chutney-for-relay-testing/lib/chutney/TorNet.py

#!/usr/bin/env python2
#
# Copyright 2011 Nick Mathewson, Michael Stone
# Copyright 2013 The Tor Project
#
#  You may do anything with this work that copyright law would normally
#  restrict, so long as you retain the above notice(s) and this license
#  in all redistributed copies and derived works.  There is no warranty.

from __future__ import print_function
from __future__ import with_statement

import cgitb
import os
import signal
import subprocess
import sys
import re
import errno
import time
import shutil
import importlib

import chutney.Templating
import chutney.Traffic

_BASE_ENVIRON = None
_TORRC_OPTIONS = None
_THE_NETWORK = None

# Get verbose tracebacks, so we can diagnose better.
cgitb.enable(format="plain")


def mkdir_p(d, mode=511):
    """Create directory 'd' and all of its parents as needed.  Unlike
       os.makedirs, does not give an error if d already exists.

       511 is the decimal representation of the octal number 0777. Since
       python2 only supports 0777 and python3 only supports 0o777, we can use
       neither.
    """
    try:
        os.makedirs(d, mode=mode)
    except OSError as e:
        if e.errno == errno.EEXIST:
            return
        raise


class Node(object):

    """A Node represents a Tor node or a set of Tor nodes.  It's created
       in a network configuration file.

       This class is responsible for holding the user's selected node
       configuration, and figuring out how the node needs to be
       configured and launched.
    """
    # Fields:
    # _parent
    # _env
    # _builder
    # _controller

    ########
    # Users are expected to call these:

    def __init__(self, parent=None, **kwargs):
        self._parent = parent
        self._env = self._createEnviron(parent, kwargs)
        self._builder = None
        self._controller = None

    def getN(self, N):
        return [Node(self) for _ in range(N)]

    def specialize(self, **kwargs):
        return Node(parent=self, **kwargs)

    ######
    # Chutney uses these:

    def getBuilder(self):
        """Return a NodeBuilder instance to set up this node (that is, to
           write all the files that need to be in place so that this
           node can be run by a NodeController).
        """
        if self._builder is None:
            self._builder = LocalNodeBuilder(self._env)
        return self._builder

    def getController(self):
        """Return a NodeController instance to control this node (that is,
           to start it, stop it, see if it's running, etc.)
        """
        if self._controller is None:
            self._controller = LocalNodeController(self._env)
        return self._controller

    def setNodenum(self, num):
        """Assign a value to the 'nodenum' element of this node.  Each node
           in a network gets its own nodenum.
        """
        self._env['nodenum'] = num

    #####
    # These are internal:

    def _createEnviron(self, parent, argdict):
        """Return an Environ that delegates to the parent node's Environ (if
           there is a parent node), or to the default environment.
        """
        if parent:
            parentenv = parent._env
        else:
            parentenv = self._getDefaultEnviron()
        return TorEnviron(parentenv, **argdict)

    def _getDefaultEnviron(self):
        """Return the default environment.  Any variables that we can't find
           set for any particular node, we look for here.
        """
        return _BASE_ENVIRON


class _NodeCommon(object):

    """Internal helper class for functionality shared by some NodeBuilders
       and some NodeControllers."""
    # XXXX maybe this should turn into a mixin.

    def __init__(self, env):
        self._env = env

    def expand(self, pat, includePath=(".",)):
        return chutney.Templating.Template(pat, includePath).format(self._env)

    def _getTorrcFname(self):
        """Return the name of the file where we'll be writing torrc"""
        return self.expand("${torrc_fname}")


class NodeBuilder(_NodeCommon):

    """Abstract base class.  A NodeBuilder is responsible for doing all the
       one-time prep needed to set up a node in a network.
    """

    def __init__(self, env):
        _NodeCommon.__init__(self, env)

    def checkConfig(self, net):
        """Try to format our torrc; raise an exception if we can't.
        """

    def preConfig(self, net):
        """Called on all nodes before any nodes configure: generates keys as
           needed.
        """

    def config(self, net):
        """Called to configure a node: creates a torrc file for it."""

    def postConfig(self, net):
        """Called on each nodes after all nodes configure."""


