mdw@git.distorted.org.uk Git - hippotat/blob - hippotatlib/__init__.py

   1 # -*- python -*-
   2 #
   3 # Hippotat - Asinine IP Over HTTP program
   4 # hippotatlib/__init__.py - common library code
   5 #
   6 # Copyright 2017 Ian Jackson
   7 #
   8 # GPLv3+
   9 #
  10 #    This program is free software: you can redistribute it and/or modify
  11 #    it under the terms of the GNU General Public License as published by
  12 #    the Free Software Foundation, either version 3 of the License, or
  13 #    (at your option) any later version.
  14 #
  15 #    This program is distributed in the hope that it will be useful,
  16 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 #    GNU General Public License for more details.
  19 #
  20 #    You should have received a copy of the GNU General Public License
  21 #    along with this program, in the file GPLv3.  If not,
  22 #    see <http://www.gnu.org/licenses/>.
  23
  24
  25 import signal
  26 signal.signal(signal.SIGINT, signal.SIG_DFL)
  27
  28 import sys
  29 import os
  30
  31 from zope.interface import implementer
  32
  33 import twisted
  34 from twisted.internet import reactor
  35 import twisted.internet.endpoints
  36 import twisted.logger
  37 from twisted.logger import LogLevel
  38 import twisted.python.constants
  39 from twisted.python.constants import NamedConstant
  40
  41 import ipaddress
  42 from ipaddress import AddressValueError
  43
  44 from optparse import OptionParser
  45 import configparser
  46 from configparser import ConfigParser
  47 from configparser import NoOptionError
  48
  49 from functools import partial
  50
  51 import collections
  52 import time
  53 import codecs
  54 import traceback
  55
  56 import re as regexp
  57
  58 import hippotatlib.slip as slip
  59
  60 class DBG(twisted.python.constants.Names):
  61   INIT = NamedConstant()
  62   CONFIG = NamedConstant()
  63   ROUTE = NamedConstant()
  64   DROP = NamedConstant()
  65   OWNSOURCE = NamedConstant()
  66   FLOW = NamedConstant()
  67   HTTP = NamedConstant()
  68   TWISTED = NamedConstant()
  69   QUEUE = NamedConstant()
  70   HTTP_CTRL = NamedConstant()
  71   QUEUE_CTRL = NamedConstant()
  72   HTTP_FULL = NamedConstant()
  73   CTRL_DUMP = NamedConstant()
  74   SLIP_FULL = NamedConstant()
  75   DATA_COMPLETE = NamedConstant()
  76
  77 _hex_codec = codecs.getencoder('hex_codec')
  78
  79 #---------- logging ----------
  80
  81 org_stderr = sys.stderr
  82
  83 log = twisted.logger.Logger()
  84
  85 debug_set = set()
  86 debug_def_detail = DBG.HTTP
  87
  88 def log_debug(dflag, msg, idof=None, d=None):
  89   if dflag not in debug_set: return
  90   #print('---------------->',repr((dflag, msg, idof, d)), file=sys.stderr)
  91   if idof is not None:
  92     msg = '[%#x] %s' % (id(idof), msg)
  93   if d is not None:
  94     trunc = ''
  95     if not DBG.DATA_COMPLETE in debug_set:
  96       if len(d) > 64:
  97         d = d[0:64]
  98         trunc = '...'
