#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright 2015 clowwindy
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

from __future__ import absolute_import, division, print_function, \
    with_statement

import time
import socket
import errno
import struct
import logging
import traceback
import random

from shadowsocks import encrypt, eventloop, shell, common
from shadowsocks.common import parse_header, onetimeauth_verify, \
    onetimeauth_gen, ONETIMEAUTH_BYTES, ONETIMEAUTH_CHUNK_BYTES, \
    ONETIMEAUTH_CHUNK_DATA_LEN, ADDRTYPE_AUTH

# we clear at most TIMEOUTS_CLEAN_SIZE timeouts each time
TIMEOUTS_CLEAN_SIZE = 512

MSG_FASTOPEN = 0x20000000

# SOCKS METHOD definition
METHOD_NOAUTH = 0

# SOCKS command definition
CMD_CONNECT = 1
CMD_BIND = 2
CMD_UDP_ASSOCIATE = 3

# for each opening port, we have a TCP Relay

# for each connection, we have a TCP Relay Handler to handle the connection

# for each handler, we have 2 sockets:
#    local:   connected to the client
#    remote:  connected to remote server

# for each handler, it could be at one of several stages:

# as sslocal:
# stage 0 auth METHOD received from local, reply with selection message
# stage 1 addr received from local, query DNS for remote
# stage 2 UDP assoc
# stage 3 DNS resolved, connect to remote
# stage 4 still connecting, more data from local received
# stage 5 remote connected, piping local and remote

# as ssserver:
# stage 0 just jump to stage 1
# stage 1 addr received from local, query DNS for remote
# stage 3 DNS resolved, connect to remote
# stage 4 still connecting, more data from local received
# stage 5 remote connected, piping local and remote

STAGE_INIT = 0
STAGE_ADDR = 1
STAGE_UDP_ASSOC = 2
STAGE_DNS = 3
STAGE_CONNECTING = 4
STAGE_STREAM = 5
STAGE_DESTROYED = -1

# for each handler, we have 2 stream directions:
#    upstream:    from client to server direction
#                 read local and write to remote
#    downstream:  from server to client direction
#                 read remote and write to local

STREAM_UP = 0
STREAM_DOWN = 1

# for each stream, it's waiting for reading, or writing, or both
WAIT_STATUS_INIT = 0
WAIT_STATUS_READING = 1
WAIT_STATUS_WRITING = 2
WAIT_STATUS_READWRITING = WAIT_STATUS_READING | WAIT_STATUS_WRITING

BUF_SIZE = 32 * 1024


# helper exceptions for TCPRelayHandler

class BadSocksHeader(Exception):
    pass


class NoAcceptableMethods(Exception):
    pass


class TCPRelayHandler(object):
    def __init__(self, server, fd_to_handlers, loop, local_sock, config,
                 dns_resolver, is_local):
        self._server = server
        self._fd_to_handlers = fd_to_handlers
        self._loop = loop
        self._local_sock = local_sock
        self._remote_sock = None
        self._config = config
        self._dns_resolver = dns_resolver

        # TCP Relay works as either sslocal or ssserver
        # if is_local, this is sslocal
        self._is_local = is_local
        self._stage = STAGE_INIT
        self._encryptor = encrypt.Encryptor(config['password'],
                                            config['method'])
        self._ota_enable = config.get('one_time_auth', False)
        self._ota_enable_session = self._ota_enable
        self._ota_buff_head = b''
        self._ota_buff_data = b''
        self._ota_len = 0
        self._ota_chunk_idx = 0
        self._fastopen_connected = False
        self._data_to_write_to_local = []
        self._data_to_write_to_remote = []
        self._upstream_status = WAIT_STATUS_READING
        self._downstream_status = WAIT_STATUS_INIT
        self._client_address = local_sock.getpeername()[:2]
        self._remote_address = None
        self._forbidden_iplist = config.get('forbidden_ip')
        if is_local:
            self._chosen_server = self._get_a_server()
        fd_to_handlers[local_sock.fileno()] = self
        local_sock.setblocking(False)
        local_sock.setsockopt(socket.SOL_TCP, socket.TCP_NODELAY, 1)
        loop.add(local_sock, eventloop.POLL_IN | eventloop.POLL_ERR,
                 self._server)
        self.last_activity = 0
        self._update_activity()

    def __hash__(self):
        # default __hash__ is id / 16
        # we want to eliminate collisions
        return id(self)

