text: /*
  
  Copyright (c) 2007-2019, Arvid Norberg
  Copyright (c) 2015, Mikhail Titov
  Copyright (c) 2016-2018, Alden Torres
  Copyright (c) 2016, Andrei Kurushin
  Copyright (c) 2017, Jan Berkel
  Copyright (c) 2017, Steven Siloti
  Copyright (c) 2019, patch3proxyheaders915360
  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/http_connection.hpp"
  #include "libtorrent/aux_/escape_string.hpp"
  #include "libtorrent/aux_/instantiate_connection.hpp"
  #include "libtorrent/gzip.hpp"
  #include "libtorrent/parse_url.hpp"
  #include "libtorrent/socket.hpp"
  #include "libtorrent/aux_/socket_type.hpp" // for async_shutdown
  #include "libtorrent/aux_/resolver_interface.hpp"
  #include "libtorrent/settings_pack.hpp"
  #include "libtorrent/aux_/time.hpp"
  #include "libtorrent/random.hpp"
  #include "libtorrent/debug.hpp"
  #include "libtorrent/time.hpp"
  #include "libtorrent/io_context.hpp"
  #include "libtorrent/i2p_stream.hpp"
  #include "libtorrent/aux_/ip_helpers.hpp"
  #include "libtorrent/ssl.hpp"
  
  #include <functional>
  #include <string>
  #include <algorithm>
  #include <sstream>
  
  using namespace std::placeholders;
  
  namespace libtorrent {
  
  http_connection::http_connection(io_context& ios
  	, aux::resolver_interface& resolver
  	, http_handler handler
  	, bool bottled
  	, int max_bottled_buffer_size
  	, http_connect_handler ch
  	, http_filter_handler fh
  #if TORRENT_USE_SSL
  	, ssl::context* ssl_ctx
  #endif
  	)
  	: m_ios(ios)
  	, m_next_ep(0)
  #if TORRENT_USE_SSL
  	, m_ssl_ctx(ssl_ctx)
  #endif
  #if TORRENT_USE_I2P
  	, m_i2p_conn(nullptr)
  #endif
  	, m_resolver(resolver)
  	, m_handler(std::move(handler))
  	, m_connect_handler(std::move(ch))
  	, m_filter_handler(std::move(fh))
  	, m_timer(ios)
  	, m_completion_timeout(seconds(5))
  	, m_limiter_timer(ios)
  	, m_last_receive(aux::time_now())
  	, m_start_time(aux::time_now())
  	, m_read_pos(0)
  	, m_redirects(5)
  	, m_max_bottled_buffer_size(max_bottled_buffer_size)
  	, m_rate_limit(0)
  	, m_download_quota(0)
  	, m_priority(0)
  	, m_resolve_flags{}
  	, m_port(0)
  	, m_bottled(bottled)
  	, m_called(false)
  	, m_limiter_timer_active(false)
  	, m_ssl(false)
  	, m_abort(false)
  	, m_connecting(false)
  {
  	TORRENT_ASSERT(m_handler);
  }
  
  http_connection::~http_connection() = default;
  
  void http_connection::get(std::string const& url, time_duration timeout, int prio
  	, aux::proxy_settings const* ps, int handle_redirects, std::string const& user_agent
  	, boost::optional<address> const& bind_addr, aux::resolver_flags const resolve_flags, std::string const& auth_
  #if TORRENT_USE_I2P
  	, i2p_connection* i2p_conn
  #endif
  	)
  {
  	m_user_agent = user_agent;
  	m_resolve_flags = resolve_flags;
  
  	std::string protocol;
  	std::string auth;
  	std::string hostname;
  	std::string path;
  	error_code ec;
  	int port;
  
  	std::tie(protocol, auth, hostname, port, path)
  		= parse_url_components(url, ec);
  
  	if (auth.empty()) auth = auth_;
  
  	m_auth = auth;
  
  	int default_port = protocol == "https" ? 443 : 80;
  	if (port == -1) port = default_port;
  