  99     d = _hex_codec(d)[0].decode('ascii')
 100     msg += ' ' + d + trunc
 101   log.info('{dflag} {msgcore}', dflag=dflag, msgcore=msg)
 102
 103 def logevent_is_boringtwisted(event):
 104   try:
 105     if event.get('log_level') != LogLevel.info:
 106       return False
 107     dflag = event.get('dflag')
 108     if dflag is False                            : return False
 109     if dflag                         in debug_set: return False
 110     if dflag is None and DBG.TWISTED in debug_set: return False
 111     return True
 112   except Exception:
 113     print('EXCEPTION (IN BORINGTWISTED CHECK)',
 114           traceback.format_exc(), file=org_stderr)
 115     return False
 116
 117 @implementer(twisted.logger.ILogFilterPredicate)
 118 class LogNotBoringTwisted:
 119   def __call__(self, event):
 120     return (
 121       twisted.logger.PredicateResult.no
 122       if logevent_is_boringtwisted(event) else
 123       twisted.logger.PredicateResult.yes
 124     )
 125
 126 #---------- default config ----------
 127
 128 defcfg = '''
 129 [DEFAULT]
 130 max_batch_down = 65536
 131 max_queue_time = 10
 132 target_requests_outstanding = 3
 133 http_timeout = 30
 134 http_timeout_grace = 5
 135 max_requests_outstanding = 6
 136 max_batch_up = 4000
 137 http_retry = 5
 138 port = 80
 139 vroutes = ''
 140 ifname_client = hippo%%d
 141 ifname_server = shippo%%d
 142
 143 #[server] or [<client>] overrides
 144 ipif = userv root ipif %(local)s,%(peer)s,%(mtu)s,slip,%(ifname)s %(rnets)s
 145
 146 # relating to virtual network
 147 mtu = 1500
 148
 149 # addrs = 127.0.0.1 ::1
 150 # url
 151
 152 # relating to virtual network
 153 vvnetwork = 172.24.230.192
 154 # vnetwork = <prefix>/<len>
 155 # vaddr    = <ipaddr>
 156 # vrelay   = <ipaddr>
 157
 158
 159 # [<client-ip4-or-ipv6-address>]
 160 # password = <password>    # used by both, must match
 161
 162 [LIMIT]
 163 max_batch_down = 262144
 164 max_queue_time = 121
 165 http_timeout = 121
 166 target_requests_outstanding = 10
 167 '''
 168
 169 # these need to be defined here so that they can be imported by import *
 170 cfg = ConfigParser(strict=False)
 171 optparser = OptionParser()
 172
 173 _mimetrans = bytes.maketrans(b'-'+slip.esc, slip.esc+b'-')
 174 def mime_translate(s):
 175   # SLIP-encoded packets cannot contain ESC ESC.
 176   # Swap `-' and ESC.  The result cannot contain `--'
 177   return s.translate(_mimetrans)
 178
 179 class ConfigResults:
 180   def __init__(self):
 181     pass
 182   def __repr__(self):
 183     return 'ConfigResults('+repr(self.__dict__)+')'
 184
 185 def log_discard(packet, iface, saddr, daddr, why):
 186   log_debug(DBG.DROP,
 187             'discarded packet [%s] %s -> %s: %s' % (iface, saddr, daddr, why),
 188             d=packet)
 189
 190 #---------- packet parsing ----------
 191
 192 def packet_addrs(packet):
 193   version = packet[0] >> 4
 194   if version == 4:
 195     addrlen = 4
 196     saddroff = 3*4
 197     factory = ipaddress.IPv4Address
 198   elif version == 6:
 199     addrlen = 16
 200     saddroff = 2*4
 201     factory = ipaddress.IPv6Address
 202   else:
 203     raise ValueError('unsupported IP version %d' % version)
 204   saddr = factory(packet[ saddroff           : saddroff + addrlen   ])
 205   daddr = factory(packet[ saddroff + addrlen : saddroff + addrlen*2 ])
 206   return (saddr, daddr)
 207
 208 #---------- address handling ----------
 209
 210 def ipaddr(input):
 211   try:
 212     r = ipaddress.IPv4Address(input)
 213   except AddressValueError:
 214     r = ipaddress.IPv6Address(input)
 215   return r
 216
 217 def ipnetwork(input):
 218   try:
 219     r = ipaddress.IPv4Network(input)
 220   except NetworkValueError:
