File

net/server_event.lua @ 12179:5e68635cdc2c

mod_http_file_share: Always measure total disk usage for statistics! Metrics available or not depending on configuration is weird, even tho it might be expensive to calculate and it's only really needed when there is a global quota. Default quota is set to infinity, which is essentially what it was. Reports NaN if there is an error, which should count as over the infinite default quota.
author Kim Alvefur <zash@zash.se>
date Tue, 11 Jan 2022 04:15:29 +0100
parent 11741:dcf38ac6a38c
child 12387:05c250fa335a
line wrap: on
line source

--[[


			server.lua based on lua/libevent by blastbeat

			notes:
			-- when using luaevent, never register 2 or more EV_READ at one socket, same for EV_WRITE
			-- you can't even register a new EV_READ/EV_WRITE callback inside another one
			-- to do some of the above, use timeout events or something what will called from outside
			-- don't let garbagecollect eventcallbacks, as long they are running
			-- when using luasec, there are 4 cases of timeout errors: wantread or wantwrite during reading or writing

--]]
-- luacheck: ignore 212/self 431/err 211/ret

local SCRIPT_NAME           = "server_event.lua"
local SCRIPT_VERSION        = "0.05"
local SCRIPT_AUTHOR         = "blastbeat"
local LAST_MODIFIED         = "2009/11/20"

local cfg = {
	MAX_CONNECTIONS       = 100000,  -- max per server connections (use "ulimit -n" on *nix)
	MAX_HANDSHAKE_ATTEMPTS= 1000,  -- attempts to finish ssl handshake
	HANDSHAKE_TIMEOUT     = 60,  -- timeout in seconds per handshake attempt
	MAX_READ_LENGTH       = 1024 * 1024 * 1024 * 1024,  -- max bytes allowed to read from sockets
	MAX_SEND_LENGTH       = 1024 * 1024 * 1024 * 1024,  -- max bytes size of write buffer (for writing on sockets)
	ACCEPT_QUEUE          = 128,  -- might influence the length of the pending sockets queue
	ACCEPT_DELAY          = 10,  -- seconds to wait until the next attempt of a full server to accept
	READ_TIMEOUT          = 14 * 60,  -- timeout in seconds for read data from socket
	WRITE_TIMEOUT         = 180,  -- timeout in seconds for write data on socket
	CONNECT_TIMEOUT       = 20,  -- timeout in seconds for connection attempts
	CLEAR_DELAY           = 5,  -- seconds to wait for clearing interface list (and calling ondisconnect listeners)
	READ_RETRY_DELAY      = 1e-06, -- if, after reading, there is still data in buffer, wait this long and continue reading
	DEBUG                 = true,  -- show debug messages
}

local pairs = pairs
local select = select
local require = require
local tostring = tostring
local setmetatable = setmetatable

local t_insert = table.insert
local t_concat = table.concat
local s_sub = string.sub

local coroutine_wrap = coroutine.wrap
local coroutine_yield = coroutine.yield

local has_luasec, ssl = pcall ( require , "ssl" )
local socket = require "socket"
local levent = require "luaevent.core"
local inet = require "util.net";
local inet_pton = inet.pton;

local socket_gettime = socket.gettime

local log = require ("util.logger").init("socket")

local function debug(...)
	return log("debug", ("%s "):rep(select('#', ...)), ...)
end
-- local vdebug = debug;

local bitor = ( function( ) -- thx Rici Lake
	local hasbit = function( x, p )
		return x % ( p + p ) >= p
	end
	return function( x, y )
		local p = 1
		local z = 0
		local limit = x > y and x or y
		while p <= limit do
			if hasbit( x, p ) or hasbit( y, p ) then
				z = z + p
			end
			p = p + p
		end
		return z
	end
end )( )

local base = levent.new( )
local addevent = base.addevent
local EV_READ = levent.EV_READ
local EV_WRITE = levent.EV_WRITE
local EV_TIMEOUT = levent.EV_TIMEOUT
local EV_SIGNAL = levent.EV_SIGNAL

local EV_READWRITE = bitor( EV_READ, EV_WRITE )

local interfacelist = { }

-- Client interface methods
local interface_mt = {}; interface_mt.__index = interface_mt;

