  					// so, it wasn't dropped
  					dropped.erase(di);
  				}
  			}
  
  			for (std::set<tcp::endpoint>::const_iterator i = dropped.begin()
  				, end(dropped.end()); i != end; ++i)
  			{
  				if (i->address().is_v4())
  					detail::write_endpoint(*i, pld_out);
  #if TORRENT_USE_IPV6
  				else
  					detail::write_endpoint(*i, pld6_out);
  #endif
  				++m_peers_in_message;
  			}
  
  			m_ut_pex_msg.clear();
  			bencode(std::back_inserter(m_ut_pex_msg), pex);
  		}
  
  	private:
  		torrent& m_torrent;
  
  		std::set<tcp::endpoint> m_old_peers;
  		time_point m_last_msg;
  		std::vector<char> m_ut_pex_msg;
  		int m_peers_in_message;
  
  		// explicitly disallow assignment, to silence msvc warning
  		ut_pex_plugin& operator=(ut_pex_plugin const&);
  	};
  
  	struct ut_pex_peer_plugin final
  		: ut_pex_peer_store, peer_plugin
  	{
  		ut_pex_peer_plugin(torrent& t, peer_connection& pc, ut_pex_plugin& tp)
  			: m_torrent(t)
  			, m_pc(pc)
  			, m_tp(tp)
  			, m_last_msg(min_time())
  			, m_message_index(0)
  			, m_first_time(true)
  		{
  			const int num_pex_timers = sizeof(m_last_pex) / sizeof(m_last_pex[0]);
  			for (int i = 0; i < num_pex_timers; ++i)
  			{
  				m_last_pex[i] = min_time();
  			}
  		}
  
  		void add_handshake(entry& h) override
  		{
  			entry& messages = h["m"];
  			messages[extension_name] = extension_index;
  		}
  
  		bool on_extension_handshake(bdecode_node const& h) override
  		{
  			m_message_index = 0;
  			if (h.type() != bdecode_node::dict_t) return false;
  			bdecode_node messages = h.dict_find_dict("m");
  			if (!messages) return false;
  
  			int index = int(messages.dict_find_int_value(extension_name, -1));
  			if (index == -1) return false;
  			m_message_index = index;
  			return true;
  		}
  
  		bool on_extended(int length, int msg, span<char const> body) override
  		{
  			if (msg != extension_index) return false;
  			if (m_message_index == 0) return false;
  
  			if (length > 500 * 1024)
  			{
  				m_pc.disconnect(errors::pex_message_too_large, op_bittorrent, 2);
  				return true;
  			}
  
  			if (int(body.size()) < length) return true;
  
  			time_point now = aux::time_now();
  			if (now - seconds(60) <  m_last_pex[0])
  			{
  				// this client appears to be trying to flood us
  				// with pex messages. Don't allow that.
  				m_pc.disconnect(errors::too_frequent_pex, op_bittorrent);
  				return true;
  			}
  
  			int const num_pex_timers = sizeof(m_last_pex) / sizeof(m_last_pex[0]);
  			for (int i = 0; i < num_pex_timers - 1; ++i)
  				m_last_pex[i] = m_last_pex[i + 1];
  			m_last_pex[num_pex_timers - 1] = now;
  
  			bdecode_node pex_msg;
  			error_code ec;
  			int const ret = bdecode(body.begin(), body.end(), pex_msg, ec);
  			if (ret != 0 || pex_msg.type() != bdecode_node::dict_t)
  			{
  				m_pc.disconnect(errors::invalid_pex_message, op_bittorrent, 2);
  				return true;
  			}
  
  			bdecode_node p = pex_msg.dict_find_string("dropped");
  
  #ifndef TORRENT_DISABLE_LOGGING
  			int num_dropped = 0;
  			int num_added = 0;
  			if (p) num_dropped += p.string_length() / 6;
  #endif
  			if (p)
  			{
  				int const num_peers = p.string_length() / 6;
  				char const* in = p.string_ptr();
  
  				for (int i = 0; i < num_peers; ++i)
  				{
  					tcp::endpoint adr = detail::read_v4_endpoint<tcp::endpoint>(in);
  					peers4_t::value_type v(adr.address().to_v4().to_bytes(), adr.port());
  					peers4_t::iterator j = std::lower_bound(m_peers.begin(), m_peers.end(), v);
  					if (j != m_peers.end() && *j == v) m_peers.erase(j);
  				}
  			}
  
  			p = pex_msg.dict_find_string("added");
  			bdecode_node pf = pex_msg.dict_find_string("added.f");
  