 221     r = ipaddress.IPv6Network(input)
 222   return r
 223
 224 #---------- ipif (SLIP) subprocess ----------
 225
 226 class SlipStreamDecoder():
 227   def __init__(self, desc, on_packet):
 228     self._buffer = b''
 229     self._on_packet = on_packet
 230     self._desc = desc
 231     self._log('__init__')
 232
 233   def _log(self, msg, **kwargs):
 234     log_debug(DBG.SLIP_FULL, 'slip %s: %s' % (self._desc, msg), **kwargs)
 235
 236   def inputdata(self, data):
 237     self._log('inputdata', d=data)
 238     data = self._buffer + data
 239     self._buffer = b''
 240     packets = slip.decode(data, True)
 241     self._buffer = packets.pop()
 242     for packet in packets:
 243       self._maybe_packet(packet)
 244     self._log('bufremain', d=self._buffer)
 245
 246   def _maybe_packet(self, packet):
 247     self._log('maybepacket', d=packet)
 248     if len(packet):
 249       self._on_packet(packet)
 250
 251   def flush(self):
 252     self._log('flush')
 253     data = self._buffer
 254     self._buffer = b''
 255     packets = slip.decode(data)
 256     assert(len(packets) == 1)
 257     self._maybe_packet(packets[0])
 258
 259 class _IpifProcessProtocol(twisted.internet.protocol.ProcessProtocol):
 260   def __init__(self, router):
 261     self._router = router
 262     self._decoder = SlipStreamDecoder('ipif', self.slip_on_packet)
 263   def connectionMade(self): pass
 264   def outReceived(self, data):
 265     self._decoder.inputdata(data)
 266   def slip_on_packet(self, packet):
 267     (saddr, daddr) = packet_addrs(packet)
 268     if saddr.is_link_local or daddr.is_link_local:
 269       log_discard(packet, 'ipif', saddr, daddr, 'link-local')
 270       return
 271     self._router(packet, saddr, daddr)
 272   def processEnded(self, status):
 273     status.raiseException()
 274
 275 def start_ipif(command, router):
 276   ipif = _IpifProcessProtocol(router)
 277   reactor.spawnProcess(ipif,
 278                        '/bin/sh',['sh','-xc', command],
 279                        childFDs={0:'w', 1:'r', 2:2},
 280                        env=None)
 281   return ipif
 282
 283 def queue_inbound(ipif, packet):
 284   log_debug(DBG.FLOW, "queue_inbound", d=packet)
 285   ipif.transport.write(slip.delimiter)
 286   ipif.transport.write(slip.encode(packet))
 287   ipif.transport.write(slip.delimiter)
 288
 289 #---------- packet queue ----------
 290
 291 class PacketQueue():
 292   def __init__(self, desc, max_queue_time):
 293     self._desc = desc
 294     assert(desc + '')
 295     self._max_queue_time = max_queue_time
 296     self._pq = collections.deque() # packets
 297
 298   def _log(self, dflag, msg, **kwargs):
 299     log_debug(dflag, self._desc+' pq: '+msg, **kwargs)
 300
 301   def append(self, packet):
 302     self._log(DBG.QUEUE, 'append', d=packet)
 303     self._pq.append((time.monotonic(), packet))
 304
 305   def nonempty(self):
 306     self._log(DBG.QUEUE, 'nonempty ?')
 307     while True:
 308       try: (queuetime, packet) = self._pq[0]
 309       except IndexError:
 310         self._log(DBG.QUEUE, 'nonempty ? empty.')
 311         return False
 312
 313       age = time.monotonic() - queuetime
 314       if age > self._max_queue_time:
 315         # strip old packets off the front
 316         self._log(DBG.QUEUE, 'dropping (old)', d=packet)
 317         self._pq.popleft()
 318         continue
 319
 320       self._log(DBG.QUEUE, 'nonempty ? nonempty.')
 321       return True
 322
 323   def process(self, sizequery, moredata, max_batch):
 324     # sizequery() should return size of batch so far
 325     # moredata(s) should add s to batch
 326     self._log(DBG.QUEUE, 'process...')