-- Private methods
function interface_mt:_close()
	return self:_destroy();
end

function interface_mt:_start_connection(plainssl) -- called from wrapclient
	local callback = function( event )
		if EV_TIMEOUT == event then  -- timeout during connection
			self.fatalerror = "connection timeout"
			self:ontimeout()  -- call timeout listener
			self:_close()
			debug( "new connection failed. id:", self.id, "error:", self.fatalerror )
		else
			if EV_READWRITE == event then
				if self.readcallback(event) == -1 then
					-- Fatal error occurred
					return -1;
				end
			end
			if plainssl and has_luasec then  -- start ssl session
				self:starttls(self._sslctx, true)
			else  -- normal connection
				self:_start_session(true)
			end
			debug( "new connection established. id:", self.id )
		end
		self.eventconnect = nil
		return -1
	end
	self.eventconnect = addevent( base, self.conn, EV_READWRITE, callback, cfg.CONNECT_TIMEOUT )
	return true
end
function interface_mt:_start_session(call_onconnect) -- new session, for example after startssl
	if self.type == "client" then
		local callback = function( )
			self:_lock( false,  false, false )
			--vdebug( "start listening on client socket with id:", self.id )
			self.eventread = addevent( base, self.conn, EV_READ, self.readcallback, cfg.READ_TIMEOUT );  -- register callback
			if call_onconnect then
				self:onconnect()
			end
			self.eventsession = nil
			return -1
		end
		self.eventsession = addevent( base, nil, EV_TIMEOUT, callback, 0 )
	else
		self:_lock( false )
		--vdebug( "start listening on server socket with id:", self.id )
		self.eventread = addevent( base, self.conn, EV_READ, self.readcallback )  -- register callback
	end
	return true
end
function interface_mt:_start_ssl(call_onconnect) -- old socket will be destroyed, therefore we have to close read/write events first
	--vdebug( "starting ssl session with client id:", self.id )
	local _
	_ = self.eventread and self.eventread:close( )  -- close events; this must be called outside of the event callbacks!
	_ = self.eventwrite and self.eventwrite:close( )
	self.eventread, self.eventwrite = nil, nil
	local err
	self.conn, err = ssl.wrap( self.conn, self._sslctx )
	if err then
		self.fatalerror = err
		self.conn = nil  -- cannot be used anymore
		if call_onconnect then
			self.ondisconnect = nil  -- don't call this when client isn't really connected
		end
		self:_close()
		debug( "fatal error while ssl wrapping:", err )
		return false
	end

	if self.conn.sni then
		if self.servername then
			self.conn:sni(self.servername);
		elseif self._server and type(self._server.hosts) == "table" and next(self._server.hosts) ~= nil then
			self.conn:sni(self._server.hosts, true);
		end
	end