class NodeController(_NodeCommon):

    """Abstract base class.  A NodeController is responsible for running a
       node on the network.
    """

    def __init__(self, env):
        _NodeCommon.__init__(self, env)

    def check(self, listRunning=True, listNonRunning=False):
        """See if this node is running, stopped, or crashed.  If it's running
           and listRunning is set, print a short statement.  If it's
           stopped and listNonRunning is set, then print a short statement.
           If it's crashed, print a statement.  Return True if the
           node is running, false otherwise.
        """

    def start(self):
        """Try to start this node; return True if we succeeded or it was
           already running, False if we failed."""

    def stop(self, sig=signal.SIGINT):
        """Try to stop this node by sending it the signal 'sig'."""


class LocalNodeBuilder(NodeBuilder):

    # Environment members used:
    # torrc -- which torrc file to use
    # torrc_template_path -- path to search for torrc files and include files
    # authority -- bool -- are we an authority?
    # bridgeauthority -- bool -- are we a bridge authority?
    # relay -- bool -- are we a relay?
    # bridge -- bool -- are we a bridge?
    # hs -- bool -- are we a hidden service?
    # nodenum -- int -- set by chutney -- which unique node index is this?
    # dir -- path -- set by chutney -- data directory for this tor
    # tor_gencert -- path to tor_gencert binary
    # tor -- path to tor binary
    # auth_cert_lifetime -- lifetime of authority certs, in months.
    # ip -- IP to listen on
    # ipv6_addr -- IPv6 address to listen on
    # orport, dirport -- used on authorities, relays, and bridges
    # fingerprint -- used only if authority
    # dirserver_flags -- used only if authority
    # nick -- nickname of this router

    # Environment members set
    # fingerprint -- hex router key fingerprint
    # nodenum -- int -- set by chutney -- which unique node index is this?

    def __init__(self, env):
        NodeBuilder.__init__(self, env)
        self._env = env

    def _createTorrcFile(self, checkOnly=False):
        """Write the torrc file for this node, disabling any options
           that are not supported by env's tor binary using comments.
           If checkOnly, just make sure that the formatting is indeed
           possible.
        """
        fn_out = self._getTorrcFname()
        torrc_template = self._getTorrcTemplate()
        output = torrc_template.format(self._env)
        if checkOnly:
            # XXXX Is it time-consuming to format? If so, cache here.
            return
        # now filter the options we're about to write, commenting out
        # the options that the current tor binary doesn't support
        tor = self._env['tor']
        # find the options the current tor binary supports, and cache them
        if tor not in _TORRC_OPTIONS:
            # Note: some versions of tor (e.g. 0.2.4.23) require
            # --list-torrc-options to be the first argument
            cmdline = [
                tor,
                "--list-torrc-options",
                "--hush"]
            try:
                opts = subprocess.check_output(cmdline, bufsize=-1,
                                               universal_newlines=True)
            except OSError as e:
                # only catch file not found error
                if e.errno == errno.ENOENT:
                    print("Cannot find tor binary %r. Use "
                          "CHUTNEY_TOR environment variable to set the "
                          "path, or put the binary into $PATH." % tor)
                    sys.exit(0)
                else:
                    raise
            # check we received a list of options, and nothing else
            assert re.match(r'(^\w+$)+', opts, flags=re.MULTILINE)
            torrc_opts = opts.split()
            # cache the options for this tor binary's path
            _TORRC_OPTIONS[tor] = torrc_opts
        else:
            torrc_opts = _TORRC_OPTIONS[tor]
        # check if each option is supported before writing it
        # TODO: what about unsupported values?
        # e.g. tor 0.2.4.23 doesn't support TestingV3AuthInitialVoteDelay 2
        # but later version do. I say throw this one to the user.
        with open(fn_out, 'w') as f:
            # we need to do case-insensitive option comparison
            # even if this is a static whitelist,
            # so we convert to lowercase as close to the loop as possible
            lower_opts = [opt.lower() for opt in torrc_opts]
            # keep ends when splitting lines, so we can write them out
            # using writelines() without messing around with "\n"s
            for line in output.splitlines(True):
                # check if the first word on the line is a supported option,
                # preserving empty lines and comment lines
                sline = line.strip()
                if (len(sline) == 0 or
                        sline[0] == '#' or
                        sline.split()[0].lower() in lower_opts):
                    f.writelines([line])
                else:
                    # well, this could get spammy
                    # TODO: warn once per option per tor binary
                    # TODO: print tor version?
                    print(("The tor binary at %r does not support the "
                           "option in the torrc line:\n"
                           "%r") % (tor, line.strip()))
                    # we could decide to skip these lines entirely
                    # TODO: write tor version?
                    f.writelines(["# " + tor + " unsupported: " + line])