 327     while True:
 328       try: (dummy, packet) = self._pq[0]
 329       except IndexError:
 330         self._log(DBG.QUEUE, 'process... empty')
 331         break
 332
 333       self._log(DBG.QUEUE_CTRL, 'process... packet', d=packet)
 334
 335       encoded = slip.encode(packet)
 336       sofar = sizequery()
 337
 338       self._log(DBG.QUEUE_CTRL,
 339                 'process... (sofar=%d, max=%d) encoded' % (sofar, max_batch),
 340                 d=encoded)
 341
 342       if sofar > 0:
 343         if sofar + len(slip.delimiter) + len(encoded) > max_batch:
 344           self._log(DBG.QUEUE_CTRL, 'process... overflow')
 345           break
 346         moredata(slip.delimiter)
 347
 348       moredata(encoded)
 349       self._pq.popleft()
 350
 351 #---------- error handling ----------
 352
 353 _crashing = False
 354
 355 def crash(err):
 356   global _crashing
 357   _crashing = True
 358   print('========== CRASH ==========', err,
 359         '===========================', file=sys.stderr)
 360   try: reactor.stop()
 361   except twisted.internet.error.ReactorNotRunning: pass
 362
 363 def crash_on_defer(defer):
 364   defer.addErrback(lambda err: crash(err))
 365
 366 def crash_on_critical(event):
 367   if event.get('log_level') >= LogLevel.critical:
 368     crash(twisted.logger.formatEvent(event))
 369
 370 #---------- config processing ----------
 371
 372 def _cfg_process_putatives():
 373   servers = { }
 374   clients = { }
 375   # maps from abstract object to canonical name for cs's
 376
 377   def putative(cmap, abstract, canoncs):
 378     try:
 379       current_canoncs = cmap[abstract]
 380     except KeyError:
 381       pass
 382     else:
 383       assert(current_canoncs == canoncs)
 384     cmap[abstract] = canoncs
 385
 386   server_pat = r'[-.0-9A-Za-z]+'
 387   client_pat = r'[.:0-9a-f]+'
 388   server_re = regexp.compile(server_pat)
 389   serverclient_re = regexp.compile(server_pat + r' ' + client_pat)
 390
 391   for cs in cfg.sections():
 392     if cs == 'LIMIT':
 393       # plan A "[LIMIT]"
 394       continue
 395
 396     try:
 397       # plan B "[<client>]" part 1
 398       ci = ipaddr(cs)
 399     except AddressValueError:
 400
 401       if server_re.fullmatch(cs):
 402         # plan C "[<servername>]"
 403         putative(servers, cs, cs)
 404         continue
 405
 406       if serverclient_re.fullmatch(cs):
 407         # plan D "[<servername> <client>]" part 1
 408         (pss,pcs) = cs.split(' ')
 409
 410         if pcs == 'LIMIT':
 411           # plan E "[<servername> LIMIT]"
 412           continue
 413
 414         try:
 415           # plan D "[<servername> <client>]" part 2
 416           ci = ipaddr(pc)
 417         except AddressValueError:
 418           # plan F "[<some thing we do not understand>]"
 419           # well, we ignore this
 420           print('warning: ignoring config section %s' % cs, file=sys.stderr)
 421           continue
 422
 423         else: # no AddressValueError
 424           # plan D "[<servername> <client]" part 3
 425           putative(clients, ci, pcs)
 426           putative(servers, pss, pss)
 427           continue
 428
 429     else: # no AddressValueError
 430       # plan B "[<client>" part 2
 431       putative(clients, ci, cs)
 432       continue
 433
 434   return (servers, clients)
 435
 436 def cfg_process_general(c, ss):
 437   c.mtu = cfg.getint(ss, 'mtu')
 438
 439 def cfg_process_saddrs(c, ss):
 440   class ServerAddr():
 441     def __init__(self, port, addrspec):
 442       self.port = port
 443       # also self.addr
 444       try:
 445         self.addr = ipaddress.IPv4Address(addrspec)
 446         self._endpointfactory = twisted.internet.endpoints.TCP4ServerEndpoint
 447         self._inurl = b'%s'
 448       except AddressValueError:
 449         self.addr = ipaddress.IPv6Address(addrspec)
 450         self._endpointfactory = twisted.internet.endpoints.TCP6ServerEndpoint
 451         self._inurl = b'[%s]'
 452     def make_endpoint(self):
 453       return self._endpointfactory(reactor, self.port,
 454                                    interface= '%s' % self.addr)
 455     def url(self):
 456       url = b'http://' + (self._inurl % str(self.addr).encode('ascii'))