    @property
    def remote_address(self):
        return self._remote_address

    def _get_a_server(self):
        server = self._config['server']
        server_port = self._config['server_port']
        if type(server_port) == list:
            server_port = random.choice(server_port)
        if type(server) == list:
            server = random.choice(server)
        logging.debug('chosen server: %s:%d', server, server_port)
        return server, server_port

    def _update_activity(self, data_len=0):
        # tell the TCP Relay we have activities recently
        # else it will think we are inactive and timed out
        self._server.update_activity(self, data_len)

    def _update_stream(self, stream, status):
        # update a stream to a new waiting status

        # check if status is changed
        # only update if dirty
        dirty = False
        if stream == STREAM_DOWN:
            if self._downstream_status != status:
                self._downstream_status = status
                dirty = True
        elif stream == STREAM_UP:
            if self._upstream_status != status:
                self._upstream_status = status
                dirty = True
        if not dirty:
            return

        if self._local_sock:
            event = eventloop.POLL_ERR
            if self._downstream_status & WAIT_STATUS_WRITING:
                event |= eventloop.POLL_OUT
            if self._upstream_status & WAIT_STATUS_READING:
                event |= eventloop.POLL_IN
            self._loop.modify(self._local_sock, event)
        if self._remote_sock:
            event = eventloop.POLL_ERR
            if self._downstream_status & WAIT_STATUS_READING:
                event |= eventloop.POLL_IN
            if self._upstream_status & WAIT_STATUS_WRITING:
                event |= eventloop.POLL_OUT
            self._loop.modify(self._remote_sock, event)

    def _write_to_sock(self, data, sock):
        # write data to sock
        # if only some of the data are written, put remaining in the buffer
        # and update the stream to wait for writing
        if not data or not sock:
            return False
        uncomplete = False
        try:
            l = len(data)
            s = sock.send(data)
            if s < l:
                data = data[s:]
                uncomplete = True
        except (OSError, IOError) as e:
            error_no = eventloop.errno_from_exception(e)
            if error_no in (errno.EAGAIN, errno.EINPROGRESS,
                            errno.EWOULDBLOCK):
                uncomplete = True
            else:
                shell.print_exception(e)
                self.destroy()
                return False
        if uncomplete:
            if sock == self._local_sock:
                self._data_to_write_to_local.append(data)
                self._update_stream(STREAM_DOWN, WAIT_STATUS_WRITING)
            elif sock == self._remote_sock:
                self._data_to_write_to_remote.append(data)
                self._update_stream(STREAM_UP, WAIT_STATUS_WRITING)
            else:
                logging.error('write_all_to_sock:unknown socket')
        else:
            if sock == self._local_sock:
                self._update_stream(STREAM_DOWN, WAIT_STATUS_READING)
            elif sock == self._remote_sock:
                self._update_stream(STREAM_UP, WAIT_STATUS_READING)
            else:
                logging.error('write_all_to_sock:unknown socket')
        return True

    def _handle_stage_connecting(self, data):
        if not self._is_local:
            if self._ota_enable_session:
                self._ota_chunk_data(data,
                                     self._data_to_write_to_remote.append)
            else:
                self._data_to_write_to_remote.append(data)
            return

        if self._ota_enable_session:
            data = self._ota_chunk_data_gen(data)
        data = self._encryptor.encrypt(data)
        self._data_to_write_to_remote.append(data)

        if self._config['fast_open'] and not self._fastopen_connected:
            # for sslocal and fastopen, we basically wait for data and use
            # sendto to connect
            try:
                # only connect once
                self._fastopen_connected = True
                remote_sock = \
                    self._create_remote_socket(self._chosen_server[0],
                                               self._chosen_server[1])
                self._loop.add(remote_sock, eventloop.POLL_ERR, self._server)
                data = b''.join(self._data_to_write_to_remote)
                l = len(data)
                s = remote_sock.sendto(data, MSG_FASTOPEN,
                                       self._chosen_server)
                if s < l:
                    data = data[s:]
                    self._data_to_write_to_remote = [data]
                else:
                    self._data_to_write_to_remote = []
                self._update_stream(STREAM_UP, WAIT_STATUS_READWRITING)
            except (OSError, IOError) as e:
                if eventloop.errno_from_exception(e) == errno.EINPROGRESS:
                    # in this case data is not sent at all
                    self._update_stream(STREAM_UP, WAIT_STATUS_READWRITING)
                elif eventloop.errno_from_exception(e) == errno.ENOTCONN:
                    logging.error('fast open not supported on this OS')
                    self._config['fast_open'] = False
                    self.destroy()
                else:
                    shell.print_exception(e)
                    if self._config['verbose']:
                        traceback.print_exc()
                    self.destroy()

