text: /*
  
  Copyright (c) 2007-2016, 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 <cstdlib>
  #include <cstdarg>
  #include <functional>
  #include <cstdio> // for vsnprintf
  
  #include "libtorrent/lsd.hpp"
  #include "libtorrent/time.hpp"
  #include "libtorrent/random.hpp"
  #include "libtorrent/http_parser.hpp"
  #include "libtorrent/socket_io.hpp" // for print_address
  #include "libtorrent/debug.hpp"
  #include "libtorrent/hex.hpp" // to_hex, from_hex
  
  using namespace std::placeholders;
  
  namespace libtorrent
  {
  namespace {
  
  int render_lsd_packet(char* dst, int const len, int const listen_port
  	, char const* info_hash_hex, int const cookie, char const* host)
  {
  	TORRENT_ASSERT(len > 0);
  	return std::snprintf(dst, len,
  		"BT-SEARCH * HTTP/1.1\r\n"
  		"Host: %s:6771\r\n"
  		"Port: %d\r\n"
  		"Infohash: %s\r\n"
  		"cookie: %x\r\n"
  		"\r\n\r\n", host, listen_port, info_hash_hex, cookie);
  }
  } // anonymous namespace
  
  static error_code dummy;
  
  lsd::lsd(io_service& ios, aux::lsd_callback& cb)
  	: m_callback(cb)
  	, m_socket(udp::endpoint(address_v4::from_string("239.192.152.143", dummy), 6771))
  #if TORRENT_USE_IPV6
  	, m_socket6(udp::endpoint(address_v6::from_string("ff15::efc0:988f", dummy), 6771))
  #endif
  	, m_broadcast_timer(ios)
  	, m_cookie((random(0x7fffffff) ^ std::uintptr_t(this)) & 0x7fffffff)
  	, m_disabled(false)
  #if TORRENT_USE_IPV6
  	, m_disabled6(false)
  #endif
  {
  }
  
  #ifndef TORRENT_DISABLE_LOGGING
  bool lsd::should_log() const
  {
  	return m_callback.should_log_lsd();
  }
  
  TORRENT_FORMAT(2, 3)
  void lsd::debug_log(char const* fmt, ...) const
  {
  	if (!should_log()) return;
  	va_list v;
  	va_start(v, fmt);
  
  	char buf[1024];
  	std::vsnprintf(buf, sizeof(buf), fmt, v);
  	va_end(v);
  	m_callback.log_lsd(buf);
  }
  #endif
  
  void lsd::start(error_code& ec)
  {
  	m_socket.open(std::bind(&lsd::on_announce, self(), _1, _2, _3)
  		, m_broadcast_timer.get_io_service(), ec);
  	if (ec) return;
  
  #if TORRENT_USE_IPV6
  	m_socket6.open(std::bind(&lsd::on_announce, self(), _1, _2, _3)
  		, m_broadcast_timer.get_io_service(), ec);
  #endif
  }
  
  lsd::~lsd() = default;
  
  void lsd::announce(sha1_hash const& ih, int listen_port, bool broadcast)
  {
  	announce_impl(ih, listen_port, broadcast, 0);
  }
  
  void lsd::announce_impl(sha1_hash const& ih, int const listen_port
  	, bool const broadcast, int retry_count)
  {
  #if TORRENT_USE_IPV6
  	if (m_disabled && m_disabled6) return;
  #else
  	if (m_disabled) return;
  #endif
  
  	char msg[200];
  
  #ifndef TORRENT_DISABLE_LOGGING
  	debug_log("==> LSD: ih: %s port: %u\n", aux::to_hex(ih).c_str(), listen_port);
  #endif
  
  	error_code ec;
  	if (!m_disabled)
  	{
  		int const msg_len = render_lsd_packet(msg, sizeof(msg), listen_port, aux::to_hex(ih).c_str()
  			, m_cookie, "239.192.152.143");
  		m_socket.send(msg, msg_len, ec, broadcast ? broadcast_socket::flag_broadcast : 0);
  		if (ec)
  		{
  			m_disabled = true;
  #ifndef TORRENT_DISABLE_LOGGING
  			if (should_log())
  			{
  				debug_log("*** LSD: failed to send message: (%d) %s", ec.value()
  					, ec.message().c_str());
  			}
  #endif
  		}
  	}
  