  	// keep ourselves alive even if the callback function
  	// deletes this object
  	std::shared_ptr<http_connection> me(shared_from_this());
  
  	if (ec)
  	{
  		post(m_ios, std::bind(&http_connection::callback
  			, me, ec, span<char>{}));
  		return;
  	}
  
  	if (protocol != "http"
  #if TORRENT_USE_SSL
  		&& protocol != "https"
  #endif
  		)
  	{
  		error_code err(errors::unsupported_url_protocol);
  		post(m_ios, std::bind(&http_connection::callback
  			, me, err, span<char>{}));
  		return;
  	}
  
  	TORRENT_ASSERT(prio >= 0 && prio < 3);
  
  	bool const ssl = (protocol == "https");
  
  	std::stringstream request;
  
  	// exclude ssl here, because SSL assumes CONNECT support in the
  	// proxy and is handled at the lower layer
  	if (ps && (ps->type == settings_pack::http
  		|| ps->type == settings_pack::http_pw)
  		&& !ssl)
  	{
  		// if we're using an http proxy and not an ssl
  		// connection, just do a regular http proxy request
  		request << "GET " << url << " HTTP/1.1\r\n";
  		if (ps->type == settings_pack::http_pw)
  			request << "Proxy-Authorization: Basic " << base64encode(
  				ps->username + ":" + ps->password) << "\r\n";
  
  		request << "Host: " << hostname;
  		if (port != default_port) request << ":" << port << "\r\n";
  		else request << "\r\n";
  
  		hostname = ps->hostname;
  		port = ps->port;
  	}
  	else
  	{
  		request << "GET " << path << " HTTP/1.1\r\nHost: " << hostname;
  		if (port != default_port) request << ":" << port << "\r\n";
  		else request << "\r\n";
  	}
  
  //	request << "Accept: */*\r\n";
  
  	if (!m_user_agent.empty())
  		request << "User-Agent: " << m_user_agent << "\r\n";
  
  	if (m_bottled)
  		request << "Accept-Encoding: gzip\r\n";
  
  	if (!auth.empty())
  		request << "Authorization: Basic " << base64encode(auth) << "\r\n";
  
  	request << "Connection: close\r\n\r\n";
  
  	m_sendbuffer.assign(request.str());
  	m_url = url;
  	start(hostname, port, timeout, prio
  		, ps, ssl, handle_redirects, bind_addr, m_resolve_flags
  #if TORRENT_USE_I2P
  		, i2p_conn
  #endif
  		);
  }
  
  void http_connection::start(std::string const& hostname, int port
  	, time_duration timeout, int prio, aux::proxy_settings const* ps, bool ssl
  	, int handle_redirects
  	, boost::optional<address> const& bind_addr
  	, aux::resolver_flags const resolve_flags
  #if TORRENT_USE_I2P
  	, i2p_connection* i2p_conn
  #endif
  	)
  {
  	TORRENT_ASSERT(prio >= 0 && prio < 3);
  
  	m_redirects = handle_redirects;
  	m_resolve_flags = resolve_flags;
  	if (ps) m_proxy = *ps;
  
  	// keep ourselves alive even if the callback function
  	// deletes this object
  	std::shared_ptr<http_connection> me(shared_from_this());
  
  	m_completion_timeout = timeout;
  	m_timer.expires_after(m_completion_timeout);
  	ADD_OUTSTANDING_ASYNC("http_connection::on_timeout");
  	m_timer.async_wait(std::bind(&http_connection::on_timeout
  		, std::weak_ptr<http_connection>(me), _1));
  	m_called = false;
  	m_parser.reset();
  	m_recvbuffer.clear();
  	m_read_pos = 0;
  	m_priority = prio;
  
  #if TORRENT_USE_SSL
  	TORRENT_ASSERT(!ssl || m_ssl_ctx != nullptr);
  #endif
  
  	if (m_sock && m_sock->is_open() && m_hostname == hostname && m_port == port
  		&& m_ssl == ssl && m_bind_addr == bind_addr)
  	{
  		ADD_OUTSTANDING_ASYNC("http_connection::on_write");
  		async_write(*m_sock, boost::asio::buffer(m_sendbuffer)
  			, std::bind(&http_connection::on_write, me, _1));
  	}
  	else
  	{
  		m_ssl = ssl;
  		m_bind_addr = bind_addr;
  		error_code err;
  		if (m_sock && m_sock->is_open()) m_sock->close(err);
  
  		aux::proxy_settings const* proxy = ps;
  
