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 [COMMON]
 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 # secret = <secret>    # 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(
 390         server_pat + r' ' + '(?:' + client_pat + '|LIMIT)')
 391
 392   for cs in cfg.sections():
 393     def dbg(m):
 394       log_debug_config('putatives: section [%s] %s' % (cs, m))
 395
 396     def log_ignore(why):
 397       dbg('X ignore: %s' % (why))
 398       print('warning: ignoring config section [%s] (%s)' % (cs, why),
 399             file=sys.stderr)
 400
 401     if cs == 'LIMIT' or cs == 'COMMON':
 402       # plan A "[LIMIT]" or "[COMMON]"
 403       dbg('A ignore')
 404       continue
 405
 406     try:
 407       # plan B "[<client>]" part 1
 408       ci = ipaddr(cs)
 409     except AddressValueError:
 410
 411       if server_re.fullmatch(cs):
 412         # plan C "[<servername>]"
 413         dbg('C <server>')
 414         putative(servers, cs, cs)
 415         continue
 416
 417       if serverclient_re.fullmatch(cs):
 418         # plan D "[<servername> <client>]" part 1
 419         (pss,pcs) = cs.split(' ')
 420
 421         if pcs == 'LIMIT':
 422           # plan E "[<servername> LIMIT]"
 423           dbg('E <server> LIMIT')
 424           continue
 425
 426         try:
 427           # plan D "[<servername> <client>]" part 2
 428           ci = ipaddr(pcs)
 429         except AddressValueError:
 430           # plan F branch 1 "[<some thing we do not understand>]"
 431           log_ignore('bad-addr')
 432           continue
 433
 434         else: # no AddressValueError
 435           # plan D "[<servername> <client>]" part 3
 436           dbg('D <server> <client>')
 437           putative(clients, ci, pcs)
 438           putative(servers, pss, pss)
 439           continue
 440       else:
 441         # plan F branch 2 "[<some thing we do not understand>]"
 442         log_ignore('nomatch '+ repr(serverclient_re))
 443
 444     else: # no AddressValueError
 445       # plan B "[<client>" part 2
 446       dbg('B <client>')
 447       putative(clients, ci, cs)
 448       continue
 449
 450   return (servers, clients)
 451
 452 def cfg_process_general(c, ss):
 453   c.mtu = cfg1getint(ss, 'mtu')
 454
 455 def cfg_process_saddrs(c, ss):
 456   class ServerAddr():
 457     def __init__(self, port, addrspec):
 458       self.port = port
 459       # also self.addr
 460       try:
 461         self.addr = ipaddress.IPv4Address(addrspec)
 462         self._endpointfactory = twisted.internet.endpoints.TCP4ServerEndpoint
 463         self._inurl = b'%s'
 464       except AddressValueError:
 465         self.addr = ipaddress.IPv6Address(addrspec)
 466         self._endpointfactory = twisted.internet.endpoints.TCP6ServerEndpoint
 467         self._inurl = b'[%s]'
 468     def make_endpoint(self):
 469       return self._endpointfactory(reactor, self.port,
 470                                    interface= '%s' % self.addr)
 471     def url(self):
 472       url = b'http://' + (self._inurl % str(self.addr).encode('ascii'))
 473       if self.port != 80: url += b':%d' % self.port
 474       url += b'/'
 475       return url
 476     def __repr__(self):
 477       return 'ServerAddr'+repr((self.port,self.addr))
 478
 479   c.port = cfg1getint(ss,'port')
 480   c.saddrs = [ ]
 481   for addrspec in cfg1get(ss, 'addrs').split():
 482     sa = ServerAddr(c.port, addrspec)
 483     c.saddrs.append(sa)
 484
 485 def cfg_process_vnetwork(c, ss):
 486   c.vnetwork = ipnetwork(cfg1get(ss,'vnetwork'))
 487   if c.vnetwork.num_addresses < 3 + 2:
 488     raise ValueError('vnetwork needs at least 2^3 addresses')
 489
 490 def cfg_process_vaddr(c, ss):
 491   try:
 492     c.vaddr = cfg1get(ss,'vaddr')
 493   except NoOptionError:
 494     cfg_process_vnetwork(c, ss)
 495     c.vaddr = next(c.vnetwork.hosts())
 496
 497 def cfg_search_section(key,sections):
