/mandos/release

#!/usr/bin/python
# -*- mode: python; coding: utf-8 -*-
# 
# Mandos server - give out binary blobs to connecting clients.
# 
# This program is partly derived from an example program for an Avahi
# service publisher, downloaded from
# <http://avahi.org/wiki/PythonPublishExample>.  This includes the
# methods "add", "remove", "server_state_changed",
# "entry_group_state_changed", "cleanup", and "activate" in the
# "AvahiService" class, and some lines in "main".
# 
# Everything else is
# Copyright © 2008,2009 Teddy Hogeborn
# Copyright © 2008,2009 Björn Påhlsson
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
#     This program is distributed in the hope that it will be useful,
#     but WITHOUT ANY WARRANTY; without even the implied warranty of
#     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#     GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/>.
# 
# Contact the authors at <mandos@fukt.bsnet.se>.
# 

from __future__ import division, with_statement, absolute_import

import SocketServer as socketserver
import socket
import optparse
import datetime
import errno
import gnutls.crypto
import gnutls.connection
import gnutls.errors
import gnutls.library.functions
import gnutls.library.constants
import gnutls.library.types
import ConfigParser as configparser
import sys
import re
import os
import signal
import subprocess
import atexit
import stat
import logging
import logging.handlers
import pwd
from contextlib import closing
import struct
import fcntl
import functools

import dbus
import dbus.service
import gobject
import avahi
from dbus.mainloop.glib import DBusGMainLoop
import ctypes
import ctypes.util

try:
    SO_BINDTODEVICE = socket.SO_BINDTODEVICE
except AttributeError:
    try:
        from IN import SO_BINDTODEVICE
    except ImportError:
        SO_BINDTODEVICE = None


version = "1.0.11"

logger = logging.Logger(u'mandos')
syslogger = (logging.handlers.SysLogHandler
             (facility = logging.handlers.SysLogHandler.LOG_DAEMON,
              address = "/dev/log"))
syslogger.setFormatter(logging.Formatter
                       (u'Mandos [%(process)d]: %(levelname)s:'
                        u' %(message)s'))
logger.addHandler(syslogger)

console = logging.StreamHandler()
console.setFormatter(logging.Formatter(u'%(name)s [%(process)d]:'
                                       u' %(levelname)s:'
                                       u' %(message)s'))
logger.addHandler(console)

class AvahiError(Exception):
    def __init__(self, value, *args, **kwargs):
        self.value = value
        super(AvahiError, self).__init__(value, *args, **kwargs)
    def __unicode__(self):
        return unicode(repr(self.value))

class AvahiServiceError(AvahiError):
    pass

class AvahiGroupError(AvahiError):
    pass


class AvahiService(object):
    """An Avahi (Zeroconf) service.
    
    Attributes:
    interface: integer; avahi.IF_UNSPEC or an interface index.
               Used to optionally bind to the specified interface.
    name: string; Example: u'Mandos'
    type: string; Example: u'_mandos._tcp'.
                  See <http://www.dns-sd.org/ServiceTypes.html>
    port: integer; what port to announce
    TXT: list of strings; TXT record for the service
    domain: string; Domain to publish on, default to .local if empty.
    host: string; Host to publish records for, default is localhost
    max_renames: integer; maximum number of renames
    rename_count: integer; counter so we only rename after collisions
                  a sensible number of times
    group: D-Bus Entry Group
    server: D-Bus Server
    bus: dbus.SystemBus()
    """
    def __init__(self, interface = avahi.IF_UNSPEC, name = None,
                 servicetype = None, port = None, TXT = None,
                 domain = u"", host = u"", max_renames = 32768,
                 protocol = avahi.PROTO_UNSPEC, bus = None):
        self.interface = interface
        self.name = name
        self.type = servicetype
        self.port = port
        self.TXT = TXT if TXT is not None else []
        self.domain = domain
        self.host = host
        self.rename_count = 0
        self.max_renames = max_renames
        self.protocol = protocol
        self.group = None       # our entry group
        self.server = None
        self.bus = bus
    def rename(self):
        """Derived from the Avahi example code"""
        if self.rename_count >= self.max_renames:
            logger.critical(u"No suitable Zeroconf service name found"
                            u" after %i retries, exiting.",
                            self.rename_count)
            raise AvahiServiceError(u"Too many renames")
        self.name = self.server.GetAlternativeServiceName(self.name)
        logger.info(u"Changing Zeroconf service name to %r ...",
                    unicode(self.name))
        syslogger.setFormatter(logging.Formatter
                               (u'Mandos (%s) [%%(process)d]:'
                                u' %%(levelname)s: %%(message)s'
                                % self.name))
        self.remove()
        self.add()
        self.rename_count += 1
    def remove(self):
        """Derived from the Avahi example code"""
        if self.group is not None:
            self.group.Reset()
    def add(self):
        """Derived from the Avahi example code"""
        if self.group is None:
            self.group = dbus.Interface(
                self.bus.get_object(avahi.DBUS_NAME,
                                    self.server.EntryGroupNew()),
                avahi.DBUS_INTERFACE_ENTRY_GROUP)
            self.group.connect_to_signal('StateChanged',
                                         self.entry_group_state_changed)
        logger.debug(u"Adding Zeroconf service '%s' of type '%s' ...",
                     self.name, self.type)
        self.group.AddService(
            self.interface,
            self.protocol,
            dbus.UInt32(0),     # flags
            self.name, self.type,
            self.domain, self.host,
            dbus.UInt16(self.port),
            avahi.string_array_to_txt_array(self.TXT))
        self.group.Commit()
    def entry_group_state_changed(self, state, error):
        """Derived from the Avahi example code"""
        logger.debug(u"Avahi state change: %i", state)
        