    @shell.exception_handle(self_=True, destroy=True, conn_err=True)
    def _handle_stage_addr(self, data):
        if self._is_local:
            cmd = common.ord(data[1])
            if cmd == CMD_UDP_ASSOCIATE:
                logging.debug('UDP associate')
                if self._local_sock.family == socket.AF_INET6:
                    header = b'\x05\x00\x00\x04'
                else:
                    header = b'\x05\x00\x00\x01'
                addr, port = self._local_sock.getsockname()[:2]
                addr_to_send = socket.inet_pton(self._local_sock.family,
                                                addr)
                port_to_send = struct.pack('>H', port)
                self._write_to_sock(header + addr_to_send + port_to_send,
                                    self._local_sock)
                self._stage = STAGE_UDP_ASSOC
                # just wait for the client to disconnect
                return
            elif cmd == CMD_CONNECT:
                # just trim VER CMD RSV
                data = data[3:]
            else:
                logging.error('unknown command %d', cmd)
                self.destroy()
                return
        header_result = parse_header(data)
        if header_result is None:
            raise Exception('can not parse header')
        addrtype, remote_addr, remote_port, header_length = header_result
        logging.info('connecting %s:%d from %s:%d' %
                     (common.to_str(remote_addr), remote_port,
                      self._client_address[0], self._client_address[1]))
        if self._is_local is False:
            # spec https://shadowsocks.org/en/spec/one-time-auth.html
            self._ota_enable_session = addrtype & ADDRTYPE_AUTH
            if self._ota_enable and not self._ota_enable_session:
                logging.warn('client one time auth is required')
                return
            if self._ota_enable_session:
                if len(data) < header_length + ONETIMEAUTH_BYTES:
                    logging.warn('one time auth header is too short')
                    return None
                offset = header_length + ONETIMEAUTH_BYTES
                _hash = data[header_length: offset]
                _data = data[:header_length]
                key = self._encryptor.decipher_iv + self._encryptor.key
                if onetimeauth_verify(_hash, _data, key) is False:
                    logging.warn('one time auth fail')
                    self.destroy()
                    return
                header_length += ONETIMEAUTH_BYTES
        self._remote_address = (common.to_str(remote_addr), remote_port)
        # pause reading
        self._update_stream(STREAM_UP, WAIT_STATUS_WRITING)
        self._stage = STAGE_DNS
        if self._is_local:
            # forward address to remote
            self._write_to_sock((b'\x05\x00\x00\x01'
                                 b'\x00\x00\x00\x00\x10\x10'),
                                self._local_sock)
            # spec https://shadowsocks.org/en/spec/one-time-auth.html
            # ATYP & 0x10 == 0x10, then OTA is enabled.
            if self._ota_enable_session:
                data = common.chr(addrtype | ADDRTYPE_AUTH) + data[1:]
                key = self._encryptor.cipher_iv + self._encryptor.key
                _header = data[:header_length]
                sha110 = onetimeauth_gen(data, key)
                data = _header + sha110 + data[header_length:]
            data_to_send = self._encryptor.encrypt(data)
            self._data_to_write_to_remote.append(data_to_send)
            # notice here may go into _handle_dns_resolved directly
            self._dns_resolver.resolve(self._chosen_server[0],
                                       self._handle_dns_resolved)
        else:
            if self._ota_enable_session:
                data = data[header_length:]
                self._ota_chunk_data(data,
                                     self._data_to_write_to_remote.append)
            elif len(data) > header_length:
                self._data_to_write_to_remote.append(data[header_length:])
            # notice here may go into _handle_dns_resolved directly
            self._dns_resolver.resolve(remote_addr,
                                       self._handle_dns_resolved)