	self.conn:settimeout( 0 )  -- set non blocking
	local handshakecallback = coroutine_wrap(function( event )
		local _, err
		local attempt = 0
		local maxattempt = cfg.MAX_HANDSHAKE_ATTEMPTS
		while attempt < maxattempt do  -- no endless loop
			attempt = attempt + 1
			debug( "ssl handshake of client with id:"..tostring(self)..", attempt:"..attempt )
			if attempt > maxattempt then
				self.fatalerror = "max handshake attempts exceeded"
			elseif EV_TIMEOUT == event then
				self.fatalerror = "timeout during handshake"
			else
				_, err = self.conn:dohandshake( )
				if not err then
					self:_lock( false, false, false )  -- unlock the interface; sending, closing etc allowed
					self.send = self.conn.send  -- caching table lookups with new client object
					self.receive = self.conn.receive
					if not call_onconnect then  -- trigger listener
						self:onstatus("ssl-handshake-complete");
					end
					self:_start_session( call_onconnect )
					debug( "ssl handshake done" )
					self.eventhandshake = nil
					return -1
				end
				if err == "wantwrite" then
					event = EV_WRITE
				elseif err == "wantread" then
					event = EV_READ
				else
					debug( "ssl handshake error:", err )
					self.fatalerror = err
				end
			end
			if self.fatalerror then
				if call_onconnect then
					self.ondisconnect = nil  -- don't call this when client isn't really connected
				end
				self:_close()
				debug( "handshake failed because:", self.fatalerror )
				self.eventhandshake = nil
				return -1
			end
			event = coroutine_yield( event, cfg.HANDSHAKE_TIMEOUT )  -- yield this monster...
		end
	end
	)
	debug "starting handshake..."
	self:_lock( false, true, true )  -- unlock read/write events, but keep interface locked
	self.eventhandshake = addevent( base, self.conn, EV_READWRITE, handshakecallback, cfg.HANDSHAKE_TIMEOUT )
	return true
end
function interface_mt:_destroy()  -- close this interface + events and call last listener
	debug( "closing client with id:", self.id, self.fatalerror )
	self:_lock( true, true, true )  -- first of all, lock the interface to avoid further actions
	local _
	_ = self.eventread and self.eventread:close( )
	if self.type == "client" then
		_ = self.eventwrite and self.eventwrite:close( )
		_ = self.eventhandshake and self.eventhandshake:close( )
		_ = self.eventstarthandshake and self.eventstarthandshake:close( )
		_ = self.eventconnect and self.eventconnect:close( )
		_ = self.eventsession and self.eventsession:close( )
		_ = self.eventwritetimeout and self.eventwritetimeout:close( )
		_ = self.eventreadtimeout and self.eventreadtimeout:close( )
		-- call ondisconnect listener (won't be the case if handshake failed on connect)
		_ = self.ondisconnect and self:ondisconnect( self.fatalerror ~= "client to close" and self.fatalerror)
		_ = self.conn and self.conn:close( ) -- close connection
		_ = self._server and self._server:counter(-1);
		self.eventread, self.eventwrite = nil, nil
		self.eventstarthandshake, self.eventhandshake, self.eventclose = nil, nil, nil
		self.readcallback, self.writecallback = nil, nil
	else
		self.conn:close( )
		self.eventread, self.eventclose = nil, nil
		self.interface, self.readcallback = nil, nil
	end
	interfacelist[ self ] = nil
	return true
end

function interface_mt:_lock(nointerface, noreading, nowriting)  -- lock or unlock this interface or events
	self.nointerface, self.noreading, self.nowriting = nointerface, noreading, nowriting
	return nointerface, noreading, nowriting
end

--TODO: Deprecate
function interface_mt:lock_read(switch)
	log("warn", ":lock_read is deprecated, use :pasue() and :resume()");
	if switch then
		return self:pause();
	else
		return self:resume();
	end
end

function interface_mt:pause()
	return self:_lock(self.nointerface, true, self.nowriting);
end

function interface_mt:resume()
	self:_lock(self.nointerface, false, self.nowriting);
	if self.readcallback and not self.eventread then
		self.eventread = addevent( base, self.conn, EV_READ, self.readcallback, cfg.READ_TIMEOUT );  -- register callback
		return true;
	end
end

function interface_mt:pause_writes()
	return self:_lock(self.nointerface, self.noreading, true);
end

function interface_mt:resume_writes()
	self:_lock(self.nointerface, self.noreading, false);
	if self.writecallback and not self.eventwrite then
		self.eventwrite = addevent( base, self.conn, EV_WRITE, self.writecallback, cfg.WRITE_TIMEOUT );  -- register callback
		return true;
	end
end


function interface_mt:counter(c)
	if c then
		self._connections = self._connections + c
	end
	return self._connections
end