 498   for section in sections:
 499     if cfg.has_option(section, key):
 500       return section
 501   raise NoOptionError(key, repr(sections))
 502
 503 def cfg_get_raw(*args, **kwargs):
 504   # for passing to cfg_search
 505   return cfg.get(*args, raw=True, **kwargs)
 506
 507 def cfg_search(getter,key,sections):
 508   section = cfg_search_section(key,sections)
 509   return getter(section, key)
 510
 511 def cfg1get(section,key, getter=cfg.get,**kwargs):
 512   section = cfg_search_section(key,[section,'COMMON'])
 513   return getter(section,key,**kwargs)
 514
 515 def cfg1getint(section,key, **kwargs):
 516   return cfg1get(section,key, getter=cfg.getint,**kwargs);
 517
 518 def cfg_process_client_limited(cc,ss,sections,key):
 519   val = cfg_search(cfg1getint, key, sections)
 520   lim = cfg_search(cfg1getint, key, ['%s LIMIT' % ss, 'LIMIT'])
 521   cc.__dict__[key] = min(val,lim)
 522
 523 def cfg_process_client_common(cc,ss,cs,ci):
 524   # returns sections to search in, iff secret is defined, otherwise None
 525   cc.ci = ci
 526
 527   sections = ['%s %s' % (ss,cs),
 528               cs,
 529               ss,
 530               'COMMON']
 531
 532   try: pwsection = cfg_search_section('secret', sections)
 533   except NoOptionError: return None
 534
 535   pw = cfg1get(pwsection, 'secret')
 536   cc.secret = pw.encode('utf-8')
 537
 538   cfg_process_client_limited(cc,ss,sections,'target_requests_outstanding')
 539   cfg_process_client_limited(cc,ss,sections,'http_timeout')
 540
 541   return sections
 542
 543 def cfg_process_ipif(c, sections, varmap):
 544   for d, s in varmap:
 545     try: v = getattr(c, s)
 546     except AttributeError: continue
 547     setattr(c, d, v)
 548
 549   #print('CFGIPIF',repr((varmap, sections, c.__dict__)),file=sys.stderr)
 550
 551   section = cfg_search_section('ipif', sections)
 552   c.ipif_command = cfg1get(section,'ipif', vars=c.__dict__)
 553
 554 #---------- startup ----------
 555
 556 def log_debug_config(m):
 557   if not DBG.CONFIG in debug_set: return
 558   print('DBG.CONFIG:', m)
 559
 560 def common_startup(process_cfg):
 561   # calls process_cfg(putative_clients, putative_servers)
 562
 563   # ConfigParser hates #-comments after values
 564   trailingcomments_re = regexp.compile(r'#.*')
 565   cfg.read_string(trailingcomments_re.sub('', defcfg))
 566   need_defcfg = True
 567
 568   def readconfig(pathname, mandatory=True):
 569     def log(m, p=pathname):
 570       if not DBG.CONFIG in debug_set: return
 571       log_debug_config('%s: %s' % (m, p))
 572
 573     try:
 574       files = os.listdir(pathname)
 575
 576     except FileNotFoundError:
 577       if mandatory: raise
 578       log('skipped')
 579       return
 580
 581     except NotADirectoryError:
 582       cfg.read(pathname)
 583       log('read file')
 584       return
 585
 586     # is a directory
 587     log('directory')
 588     re = regexp.compile('[^-A-Za-z0-9_]')
 589     for f in os.listdir(pathname):
 590       if re.search(f): continue
 591       subpath = pathname + '/' + f
 592       try:
 593         os.stat(subpath)
 594       except FileNotFoundError:
 595         log('entry skipped', subpath)
 596         continue
 597       cfg.read(subpath)
 598       log('entry read', subpath)
 599
 600   def oc_config(od,os, value, op):
 601     nonlocal need_defcfg
 602     need_defcfg = False
 603     readconfig(value)
 604
 605   def oc_extra_config(od,os, value, op):
 606     readconfig(value)
 607
 608   def read_defconfig():
 609     readconfig('/etc/hippotat/config.d', False)
 610     readconfig('/etc/hippotat/secrets.d', False)
 611     readconfig('/etc/hippotat/master.cfg',   False)
 612
 613   def oc_defconfig(od,os, value, op):
 614     nonlocal need_defcfg
 615     need_defcfg = False
 616     read_defconfig(value)
 617
 618   def dfs_less_detailed(dl):
 619     return [df for df in DBG.iterconstants() if df <= dl]