    def _getTorrcTemplate(self):
        """Return the template used to write the torrc for this node."""
        template_path = self._env['torrc_template_path']
        return chutney.Templating.Template("$${include:$torrc}",
                                           includePath=template_path)

    def _getFreeVars(self):
        """Return a set of the free variables in the torrc template for this
           node.
        """
        template = self._getTorrcTemplate()
        return template.freevars(self._env)

    def checkConfig(self, net):
        """Try to format our torrc; raise an exception if we can't.
        """
        self._createTorrcFile(checkOnly=True)

    def preConfig(self, net):
        """Called on all nodes before any nodes configure: generates keys and
           hidden service directories as needed.
        """
        self._makeDataDir()
        if self._env['authority']:
            self._genAuthorityKey()
        if self._env['relay']:
            self._genRouterKey()
        if self._env['hs']:
            self._makeHiddenServiceDir()

    def config(self, net):
        """Called to configure a node: creates a torrc file for it."""
        self._createTorrcFile()
        # self._createScripts()

    def postConfig(self, net):
        """Called on each nodes after all nodes configure."""
        # self.net.addNode(self)
        pass

    def _makeDataDir(self):
        """Create the data directory (with keys subdirectory) for this node.
        """
        datadir = self._env['dir']
        mkdir_p(os.path.join(datadir, 'keys'))

    def _makeHiddenServiceDir(self):
        """Create the hidden service subdirectory for this node.

          The directory name is stored under the 'hs_directory' environment
          key. It is combined with the 'dir' data directory key to yield the
          path to the hidden service directory.

          448 is the decimal representation of the octal number 0700. Since
          python2 only supports 0700 and python3 only supports 0o700, we can
          use neither.
        """
        datadir = self._env['dir']
        mkdir_p(os.path.join(datadir, self._env['hs_directory']), 448)

    def _genAuthorityKey(self):
        """Generate an authority identity and signing key for this authority,
           if they do not already exist."""
        datadir = self._env['dir']
        tor_gencert = self._env['tor_gencert']
        lifetime = self._env['auth_cert_lifetime']
        idfile = os.path.join(datadir, 'keys', "authority_identity_key")
        skfile = os.path.join(datadir, 'keys', "authority_signing_key")
        certfile = os.path.join(datadir, 'keys', "authority_certificate")
        addr = self.expand("${ip}:${dirport}")
        passphrase = self._env['auth_passphrase']
        if all(os.path.exists(f) for f in [idfile, skfile, certfile]):
            return
        cmdline = [
            tor_gencert,
            '--create-identity-key',
            '--passphrase-fd', '0',
            '-i', idfile,
            '-s', skfile,
            '-c', certfile,
            '-m', str(lifetime),
            '-a', addr]
        print("Creating identity key %s for %s with %s" % (
            idfile, self._env['nick'], " ".join(cmdline)))
        try:
            p = subprocess.Popen(cmdline, stdin=subprocess.PIPE)
        except OSError as e:
            # only catch file not found error
            if e.errno == errno.ENOENT:
                print("Cannot find tor-gencert binary %r. Use "
                      "CHUTNEY_TOR_GENCERT environment variable to set the "
                      "path, or put the binary into $PATH." % tor_gencert)
                sys.exit(0)
            else:
                raise
        p.communicate(passphrase + "\n")
        assert p.returncode == 0  # XXXX BAD!