    def _create_remote_socket(self, ip, port):
        addrs = socket.getaddrinfo(ip, port, 0, socket.SOCK_STREAM,
                                   socket.SOL_TCP)
        if len(addrs) == 0:
            raise Exception("getaddrinfo failed for %s:%d" % (ip, port))
        af, socktype, proto, canonname, sa = addrs[0]
        if self._forbidden_iplist:
            if common.to_str(sa[0]) in self._forbidden_iplist:
                raise Exception('IP %s is in forbidden list, reject' %
                                common.to_str(sa[0]))
        remote_sock = socket.socket(af, socktype, proto)
        self._remote_sock = remote_sock
        self._fd_to_handlers[remote_sock.fileno()] = self
        remote_sock.setblocking(False)
        remote_sock.setsockopt(socket.SOL_TCP, socket.TCP_NODELAY, 1)
        return remote_sock

    @shell.exception_handle(self_=True)
    def _handle_dns_resolved(self, result, error):
        if error:
            addr, port = self._client_address[0], self._client_address[1]
            logging.error('%s when handling connection from %s:%d' %
                          (error, addr, port))
            self.destroy()
            return
        if not (result and result[1]):
            self.destroy()
            return

        ip = result[1]
        self._stage = STAGE_CONNECTING
        remote_addr = ip
        if self._is_local:
            remote_port = self._chosen_server[1]
        else:
            remote_port = self._remote_address[1]

        if self._is_local and self._config['fast_open']:
            # for fastopen:
            # wait for more data arrive and send them in one SYN
            self._stage = STAGE_CONNECTING
            # we don't have to wait for remote since it's not
            # created
            self._update_stream(STREAM_UP, WAIT_STATUS_READING)
            # TODO when there is already data in this packet
        else:
            # else do connect
            remote_sock = self._create_remote_socket(remote_addr,
                                                     remote_port)
            try:
                remote_sock.connect((remote_addr, remote_port))
            except (OSError, IOError) as e:
                if eventloop.errno_from_exception(e) == \
                        errno.EINPROGRESS:
                    pass
            self._loop.add(remote_sock,
                           eventloop.POLL_ERR | eventloop.POLL_OUT,
                           self._server)
            self._stage = STAGE_CONNECTING
            self._update_stream(STREAM_UP, WAIT_STATUS_READWRITING)
            self._update_stream(STREAM_DOWN, WAIT_STATUS_READING)

    def _write_to_sock_remote(self, data):
        self._write_to_sock(data, self._remote_sock)

    def _ota_chunk_data(self, data, data_cb):
        # spec https://shadowsocks.org/en/spec/one-time-auth.html
        unchunk_data = b''
        while len(data) > 0:
            if self._ota_len == 0:
                # get DATA.LEN + HMAC-SHA1
                length = ONETIMEAUTH_CHUNK_BYTES - len(self._ota_buff_head)
                self._ota_buff_head += data[:length]
                data = data[length:]
                if len(self._ota_buff_head) < ONETIMEAUTH_CHUNK_BYTES:
                    # wait more data
                    return
                data_len = self._ota_buff_head[:ONETIMEAUTH_CHUNK_DATA_LEN]
                self._ota_len = struct.unpack('>H', data_len)[0]
            length = min(self._ota_len - len(self._ota_buff_data), len(data))
            self._ota_buff_data += data[:length]
            data = data[length:]
            if len(self._ota_buff_data) == self._ota_len:
                # get a chunk data
                _hash = self._ota_buff_head[ONETIMEAUTH_CHUNK_DATA_LEN:]
                _data = self._ota_buff_data
                index = struct.pack('>I', self._ota_chunk_idx)
                key = self._encryptor.decipher_iv + index
                if onetimeauth_verify(_hash, _data, key) is False:
                    logging.warn('one time auth fail, drop chunk !')
                else:
                    unchunk_data += _data
                    self._ota_chunk_idx += 1
                self._ota_buff_head = b''
                self._ota_buff_data = b''
                self._ota_len = 0
        data_cb(unchunk_data)
        return