        if state == avahi.ENTRY_GROUP_ESTABLISHED:
            logger.debug(u"Zeroconf service established.")
        elif state == avahi.ENTRY_GROUP_COLLISION:
            logger.warning(u"Zeroconf service name collision.")
            self.rename()
        elif state == avahi.ENTRY_GROUP_FAILURE:
            logger.critical(u"Avahi: Error in group state changed %s",
                            unicode(error))
            raise AvahiGroupError(u"State changed: %s"
                                  % unicode(error))
    def cleanup(self):
        """Derived from the Avahi example code"""
        if self.group is not None:
            self.group.Free()
            self.group = None
    def server_state_changed(self, state):
        """Derived from the Avahi example code"""
        if state == avahi.SERVER_COLLISION:
            logger.error(u"Zeroconf server name collision")
            self.remove()
        elif state == avahi.SERVER_RUNNING:
            self.add()
    def activate(self):
        """Derived from the Avahi example code"""
        if self.server is None:
            self.server = dbus.Interface(
                self.bus.get_object(avahi.DBUS_NAME,
                                    avahi.DBUS_PATH_SERVER),
                avahi.DBUS_INTERFACE_SERVER)
        self.server.connect_to_signal(u"StateChanged",
                                 self.server_state_changed)
        self.server_state_changed(self.server.GetState())


class Client(object):
    """A representation of a client host served by this server.
    
    Attributes:
    name:       string; from the config file, used in log messages and
                        D-Bus identifiers
    fingerprint: string (40 or 32 hexadecimal digits); used to
                 uniquely identify the client
    secret:     bytestring; sent verbatim (over TLS) to client
    host:       string; available for use by the checker command
    created:    datetime.datetime(); (UTC) object creation
    last_enabled: datetime.datetime(); (UTC)
    enabled:    bool()
    last_checked_ok: datetime.datetime(); (UTC) or None
    timeout:    datetime.timedelta(); How long from last_checked_ok
                                      until this client is invalid
    interval:   datetime.timedelta(); How often to start a new checker
    disable_hook:  If set, called by disable() as disable_hook(self)
    checker:    subprocess.Popen(); a running checker process used
                                    to see if the client lives.
                                    'None' if no process is running.
    checker_initiator_tag: a gobject event source tag, or None
    disable_initiator_tag:    - '' -
    checker_callback_tag:  - '' -
    checker_command: string; External command which is run to check if
                     client lives.  %() expansions are done at
                     runtime with vars(self) as dict, so that for
                     instance %(name)s can be used in the command.
    current_checker_command: string; current running checker_command
    """
    
    @staticmethod
    def _datetime_to_milliseconds(dt):
        "Convert a datetime.datetime() to milliseconds"
        return ((dt.days * 24 * 60 * 60 * 1000)
                + (dt.seconds * 1000)
                + (dt.microseconds // 1000))
    
    def timeout_milliseconds(self):
        "Return the 'timeout' attribute in milliseconds"
        return self._datetime_to_milliseconds(self.timeout)
    
    def interval_milliseconds(self):
        "Return the 'interval' attribute in milliseconds"
        return self._datetime_to_milliseconds(self.interval)
    
    def __init__(self, name = None, disable_hook=None, config=None):
        """Note: the 'checker' key in 'config' sets the
        'checker_command' attribute and *not* the 'checker'
        attribute."""
        self.name = name
        if config is None:
            config = {}
        logger.debug(u"Creating client %r", self.name)
        # Uppercase and remove spaces from fingerprint for later
        # comparison purposes with return value from the fingerprint()
        # function
        self.fingerprint = (config[u"fingerprint"].upper()
                            .replace(u" ", u""))
        logger.debug(u"  Fingerprint: %s", self.fingerprint)
        if u"secret" in config:
            self.secret = config[u"secret"].decode(u"base64")
        elif u"secfile" in config:
            with closing(open(os.path.expanduser
                              (os.path.expandvars
                               (config[u"secfile"])))) as secfile:
                self.secret = secfile.read()
        else:
            raise TypeError(u"No secret or secfile for client %s"
                            % self.name)
        self.host = config.get(u"host", u"")
        self.created = datetime.datetime.utcnow()
        self.enabled = False
        self.last_enabled = None
        self.last_checked_ok = None
        self.timeout = string_to_delta(config[u"timeout"])
        self.interval = string_to_delta(config[u"interval"])
        self.disable_hook = disable_hook
        self.checker = None
        self.checker_initiator_tag = None
        self.disable_initiator_tag = None
        self.checker_callback_tag = None
        self.checker_command = config[u"checker"]
        self.current_checker_command = None
        self.last_connect = None
    
    def enable(self):
        """Start this client's checker and timeout hooks"""
        if getattr(self, u"enabled", False):
            # Already enabled
            return
        self.last_enabled = datetime.datetime.utcnow()
        # Schedule a new checker to be started an 'interval' from now,
        # and every interval from then on.
        self.checker_initiator_tag = (gobject.timeout_add
                                      (self.interval_milliseconds(),
                                       self.start_checker))
        # Also start a new checker *right now*.
        self.start_checker()
        # Schedule a disable() when 'timeout' has passed
        self.disable_initiator_tag = (gobject.timeout_add
                                   (self.timeout_milliseconds(),
                                    self.disable))
        self.enabled = True
    