  #ifndef TORRENT_DISABLE_LOGGING
  			if (p) num_added += p.string_length() / 6;
  #endif
  			if (p && pf && pf.string_length() == p.string_length() / 6)
  			{
  				int const num_peers = pf.string_length();
  				char const* in = p.string_ptr();
  				char const* fin = pf.string_ptr();
  
  				for (int i = 0; i < num_peers; ++i)
  				{
  					tcp::endpoint adr = detail::read_v4_endpoint<tcp::endpoint>(in);
  					char const flags = *fin++;
  
  					if (int(m_peers.size()) >= m_torrent.settings().get_int(settings_pack::max_pex_peers))
  						break;
  
  					// ignore local addresses unless the peer is local to us
  					if (is_local(adr.address()) && !is_local(m_pc.remote().address())) continue;
  
  					peers4_t::value_type v(adr.address().to_v4().to_bytes(), adr.port());
  					peers4_t::iterator j = std::lower_bound(m_peers.begin(), m_peers.end(), v);
  					// do we already know about this peer?
  					if (j != m_peers.end() && *j == v) continue;
  					m_peers.insert(j, v);
  					m_torrent.add_peer(adr, peer_info::pex, flags);
  				}
  			}
  
  #if TORRENT_USE_IPV6
  
  			bdecode_node p6 = pex_msg.dict_find("dropped6");
  #ifndef TORRENT_DISABLE_LOGGING
  			if (p6) num_dropped += p6.string_length() / 18;
  #endif
  			if (p6.type() == bdecode_node::string_t)
  			{
  				int const num_peers = p6.string_length() / 18;
  				char const* in = p6.string_ptr();
  
  				for (int i = 0; i < num_peers; ++i)
  				{
  					tcp::endpoint adr = detail::read_v6_endpoint<tcp::endpoint>(in);
  					peers6_t::value_type v(adr.address().to_v6().to_bytes(), adr.port());
  					peers6_t::iterator j = std::lower_bound(m_peers6.begin(), m_peers6.end(), v);
  					if (j != m_peers6.end() && *j == v) m_peers6.erase(j);
  				}
  			}
  
  			p6 = pex_msg.dict_find("added6");
  #ifndef TORRENT_DISABLE_LOGGING
  			if (p6) num_added += p6.string_length() / 18;
  #endif
  			bdecode_node p6f = pex_msg.dict_find("added6.f");
  			if (p6.type() == bdecode_node::string_t
  				&& p6f.type() == bdecode_node::string_t
  				&& p6f.string_length() == p6.string_length() / 18)
  			{
  				int const num_peers = p6f.string_length();
  				char const* in = p6.string_ptr();
  				char const* fin = p6f.string_ptr();
  
  				for (int i = 0; i < num_peers; ++i)
  				{
  					tcp::endpoint adr = detail::read_v6_endpoint<tcp::endpoint>(in);
  					char const flags = *fin++;
  					// ignore local addresses unless the peer is local to us
  					if (is_local(adr.address()) && !is_local(m_pc.remote().address())) continue;
  					if (int(m_peers6.size()) >= m_torrent.settings().get_int(settings_pack::max_pex_peers))
  						break;
  
  					peers6_t::value_type v(adr.address().to_v6().to_bytes(), adr.port());
  					peers6_t::iterator j = std::lower_bound(m_peers6.begin(), m_peers6.end(), v);
  					// do we already know about this peer?
  					if (j != m_peers6.end() && *j == v) continue;
  					m_peers6.insert(j, v);
  					m_torrent.add_peer(adr, peer_info::pex, flags);
  				}
  			}
  #endif
  #ifndef TORRENT_DISABLE_LOGGING
  			m_pc.peer_log(peer_log_alert::incoming_message, "PEX", "dropped: %d added: %d"
  				, num_dropped, num_added);
  #endif
  
  			m_pc.stats_counters().inc_stats_counter(counters::num_incoming_pex);
  			return true;
  		}
  
  		// the peers second tick
  		// every minute we send a pex message
  		void tick() override
  		{
  			// no handshake yet
  			if (!m_message_index) return;
  
  			time_point const now = aux::time_now();
  			if (now - seconds(60) < m_last_msg)
  			{
  #ifndef TORRENT_DISABLE_LOGGING
  //				m_pc.peer_log(peer_log_alert::info, "PEX", "waiting: %d seconds to next msg"
  //					, int(total_seconds(seconds(60) - (now - m_last_msg))));
  #endif
  				return;
  			}
  			static time_point global_last = min_time();
  
  			int const num_peers = m_torrent.num_peers();
  			if (num_peers <= 1) return;
  