  #if TORRENT_USE_I2P
  		bool is_i2p = false;
  		char const* top_domain = strrchr(hostname.c_str(), '.');
  		aux::proxy_settings i2p_proxy;
  		if (top_domain && top_domain == ".i2p"_sv && i2p_conn)
  		{
  			// this is an i2p name, we need to use the sam connection
  			// to do the name lookup
  			is_i2p = true;
  			m_i2p_conn = i2p_conn;
  			// quadruple the timeout for i2p destinations
  			// because i2p is sloooooow
  			m_completion_timeout *= 4;
  
  #if TORRENT_USE_I2P
  			if (i2p_conn->proxy().type != settings_pack::i2p_proxy)
  			{
  				post(m_ios, std::bind(&http_connection::callback
  					, me, error_code(errors::no_i2p_router), span<char>{}));
  				return;
  			}
  #endif
  
  			i2p_proxy = i2p_conn->proxy();
  			proxy = &i2p_proxy;
  		}
  #endif
  
  		// in this case, the upper layer is assumed to have taken
  		// care of the proxying already. Don't instantiate the socket
  		// with this proxy
  		if (proxy && (proxy->type == settings_pack::http
  			|| proxy->type == settings_pack::http_pw)
  			&& !ssl)
  		{
  			proxy = nullptr;
  		}
  		aux::proxy_settings null_proxy;
  
  		void* userdata = nullptr;
  #if TORRENT_USE_SSL
  		if (m_ssl)
  		{
  			TORRENT_ASSERT(m_ssl_ctx != nullptr);
  			userdata = m_ssl_ctx;
  		}
  #endif
  		// assume this is not a tracker connection. Tracker connections that
  		// shouldn't be subject to the proxy should pass in nullptr as the proxy
  		// pointer.
  		m_sock.emplace(instantiate_connection(m_ios
  			, proxy ? *proxy : null_proxy, userdata, nullptr, false, false));
  
  		if (m_bind_addr)
  		{
  			error_code ec;
  			m_sock->open(m_bind_addr->is_v4() ? tcp::v4() : tcp::v6(), ec);
  			m_sock->bind(tcp::endpoint(*m_bind_addr, 0), ec);
  			if (ec)
  			{
  				post(m_ios, std::bind(&http_connection::callback
  					, me, ec, span<char>{}));
  				return;
  			}
  		}
  
  		error_code ec;
  		setup_ssl_hostname(*m_sock, hostname, ec);
  		if (ec)
  		{
  			post(m_ios, std::bind(&http_connection::callback
  				, me, ec, span<char>{}));
  			return;
  		}
  
  		m_endpoints.clear();
  		m_next_ep = 0;
  
  #if TORRENT_USE_I2P
  		if (is_i2p)
  		{
  			if (hostname.length() < 516) // Base64 encoded  destination with optional .i2p
  			{
  				ADD_OUTSTANDING_ASYNC("http_connection::on_i2p_resolve");
  				i2p_conn->async_name_lookup(hostname.c_str(), std::bind(&http_connection::on_i2p_resolve
  					, me, _1, _2));
  			}
  			else
  				connect_i2p_tracker(hostname.c_str());
  		}
  		else
  #endif
  		m_hostname = hostname;
  		if (ps && ps->proxy_hostnames
  			&& (ps->type == settings_pack::socks5
  				|| ps->type == settings_pack::socks5_pw))
  		{
  			m_port = std::uint16_t(port);
  			m_endpoints.emplace_back(address(), m_port);
  			connect();
  		}
  		else
  		{
  			ADD_OUTSTANDING_ASYNC("http_connection::on_resolve");
  			m_resolver.async_resolve(hostname, m_resolve_flags
  				, std::bind(&http_connection::on_resolve
  				, me, _1, _2));
  		}
  		m_port = std::uint16_t(port);
  	}
  }
  
  void http_connection::on_timeout(std::weak_ptr<http_connection> p
  	, error_code const& e)
  {
  	COMPLETE_ASYNC("http_connection::on_timeout");
  	std::shared_ptr<http_connection> c = p.lock();
  	if (!c) return;
  