    def disable(self):
        """Disable this client."""
        if not getattr(self, "enabled", False):
            return False
        logger.info(u"Disabling client %s", self.name)
        if getattr(self, u"disable_initiator_tag", False):
            gobject.source_remove(self.disable_initiator_tag)
            self.disable_initiator_tag = None
        if getattr(self, u"checker_initiator_tag", False):
            gobject.source_remove(self.checker_initiator_tag)
            self.checker_initiator_tag = None
        self.stop_checker()
        if self.disable_hook:
            self.disable_hook(self)
        self.enabled = False
        # Do not run this again if called by a gobject.timeout_add
        return False
    
    def __del__(self):
        self.disable_hook = None
        self.disable()
    
    def checker_callback(self, pid, condition, command):
        """The checker has completed, so take appropriate actions."""
        self.checker_callback_tag = None
        self.checker = None
        if os.WIFEXITED(condition):
            exitstatus = os.WEXITSTATUS(condition)
            if exitstatus == 0:
                logger.info(u"Checker for %(name)s succeeded",
                            vars(self))
                self.checked_ok()
            else:
                logger.info(u"Checker for %(name)s failed",
                            vars(self))
        else:
            logger.warning(u"Checker for %(name)s crashed?",
                           vars(self))
    
    def checked_ok(self):
        """Bump up the timeout for this client.
        
        This should only be called when the client has been seen,
        alive and well.
        """
        self.last_checked_ok = datetime.datetime.utcnow()
        gobject.source_remove(self.disable_initiator_tag)
        self.disable_initiator_tag = (gobject.timeout_add
                                      (self.timeout_milliseconds(),
                                       self.disable))
    
    def start_checker(self):
        """Start a new checker subprocess if one is not running.
        
        If a checker already exists, leave it running and do
        nothing."""
        # The reason for not killing a running checker is that if we
        # did that, then if a checker (for some reason) started
        # running slowly and taking more than 'interval' time, the
        # client would inevitably timeout, since no checker would get
        # a chance to run to completion.  If we instead leave running
        # checkers alone, the checker would have to take more time
        # than 'timeout' for the client to be declared invalid, which
        # is as it should be.
        
        # If a checker exists, make sure it is not a zombie
        if self.checker is not None:
            pid, status = os.waitpid(self.checker.pid, os.WNOHANG)
            if pid:
                logger.warning(u"Checker was a zombie")
                gobject.source_remove(self.checker_callback_tag)
                self.checker_callback(pid, status,
                                      self.current_checker_command)
        # Start a new checker if needed
        if self.checker is None:
            try:
                # In case checker_command has exactly one % operator
                command = self.checker_command % self.host
            except TypeError:
                # Escape attributes for the shell
                escaped_attrs = dict((key,
                                      re.escape(unicode(str(val),
                                                        errors=
                                                        u'replace')))
                                     for key, val in
                                     vars(self).iteritems())
                try:
                    command = self.checker_command % escaped_attrs
                except TypeError, error:
                    logger.error(u'Could not format string "%s":'
                                 u' %s', self.checker_command, error)
                    return True # Try again later
            self.current_checker_command = command
            try:
                logger.info(u"Starting checker %r for %s",
                            command, self.name)
                # We don't need to redirect stdout and stderr, since
                # in normal mode, that is already done by daemon(),
                # and in debug mode we don't want to.  (Stdin is
                # always replaced by /dev/null.)
                self.checker = subprocess.Popen(command,
                                                close_fds=True,
                                                shell=True, cwd=u"/")
                self.checker_callback_tag = (gobject.child_watch_add
                                             (self.checker.pid,
                                              self.checker_callback,
                                              data=command))
                # The checker may have completed before the gobject
                # watch was added.  Check for this.
                pid, status = os.waitpid(self.checker.pid, os.WNOHANG)
                if pid:
                    gobject.source_remove(self.checker_callback_tag)
                    self.checker_callback(pid, status, command)
            except OSError, error:
                logger.error(u"Failed to start subprocess: %s",
                             error)
        # Re-run this periodically if run by gobject.timeout_add
        return True
    
    def stop_checker(self):
        """Force the checker process, if any, to stop."""
        if self.checker_callback_tag:
            gobject.source_remove(self.checker_callback_tag)
            self.checker_callback_tag = None
        if getattr(self, u"checker", None) is None:
            return
        logger.debug(u"Stopping checker for %(name)s", vars(self))
        try:
            os.kill(self.checker.pid, signal.SIGTERM)
            #os.sleep(0.5)
            #if self.checker.poll() is None:
            #    os.kill(self.checker.pid, signal.SIGKILL)
        except OSError, error:
            if error.errno != errno.ESRCH: # No such process
                raise
        self.checker = None
    
    def still_valid(self):
        """Has the timeout not yet passed for this client?"""
        if not getattr(self, u"enabled", False):
            return False
        now = datetime.datetime.utcnow()
        if self.last_checked_ok is None:
            return now < (self.created + self.timeout)
        else:
            return now < (self.last_checked_ok + self.timeout)


class ClientDBus(Client, dbus.service.Object):
    """A Client class using D-Bus
    
    Attributes:
    dbus_object_path: dbus.ObjectPath
    bus: dbus.SystemBus()
    """
    # dbus.service.Object doesn't use super(), so we can't either.
    
    def __init__(self, bus = None, *args, **kwargs):
        self.bus = bus
        Client.__init__(self, *args, **kwargs)
        # Only now, when this client is initialized, can it show up on
        # the D-Bus
        self.dbus_object_path = (dbus.ObjectPath
                                 (u"/clients/"
                                  + self.name.replace(u".", u"_")))
        dbus.service.Object.__init__(self, self.bus,
                                     self.dbus_object_path)
    