    def _ota_chunk_data_gen(self, data):
        data_len = struct.pack(">H", len(data))
        index = struct.pack('>I', self._ota_chunk_idx)
        key = self._encryptor.cipher_iv + index
        sha110 = onetimeauth_gen(data, key)
        self._ota_chunk_idx += 1
        return data_len + sha110 + data

    def _handle_stage_stream(self, data):
        if self._is_local:
            if self._ota_enable_session:
                data = self._ota_chunk_data_gen(data)
            data = self._encryptor.encrypt(data)
            self._write_to_sock(data, self._remote_sock)
        else:
            if self._ota_enable_session:
                self._ota_chunk_data(data, self._write_to_sock_remote)
            else:
                self._write_to_sock(data, self._remote_sock)
        return

    def _check_auth_method(self, data):
        # VER, NMETHODS, and at least 1 METHODS
        if len(data) < 3:
            logging.warning('method selection header too short')
            raise BadSocksHeader
        socks_version = common.ord(data[0])
        nmethods = common.ord(data[1])
        if socks_version != 5:
            logging.warning('unsupported SOCKS protocol version ' +
                            str(socks_version))
            raise BadSocksHeader
        if nmethods < 1 or len(data) != nmethods + 2:
            logging.warning('NMETHODS and number of METHODS mismatch')
            raise BadSocksHeader
        noauth_exist = False
        for method in data[2:]:
            if common.ord(method) == METHOD_NOAUTH:
                noauth_exist = True
                break
        if not noauth_exist:
            logging.warning('none of SOCKS METHOD\'s '
                            'requested by client is supported')
            raise NoAcceptableMethods

    def _handle_stage_init(self, data):
        try:
            self._check_auth_method(data)
        except BadSocksHeader:
            self.destroy()
            return
        except NoAcceptableMethods:
            self._write_to_sock(b'\x05\xff', self._local_sock)
            self.destroy()
            return

        self._write_to_sock(b'\x05\00', self._local_sock)
        self._stage = STAGE_ADDR

    def _on_local_read(self):
        # handle all local read events and dispatch them to methods for
        # each stage
        if not self._local_sock:
            return
        is_local = self._is_local
        data = None
        try:
            data = self._local_sock.recv(BUF_SIZE)
        except (OSError, IOError) as e:
            if eventloop.errno_from_exception(e) in \
                    (errno.ETIMEDOUT, errno.EAGAIN, errno.EWOULDBLOCK):
                return
        if not data:
            self.destroy()
            return
        self._update_activity(len(data))
        if not is_local:
            data = self._encryptor.decrypt(data)
            if not data:
                return
        if self._stage == STAGE_STREAM:
            self._handle_stage_stream(data)
            return
        elif is_local and self._stage == STAGE_INIT:
            self._handle_stage_init(data)
        elif self._stage == STAGE_CONNECTING:
            self._handle_stage_connecting(data)
        elif (is_local and self._stage == STAGE_ADDR) or \
                (not is_local and self._stage == STAGE_INIT):
            self._handle_stage_addr(data)

    def _on_remote_read(self):
        # handle all remote read events
        data = None
        try:
            data = self._remote_sock.recv(BUF_SIZE)

        except (OSError, IOError) as e:
            if eventloop.errno_from_exception(e) in \
                    (errno.ETIMEDOUT, errno.EAGAIN, errno.EWOULDBLOCK):
                return
        if not data:
            self.destroy()
            return
        self._update_activity(len(data))
        if self._is_local:
            data = self._encryptor.decrypt(data)
        else:
            data = self._encryptor.encrypt(data)
        try:
            self._write_to_sock(data, self._local_sock)
        except Exception as e:
            shell.print_exception(e)
            if self._config['verbose']:
                traceback.print_exc()
            # TODO use logging when debug completed
            self.destroy()

    def _on_local_write(self):
        # handle local writable event
        if self._data_to_write_to_local:
            data = b''.join(self._data_to_write_to_local)
            self._data_to_write_to_local = []
            self._write_to_sock(data, self._local_sock)
        else:
            self._update_stream(STREAM_DOWN, WAIT_STATUS_READING)

    def _on_remote_write(self):
        # handle remote writable event
        self._stage = STAGE_STREAM
        if self._data_to_write_to_remote:
            data = b''.join(self._data_to_write_to_remote)
            self._data_to_write_to_remote = []
            self._write_to_sock(data, self._remote_sock)
        else:
            self._update_stream(STREAM_UP, WAIT_STATUS_READING)