    def _genRouterKey(self):
        """Generate an identity key for this router, unless we already have,
           and set up the 'fingerprint' entry in the Environ.
        """
        datadir = self._env['dir']
        tor = self._env['tor']
        torrc = self._getTorrcFname()
        cmdline = [
            tor,
            "--quiet",
            "--ignore-missing-torrc",
            "-f", torrc,
            "--list-fingerprint",
            "--orport", "1",
            "--datadirectory", datadir]
        try:
            p = subprocess.Popen(cmdline, stdout=subprocess.PIPE)
        except OSError as e:
            # only catch file not found error
            if e.errno == errno.ENOENT:
                print("Cannot find tor binary %r. Use "
                      "CHUTNEY_TOR environment variable to set the "
                      "path, or put the binary into $PATH." % tor)
                sys.exit(0)
            else:
                raise
        stdout, stderr = p.communicate()
        fingerprint = "".join((stdout.rstrip().split('\n')[-1]).split()[1:])
        if not re.match(r'^[A-F0-9]{40}$', fingerprint):
            print(("Error when calling %r. It gave %r as a fingerprint "
                   " and %r on stderr.") % (" ".join(cmdline), stdout, stderr))
            sys.exit(1)
        self._env['fingerprint'] = fingerprint

    def _getAltAuthLines(self, hasbridgeauth=False):
        """Return a combination of AlternateDirAuthority,
        AlternateHSAuthority and AlternateBridgeAuthority lines for
        this Node, appropriately.  Non-authorities return ""."""
        if not self._env['authority']:
            return ""

        datadir = self._env['dir']
        certfile = os.path.join(datadir, 'keys', "authority_certificate")
        v3id = None
        with open(certfile, 'r') as f:
            for line in f:
                if line.startswith("fingerprint"):
                    v3id = line.split()[1].strip()
                    break

        assert v3id is not None

        if self._env['bridgeauthority']:
            # Bridge authorities return AlternateBridgeAuthority with
            # the 'bridge' flag set.
            options = ("AlternateBridgeAuthority",)
            self._env['dirserver_flags'] += " bridge"
        else:
            # Directory authorities return AlternateDirAuthority with
            # the 'hs' and 'v3ident' flags set.
            # XXXX This next line is needed for 'bridges' but breaks
            # 'basic'
            if hasbridgeauth:
                options = ("AlternateDirAuthority",)
            else:
                options = ("DirAuthority",)
            self._env['dirserver_flags'] += " hs v3ident=%s" % v3id

        authlines = ""
        for authopt in options:
            authlines += "%s %s orport=%s" % (
                authopt, self._env['nick'], self._env['orport'])
            # It's ok to give an authority's IPv6 address to an IPv4-only
            # client or relay: it will and must ignore it
            if self._env['ipv6_addr'] is not None:
                authlines += " ipv6=%s:%s" % (self._env['ipv6_addr'],
                                              self._env['orport'])
            authlines += " %s %s:%s %s\n" % (
                self._env['dirserver_flags'], self._env['ip'],
                self._env['dirport'], self._env['fingerprint'])
        return authlines

    def _getBridgeLines(self):
        """Return potential Bridge line for this Node. Non-bridge
        relays return "".
        """
        if not self._env['bridge']:
            return ""

        bridgelines = "Bridge %s:%s\n" % (self._env['ip'],
                                          self._env['orport'])
        if self._env['ipv6_addr'] is not None:
            bridgelines += "Bridge %s:%s\n" % (self._env['ipv6_addr'],
                                               self._env['orport'])
        return bridgelines


class LocalNodeController(NodeController):

    def __init__(self, env):
        NodeController.__init__(self, env)
        self._env = env

    def getPid(self):
        """Assuming that this node has its pidfile in ${dir}/pid, return
           the pid of the running process, or None if there is no pid in the
           file.
        """
        pidfile = os.path.join(self._env['dir'], 'pid')
        if not os.path.exists(pidfile):
            return None

        with open(pidfile, 'r') as f:
            return int(f.read())

    def isRunning(self, pid=None):
        """Return true iff this node is running.  (If 'pid' is provided, we
           assume that the pid provided is the one of this node.  Otherwise
           we call getPid().
        """
        if pid is None:
            pid = self.getPid()
        if pid is None:
            return False

        try:
            os.kill(pid, 0)  # "kill 0" == "are you there?"
        except OSError as e:
            if e.errno == errno.ESRCH:
                return False
            raise