  	if (e == boost::asio::error::operation_aborted) return;
  
  	if (c->m_abort) return;
  
  	time_point const now = clock_type::now();
  
  	if (c->m_start_time + c->m_completion_timeout <= now)
  	{
  		// the connection timed out. If we have more endpoints to try, just
  		// close this connection. The on_connect handler will try the next
  		// endpoint in the list.
  		if (c->m_next_ep < int(c->m_endpoints.size()))
  		{
  			error_code ec;
  			c->m_sock->close(ec);
  			if (!c->m_connecting) c->connect();
  			c->m_last_receive = now;
  			c->m_start_time = c->m_last_receive;
  		}
  		else
  		{
  			// the socket may have an outstanding operation, that keeps the
  			// http_connection object alive. We want to cancel all that.
  			error_code ec;
  			c->m_sock->close(ec);
  			c->callback(boost::asio::error::timed_out);
  			return;
  		}
  	}
  	else
  	{
  		if (!c->m_sock->is_open()) return;
  	}
  
  	ADD_OUTSTANDING_ASYNC("http_connection::on_timeout");
  	c->m_timer.expires_at(c->m_start_time + c->m_completion_timeout);
  	c->m_timer.async_wait(std::bind(&http_connection::on_timeout, p, _1));
  }
  
  void http_connection::close(bool force)
  {
  	if (m_abort) return;
  
  	if (m_sock)
  	{
  		error_code ec;
  		if (force)
  		{
  			m_sock->close(ec);
  			m_timer.cancel();
  		}
  		else
  		{
  			async_shutdown(*m_sock, shared_from_this());
  		}
  	}
  	else
  		m_timer.cancel();
  
  	m_limiter_timer.cancel();
  
  	m_hostname.clear();
  	m_port = 0;
  	m_handler = nullptr;
  	m_abort = true;
  }
  
  #if TORRENT_USE_I2P
  void http_connection::connect_i2p_tracker(char const* destination)
  {
  	TORRENT_ASSERT(boost::get<i2p_stream>(m_sock.get_ptr()));
  #if TORRENT_USE_SSL
  	TORRENT_ASSERT(m_ssl == false);
  #endif
  	boost::get<i2p_stream>(*m_sock).set_destination(destination);
  	boost::get<i2p_stream>(*m_sock).set_command(i2p_stream::cmd_connect);
  	boost::get<i2p_stream>(*m_sock).set_session_id(m_i2p_conn->session_id());
  	ADD_OUTSTANDING_ASYNC("http_connection::on_connect");
  	TORRENT_ASSERT(!m_connecting);
  	m_connecting = true;
  	m_sock->async_connect(tcp::endpoint(), std::bind(&http_connection::on_connect
  		, shared_from_this(), _1));
  }
  
  void http_connection::on_i2p_resolve(error_code const& e, char const* destination)
  {
  	COMPLETE_ASYNC("http_connection::on_i2p_resolve");
  	if (e)
  	{
  		callback(e);
  		return;
  	}
  	connect_i2p_tracker(destination);
  }
  #endif
  
  void http_connection::on_resolve(error_code const& e
  	, std::vector<address> const& addresses)
  {
  	COMPLETE_ASYNC("http_connection::on_resolve");
  	if (e)
  	{
  		callback(e);
  		return;
  	}
  	TORRENT_ASSERT(!addresses.empty());
  
  	for (auto const& addr : addresses)
  		m_endpoints.emplace_back(addr, m_port);
  
  	if (m_filter_handler) m_filter_handler(*this, m_endpoints);
  	if (m_endpoints.empty())
  	{
  		close();
  		return;
  	}
  
  	aux::random_shuffle(m_endpoints);
  