 457       if self.port != 80: url += b':%d' % self.port
 458       url += b'/'
 459       return url
 460     def __repr__(self):
 461       return 'ServerAddr'+repr((self.port,self.addr))
 462
 463   c.port = cfg.getint(ss,'port')
 464   c.saddrs = [ ]
 465   for addrspec in cfg.get(ss, 'addrs').split():
 466     sa = ServerAddr(c.port, addrspec)
 467     c.saddrs.append(sa)
 468
 469 def cfg_process_vnetwork(c, ss):
 470   c.vnetwork = ipnetwork(cfg.get(ss,'vnetwork'))
 471   if c.vnetwork.num_addresses < 3 + 2:
 472     raise ValueError('vnetwork needs at least 2^3 addresses')
 473
 474 def cfg_process_vaddr(c, ss):
 475   try:
 476     c.vaddr = cfg.get(ss,'vaddr')
 477   except NoOptionError:
 478     cfg_process_vnetwork(c, ss)
 479     c.vaddr = next(c.vnetwork.hosts())
 480
 481 def cfg_search_section(key,sections):
 482   for section in sections:
 483     if cfg.has_option(section, key):
 484       return section
 485   raise NoOptionError(key, repr(sections))
 486
 487 def cfg_get_raw(*args, **kwargs):
 488   # for passing to cfg_search
 489   return cfg.get(*args, raw=True, **kwargs)
 490
 491 def cfg_search(getter,key,sections):
 492   section = cfg_search_section(key,sections)
 493   return getter(section, key)
 494
 495 def cfg_process_client_limited(cc,ss,sections,key):
 496   val = cfg_search(cfg.getint, key, sections)
 497   lim = cfg_search(cfg.getint, key, ['%s LIMIT' % ss, 'LIMIT'])
 498   cc.__dict__[key] = min(val,lim)
 499
 500 def cfg_process_client_common(cc,ss,cs,ci):
 501   # returns sections to search in, iff password is defined, otherwise None
 502   cc.ci = ci
 503
 504   sections = ['%s %s' % (ss,cs),
 505               cs,
 506               ss,
 507               'DEFAULT']
 508
 509   try: pwsection = cfg_search_section('password', sections)
 510   except NoOptionError: return None
 511
 512   pw = cfg.get(pwsection, 'password')
 513   cc.password = pw.encode('utf-8')
 514
 515   cfg_process_client_limited(cc,ss,sections,'target_requests_outstanding')
 516   cfg_process_client_limited(cc,ss,sections,'http_timeout')
 517
 518   return sections
 519
 520 def cfg_process_ipif(c, sections, varmap):
 521   for d, s in varmap:
 522     try: v = getattr(c, s)
 523     except AttributeError: continue
 524     setattr(c, d, v)
 525
 526   #print('CFGIPIF',repr((varmap, sections, c.__dict__)),file=sys.stderr)
 527
 528   section = cfg_search_section('ipif', sections)
 529   c.ipif_command = cfg.get(section,'ipif', vars=c.__dict__)
 530
 531 #---------- startup ----------
 532
 533 def log_debug_config(m):
 534   if not DBG.CONFIG in debug_set: return
 535   print('DBG.CONFIG:', m)
 536
 537 def common_startup(process_cfg):
 538   # calls process_cfg(putative_clients, putative_servers)
 539
 540   # ConfigParser hates #-comments after values
 541   trailingcomments_re = regexp.compile(r'#.*')
 542   cfg.read_string(trailingcomments_re.sub('', defcfg))
 543   need_defcfg = True
 544
 545   def readconfig(pathname, mandatory=True):
 546     def log(m, p=pathname):
 547       if not DBG.CONFIG in debug_set: return
 548       log_debug_config('%s: %s' % (m, p))
 549
 550     try:
 551       files = os.listdir(pathname)
 552
 553     except FileNotFoundError:
 554       if mandatory: raise
 555       log('skipped')
 556       return
 557
 558     except NotADirectoryError:
 559       cfg.read(pathname)
 560       log('read file')
 561       return
 562
 563     # is a directory
 564     log('directory')
 565     re = regexp.compile('[^-A-Za-z0-9_]')
 566     for f in os.listdir(pathname):
 567       if re.search(f): continue
 568       subpath = pathname + '/' + f
 569       try:
 570         os.stat(subpath)
 571       except FileNotFoundError:
 572         log('entry skipped', subpath)
 573         continue
 574       cfg.read(subpath)
 575       log('entry read', subpath)
 576
 577   def oc_config(od,os, value, op):
 578     nonlocal need_defcfg
 579     need_defcfg = False
 580     readconfig(value)
 581
 582   def oc_extra_config(od,os, value, op):
 583     readconfig(value)
 584
 585   def read_defconfig():
 586     readconfig('/etc/hippotat/config.d', False)
 587     readconfig('/etc/hippotat/passwords.d', False)