        # okay, so the process exists.  Say "True" for now.
        # XXXX check if this is really tor!
        return True

    def check(self, listRunning=True, listNonRunning=False):
        """See if this node is running, stopped, or crashed.  If it's running
           and listRunning is set, print a short statement.  If it's
           stopped and listNonRunning is set, then print a short statement.
           If it's crashed, print a statement.  Return True if the
           node is running, false otherwise.
        """
        # XXX Split this into "check" and "print" parts.
        pid = self.getPid()
        nick = self._env['nick']
        datadir = self._env['dir']
        corefile = "core.%s" % pid
        if self.isRunning(pid):
            if listRunning:
                print("%s is running with PID %s" % (nick, pid))
            return True
        elif os.path.exists(os.path.join(datadir, corefile)):
            if listNonRunning:
                print("%s seems to have crashed, and left core file %s" % (
                    nick, corefile))
            return False
        else:
            if listNonRunning:
                print("%s is stopped" % nick)
            return False

    def hup(self):
        """Send a SIGHUP to this node, if it's running."""
        pid = self.getPid()
        nick = self._env['nick']
        if self.isRunning(pid):
            print("Sending sighup to %s" % nick)
            os.kill(pid, signal.SIGHUP)
            return True
        else:
            print("%s is not running" % nick)
            return False

    def start(self):
        """Try to start this node; return True if we succeeded or it was
           already running, False if we failed."""

        if self.isRunning():
            print("%s is already running" % self._env['nick'])
            return True
        tor_path = self._env['tor']
        torrc = self._getTorrcFname()
        cmdline = [
            tor_path,
            "--quiet",
            "-f", torrc,
        ]
        try:
            p = subprocess.Popen(cmdline)
        except OSError as e:
            # only catch file not found error
            if e.errno == errno.ENOENT:
                print("Cannot find tor binary %r. Use CHUTNEY_TOR "
                      "environment variable to set the path, or put the "
                      "binary into $PATH." % tor_path)
                sys.exit(0)
            else:
                raise
        if self.waitOnLaunch():
            # this requires that RunAsDaemon is set
            p.wait()
        else:
            # this does not require RunAsDaemon to be set, but is slower.
            #
            # poll() only catches failures before the call itself
            # so let's sleep a little first
            # this does, of course, slow down process launch
            # which can require an adjustment to the voting interval
            #
            # avoid writing a newline or space when polling
            # so output comes out neatly
            sys.stdout.write('.')
            sys.stdout.flush()
            time.sleep(self._env['poll_launch_time'])
            p.poll()
        if p.returncode is not None and p.returncode != 0:
            if self._env['poll_launch_time'] is None:
                print("Couldn't launch %s (%s): %s" % (self._env['nick'],
                                                       " ".join(cmdline),
                                                       p.returncode))
            else:
                print("Couldn't poll %s (%s) "
                      "after waiting %s seconds for launch"
                      ": %s" % (self._env['nick'],
                                " ".join(cmdline),
                                self._env['poll_launch_time'],
                                p.returncode))
            return False
        return True

    def stop(self, sig=signal.SIGINT):
        """Try to stop this node by sending it the signal 'sig'."""
        pid = self.getPid()
        if not self.isRunning(pid):
            print("%s is not running" % self._env['nick'])
            return
        os.kill(pid, sig)

    def cleanup_lockfile(self):
        lf = self._env['lockfile']
        if not self.isRunning() and os.path.exists(lf):
            print('Removing stale lock file for {0} ...'.format(
                self._env['nick']))
            os.remove(lf)

    def waitOnLaunch(self):
        """Check whether we can wait() for the tor process to launch"""
        # TODO: is this the best place for this code?
        # RunAsDaemon default is 0
        runAsDaemon = False
        with open(self._getTorrcFname(), 'r') as f:
            for line in f.readlines():
                stline = line.strip()
                # if the line isn't all whitespace or blank
                if len(stline) > 0:
                    splline = stline.split()
                    # if the line has at least two tokens on it
                    if (len(splline) > 0 and
                            splline[0].lower() == "RunAsDaemon".lower() and
                            splline[1] == "1"):
                        # use the RunAsDaemon value from the torrc
                        # TODO: multiple values?
                        runAsDaemon = True
        if runAsDaemon:
            # we must use wait() instead of poll()
            self._env['poll_launch_time'] = None
            return True
        else:
            # we must use poll() instead of wait()
            if self._env['poll_launch_time'] is None:
                self._env['poll_launch_time'] = \
                    self._env['poll_launch_time_default']
            return False