  	// if we have been told to bind to a particular address
  	// only connect to addresses of the same family
  	if (m_bind_addr)
  	{
  		auto const new_end = std::remove_if(m_endpoints.begin(), m_endpoints.end()
  			, [&](tcp::endpoint const& ep) { return aux::is_v4(ep) != m_bind_addr->is_v4(); });
  
  		m_endpoints.erase(new_end, m_endpoints.end());
  		if (m_endpoints.empty())
  		{
  			callback(error_code(boost::system::errc::address_family_not_supported, generic_category()));
  			close();
  			return;
  		}
  	}
  
  	connect();
  }
  
  void http_connection::connect()
  {
  	TORRENT_ASSERT(m_next_ep < int(m_endpoints.size()));
  
  	std::shared_ptr<http_connection> me(shared_from_this());
  
  	if (m_proxy.proxy_hostnames
  		&& (m_proxy.type == settings_pack::socks5
  			|| m_proxy.type == settings_pack::socks5_pw))
  	{
  		// test to see if m_hostname really just is an IP (and not a hostname). If it
  		// is, ec will be represent "success". If so, don't set it as the socks5
  		// hostname, just connect to the IP
  		error_code ec;
  		address adr = make_address(m_hostname, ec);
  
  		if (ec)
  		{
  			// we're using a socks proxy and we're resolving
  			// hostnames through it
  #if TORRENT_USE_SSL
  			if (m_ssl)
  			{
  				TORRENT_ASSERT(boost::get<ssl_stream<socks5_stream>>(m_sock.get_ptr()));
  				boost::get<ssl_stream<socks5_stream>>(*m_sock).next_layer().set_dst_name(m_hostname);
  			}
  			else
  #endif
  			{
  				TORRENT_ASSERT(boost::get<socks5_stream>(m_sock.get_ptr()));
  				boost::get<socks5_stream>(*m_sock).set_dst_name(m_hostname);
  			}
  		}
  		else
  		{
  			m_endpoints[0].address(adr);
  		}
  	}
  
  	TORRENT_ASSERT(m_next_ep < int(m_endpoints.size()));
  	if (m_next_ep >= int(m_endpoints.size())) return;
  
  	tcp::endpoint target_address = m_endpoints[m_next_ep];
  	++m_next_ep;
  
  	ADD_OUTSTANDING_ASYNC("http_connection::on_connect");
  	TORRENT_ASSERT(!m_connecting);
  	m_connecting = true;
  	m_sock->async_connect(target_address, std::bind(&http_connection::on_connect
  		, me, _1));
  }
  
  void http_connection::on_connect(error_code const& e)
  {
  	COMPLETE_ASYNC("http_connection::on_connect");
  	TORRENT_ASSERT(m_connecting);
  	m_connecting = false;
  
  	m_last_receive = clock_type::now();
  	m_start_time = m_last_receive;
  	if (!e)
  	{
  		if (m_connect_handler) m_connect_handler(*this);
  		ADD_OUTSTANDING_ASYNC("http_connection::on_write");
  		async_write(*m_sock, boost::asio::buffer(m_sendbuffer)
  			, std::bind(&http_connection::on_write, shared_from_this(), _1));
  	}
  	else if (m_next_ep < int(m_endpoints.size()) && !m_abort)
  	{
  		// The connection failed. Try the next endpoint in the list.
  		error_code ec;
  		m_sock->close(ec);
  		connect();
  	}
  	else
  	{
  		error_code ec;
  		m_sock->close(ec);
  		callback(e);
  	}
  }
  
  void http_connection::callback(error_code e, span<char> data)
  {
  	if (m_bottled && m_called) return;
  
  	std::vector<char> buf;
  	if (!data.empty() && m_bottled && m_parser.header_finished())
  	{
  		data = m_parser.collapse_chunk_headers(data);
  
  		std::string const& encoding = m_parser.header("content-encoding");
  		if (encoding == "gzip" || encoding == "x-gzip")
  		{
  			error_code ec;
  			inflate_gzip(data, buf, m_max_bottled_buffer_size, ec);
  
  			if (ec)
  			{
  				if (m_handler) m_handler(ec, m_parser, data, *this);
  				return;
  			}
  			data = buf;
  		}
  