    @staticmethod
    def _datetime_to_dbus(dt, variant_level=0):
        """Convert a UTC datetime.datetime() to a D-Bus type."""
        return dbus.String(dt.isoformat(),
                           variant_level=variant_level)
    
    def enable(self):
        oldstate = getattr(self, u"enabled", False)
        r = Client.enable(self)
        if oldstate != self.enabled:
            # Emit D-Bus signals
            self.PropertyChanged(dbus.String(u"enabled"),
                                 dbus.Boolean(True, variant_level=1))
            self.PropertyChanged(
                dbus.String(u"last_enabled"),
                self._datetime_to_dbus(self.last_enabled,
                                       variant_level=1))
        return r
    
    def disable(self, signal = True):
        oldstate = getattr(self, u"enabled", False)
        r = Client.disable(self)
        if signal and oldstate != self.enabled:
            # Emit D-Bus signal
            self.PropertyChanged(dbus.String(u"enabled"),
                                 dbus.Boolean(False, variant_level=1))
        return r
    
    def __del__(self, *args, **kwargs):
        try:
            self.remove_from_connection()
        except LookupError:
            pass
        if hasattr(dbus.service.Object, u"__del__"):
            dbus.service.Object.__del__(self, *args, **kwargs)
        Client.__del__(self, *args, **kwargs)
    
    def checker_callback(self, pid, condition, command,
                         *args, **kwargs):
        self.checker_callback_tag = None
        self.checker = None
        # Emit D-Bus signal
        self.PropertyChanged(dbus.String(u"checker_running"),
                             dbus.Boolean(False, variant_level=1))
        if os.WIFEXITED(condition):
            exitstatus = os.WEXITSTATUS(condition)
            # Emit D-Bus signal
            self.CheckerCompleted(dbus.Int16(exitstatus),
                                  dbus.Int64(condition),
                                  dbus.String(command))
        else:
            # Emit D-Bus signal
            self.CheckerCompleted(dbus.Int16(-1),
                                  dbus.Int64(condition),
                                  dbus.String(command))
        
        return Client.checker_callback(self, pid, condition, command,
                                       *args, **kwargs)
    
    def checked_ok(self, *args, **kwargs):
        r = Client.checked_ok(self, *args, **kwargs)
        # Emit D-Bus signal
        self.PropertyChanged(
            dbus.String(u"last_checked_ok"),
            (self._datetime_to_dbus(self.last_checked_ok,
                                    variant_level=1)))
        return r
    
    def start_checker(self, *args, **kwargs):
        old_checker = self.checker
        if self.checker is not None:
            old_checker_pid = self.checker.pid
        else:
            old_checker_pid = None
        r = Client.start_checker(self, *args, **kwargs)
        # Only if new checker process was started
        if (self.checker is not None
            and old_checker_pid != self.checker.pid):
            # Emit D-Bus signal
            self.CheckerStarted(self.current_checker_command)
            self.PropertyChanged(
                dbus.String(u"checker_running"),
                dbus.Boolean(True, variant_level=1))
        return r
    
    def stop_checker(self, *args, **kwargs):
        old_checker = getattr(self, u"checker", None)
        r = Client.stop_checker(self, *args, **kwargs)
        if (old_checker is not None
            and getattr(self, u"checker", None) is None):
            self.PropertyChanged(dbus.String(u"checker_running"),
                                 dbus.Boolean(False, variant_level=1))
        return r
    
    ## D-Bus methods & signals
    _interface = u"se.bsnet.fukt.Mandos.Client"
    
    # CheckedOK - method
    @dbus.service.method(_interface)
    def CheckedOK(self):
        return self.checked_ok()
    
    # CheckerCompleted - signal
    @dbus.service.signal(_interface, signature=u"nxs")
    def CheckerCompleted(self, exitcode, waitstatus, command):
        "D-Bus signal"
        pass
    
    # CheckerStarted - signal
    @dbus.service.signal(_interface, signature=u"s")
    def CheckerStarted(self, command):
        "D-Bus signal"
        pass
    
    # GetAllProperties - method
    @dbus.service.method(_interface, out_signature=u"a{sv}")
    def GetAllProperties(self):
        "D-Bus method"
        return dbus.Dictionary({
                dbus.String(u"name"):
                    dbus.String(self.name, variant_level=1),
                dbus.String(u"fingerprint"):
                    dbus.String(self.fingerprint, variant_level=1),
                dbus.String(u"host"):
                    dbus.String(self.host, variant_level=1),
                dbus.String(u"created"):
                    self._datetime_to_dbus(self.created,
                                           variant_level=1),
                dbus.String(u"last_enabled"):
                    (self._datetime_to_dbus(self.last_enabled,
                                            variant_level=1)
                     if self.last_enabled is not None
                     else dbus.Boolean(False, variant_level=1)),
                dbus.String(u"enabled"):
                    dbus.Boolean(self.enabled, variant_level=1),
                dbus.String(u"last_checked_ok"):
                    (self._datetime_to_dbus(self.last_checked_ok,
                                            variant_level=1)
                     if self.last_checked_ok is not None
                     else dbus.Boolean (False, variant_level=1)),
                dbus.String(u"timeout"):
                    dbus.UInt64(self.timeout_milliseconds(),
                                variant_level=1),
                dbus.String(u"interval"):
                    dbus.UInt64(self.interval_milliseconds(),
                                variant_level=1),
                dbus.String(u"checker"):
                    dbus.String(self.checker_command,
                                variant_level=1),
                dbus.String(u"checker_running"):
                    dbus.Boolean(self.checker is not None,
                                 variant_level=1),
                dbus.String(u"object_path"):
                    dbus.ObjectPath(self.dbus_object_path,
                                    variant_level=1)
                }, signature=u"sv")
    