-- Public methods
function interface_mt:write(data)
	if self.nointerface then return nil, "locked"; end
	--vdebug( "try to send data to client, id/data:", self.id, data )
	data = tostring( data )
	local len = #data
	local total = len + self.writebufferlen
	if total > cfg.MAX_SEND_LENGTH then  -- check buffer length
		local err = "send buffer exceeded"
		debug( "error:", err )  -- to much, check your app
		return nil, err
	end
	t_insert(self.writebuffer, data) -- new buffer
	self.writebufferlen = total
	if not self.eventwrite and not self.nowriting  then  -- register new write event
		--vdebug( "register new write event" )
		self.eventwrite = addevent( base, self.conn, EV_WRITE, self.writecallback, cfg.WRITE_TIMEOUT )
	end
	return true
end
function interface_mt:close()
	if self.nointerface then return nil, "locked"; end
	debug( "try to close client connection with id:", self.id )
	if self.type == "client" then
		self.fatalerror = "client to close"
		if self.eventwrite then -- wait for incomplete write request
			self:_lock( true, true, false )
			debug "closing delayed until writebuffer is empty"
			return nil, "writebuffer not empty, waiting"
		else -- close now
			self:_lock( true, true, true )
			self:_close()
			return true
		end
	else
		debug( "try to close server with id:", tostring(self.id))
		self.fatalerror = "server to close"
		self:_lock( true )
		self:_close( 0 )
		return true
	end
end

function interface_mt:socket()
	return self.conn
end

function interface_mt:server()
	return self._server or self;
end

function interface_mt:port()
	return self._port
end

function interface_mt:serverport()
	return self._serverport
end

function interface_mt:ip()
	return self._ip
end

function interface_mt:ssl()
	return self._usingssl
end
interface_mt.clientport = interface_mt.port -- COMPAT server_select

function interface_mt:type()
	return self._type or "client"
end

function interface_mt:connections()
	return self._connections
end

function interface_mt:address()
	return self.addr
end

function interface_mt:set_sslctx(sslctx)
	self._sslctx = sslctx;
	if sslctx then
		self.starttls = nil; -- use starttls() of interface_mt
	else
		self.starttls = false; -- prevent starttls()
	end
end

function interface_mt:set_mode(pattern)
	if pattern then
		self._pattern = pattern;
	end
	return self._pattern;
end

function interface_mt:set_send(new_send) -- luacheck: ignore 212
	-- No-op, we always use the underlying connection's send
end

function interface_mt:starttls(sslctx, call_onconnect)
	debug( "try to start ssl at client id:", self.id )
	local err
	self._sslctx = sslctx;
	if self._usingssl then  -- startssl was already called
		err = "ssl already active"
	end
	if err then
		debug( "error:", err )
		return nil, err
	end
	self._usingssl = true
	self.startsslcallback = function( )  -- we have to start the handshake outside of a read/write event
		self.startsslcallback = nil
		self:_start_ssl(call_onconnect);
		self.eventstarthandshake = nil
		return -1
	end
	if not self.eventwrite then
		self:_lock( true, true, true )  -- lock the interface, to not disturb the handshake
		self.eventstarthandshake = addevent( base, nil, EV_TIMEOUT, self.startsslcallback, 0 )  -- add event to start handshake
	else
		-- wait until writebuffer is empty
		self:_lock( true, true, false )
		debug "ssl session delayed until writebuffer is empty..."
	end
	self.starttls = false;
	return true
end

function interface_mt:setoption(option, value)
	if self.conn.setoption then
		return self.conn:setoption(option, value);
	end
	return false, "setoption not implemented";
end

function interface_mt:setlistener(listener, data)
	self:ondetach(); -- Notify listener that it is no longer responsible for this connection
	self.onconnect = listener.onconnect;
	self.ondisconnect = listener.ondisconnect;
	self.onincoming = listener.onincoming;
	self.ontimeout = listener.ontimeout;
	self.onreadtimeout = listener.onreadtimeout;
	self.onstatus = listener.onstatus;
	self.ondetach = listener.ondetach;
	self.onattach = listener.onattach;
	self.onpredrain = listener.onpredrain;
	self.ondrain = listener.ondrain;
	self:onattach(data);
end

-- Stub handlers
function interface_mt:onconnect()
end
function interface_mt:onincoming()
end
function interface_mt:ondisconnect()
end
function interface_mt:ontimeout()
end
function interface_mt:onreadtimeout()
end
function interface_mt:onpredrain()
end
function interface_mt:ondrain()
end
function interface_mt:ondetach()
end
function interface_mt:onattach()
end
function interface_mt:onstatus()
end