  			// don't send pex messages more often than 1 every 100 ms, and
  			// allow pex messages to be sent 5 seconds apart if there isn't
  			// contention
  			int delay = (std::min)((std::max)(60000 / num_peers, 100), 3000);
  
  			if (now - milliseconds(delay) < global_last)
  			{
  #ifndef TORRENT_DISABLE_LOGGING
  //				m_pc.peer_log(peer_log_alert::info, "PEX", "global-wait: %d"
  //					, int(total_seconds(milliseconds(delay) - (now - global_last))));
  #endif
  				return;
  			}
  
  			// this will allow us to catch up, even if our timer
  			// has lower resolution than delay
  			if (global_last == min_time())
  				global_last = now;
  			else
  				global_last += milliseconds(delay);
  
  			m_last_msg = now;
  
  			if (m_first_time)
  			{
  				send_ut_peer_list();
  				m_first_time = false;
  			}
  			else
  			{
  				send_ut_peer_diff();
  			}
  		}
  
  		void send_ut_peer_diff()
  		{
  			// if there's no change in out peer set, don't send anything
  			if (m_tp.peers_in_msg() == 0) return;
  
  			std::vector<char> const& pex_msg = m_tp.get_ut_pex_msg();
  
  			char msg[6];
  			char* ptr = msg;
  
  			detail::write_uint32(1 + 1 + int(pex_msg.size()), ptr);
  			detail::write_uint8(bt_peer_connection::msg_extended, ptr);
  			detail::write_uint8(m_message_index, ptr);
  			m_pc.send_buffer(msg, sizeof(msg));
  			m_pc.send_buffer(&pex_msg[0], int(pex_msg.size()));
  
  			m_pc.stats_counters().inc_stats_counter(counters::num_outgoing_extended);
  			m_pc.stats_counters().inc_stats_counter(counters::num_outgoing_pex);
  
  #ifndef TORRENT_DISABLE_LOGGING
  			if (m_pc.should_log(peer_log_alert::outgoing_message))
  			{
  				bdecode_node m;
  				error_code ec;
  				int ret = bdecode(&pex_msg[0], &pex_msg[0] + pex_msg.size(), m, ec);
  				TORRENT_ASSERT(ret == 0);
  				TORRENT_ASSERT(!ec);
  				TORRENT_UNUSED(ret);
  				int num_dropped = 0;
  				int num_added = 0;
  				bdecode_node e = m.dict_find_string("added");
  				if (e) num_added += e.string_length() / 6;
  				e = m.dict_find_string("dropped");
  				if (e) num_dropped += e.string_length() / 6;
  				e = m.dict_find_string("added6");
  				if (e) num_added += e.string_length() / 18;
  				e = m.dict_find_string("dropped6");
  				if (e) num_dropped += e.string_length() / 18;
  				m_pc.peer_log(peer_log_alert::outgoing_message, "PEX_DIFF", "dropped: %d added: %d msg_size: %d"
  					, num_dropped, num_added, int(pex_msg.size()));
  			}
  #endif
  		}
  
  		void send_ut_peer_list()
  		{
  			entry pex;
  			// leave the dropped string empty
  			pex["dropped"].string();
  			std::string& pla = pex["added"].string();
  			std::string& plf = pex["added.f"].string();
  			std::back_insert_iterator<std::string> pla_out(pla);
  			std::back_insert_iterator<std::string> plf_out(plf);
  
  #if TORRENT_USE_IPV6
  			pex["dropped6"].string();
  			std::string& pla6 = pex["added6"].string();
  			std::string& plf6 = pex["added6.f"].string();
  			std::back_insert_iterator<std::string> pla6_out(pla6);
  			std::back_insert_iterator<std::string> plf6_out(plf6);
  #endif
  
  			int num_added = 0;
  			for (torrent::peer_iterator i = m_torrent.begin()
  				, end(m_torrent.end()); i != end; ++i)
  			{
  				peer_connection* peer = *i;
  				if (!send_peer(*peer)) continue;
  
  				// don't write too big of a package
  				if (num_added >= max_peer_entries) break;
  
  				// only send proper bittorrent peers
  				if (peer->type() != connection_type::bittorrent)
  					continue;
  
  				bt_peer_connection* p = static_cast<bt_peer_connection*>(peer);
  