    # IsStillValid - method
    @dbus.service.method(_interface, out_signature=u"b")
    def IsStillValid(self):
        return self.still_valid()
    
    # PropertyChanged - signal
    @dbus.service.signal(_interface, signature=u"sv")
    def PropertyChanged(self, property, value):
        "D-Bus signal"
        pass
    
    # ReceivedSecret - signal
    @dbus.service.signal(_interface)
    def ReceivedSecret(self):
        "D-Bus signal"
        pass
    
    # Rejected - signal
    @dbus.service.signal(_interface)
    def Rejected(self):
        "D-Bus signal"
        pass
    
    # SetChecker - method
    @dbus.service.method(_interface, in_signature=u"s")
    def SetChecker(self, checker):
        "D-Bus setter method"
        self.checker_command = checker
        # Emit D-Bus signal
        self.PropertyChanged(dbus.String(u"checker"),
                             dbus.String(self.checker_command,
                                         variant_level=1))
    
    # SetHost - method
    @dbus.service.method(_interface, in_signature=u"s")
    def SetHost(self, host):
        "D-Bus setter method"
        self.host = host
        # Emit D-Bus signal
        self.PropertyChanged(dbus.String(u"host"),
                             dbus.String(self.host, variant_level=1))
    
    # SetInterval - method
    @dbus.service.method(_interface, in_signature=u"t")
    def SetInterval(self, milliseconds):
        self.interval = datetime.timedelta(0, 0, 0, milliseconds)
        # Emit D-Bus signal
        self.PropertyChanged(dbus.String(u"interval"),
                             (dbus.UInt64(self.interval_milliseconds(),
                                          variant_level=1)))
    
    # SetSecret - method
    @dbus.service.method(_interface, in_signature=u"ay",
                         byte_arrays=True)
    def SetSecret(self, secret):
        "D-Bus setter method"
        self.secret = str(secret)
    
    # SetTimeout - method
    @dbus.service.method(_interface, in_signature=u"t")
    def SetTimeout(self, milliseconds):
        self.timeout = datetime.timedelta(0, 0, 0, milliseconds)
        # Emit D-Bus signal
        self.PropertyChanged(dbus.String(u"timeout"),
                             (dbus.UInt64(self.timeout_milliseconds(),
                                          variant_level=1)))
    
    # Enable - method
    @dbus.service.method(_interface)
    def Enable(self):
        "D-Bus method"
        self.enable()
    
    # StartChecker - method
    @dbus.service.method(_interface)
    def StartChecker(self):
        "D-Bus method"
        self.start_checker()
    
    # Disable - method
    @dbus.service.method(_interface)
    def Disable(self):
        "D-Bus method"
        self.disable()
    
    # StopChecker - method
    @dbus.service.method(_interface)
    def StopChecker(self):
        self.stop_checker()
    
    del _interface


class ClientHandler(socketserver.BaseRequestHandler, object):
    """A class to handle client connections.
    
    Instantiated once for each connection to handle it.
    Note: This will run in its own forked process."""
    
    def handle(self):
        logger.info(u"TCP connection from: %s",
                    unicode(self.client_address))
        logger.debug(u"IPC Pipe FD: %d", self.server.pipe[1])
        # Open IPC pipe to parent process
        with closing(os.fdopen(self.server.pipe[1], u"w", 1)) as ipc:
            session = (gnutls.connection
                       .ClientSession(self.request,
                                      gnutls.connection
                                      .X509Credentials()))
            
            line = self.request.makefile().readline()
            logger.debug(u"Protocol version: %r", line)
            try:
                if int(line.strip().split()[0]) > 1:
                    raise RuntimeError
            except (ValueError, IndexError, RuntimeError), error:
                logger.error(u"Unknown protocol version: %s", error)
                return
            
            # Note: gnutls.connection.X509Credentials is really a
            # generic GnuTLS certificate credentials object so long as
            # no X.509 keys are added to it.  Therefore, we can use it
            # here despite using OpenPGP certificates.
            
            #priority = u':'.join((u"NONE", u"+VERS-TLS1.1",
            #                      u"+AES-256-CBC", u"+SHA1",
            #                      u"+COMP-NULL", u"+CTYPE-OPENPGP",
            #                      u"+DHE-DSS"))
            # Use a fallback default, since this MUST be set.
            priority = self.server.gnutls_priority
            if priority is None:
                priority = u"NORMAL"
            (gnutls.library.functions
             .gnutls_priority_set_direct(session._c_object,
                                         priority, None))
            
            try:
                session.handshake()
            except gnutls.errors.GNUTLSError, error:
                logger.warning(u"Handshake failed: %s", error)
                # Do not run session.bye() here: the session is not
                # established.  Just abandon the request.
                return
            logger.debug(u"Handshake succeeded")
            try:
                fpr = self.fingerprint(self.peer_certificate(session))
            except (TypeError, gnutls.errors.GNUTLSError), error:
                logger.warning(u"Bad certificate: %s", error)
                session.bye()
                return
            logger.debug(u"Fingerprint: %s", fpr)
            
            for c in self.server.clients:
                if c.fingerprint == fpr:
                    client = c
                    break
            else:
                ipc.write(u"NOTFOUND %s %s\n"
                          % (fpr, unicode(self.client_address)))
                session.bye()
                return
            # Have to check if client.still_valid(), since it is
            # possible that the client timed out while establishing
            # the GnuTLS session.
            if not client.still_valid():
                ipc.write(u"INVALID %s\n" % client.name)
                session.bye()
                return
            ipc.write(u"SENDING %s\n" % client.name)
            sent_size = 0
            while sent_size < len(client.secret):
                sent = session.send(client.secret[sent_size:])
                logger.debug(u"Sent: %d, remaining: %d",
                             sent, len(client.secret)
                             - (sent_size + sent))
                sent_size += sent
            session.bye()
    