DEFAULTS = {
    'authority': False,
    'bridgeauthority': False,
    'hasbridgeauth': False,
    'relay': False,
    'bridge': False,
    'hs': False,
    'hs_directory': 'hidden_service',
    'hs-hostname': None,
    'connlimit': 60,
    'net_base_dir': os.environ.get('CHUTNEY_DATA_DIR', 'net'),
    'tor': os.environ.get('CHUTNEY_TOR', 'tor'),
    'tor-gencert': os.environ.get('CHUTNEY_TOR_GENCERT', None),
    'auth_cert_lifetime': 12,
    'ip': os.environ.get('CHUTNEY_LISTEN_ADDRESS', '127.0.0.1'),
    # Pre-0.2.8 clients will fail to parse ipv6 auth lines,
    # so we default to ipv6_addr None
    'ipv6_addr': os.environ.get('CHUTNEY_LISTEN_ADDRESS_V6', None),
    'dirserver_flags': 'no-v2',
    'chutney_dir': '.',
    'torrc_fname': '${dir}/torrc',
    'orport_base': 5000,
    'dirport_base': 7000,
    'controlport_base': 8000,
    'socksport_base': 9000,
    'authorities': "AlternateDirAuthority bleargh bad torrc file!",
    'bridges': "Bridge bleargh bad torrc file!",
    'core': True,
    # poll_launch_time: None means wait on launch (requires RunAsDaemon),
    # otherwise, poll after that many seconds (can be fractional/decimal)
    'poll_launch_time': None,
    # Used when poll_launch_time is None, but RunAsDaemon is not set
    # Set low so that we don't interfere with the voting interval
    'poll_launch_time_default': 0.1,
    # the number of bytes of random data we send on each connection
    'data_bytes': int(os.environ.get('CHUTNEY_DATA_BYTES', 10 * 1024)),
    # the number of times each client will connect
    'connection_count': int(os.environ.get('CHUTNEY_CONNECTIONS', 1)),
    # Do we want every client to connect to every HS, or one client
    # to connect to each HS?
    # (Clients choose an exit at random, so this doesn't apply to exits.)
    'hs_multi_client': int(os.environ.get('CHUTNEY_HS_MULTI_CLIENT', 0)),
    # How long should verify (and similar commands) wait for a successful
    # outcome? (seconds)
    # We check BOOTSTRAP_TIME for compatibility with old versions of
    # test-network.sh
    'bootstrap_time': int(os.environ.get('CHUTNEY_BOOTSTRAP_TIME',
                                         os.environ.get('BOOTSTRAP_TIME',
                                                        60))),
}


class TorEnviron(chutney.Templating.Environ):

    """Subclass of chutney.Templating.Environ to implement commonly-used
       substitutions.

       Environment fields provided:

          orport, controlport, socksport, dirport:
          dir:
          nick:
          tor_gencert:
          auth_passphrase:
          torrc_template_path:
          hs_hostname:

       Environment fields used:
          nodenum
          tag
          orport_base, controlport_base, socksport_base, dirport_base
          tor-gencert (note hyphen)
          chutney_dir
          tor
          dir
          hs_directory
          nick (debugging only)
          hs-hostname (note hyphen)