-- End of client interface methods

local function handleclient( client, ip, port, server, pattern, listener, sslctx, extra )  -- creates an client interface
	--vdebug("creating client interfacce...")
	local interface = {
		type = "client";
		conn = client;
		currenttime = socket_gettime( );  -- safe the origin
		writebuffer = {};  -- writebuffer
		writebufferlen = 0;  -- length of writebuffer
		send = client.send;  -- caching table lookups
		receive = client.receive;
		onconnect = listener.onconnect;  -- will be called when client disconnects
		ondisconnect = listener.ondisconnect;  -- will be called when client disconnects
		onincoming = listener.onincoming;  -- will be called when client sends data
		ontimeout = listener.ontimeout; -- called when fatal socket timeout occurs
		onreadtimeout = listener.onreadtimeout; -- called when socket inactivity timeout occurs
		onpredrain = listener.onpredrain; -- called before writes
		ondrain = listener.ondrain; -- called when writebuffer is empty
		ondetach = listener.ondetach; -- called when disassociating this listener from this connection
		onstatus = listener.onstatus; -- called for status changes (e.g. of SSL/TLS)
		eventread = false, eventwrite = false, eventclose = false,
		eventhandshake = false, eventstarthandshake = false;  -- event handler
		eventconnect = false, eventsession = false;  -- more event handler...
		eventwritetimeout = false;  -- even more event handler...
		eventreadtimeout = false;
		fatalerror = false;  -- error message
		writecallback = false;  -- will be called on write events
		readcallback = false;  -- will be called on read events
		nointerface = true;  -- lock/unlock parameter of this interface
		noreading = false, nowriting = false;  -- locks of the read/writecallback
		startsslcallback = false;  -- starting handshake callback
		position = false;  -- position of client in interfacelist

		-- Properties
		_ip = ip, _port = port, _server = server, _pattern = pattern,
		_serverport = (server and server:port() or nil),
		_sslctx = sslctx; -- parameters
		_usingssl = false;  -- client is using ssl;
		extra = extra;
		servername = extra and extra.servername;
	}
	if not has_luasec then interface.starttls = false; end
	interface.id = tostring(interface):match("%x+$");
	interface.writecallback = function( event )  -- called on write events
		--vdebug( "new client write event, id/ip/port:", interface, ip, port )
		if interface.nowriting or ( interface.fatalerror and ( "client to close" ~= interface.fatalerror ) ) then  -- leave this event
			--vdebug( "leaving this event because:", interface.nowriting or interface.fatalerror )
			interface.eventwrite = false
			return -1
		end
		if EV_TIMEOUT == event then  -- took too long to write some data to socket -> disconnect
			interface.fatalerror = "timeout during writing"
			debug( "writing failed:", interface.fatalerror )
			interface:_close()
			interface.eventwrite = false
			return -1
		else  -- can write :)
			if interface._usingssl then  -- handle luasec
				if interface.eventreadtimeout then  -- we have to read first
					local ret = interface.readcallback( )  -- call readcallback
					--vdebug( "tried to read in writecallback, result:", ret )
				end
				if interface.eventwritetimeout then  -- luasec only
					interface.eventwritetimeout:close( )  -- first we have to close timeout event which where regged after a wantread error
					interface.eventwritetimeout = false
				end
			end
			interface:onpredrain();
			interface.writebuffer = { t_concat(interface.writebuffer) }
			local succ, err, byte = interface.conn:send( interface.writebuffer[1], 1, interface.writebufferlen )
			--vdebug( "write data:", interface.writebuffer, "error:", err, "part:", byte )
			if succ then  -- writing successful
				interface.writebuffer[1] = nil
				interface.writebufferlen = 0
				interface:ondrain();
				if interface.fatalerror then
					debug "closing client after writing"
					interface:_close()  -- close interface if needed
				elseif interface.startsslcallback then  -- start ssl connection if needed
					debug "starting ssl handshake after writing"
					interface.eventstarthandshake = addevent( base, nil, EV_TIMEOUT, interface.startsslcallback, 0 )
				elseif interface.writebufferlen ~= 0 then
					-- data possibly written from ondrain
					return EV_WRITE, cfg.WRITE_TIMEOUT
				elseif interface.eventreadtimeout then
					return EV_WRITE, cfg.WRITE_TIMEOUT
				end
				interface.eventwrite = nil
				return -1
			elseif byte and (err == "timeout" or err == "wantwrite") then  -- want write again
				--vdebug( "writebuffer is not empty:", err )
				interface.writebuffer[1] = s_sub( interface.writebuffer[1], byte + 1, interface.writebufferlen )  -- new buffer
				interface.writebufferlen = interface.writebufferlen - byte
				if "wantread" == err then  -- happens only with luasec
					local callback = function( )
						interface:_close()
						interface.eventwritetimeout = nil
						return -1;
					end
					interface.eventwritetimeout = addevent( base, nil, EV_TIMEOUT, callback, cfg.WRITE_TIMEOUT )  -- reg a new timeout event
					debug( "wantread during write attempt, reg it in readcallback but don't know what really happens next..." )
					-- hopefully this works with luasec; its simply not possible to use 2 different write events on a socket in luaevent
					return -1
				end
				return EV_WRITE, cfg.WRITE_TIMEOUT
			else  -- connection was closed during writing or fatal error
				interface.fatalerror = err or "fatal error"
				debug( "connection failed in write event:", interface.fatalerror )
				interface:_close()
				interface.eventwrite = nil
				return -1
			end
		end
	end