    @staticmethod
    def peer_certificate(session):
        "Return the peer's OpenPGP certificate as a bytestring"
        # If not an OpenPGP certificate...
        if (gnutls.library.functions
            .gnutls_certificate_type_get(session._c_object)
            != gnutls.library.constants.GNUTLS_CRT_OPENPGP):
            # ...do the normal thing
            return session.peer_certificate
        list_size = ctypes.c_uint(1)
        cert_list = (gnutls.library.functions
                     .gnutls_certificate_get_peers
                     (session._c_object, ctypes.byref(list_size)))
        if not bool(cert_list) and list_size.value != 0:
            raise gnutls.errors.GNUTLSError(u"error getting peer"
                                            u" certificate")
        if list_size.value == 0:
            return None
        cert = cert_list[0]
        return ctypes.string_at(cert.data, cert.size)
    
    @staticmethod
    def fingerprint(openpgp):
        "Convert an OpenPGP bytestring to a hexdigit fingerprint"
        # New GnuTLS "datum" with the OpenPGP public key
        datum = (gnutls.library.types
                 .gnutls_datum_t(ctypes.cast(ctypes.c_char_p(openpgp),
                                             ctypes.POINTER
                                             (ctypes.c_ubyte)),
                                 ctypes.c_uint(len(openpgp))))
        # New empty GnuTLS certificate
        crt = gnutls.library.types.gnutls_openpgp_crt_t()
        (gnutls.library.functions
         .gnutls_openpgp_crt_init(ctypes.byref(crt)))
        # Import the OpenPGP public key into the certificate
        (gnutls.library.functions
         .gnutls_openpgp_crt_import(crt, ctypes.byref(datum),
                                    gnutls.library.constants
                                    .GNUTLS_OPENPGP_FMT_RAW))
        # Verify the self signature in the key
        crtverify = ctypes.c_uint()
        (gnutls.library.functions
         .gnutls_openpgp_crt_verify_self(crt, 0,
                                         ctypes.byref(crtverify)))
        if crtverify.value != 0:
            gnutls.library.functions.gnutls_openpgp_crt_deinit(crt)
            raise (gnutls.errors.CertificateSecurityError
                   (u"Verify failed"))
        # New buffer for the fingerprint
        buf = ctypes.create_string_buffer(20)
        buf_len = ctypes.c_size_t()
        # Get the fingerprint from the certificate into the buffer
        (gnutls.library.functions
         .gnutls_openpgp_crt_get_fingerprint(crt, ctypes.byref(buf),
                                             ctypes.byref(buf_len)))
        # Deinit the certificate
        gnutls.library.functions.gnutls_openpgp_crt_deinit(crt)
        # Convert the buffer to a Python bytestring
        fpr = ctypes.string_at(buf, buf_len.value)
        # Convert the bytestring to hexadecimal notation
        hex_fpr = u''.join(u"%02X" % ord(char) for char in fpr)
        return hex_fpr


class ForkingMixInWithPipe(socketserver.ForkingMixIn, object):
    """Like socketserver.ForkingMixIn, but also pass a pipe."""
    def process_request(self, request, client_address):
        """Overrides and wraps the original process_request().
        
        This function creates a new pipe in self.pipe
        """
        self.pipe = os.pipe()
        super(ForkingMixInWithPipe,
              self).process_request(request, client_address)
        os.close(self.pipe[1])  # close write end
        self.add_pipe(self.pipe[0])
    def add_pipe(self, pipe):
        """Dummy function; override as necessary"""
        os.close(pipe)


class IPv6_TCPServer(ForkingMixInWithPipe,
                     socketserver.TCPServer, object):
    """IPv6-capable TCP server.  Accepts 'None' as address and/or port
    
    Attributes:
        enabled:        Boolean; whether this server is activated yet
        interface:      None or a network interface name (string)
        use_ipv6:       Boolean; to use IPv6 or not
    """
    def __init__(self, server_address, RequestHandlerClass,
                 interface=None, use_ipv6=True):
        self.interface = interface
        if use_ipv6:
            self.address_family = socket.AF_INET6
        socketserver.TCPServer.__init__(self, server_address,
                                        RequestHandlerClass)
    def server_bind(self):
        """This overrides the normal server_bind() function
        to bind to an interface if one was specified, and also NOT to
        bind to an address or port if they were not specified."""
        if self.interface is not None:
            if SO_BINDTODEVICE is None:
                logger.error(u"SO_BINDTODEVICE does not exist;"
                             u" cannot bind to interface %s",
                             self.interface)
            else:
                try:
                    self.socket.setsockopt(socket.SOL_SOCKET,
                                           SO_BINDTODEVICE,
                                           str(self.interface
                                               + u'\0'))
                except socket.error, error:
                    if error[0] == errno.EPERM:
                        logger.error(u"No permission to"
                                     u" bind to interface %s",
                                     self.interface)
                    elif error[0] == errno.ENOPROTOOPT:
                        logger.error(u"SO_BINDTODEVICE not available;"
                                     u" cannot bind to interface %s",
                                     self.interface)
                    else:
                        raise
        # Only bind(2) the socket if we really need to.
        if self.server_address[0] or self.server_address[1]:
            if not self.server_address[0]:
                if self.address_family == socket.AF_INET6:
                    any_address = u"::" # in6addr_any
                else:
                    any_address = socket.INADDR_ANY
                self.server_address = (any_address,
                                       self.server_address[1])
            elif not self.server_address[1]:
                self.server_address = (self.server_address[0],
                                       0)
#                 if self.interface:
#                     self.server_address = (self.server_address[0],
#                                            0, # port
#                                            0, # flowinfo
#                                            if_nametoindex
#                                            (self.interface))
            return socketserver.TCPServer.server_bind(self)


class MandosServer(IPv6_TCPServer):
    """Mandos server.
    