  #if TORRENT_USE_IPV6
  	if (!m_disabled6)
  	{
  		int const msg_len = render_lsd_packet(msg, sizeof(msg), listen_port, aux::to_hex(ih).c_str()
  			, m_cookie, "[ff15::efc0:988f]");
  		m_socket6.send(msg, msg_len, ec, broadcast ? broadcast_socket::flag_broadcast : 0);
  		if (ec)
  		{
  			m_disabled6 = true;
  #ifndef TORRENT_DISABLE_LOGGING
  			if (should_log())
  			{
  				debug_log("*** LSD: failed to send message6: (%d) %s", ec.value()
  					, ec.message().c_str());
  			}
  #endif
  		}
  	}
  #endif
  
  	++retry_count;
  	if (retry_count >= 3) return;
  
  #if TORRENT_USE_IPV6
  	if (m_disabled && m_disabled6) return;
  #else
  	if (m_disabled) return;
  #endif
  
  	ADD_OUTSTANDING_ASYNC("lsd::resend_announce");
  	m_broadcast_timer.expires_from_now(seconds(2 * retry_count), ec);
  	m_broadcast_timer.async_wait(std::bind(&lsd::resend_announce, self(), _1
  		, ih, listen_port, retry_count));
  }
  
  void lsd::resend_announce(error_code const& e, sha1_hash const& info_hash
  	, int listen_port, int retry_count)
  {
  	COMPLETE_ASYNC("lsd::resend_announce");
  	if (e) return;
  
  	announce_impl(info_hash, listen_port, false, retry_count);
  }
  
  void lsd::on_announce(udp::endpoint const& from, char const* buf
  	, std::size_t const bytes_transferred)
  {
  	http_parser p;
  
  	bool error = false;
  	p.incoming({buf, bytes_transferred}, error);
  
  	if (!p.header_finished() || error)
  	{
  #ifndef TORRENT_DISABLE_LOGGING
  		debug_log("<== LSD: incomplete HTTP message");
  #endif
  		return;
  	}
  
  	if (p.method() != "bt-search")
  	{
  #ifndef TORRENT_DISABLE_LOGGING
  		debug_log("<== LSD: invalid HTTP method: %s", p.method().c_str());
  #endif
  		return;
  	}
  
  	std::string const& port_str = p.header("port");
  	if (port_str.empty())
  	{
  #ifndef TORRENT_DISABLE_LOGGING
  		debug_log("<== LSD: invalid BT-SEARCH, missing port");
  #endif
  		return;
  	}
  
  	long const port = std::strtol(port_str.c_str(), nullptr, 10);
  	if (port <= 0 || port >= int(std::numeric_limits<std::uint16_t>::max()))
  	{
  #ifndef TORRENT_DISABLE_LOGGING
  		debug_log("<== LSD: invalid BT-SEARCH port value: %s", port_str.c_str());
  #endif
  		return;
  	}
  
  	auto const& headers = p.headers();
  
  	auto const cookie_iter = headers.find("cookie");
  	if (cookie_iter != headers.end())
  	{
  		// we expect it to be hexadecimal
  		// if it isn't, it's not our cookie anyway
  		long const cookie = std::strtol(cookie_iter->second.c_str(), nullptr, 16);
  		if (cookie == m_cookie)
  		{
  #ifndef TORRENT_DISABLE_LOGGING
  			debug_log("<== LSD: ignoring packet (cookie matched our own): %x"
  				, m_cookie);
  #endif
  			return;
  		}
  	}
  
  	auto const ihs = headers.equal_range("infohash");
  	for (auto i = ihs.first; i != ihs.second; ++i)
  	{
  		std::string const& ih_str = i->second;
  		if (ih_str.size() != 40)
  		{
  #ifndef TORRENT_DISABLE_LOGGING
  			debug_log("<== LSD: invalid BT-SEARCH, invalid infohash: %s"
  				, ih_str.c_str());
  #endif
  			continue;
  		}
  
  		sha1_hash ih;
  		aux::from_hex(ih_str, ih.data());
  
  		if (!ih.is_all_zeros() && port != 0)
  		{
  #ifndef TORRENT_DISABLE_LOGGING
  			if (should_log())
  			{
  				debug_log("<== LSD: %s:%d ih: %s"
  					, print_address(from.address()).c_str()
  					, int(port), ih_str.c_str());
  			}
  #endif
  			// we got an announce, pass it on through the callback
  			m_callback.on_lsd_peer(tcp::endpoint(from.address(), std::uint16_t(port)), ih);
  		}
  	}
  }
  
  void lsd::close()
  {
  	m_socket.close();
  #if TORRENT_USE_IPV6
  	m_socket6.close();
  #endif
  	error_code ec;
  	m_broadcast_timer.cancel(ec);
  	m_disabled = true;
  #if TORRENT_USE_IPV6
  	m_disabled6 = true;
  #endif
  }
  
  } // libtorrent namespace
  