	interface.readcallback = function( event )  -- called on read events
		--vdebug( "new client read event, id/ip/port:", tostring(interface.id), tostring(ip), tostring(port) )
		if interface.noreading or interface.fatalerror then  -- leave this event
			--vdebug( "leaving this event because:", tostring(interface.noreading or interface.fatalerror) )
			interface.eventread = nil
			return -1
		end
		if EV_TIMEOUT == event and not interface.conn:dirty() and interface:onreadtimeout() ~= true then
			interface.fatalerror = "timeout during receiving"
			debug( "connection failed:", interface.fatalerror )
			interface:_close()
			interface.eventread = nil
			return -1 -- took too long to get some data from client -> disconnect
		end
		if interface._usingssl then  -- handle luasec
			if interface.eventwritetimeout then  -- ok, in the past writecallback was regged
				local ret = interface.writecallback( )  -- call it
				--vdebug( "tried to write in readcallback, result:", tostring(ret) )
			end
			if interface.eventreadtimeout then
				interface.eventreadtimeout:close( )
				interface.eventreadtimeout = nil
			end
		end
		local buffer, err, part = interface.conn:receive( interface._pattern )  -- receive buffer with "pattern"
		--vdebug( "read data:", tostring(buffer), "error:", tostring(err), "part:", tostring(part) )
		buffer = buffer or part
		if buffer and #buffer > cfg.MAX_READ_LENGTH then  -- check buffer length
			interface.fatalerror = "receive buffer exceeded"
			debug( "fatal error:", interface.fatalerror )
			interface:_close()
			interface.eventread = nil
			return -1
		end
		if err and ( err ~= "timeout" and err ~= "wantread" ) then
			if "wantwrite" == err then -- need to read on write event
				if not interface.eventwrite then  -- register new write event if needed
					interface.eventwrite = addevent( base, interface.conn, EV_WRITE, interface.writecallback, cfg.WRITE_TIMEOUT )
				end
				interface.eventreadtimeout = addevent( base, nil, EV_TIMEOUT,
					function( ) interface:_close() end, cfg.READ_TIMEOUT)
				debug( "wantwrite during read attempt, reg it in writecallback but don't know what really happens next..." )
				-- to be honest i don't know what happens next, if it is allowed to first read, the write etc...
			else  -- connection was closed or fatal error
				interface.fatalerror = err
				debug( "connection failed in read event:", interface.fatalerror )
				interface:_close()
				interface.eventread = nil
				return -1
			end
		else
			interface.onincoming( interface, buffer, err )  -- send new data to listener
		end
		if interface.noreading then
			interface.eventread = nil;
			return -1;
		end
		if interface.conn:dirty() then -- still data left in buffer
			return EV_TIMEOUT, cfg.READ_RETRY_DELAY;
		end
		return EV_READ, cfg.READ_TIMEOUT
	end