    def _on_local_error(self):
        logging.debug('got local error')
        if self._local_sock:
            logging.error(eventloop.get_sock_error(self._local_sock))
        self.destroy()

    def _on_remote_error(self):
        logging.debug('got remote error')
        if self._remote_sock:
            logging.error(eventloop.get_sock_error(self._remote_sock))
        self.destroy()

    def handle_event(self, sock, event):
        # handle all events in this handler and dispatch them to methods
        if self._stage == STAGE_DESTROYED:
            logging.debug('ignore handle_event: destroyed')
            return
        # order is important
        if sock == self._remote_sock:
            if event & eventloop.POLL_ERR:
                self._on_remote_error()
                if self._stage == STAGE_DESTROYED:
                    return
            if event & (eventloop.POLL_IN | eventloop.POLL_HUP):
                self._on_remote_read()
                if self._stage == STAGE_DESTROYED:
                    return
            if event & eventloop.POLL_OUT:
                self._on_remote_write()
        elif sock == self._local_sock:
            if event & eventloop.POLL_ERR:
                self._on_local_error()
                if self._stage == STAGE_DESTROYED:
                    return
            if event & (eventloop.POLL_IN | eventloop.POLL_HUP):
                self._on_local_read()
                if self._stage == STAGE_DESTROYED:
                    return
            if event & eventloop.POLL_OUT:
                self._on_local_write()
        else:
            logging.warn('unknown socket')

    def destroy(self):
        # destroy the handler and release any resources
        # promises:
        # 1. destroy won't make another destroy() call inside
        # 2. destroy releases resources so it prevents future call to destroy
        # 3. destroy won't raise any exceptions
        # if any of the promises are broken, it indicates a bug has been
        # introduced! mostly likely memory leaks, etc
        if self._stage == STAGE_DESTROYED:
            # this couldn't happen
            logging.debug('already destroyed')
            return
        self._stage = STAGE_DESTROYED
        if self._remote_address:
            logging.debug('destroy: %s:%d' %
                          self._remote_address)
        else:
            logging.debug('destroy')
        if self._remote_sock:
            logging.debug('destroying remote')
            self._loop.remove(self._remote_sock)
            del self._fd_to_handlers[self._remote_sock.fileno()]
            self._remote_sock.close()
            self._remote_sock = None
        if self._local_sock:
            logging.debug('destroying local')
            self._loop.remove(self._local_sock)
            del self._fd_to_handlers[self._local_sock.fileno()]
            self._local_sock.close()
            self._local_sock = None
        self._dns_resolver.remove_callback(self._handle_dns_resolved)
        self._server.remove_handler(self)


class TCPRelay(object):
    def __init__(self, config, dns_resolver, is_local, stat_callback=None):
        self._config = config
        self._is_local = is_local
        self._dns_resolver = dns_resolver
        self._closed = False
        self._eventloop = None
        self._fd_to_handlers = {}

        self._timeout = config['timeout']
        self._timeouts = []  # a list for all the handlers
        # we trim the timeouts once a while
        self._timeout_offset = 0   # last checked position for timeout
        self._handler_to_timeouts = {}  # key: handler value: index in timeouts

        if is_local:
            listen_addr = config['local_address']
            listen_port = config['local_port']
        else:
            listen_addr = config['server']
            listen_port = config['server_port']
        self._listen_port = listen_port

        addrs = socket.getaddrinfo(listen_addr, listen_port, 0,
                                   socket.SOCK_STREAM, socket.SOL_TCP)
        if len(addrs) == 0:
            raise Exception("can't get addrinfo for %s:%d" %
                            (listen_addr, listen_port))
        af, socktype, proto, canonname, sa = addrs[0]
        server_socket = socket.socket(af, socktype, proto)
        server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        server_socket.bind(sa)
        server_socket.setblocking(False)
        if config['fast_open']:
            try:
                server_socket.setsockopt(socket.SOL_TCP, 23, 5)
            except socket.error:
                logging.error('warning: fast open is not available')
                self._config['fast_open'] = False
        server_socket.listen(1024)
        self._server_socket = server_socket
        self._stat_callback = stat_callback