 620
 621   def ds_default(od,os,dl,op):
 622     global debug_set
 623     debug_set.clear
 624     debug_set |= set(dfs_less_detailed(debug_def_detail))
 625
 626   def ds_select(od,os, spec, op):
 627     for it in spec.split(','):
 628
 629       if it.startswith('-'):
 630         mutator = debug_set.discard
 631         it = it[1:]
 632       else:
 633         mutator = debug_set.add
 634
 635       if it == '+':
 636         dfs = DBG.iterconstants()
 637
 638       else:
 639         if it.endswith('+'):
 640           mapper = dfs_less_detailed
 641           it = it[0:len(it)-1]
 642         else:
 643           mapper = lambda x: [x]
 644
 645           try:
 646             dfspec = DBG.lookupByName(it)
 647           except ValueError:
 648             optparser.error('unknown debug flag %s in --debug-select' % it)
 649
 650         dfs = mapper(dfspec)
 651
 652       for df in dfs:
 653         mutator(df)
 654
 655   optparser.add_option('-D', '--debug',
 656                        nargs=0,
 657                        action='callback',
 658                        help='enable default debug (to stdout)',
 659                        callback= ds_default)
 660
 661   optparser.add_option('--debug-select',
 662                        nargs=1,
 663                        type='string',
 664                        metavar='[-]DFLAG[+]|[-]+,...',
 665                        help=
 666 '''enable (`-': disable) each specified DFLAG;
 667 `+': do same for all "more interesting" DFLAGSs;
 668 just `+': all DFLAGs.
 669   DFLAGS: ''' + ' '.join([df.name for df in DBG.iterconstants()]),
 670                        action='callback',
 671                        callback= ds_select)
 672
 673   optparser.add_option('-c', '--config',
 674                        nargs=1,
 675                        type='string',
 676                        metavar='CONFIGFILE',
 677                        dest='configfile',
 678                        action='callback',
 679                        callback= oc_config)
 680
 681   optparser.add_option('--extra-config',
 682                        nargs=1,
 683                        type='string',
 684                        metavar='CONFIGFILE',
 685                        dest='configfile',
 686                        action='callback',
 687                        callback= oc_extra_config)
 688
 689   optparser.add_option('--default-config',
 690                        action='callback',
 691                        callback= oc_defconfig)
 692
 693   (opts, args) = optparser.parse_args()
 694   if len(args): optparser.error('no non-option arguments please')
 695
 696   if need_defcfg:
 697     read_defconfig()
 698
 699   try:
 700     (pss, pcs) = _cfg_process_putatives()
 701     process_cfg(opts, pss, pcs)
 702   except (configparser.Error, ValueError):
 703     traceback.print_exc(file=sys.stderr)
 704     print('\nInvalid configuration, giving up.', file=sys.stderr)
 705     sys.exit(12)
 706
 707
 708   #print('X', debug_set, file=sys.stderr)
 709
 710   log_formatter = twisted.logger.formatEventAsClassicLogText
 711   stdout_obs = twisted.logger.FileLogObserver(sys.stdout, log_formatter)
 712   stderr_obs = twisted.logger.FileLogObserver(sys.stderr, log_formatter)
 713   pred = twisted.logger.LogLevelFilterPredicate(LogLevel.error)
 714   stdsomething_obs = twisted.logger.FilteringLogObserver(
 715     stderr_obs, [pred], stdout_obs
 716   )
 717   global file_log_observer
 718   file_log_observer = twisted.logger.FilteringLogObserver(
 719     stdsomething_obs, [LogNotBoringTwisted()]
 720   )
 721   #log_observer = stdsomething_obs
 722   twisted.logger.globalLogBeginner.beginLoggingTo(
 723     [ file_log_observer, crash_on_critical ]
 724     )
 725
 726 def common_run():
 727   log_debug(DBG.INIT, 'entering reactor')
 728   if not _crashing: reactor.run()
 729   print('ENDED', file=sys.stderr)
 730   sys.exit(16)