	client:settimeout( 0 )  -- set non blocking
	setmetatable(interface, interface_mt)
	interfacelist[ interface ] = true  -- add to interfacelist
	return interface
end

local function handleserver( server, addr, port, pattern, listener, sslctx, startssl )  -- creates a server interface
	debug "creating server interface..."
	local interface = {
		_connections = 0;

		type = "server";
		conn = server;
		onconnect = listener.onconnect;  -- will be called when new client connected
		eventread = false;  -- read event handler
		eventclose = false; -- close event handler
		readcallback = false; -- read event callback
		fatalerror = false; -- error message
		nointerface = true;  -- lock/unlock parameter

		_ip = addr, _port = port, _pattern = pattern,
		_sslctx = sslctx;
		hosts = {};
	}
	interface.id = tostring(interface):match("%x+$");
	interface.readcallback = function( event )  -- server handler, called on incoming connections
		--vdebug( "server can accept, id/addr/port:", interface, addr, port )
		if interface.fatalerror then
			--vdebug( "leaving this event because:", self.fatalerror )
			interface.eventread = nil
			return -1
		end
		local delay = cfg.ACCEPT_DELAY
		if EV_TIMEOUT == event then
			if interface._connections >= cfg.MAX_CONNECTIONS then  -- check connection count
				debug( "to many connections, seconds to wait for next accept:", delay )
				return EV_TIMEOUT, delay  -- timeout...
			else
				return EV_READ  -- accept again
			end
		end
		--vdebug("max connection check ok, accepting...")
		-- luacheck: ignore 231/err
		local client, err = server:accept()    -- try to accept; TODO: check err
		while client do
			if interface._connections >= cfg.MAX_CONNECTIONS then
				client:close( )  -- refuse connection
				debug( "maximal connections reached, refuse client connection; accept delay:", delay )
				return EV_TIMEOUT, delay  -- delay for next accept attempt
			end
			local client_ip, client_port = client:getpeername( )
			interface._connections = interface._connections + 1  -- increase connection count
			local clientinterface = handleclient( client, client_ip, client_port, interface, pattern, listener, sslctx )
			--vdebug( "client id:", clientinterface, "startssl:", startssl )
			if has_luasec and startssl then
				clientinterface:starttls(sslctx, true)
			else
				clientinterface:_start_session( true )
			end
			debug( "accepted incoming client connection from:", client_ip or "<unknown IP>", client_port or "<unknown port>", "to", port or "<unknown port>");

			client, err = server:accept()    -- try to accept again
		end
		return EV_READ
	end

	server:settimeout( 0 )
	setmetatable(interface, interface_mt)
	interfacelist[ interface ] = true
	interface:_start_session()
	return interface
end

local function listen(addr, port, listener, config)
	config = config or {}
	if config.sslctx and not has_luasec then
		debug "fatal error: luasec not found"
		return nil, "luasec not found"
	end
	local server, err = socket.bind( addr, port, cfg.ACCEPT_QUEUE )  -- create server socket
	if not server then
		debug( "creating server socket on "..addr.." port "..port.." failed:", err )
		return nil, err
	end
	local interface = handleserver( server, addr, port, config.read_size, listener, config.tls_ctx, config.tls_direct)  -- new server handler
	debug( "new server created with id:", tostring(interface))
	return interface
end

local function addserver( addr, port, listener, pattern, sslctx )  -- TODO: check arguments
	--vdebug( "creating new tcp server with following parameters:", addr or "nil", port or "nil", sslctx or "nil", startssl or "nil")
	return listen( addr, port, listener, {
		read_size = pattern,
		tls_ctx = sslctx,
		tls_direct = not not sslctx,
	});
end

local function wrapclient( client, ip, port, listeners, pattern, sslctx, extra )
	local interface = handleclient( client, ip, port, nil, pattern, listeners, sslctx, extra )
	interface:_start_connection(sslctx)
	return interface, client
	--function handleclient( client, ip, port, server, pattern, listener, _, sslctx )  -- creates an client interface
end