  				// no supported flags to set yet
  				// 0x01 - peer supports encryption
  				// 0x02 - peer is a seed
  				// 0x04 - supports uTP. This is only a positive flags
  				//        passing 0 doesn't mean the peer doesn't
  				//        support uTP
  				// 0x08 - supports holepunching protocol. If this
  				//        flag is received from a peer, it can be
  				//        used as a rendezvous point in case direct
  				//        connections to the peer fail
  				int flags = p->is_seed() ? 2 : 0;
  #if !defined(TORRENT_DISABLE_ENCRYPTION) && !defined(TORRENT_DISABLE_EXTENSIONS)
  				flags |= p->supports_encryption() ? 1 : 0;
  #endif
  				flags |= is_utp(*p->get_socket()) ? 4 :  0;
  				flags |= p->supports_holepunch() ? 8 : 0;
  
  				tcp::endpoint remote = peer->remote();
  
  				if (!p->is_outgoing())
  				{
  					torrent_peer const* const pi = peer->peer_info_struct();
  					if (pi != nullptr && pi->port > 0)
  						remote.port(pi->port);
  				}
  
  				// i->first was added since the last time
  				if (remote.address().is_v4())
  				{
  					detail::write_endpoint(remote, pla_out);
  					detail::write_uint8(flags, plf_out);
  				}
  #if TORRENT_USE_IPV6
  				else
  				{
  					detail::write_endpoint(remote, pla6_out);
  					detail::write_uint8(flags, plf6_out);
  				}
  #endif
  				++num_added;
  			}
  			std::vector<char> pex_msg;
  			bencode(std::back_inserter(pex_msg), pex);
  
  			char msg[6];
  			char* ptr = msg;
  
  			detail::write_uint32(1 + 1 + int(pex_msg.size()), ptr);
  			detail::write_uint8(bt_peer_connection::msg_extended, ptr);
  			detail::write_uint8(m_message_index, ptr);
  			m_pc.send_buffer(msg, sizeof(msg));
  			m_pc.send_buffer(&pex_msg[0], int(pex_msg.size()));
  
  			m_pc.stats_counters().inc_stats_counter(counters::num_outgoing_extended);
  			m_pc.stats_counters().inc_stats_counter(counters::num_outgoing_pex);
  
  #ifndef TORRENT_DISABLE_LOGGING
  			m_pc.peer_log(peer_log_alert::outgoing_message, "PEX_FULL"
  				, "added: %d msg_size: %d", num_added, int(pex_msg.size()));
  #endif
  		}
  
  		torrent& m_torrent;
  		peer_connection& m_pc;
  		ut_pex_plugin& m_tp;
  
  		// the last pex messages we received
  		// [0] is the oldest one. There is a problem with
  		// rate limited connections, because we may sit
  		// for a long time, accumulating pex messages, and
  		// then once we read from the socket it will look like
  		// we received them all back to back. That's why
  		// we look at 6 pex messages back.
  		time_point m_last_pex[6];
  
  		time_point m_last_msg;
  		int m_message_index;
  
  		// this is initialized to true, and set to
  		// false after the first pex message has been sent.
  		// it is used to know if a diff message or a) ful
  		// message should be sent.
  		bool m_first_time;
  
  		// explicitly disallow assignment, to silence msvc warning
  		ut_pex_peer_plugin& operator=(ut_pex_peer_plugin const&);
  	};
  
  	std::shared_ptr<peer_plugin> ut_pex_plugin::new_connection(peer_connection_handle const& pc)
  	{
  		if (pc.type() != connection_type::bittorrent)
  			return std::shared_ptr<peer_plugin>();
  
  		bt_peer_connection* c = static_cast<bt_peer_connection*>(pc.native_handle().get());
  		auto p = std::make_shared<ut_pex_peer_plugin>(m_torrent, *c, *this);
  		c->set_ut_pex(p);
  		return p;
  	}
  } }
  
  namespace libtorrent
  {
  	std::shared_ptr<torrent_plugin> create_ut_pex_plugin(torrent_handle const& th, void*)
  	{
  		torrent* t = th.native_handle().get();
  		if (t->torrent_file().priv() || (t->torrent_file().is_i2p()
  			&& !t->settings().get_bool(settings_pack::allow_i2p_mixed)))
  		{
  			return std::shared_ptr<torrent_plugin>();
  		}
  		return std::make_shared<ut_pex_plugin>(*t);
  	}
  }
  
  #endif
  