    Attributes:
        clients:        set of Client objects
        gnutls_priority GnuTLS priority string
        use_dbus:       Boolean; to emit D-Bus signals or not
        clients:        set of Client objects
        gnutls_priority GnuTLS priority string
        use_dbus:       Boolean; to emit D-Bus signals or not
    
    Assumes a gobject.MainLoop event loop.
    """
    def __init__(self, server_address, RequestHandlerClass,
                 interface=None, use_ipv6=True, clients=None,
                 gnutls_priority=None, use_dbus=True):
        self.enabled = False
        self.clients = clients
        if self.clients is None:
            self.clients = set()
        self.use_dbus = use_dbus
        self.gnutls_priority = gnutls_priority
        IPv6_TCPServer.__init__(self, server_address,
                                RequestHandlerClass,
                                interface = interface,
                                use_ipv6 = use_ipv6)
    def server_activate(self):
        if self.enabled:
            return socketserver.TCPServer.server_activate(self)
    def enable(self):
        self.enabled = True
    def add_pipe(self, pipe):
        # Call "handle_ipc" for both data and EOF events
        gobject.io_add_watch(pipe, gobject.IO_IN | gobject.IO_HUP,
                             self.handle_ipc)
    def handle_ipc(self, source, condition, file_objects={}):
        condition_names = {
            gobject.IO_IN: u"IN",   # There is data to read.
            gobject.IO_OUT: u"OUT", # Data can be written (without
                                    # blocking).
            gobject.IO_PRI: u"PRI", # There is urgent data to read.
            gobject.IO_ERR: u"ERR", # Error condition.
            gobject.IO_HUP: u"HUP"  # Hung up (the connection has been
                                    # broken, usually for pipes and
                                    # sockets).
            }
        conditions_string = ' | '.join(name
                                       for cond, name in
                                       condition_names.iteritems()
                                       if cond & condition)
        logger.debug(u"Handling IPC: FD = %d, condition = %s", source,
                     conditions_string)
        
        # Turn the pipe file descriptor into a Python file object
        if source not in file_objects:
            file_objects[source] = os.fdopen(source, u"r", 1)
        
        # Read a line from the file object
        cmdline = file_objects[source].readline()
        if not cmdline:             # Empty line means end of file
            # close the IPC pipe
            file_objects[source].close()
            del file_objects[source]
            
            # Stop calling this function
            return False
        
        logger.debug(u"IPC command: %r", cmdline)
        
        # Parse and act on command
        cmd, args = cmdline.rstrip(u"\r\n").split(None, 1)
        
        if cmd == u"NOTFOUND":
            logger.warning(u"Client not found for fingerprint: %s",
                           args)
            if self.use_dbus:
                # Emit D-Bus signal
                mandos_dbus_service.ClientNotFound(args)
        elif cmd == u"INVALID":
            for client in self.clients:
                if client.name == args:
                    logger.warning(u"Client %s is invalid", args)
                    if self.use_dbus:
                        # Emit D-Bus signal
                        client.Rejected()
                    break
            else:
                logger.error(u"Unknown client %s is invalid", args)
        elif cmd == u"SENDING":
            for client in self.clients:
                if client.name == args:
                    logger.info(u"Sending secret to %s", client.name)
                    client.checked_ok()
                    if self.use_dbus:
                        # Emit D-Bus signal
                        client.ReceivedSecret()
                    break
            else:
                logger.error(u"Sending secret to unknown client %s",
                             args)
        else:
            logger.error(u"Unknown IPC command: %r", cmdline)
        
        # Keep calling this function
        return True


def string_to_delta(interval):
    """Parse a string and return a datetime.timedelta
    
    >>> string_to_delta(u'7d')
    datetime.timedelta(7)
    >>> string_to_delta(u'60s')
    datetime.timedelta(0, 60)
    >>> string_to_delta(u'60m')
    datetime.timedelta(0, 3600)
    >>> string_to_delta(u'24h')
    datetime.timedelta(1)
    >>> string_to_delta(u'1w')
    datetime.timedelta(7)
    >>> string_to_delta(u'5m 30s')
    datetime.timedelta(0, 330)
    """
    timevalue = datetime.timedelta(0)
    for s in interval.split():
        try:
            suffix = unicode(s[-1])
            value = int(s[:-1])
            if suffix == u"d":
                delta = datetime.timedelta(value)
            elif suffix == u"s":
                delta = datetime.timedelta(0, value)
            elif suffix == u"m":
                delta = datetime.timedelta(0, 0, 0, 0, value)
            elif suffix == u"h":
                delta = datetime.timedelta(0, 0, 0, 0, 0, value)
            elif suffix == u"w":
                delta = datetime.timedelta(0, 0, 0, 0, 0, 0, value)
            else:
                raise ValueError
        except (ValueError, IndexError):
            raise ValueError
        timevalue += delta
    return timevalue


def if_nametoindex(interface):
    """Call the C function if_nametoindex(), or equivalent
    
    Note: This function cannot accept a unicode string."""
    global if_nametoindex
    try:
        if_nametoindex = (ctypes.cdll.LoadLibrary
                          (ctypes.util.find_library(u"c"))
                          .if_nametoindex)
    except (OSError, AttributeError):
        logger.warning(u"Doing if_nametoindex the hard way")
        def if_nametoindex(interface):
            "Get an interface index the hard way, i.e. using fcntl()"
            SIOCGIFINDEX = 0x8933  # From /usr/include/linux/sockios.h
            with closing(socket.socket()) as s:
                ifreq = fcntl.ioctl(s, SIOCGIFINDEX,
                                    struct.pack(str(u"16s16x"),
                                                interface))
            interface_index = struct.unpack(str(u"I"),
                                            ifreq[16:20])[0]
            return interface_index
    return if_nametoindex(interface)


def daemon(nochdir = False, noclose = False):
    """See daemon(3).  Standard BSD Unix function.
    