       XXXX document the above.  Or document all fields in one place?
    """

    def __init__(self, parent=None, **kwargs):
        chutney.Templating.Environ.__init__(self, parent=parent, **kwargs)

    def _get_orport(self, my):
        return my['orport_base'] + my['nodenum']

    def _get_controlport(self, my):
        return my['controlport_base'] + my['nodenum']

    def _get_socksport(self, my):
        return my['socksport_base'] + my['nodenum']

    def _get_dirport(self, my):
        return my['dirport_base'] + my['nodenum']

    def _get_dir(self, my):
        return os.path.abspath(os.path.join(my['net_base_dir'],
                                            "nodes",
                                            "%03d%s" % (
                                                my['nodenum'], my['tag'])))

    def _get_nick(self, my):
        return "test%03d%s" % (my['nodenum'], my['tag'])

    def _get_tor_gencert(self, my):
        return my['tor-gencert'] or '{0}-gencert'.format(my['tor'])

    def _get_auth_passphrase(self, my):
        return self['nick']  # OMG TEH SECURE!

    def _get_torrc_template_path(self, my):
        return [os.path.join(my['chutney_dir'], 'torrc_templates')]

    def _get_lockfile(self, my):
        return os.path.join(self['dir'], 'lock')

    # A hs generates its key on first run,
    # so check for it at the last possible moment,
    # but cache it in memory to avoid repeatedly reading the file
    # XXXX - this is not like the other functions in this class,
    # as it reads from a file created by the hidden service
    def _get_hs_hostname(self, my):
        if my['hs-hostname'] is None:
            datadir = my['dir']
            # a file containing a single line with the hs' .onion address
            hs_hostname_file = os.path.join(datadir, my['hs_directory'],
                                            'hostname')
            try:
                with open(hs_hostname_file, 'r') as hostnamefp:
                    hostname = hostnamefp.read()
                # the hostname file ends with a newline
                hostname = hostname.strip()
                my['hs-hostname'] = hostname
            except IOError as e:
                print("Error: hs %r error %d: %r opening hostname file '%r'" %
                      (my['nick'], e.errno, e.strerror, hs_hostname_file))
        return my['hs-hostname']


class Network(object):

    """A network of Tor nodes, plus functions to manipulate them
    """

    def __init__(self, defaultEnviron):
        self._nodes = []
        self._dfltEnv = defaultEnviron
        self._nextnodenum = 0

    def _addNode(self, n):
        n.setNodenum(self._nextnodenum)
        self._nextnodenum += 1
        self._nodes.append(n)

    def move_aside_nodes(self):
        net_base_dir = os.environ.get('CHUTNEY_DATA_DIR', 'net')
        nodesdir = os.path.join(net_base_dir, 'nodes')

        if not os.path.exists(nodesdir):
            return

        newdir = newdirbase = "%s.%d" % (nodesdir, time.time())
        i = 0
        while os.path.exists(newdir):
            i += 1
            newdir = "%s.%d" % (newdirbase, i)

        print("NOTE: renaming %r to %r" % (nodesdir, newdir))
        os.rename(nodesdir, newdir)

    def _checkConfig(self):
        for n in self._nodes:
            n.getBuilder().checkConfig(self)

    def configure(self):
        # shutil.rmtree(os.path.join(os.getcwd(),'net','nodes'),ignore_errors=True)
        self.move_aside_nodes()
        network = self
        altauthlines = []
        bridgelines = []
        builders = [n.getBuilder() for n in self._nodes]
        self._checkConfig()

        # XXX don't change node names or types or count if anything is
        # XXX running!

        for b in builders:
            b.preConfig(network)
            altauthlines.append(b._getAltAuthLines(
                self._dfltEnv['hasbridgeauth']))
            bridgelines.append(b._getBridgeLines())

        self._dfltEnv['authorities'] = "".join(altauthlines)
        self._dfltEnv['bridges'] = "".join(bridgelines)

        for b in builders:
            b.config(network)

        for b in builders:
            b.postConfig(network)

    def status(self):
        statuses = [n.getController().check() for n in self._nodes]
        n_ok = len([x for x in statuses if x])
        print("%d/%d nodes are running" % (n_ok, len(self._nodes)))
        return n_ok == len(self._nodes)

    def restart(self):
        self.stop()
        self.start()