  		// if we completed the whole response, no need
  		// to tell the user that the connection was closed by
  		// the server or by us. Just clear any error
  		if (m_parser.finished()) e.clear();
  	}
  	m_called = true;
  	m_timer.cancel();
  	if (m_handler) m_handler(e, m_parser, data, *this);
  }
  
  void http_connection::on_write(error_code const& e)
  {
  	COMPLETE_ASYNC("http_connection::on_write");
  
  	if (e == boost::asio::error::operation_aborted) return;
  
  	if (e)
  	{
  		callback(e);
  		return;
  	}
  
  	if (m_abort) return;
  
  	std::string().swap(m_sendbuffer);
  	m_recvbuffer.resize(4096);
  
  	int amount_to_read = int(m_recvbuffer.size()) - m_read_pos;
  	if (m_rate_limit > 0 && amount_to_read > m_download_quota)
  	{
  		amount_to_read = m_download_quota;
  		if (m_download_quota == 0)
  		{
  			if (!m_limiter_timer_active)
  			{
  				ADD_OUTSTANDING_ASYNC("http_connection::on_assign_bandwidth");
  				on_assign_bandwidth(error_code());
  			}
  			return;
  		}
  	}
  	ADD_OUTSTANDING_ASYNC("http_connection::on_read");
  	m_sock->async_read_some(boost::asio::buffer(m_recvbuffer.data() + m_read_pos
  		, std::size_t(amount_to_read))
  		, std::bind(&http_connection::on_read
  			, shared_from_this(), _1, _2));
  }
  
  void http_connection::on_read(error_code const& e
  	, std::size_t bytes_transferred)
  {
  	COMPLETE_ASYNC("http_connection::on_read");
  
  	if (m_rate_limit)
  	{
  		m_download_quota -= int(bytes_transferred);
  		TORRENT_ASSERT(m_download_quota >= 0);
  	}
  
  	if (e == boost::asio::error::operation_aborted) return;
  
  	if (m_abort) return;
  
  	// keep ourselves alive even if the callback function
  	// deletes this object
  	std::shared_ptr<http_connection> me(shared_from_this());
  
  	// when using the asio SSL wrapper, it seems like
  	// we get the shut_down error instead of EOF
  	if (e == boost::asio::error::eof || e == boost::asio::error::shut_down)
  	{
  		error_code ec = boost::asio::error::eof;
  		TORRENT_ASSERT(bytes_transferred == 0);
  		span<char> body;
  		if (m_bottled && m_parser.header_finished())
  		{
  			body = span<char>(m_recvbuffer.data() + m_parser.body_start()
  				, m_parser.get_body().size());
  		}
  		callback(ec, body);
  		return;
  	}
  
  	if (e)
  	{
  		TORRENT_ASSERT(bytes_transferred == 0);
  		callback(e);
  		return;
  	}
  
  	m_read_pos += int(bytes_transferred);
  	TORRENT_ASSERT(m_read_pos <= int(m_recvbuffer.size()));
  
  	if (m_bottled || !m_parser.header_finished())
  	{
  		span<char const> rcv_buf(m_recvbuffer);
  		bool error = false;
  		m_parser.incoming(rcv_buf.first(m_read_pos), error);
  		if (error)
  		{
  			// HTTP parse error
  			error_code ec = errors::http_parse_error;
  			callback(ec);
  			return;
  		}
  
  		// having a nonempty path means we should handle redirects
  		if (m_redirects && m_parser.header_finished())
  		{
  			int code = m_parser.status_code();
  
  			if (is_redirect(code))
  			{
  				// attempt a redirect
  				std::string const& location = m_parser.header("location");
  				if (location.empty())
  				{
  					// missing location header
  					callback(error_code(errors::http_missing_location));
  					return;
  				}
  
  				error_code ec;
  				// it would be nice to gracefully shut down SSL here
  				// but then we'd have to do all the reconnect logic
  				// in its handler. For now, just kill the connection.
  //				async_shutdown(m_sock, me);
  				m_sock->close(ec);
  
  				std::string url = resolve_redirect_location(m_url, location);
  				get(url, m_completion_timeout, m_priority, &m_proxy, m_redirects - 1
  					, m_user_agent, m_bind_addr, m_resolve_flags, m_auth
  #if TORRENT_USE_I2P
  					, m_i2p_conn
  #endif
  					);
  				return;
  			}
  