 588     readconfig('/etc/hippotat/master.cfg',   False)
 589
 590   def oc_defconfig(od,os, value, op):
 591     nonlocal need_defcfg
 592     need_defcfg = False
 593     read_defconfig(value)
 594
 595   def dfs_less_detailed(dl):
 596     return [df for df in DBG.iterconstants() if df <= dl]
 597
 598   def ds_default(od,os,dl,op):
 599     global debug_set
 600     debug_set.clear
 601     debug_set |= set(dfs_less_detailed(debug_def_detail))
 602
 603   def ds_select(od,os, spec, op):
 604     for it in spec.split(','):
 605
 606       if it.startswith('-'):
 607         mutator = debug_set.discard
 608         it = it[1:]
 609       else:
 610         mutator = debug_set.add
 611
 612       if it == '+':
 613         dfs = DBG.iterconstants()
 614
 615       else:
 616         if it.endswith('+'):
 617           mapper = dfs_less_detailed
 618           it = it[0:len(it)-1]
 619         else:
 620           mapper = lambda x: [x]
 621
 622           try:
 623             dfspec = DBG.lookupByName(it)
 624           except ValueError:
 625             optparser.error('unknown debug flag %s in --debug-select' % it)
 626
 627         dfs = mapper(dfspec)
 628
 629       for df in dfs:
 630         mutator(df)
 631
 632   optparser.add_option('-D', '--debug',
 633                        nargs=0,
 634                        action='callback',
 635                        help='enable default debug (to stdout)',
 636                        callback= ds_default)
 637
 638   optparser.add_option('--debug-select',
 639                        nargs=1,
 640                        type='string',
 641                        metavar='[-]DFLAG[+]|[-]+,...',
 642                        help=
 643 '''enable (`-': disable) each specified DFLAG;
 644 `+': do same for all "more interesting" DFLAGSs;
 645 just `+': all DFLAGs.
 646   DFLAGS: ''' + ' '.join([df.name for df in DBG.iterconstants()]),
 647                        action='callback',
 648                        callback= ds_select)
 649
 650   optparser.add_option('-c', '--config',
 651                        nargs=1,
 652                        type='string',
 653                        metavar='CONFIGFILE',
 654                        dest='configfile',
 655                        action='callback',
 656                        callback= oc_config)
 657
 658   optparser.add_option('--extra-config',
 659                        nargs=1,
 660                        type='string',
 661                        metavar='CONFIGFILE',
 662                        dest='configfile',
 663                        action='callback',
 664                        callback= oc_extra_config)
 665
 666   optparser.add_option('--default-config',
 667                        action='callback',
 668                        callback= oc_defconfig)
 669
 670   (opts, args) = optparser.parse_args()
 671   if len(args): optparser.error('no non-option arguments please')
 672
 673   if need_defcfg:
 674     read_defconfig()
 675
 676   try:
 677     (pss, pcs) = _cfg_process_putatives()
 678     process_cfg(opts, pss, pcs)
 679   except (configparser.Error, ValueError):
 680     traceback.print_exc(file=sys.stderr)
 681     print('\nInvalid configuration, giving up.', file=sys.stderr)
 682     sys.exit(12)
 683
 684
 685   #print('X', debug_set, file=sys.stderr)
 686
 687   log_formatter = twisted.logger.formatEventAsClassicLogText
 688   stdout_obs = twisted.logger.FileLogObserver(sys.stdout, log_formatter)
 689   stderr_obs = twisted.logger.FileLogObserver(sys.stderr, log_formatter)
 690   pred = twisted.logger.LogLevelFilterPredicate(LogLevel.error)
 691   stdsomething_obs = twisted.logger.FilteringLogObserver(
 692     stderr_obs, [pred], stdout_obs
 693   )
 694   global file_log_observer
 695   file_log_observer = twisted.logger.FilteringLogObserver(
 696     stdsomething_obs, [LogNotBoringTwisted()]
 697   )
 698   #log_observer = stdsomething_obs
 699   twisted.logger.globalLogBeginner.beginLoggingTo(
 700     [ file_log_observer, crash_on_critical ]
 701     )
 702
 703 def common_run():
 704   log_debug(DBG.INIT, 'entering reactor')
 705   if not _crashing: reactor.run()
 706   print('ENDED', file=sys.stderr)
 707   sys.exit(16)