local function addclient( addr, serverport, listener, pattern, sslctx, typ, extra )
	if sslctx and not has_luasec then
		debug "need luasec, but not available"
		return nil, "luasec not found"
	end
	if not typ then
		local n = inet_pton(addr);
		if not n then return nil, "invalid-ip"; end
		if #n == 16 then
			typ = "tcp6";
		elseif #n == 4 then
			typ = "tcp4";
		end
	end
	local create = socket[typ];
	if type( create ) ~= "function"  then
		return nil, "invalid socket type"
	end
	local client, err = create()  -- creating new socket
	if not client then
		debug( "cannot create socket:", err )
		return nil, err
	end
	client:settimeout( 0 )  -- set nonblocking
	local res, err = client:setpeername( addr, serverport )  -- connect
	if res or ( err == "timeout" ) then
		-- luacheck: ignore 211/port
		local ip, port = client:getsockname( )
		local interface = wrapclient( client, ip, serverport, listener, pattern, sslctx, extra )
		debug( "new connection id:", interface.id )
		return interface, err
	else
		debug( "new connection failed:", err )
		return nil, err
	end
end

local function loop( )  -- starts the event loop
	base:loop( )
	return "quitting";
end

local function newevent( ... )
	return addevent( base, ... )
end

local function closeallservers ( arg )
	for item in pairs( interfacelist ) do
		if item.type == "server" then
			item:close( arg )
		end
	end
end

local function setquitting(yes)
	if yes then
		-- Quit now
		if yes ~= "once" then
			closeallservers();
		end
		base:loopexit();
	end
end

local function get_backend()
	return "libevent " .. base:method();
end

-- We need to hold onto the events to stop them
-- being garbage-collected
local signal_events = {}; -- [signal_num] -> event object
local function hook_signal(signal_num, handler)
	local function _handler()
		local ret = handler();
		if ret ~= false then -- Continue handling this signal?
			return EV_SIGNAL; -- Yes
		end
		return -1; -- Close this event
	end
	signal_events[signal_num] = base:addevent(signal_num, EV_SIGNAL, _handler);
	return signal_events[signal_num];
end

local function link(sender, receiver, buffersize)
	local sender_locked;

	function receiver:ondrain()
		if sender_locked then
			sender:resume();
			sender_locked = nil;
		end
	end

	function sender:onincoming(data)
		receiver:write(data);
		if receiver.writebufferlen >= buffersize then
			sender_locked = true;
			sender:pause();
		end
	end
	sender:set_mode("*a");
end

local function add_task(delay, callback)
	local event_handle;
	event_handle = base:addevent(nil, 0, function ()
		local ret = callback(socket_gettime());
		if ret then
			return 0, ret;
		elseif event_handle then
			return -1;
		end
	end
	, delay);
	return event_handle;
end

local function watchfd(fd, onreadable, onwriteable)
	local handle = {};
	function handle:setflags(r,w)
		if r ~= nil then
			if r and not self.wantread then
				self.wantread = base:addevent(fd, EV_READ, function ()
					onreadable(self);
				end);
			elseif not r and self.wantread then
				self.wantread:close();
				self.wantread = nil;
			end
		end
		if w ~= nil then
			if w and not self.wantwrite then
				self.wantwrite = base:addevent(fd, EV_WRITE, function ()
					onwriteable(self);
				end);
			elseif not r and self.wantread then
				self.wantwrite:close();
				self.wantwrite = nil;
			end
		end
	end
	handle:setflags(onreadable, onwriteable);
	return handle;
end

return {
	cfg = cfg,
	base = base,
	loop = loop,
	link = link,
	event = levent,
	event_base = base,
	addevent = newevent,
	addserver = addserver,
	listen = listen,
	addclient = addclient,
	wrapclient = wrapclient,
	setquitting = setquitting,
	closeall = closeallservers,
	get_backend = get_backend,
	hook_signal = hook_signal,
	add_task = add_task,
	watchfd = watchfd,

	__NAME = SCRIPT_NAME,
	__DATE = LAST_MODIFIED,
	__AUTHOR = SCRIPT_AUTHOR,
	__VERSION = SCRIPT_VERSION,

}