    def add_to_loop(self, loop):
        if self._eventloop:
            raise Exception('already add to loop')
        if self._closed:
            raise Exception('already closed')
        self._eventloop = loop
        self._eventloop.add(self._server_socket,
                            eventloop.POLL_IN | eventloop.POLL_ERR, self)
        self._eventloop.add_periodic(self.handle_periodic)

    def remove_handler(self, handler):
        index = self._handler_to_timeouts.get(hash(handler), -1)
        if index >= 0:
            # delete is O(n), so we just set it to None
            self._timeouts[index] = None
            del self._handler_to_timeouts[hash(handler)]

    def update_activity(self, handler, data_len):
        if data_len and self._stat_callback:
            self._stat_callback(self._listen_port, data_len)

        # set handler to active
        now = int(time.time())
        if now - handler.last_activity < eventloop.TIMEOUT_PRECISION:
            # thus we can lower timeout modification frequency
            return
        handler.last_activity = now
        index = self._handler_to_timeouts.get(hash(handler), -1)
        if index >= 0:
            # delete is O(n), so we just set it to None
            self._timeouts[index] = None
        length = len(self._timeouts)
        self._timeouts.append(handler)
        self._handler_to_timeouts[hash(handler)] = length

    def _sweep_timeout(self):
        # tornado's timeout memory management is more flexible than we need
        # we just need a sorted last_activity queue and it's faster than heapq
        # in fact we can do O(1) insertion/remove so we invent our own
        if self._timeouts:
            logging.log(shell.VERBOSE_LEVEL, 'sweeping timeouts')
            now = time.time()
            length = len(self._timeouts)
            pos = self._timeout_offset
            while pos < length:
                handler = self._timeouts[pos]
                if handler:
                    if now - handler.last_activity < self._timeout:
                        break
                    else:
                        if handler.remote_address:
                            logging.warn('timed out: %s:%d' %
                                         handler.remote_address)
                        else:
                            logging.warn('timed out')
                        handler.destroy()
                        self._timeouts[pos] = None  # free memory
                        pos += 1
                else:
                    pos += 1
            if pos > TIMEOUTS_CLEAN_SIZE and pos > length >> 1:
                # clean up the timeout queue when it gets larger than half
                # of the queue
                self._timeouts = self._timeouts[pos:]
                for key in self._handler_to_timeouts:
                    self._handler_to_timeouts[key] -= pos
                pos = 0
            self._timeout_offset = pos

    def handle_event(self, sock, fd, event):
        # handle events and dispatch to handlers
        if sock:
            logging.log(shell.VERBOSE_LEVEL, 'fd %d %s', fd,
                        eventloop.EVENT_NAMES.get(event, event))
        if sock == self._server_socket:
            if event & eventloop.POLL_ERR:
                # TODO
                raise Exception('server_socket error')
            try:
                logging.debug('accept')
                conn = self._server_socket.accept()
                TCPRelayHandler(self, self._fd_to_handlers,
                                self._eventloop, conn[0], self._config,
                                self._dns_resolver, self._is_local)
            except (OSError, IOError) as e:
                error_no = eventloop.errno_from_exception(e)
                if error_no in (errno.EAGAIN, errno.EINPROGRESS,
                                errno.EWOULDBLOCK):
                    return
                else:
                    shell.print_exception(e)
                    if self._config['verbose']:
                        traceback.print_exc()
        else:
            if sock:
                handler = self._fd_to_handlers.get(fd, None)
                if handler:
                    handler.handle_event(sock, event)
            else:
                logging.warn('poll removed fd')

    def handle_periodic(self):
        if self._closed:
            if self._server_socket:
                self._eventloop.remove(self._server_socket)
                self._server_socket.close()
                self._server_socket = None
                logging.info('closed TCP port %d', self._listen_port)
            if not self._fd_to_handlers:
                logging.info('stopping')
                self._eventloop.stop()
        self._sweep_timeout()

    def close(self, next_tick=False):
        logging.debug('TCP close')
        self._closed = True
        if not next_tick:
            if self._eventloop:
                self._eventloop.remove_periodic(self.handle_periodic)
                self._eventloop.remove(self._server_socket)
            self._server_socket.close()
            for handler in list(self._fd_to_handlers.values()):
                handler.destroy()