  			m_redirects = 0;
  		}
  
  		if (!m_bottled && m_parser.header_finished())
  		{
  			if (m_read_pos > m_parser.body_start())
  			{
  				callback(e, span<char>(m_recvbuffer)
  					.first(m_read_pos)
  					.subspan(m_parser.body_start()));
  			}
  			m_read_pos = 0;
  			m_last_receive = clock_type::now();
  		}
  		else if (m_bottled && m_parser.finished())
  		{
  			m_timer.cancel();
  			callback(e, span<char>(m_recvbuffer)
  				.first(m_read_pos)
  				.subspan(m_parser.body_start()));
  		}
  	}
  	else
  	{
  		TORRENT_ASSERT(!m_bottled);
  		callback(e, span<char>(m_recvbuffer).first(m_read_pos));
  		m_read_pos = 0;
  		m_last_receive = clock_type::now();
  	}
  
  	// if we've hit the limit, double the buffer size
  	if (int(m_recvbuffer.size()) == m_read_pos)
  		m_recvbuffer.resize(std::min(m_read_pos * 2, m_max_bottled_buffer_size));
  
  	if (m_read_pos == m_max_bottled_buffer_size)
  	{
  		// if we've reached the size limit, terminate the connection and
  		// report the error
  		callback(error_code(boost::system::errc::file_too_large, generic_category()));
  		return;
  	}
  	int amount_to_read = int(m_recvbuffer.size()) - m_read_pos;
  	if (m_rate_limit > 0 && amount_to_read > m_download_quota)
  	{
  		amount_to_read = m_download_quota;
  		if (m_download_quota == 0)
  		{
  			if (!m_limiter_timer_active)
  			{
  				ADD_OUTSTANDING_ASYNC("http_connection::on_assign_bandwidth");
  				on_assign_bandwidth(error_code());
  			}
  			return;
  		}
  	}
  	ADD_OUTSTANDING_ASYNC("http_connection::on_read");
  	m_sock->async_read_some(boost::asio::buffer(m_recvbuffer.data() + m_read_pos
  		, std::size_t(amount_to_read))
  		, std::bind(&http_connection::on_read
  			, me, _1, _2));
  }
  
  void http_connection::on_assign_bandwidth(error_code const& e)
  {
  	COMPLETE_ASYNC("http_connection::on_assign_bandwidth");
  	if ((e == boost::asio::error::operation_aborted
  		&& m_limiter_timer_active)
  		|| !m_sock->is_open())
  	{
  		callback(boost::asio::error::eof);
  		return;
  	}
  	m_limiter_timer_active = false;
  	if (e) return;
  
  	if (m_abort) return;
  
  	if (m_download_quota > 0) return;
  
  	m_download_quota = m_rate_limit / 4;
  
  	int amount_to_read = int(m_recvbuffer.size()) - m_read_pos;
  	if (amount_to_read > m_download_quota)
  		amount_to_read = m_download_quota;
  
  	if (!m_sock->is_open()) return;
  
  	ADD_OUTSTANDING_ASYNC("http_connection::on_read");
  	m_sock->async_read_some(boost::asio::buffer(m_recvbuffer.data() + m_read_pos
  		, std::size_t(amount_to_read))
  		, std::bind(&http_connection::on_read
  			, shared_from_this(), _1, _2));
  
  	m_limiter_timer_active = true;
  	m_limiter_timer.expires_after(milliseconds(250));
  	ADD_OUTSTANDING_ASYNC("http_connection::on_assign_bandwidth");
  	m_limiter_timer.async_wait(std::bind(&http_connection::on_assign_bandwidth
  		, shared_from_this(), _1));
  }
  
  void http_connection::rate_limit(int limit)
  {
  	if (!m_sock->is_open()) return;
  
  	if (!m_limiter_timer_active)
  	{
  		m_limiter_timer_active = true;
  		m_limiter_timer.expires_after(milliseconds(250));
  		ADD_OUTSTANDING_ASYNC("http_connection::on_assign_bandwidth");
  		m_limiter_timer.async_wait(std::bind(&http_connection::on_assign_bandwidth
  			, shared_from_this(), _1));
  	}
  	m_rate_limit = limit;
  }
  
  }
  