    def start(self):
        if self._dfltEnv['poll_launch_time'] is not None:
            # format polling correctly - avoid printing a newline
            sys.stdout.write("Starting nodes")
            sys.stdout.flush()
        else:
            print("Starting nodes")
        rv = all([n.getController().start() for n in self._nodes])
        # now print a newline unconditionally - this stops poll()ing
        # output from being squashed together, at the cost of a blank
        # line in wait()ing output
        print("")
        return rv

    def hup(self):
        print("Sending SIGHUP to nodes")
        return all([n.getController().hup() for n in self._nodes])

    def stop(self):
        controllers = [n.getController() for n in self._nodes]
        for sig, desc in [(signal.SIGINT, "SIGINT"),
                          (signal.SIGINT, "another SIGINT"),
                          (signal.SIGKILL, "SIGKILL")]:
            print("Sending %s to nodes" % desc)
            for c in controllers:
                if c.isRunning():
                    c.stop(sig=sig)
            print("Waiting for nodes to finish.")
            for n in range(15):
                time.sleep(1)
                if all(not c.isRunning() for c in controllers):
                    # check for stale lock file when Tor crashes
                    for c in controllers:
                        c.cleanup_lockfile()
                    return
                sys.stdout.write(".")
                sys.stdout.flush()
            for c in controllers:
                c.check(listNonRunning=False)


def ConfigureNodes(nodelist):
    network = _THE_NETWORK

    for n in nodelist:
        network._addNode(n)
        if n._env['bridgeauthority']:
            network._dfltEnv['hasbridgeauth'] = True


def getTests():
    tests = []
    chutney_path = os.environ.get('CHUTNEY_PATH', '')
    if len(chutney_path) > 0 and chutney_path[-1] != '/':
        chutney_path += "/"
    for x in os.listdir(chutney_path + "scripts/chutney_tests/"):
        if not x.startswith("_") and os.path.splitext(x)[1] == ".py":
            tests.append(os.path.splitext(x)[0])
    return tests


def usage(network):
    return "\n".join(["Usage: chutney {command/test} {networkfile}",
                      "Known commands are: %s" % (
                          " ".join(x for x in dir(network)
                                   if not x.startswith("_"))),
                      "Known tests are: %s" % (
                          " ".join(getTests()))
                      ])


def exit_on_error(err_msg):
    print("Error: {0}\n".format(err_msg))
    print(usage(_THE_NETWORK))
    sys.exit(1)


def runConfigFile(verb, data):
    _GLOBALS = dict(_BASE_ENVIRON=_BASE_ENVIRON,
                    Node=Node,
                    ConfigureNodes=ConfigureNodes,
                    _THE_NETWORK=_THE_NETWORK)

    exec(data, _GLOBALS)
    network = _GLOBALS['_THE_NETWORK']

    # let's check if the verb is a valid test and run it
    if verb in getTests():
        test_module = importlib.import_module("chutney_tests.{}".format(verb))
        try:
            return test_module.run_test(network)
        except AttributeError:
            print("Test {!r} has no 'run_test(network)' function".format(verb))
            return False

    # tell the user we don't know what their verb meant
    if not hasattr(network, verb):
        print(usage(network))
        print("Error: I don't know how to %s." % verb)
        return

    return getattr(network, verb)()


def parseArgs():
    if len(sys.argv) < 3:
        exit_on_error("Not enough arguments given.")
    if not os.path.isfile(sys.argv[2]):
        exit_on_error("Cannot find networkfile: {0}.".format(sys.argv[2]))
    return {'network_cfg': sys.argv[2], 'action': sys.argv[1]}


def main():
    global _BASE_ENVIRON
    global _TORRC_OPTIONS
    global _THE_NETWORK
    _BASE_ENVIRON = TorEnviron(chutney.Templating.Environ(**DEFAULTS))
    # _TORRC_OPTIONS gets initialised on demand as a map of
    # "/path/to/tor" => ["SupportedOption1", "SupportedOption2", ...]
    # Or it can be pre-populated as a static whitelist of options
    _TORRC_OPTIONS = dict()
    _THE_NETWORK = Network(_BASE_ENVIRON)

    args = parseArgs()
    f = open(args['network_cfg'])
    result = runConfigFile(args['action'], f)
    if result is False:
        return -1
    return 0

if __name__ == '__main__':
    sys.exit(main())