    This should really exist as os.daemon, but it doesn't (yet)."""
    if os.fork():
        sys.exit()
    os.setsid()
    if not nochdir:
        os.chdir(u"/")
    if os.fork():
        sys.exit()
    if not noclose:
        # Close all standard open file descriptors
        null = os.open(os.path.devnull, os.O_NOCTTY | os.O_RDWR)
        if not stat.S_ISCHR(os.fstat(null).st_mode):
            raise OSError(errno.ENODEV,
                          u"/dev/null not a character device")
        os.dup2(null, sys.stdin.fileno())
        os.dup2(null, sys.stdout.fileno())
        os.dup2(null, sys.stderr.fileno())
        if null > 2:
            os.close(null)


def main():
    
    ######################################################################
    # Parsing of options, both command line and config file
    
    parser = optparse.OptionParser(version = "%%prog %s" % version)
    parser.add_option("-i", u"--interface", type=u"string",
                      metavar="IF", help=u"Bind to interface IF")
    parser.add_option("-a", u"--address", type=u"string",
                      help=u"Address to listen for requests on")
    parser.add_option("-p", u"--port", type=u"int",
                      help=u"Port number to receive requests on")
    parser.add_option("--check", action=u"store_true",
                      help=u"Run self-test")
    parser.add_option("--debug", action=u"store_true",
                      help=u"Debug mode; run in foreground and log to"
                      u" terminal")
    parser.add_option("--priority", type=u"string", help=u"GnuTLS"
                      u" priority string (see GnuTLS documentation)")
    parser.add_option("--servicename", type=u"string",
                      metavar=u"NAME", help=u"Zeroconf service name")
    parser.add_option("--configdir", type=u"string",
                      default=u"/etc/mandos", metavar=u"DIR",
                      help=u"Directory to search for configuration"
                      u" files")
    parser.add_option("--no-dbus", action=u"store_false",
                      dest=u"use_dbus", help=u"Do not provide D-Bus"
                      u" system bus interface")
    parser.add_option("--no-ipv6", action=u"store_false",
                      dest=u"use_ipv6", help=u"Do not use IPv6")
    options = parser.parse_args()[0]
    
    if options.check:
        import doctest
        doctest.testmod()
        sys.exit()
    
    # Default values for config file for server-global settings
    server_defaults = { u"interface": u"",
                        u"address": u"",
                        u"port": u"",
                        u"debug": u"False",
                        u"priority":
                        u"SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP",
                        u"servicename": u"Mandos",
                        u"use_dbus": u"True",
                        u"use_ipv6": u"True",
                        }
    
    # Parse config file for server-global settings
    server_config = configparser.SafeConfigParser(server_defaults)
    del server_defaults
    server_config.read(os.path.join(options.configdir,
                                    u"mandos.conf"))
    # Convert the SafeConfigParser object to a dict
    server_settings = server_config.defaults()
    # Use the appropriate methods on the non-string config options
    for option in (u"debug", u"use_dbus", u"use_ipv6"):
        server_settings[option] = server_config.getboolean(u"DEFAULT",
                                                           option)
    if server_settings["port"]:
        server_settings["port"] = server_config.getint(u"DEFAULT",
                                                       u"port")
    del server_config
    
    # Override the settings from the config file with command line
    # options, if set.
    for option in (u"interface", u"address", u"port", u"debug",
                   u"priority", u"servicename", u"configdir",
                   u"use_dbus", u"use_ipv6"):
        value = getattr(options, option)
        if value is not None:
            server_settings[option] = value
    del options
    # Force all strings to be unicode
    for option in server_settings.keys():
        if type(server_settings[option]) is str:
            server_settings[option] = unicode(server_settings[option])
    # Now we have our good server settings in "server_settings"
    
    ##################################################################
    
    # For convenience
    debug = server_settings[u"debug"]
    use_dbus = server_settings[u"use_dbus"]
    use_ipv6 = server_settings[u"use_ipv6"]
    
    if not debug:
        syslogger.setLevel(logging.WARNING)
        console.setLevel(logging.WARNING)
    
    if server_settings[u"servicename"] != u"Mandos":
        syslogger.setFormatter(logging.Formatter
                               (u'Mandos (%s) [%%(process)d]:'
                                u' %%(levelname)s: %%(message)s'
                                % server_settings[u"servicename"]))
    
    # Parse config file with clients
    client_defaults = { u"timeout": u"1h",
                        u"interval": u"5m",
                        u"checker": u"fping -q -- %%(host)s",
                        u"host": u"",
                        }
    client_config = configparser.SafeConfigParser(client_defaults)
    client_config.read(os.path.join(server_settings[u"configdir"],
                                    u"clients.conf"))
    
    global mandos_dbus_service
    mandos_dbus_service = None
    
    tcp_server = MandosServer((server_settings[u"address"],
                               server_settings[u"port"]),
                              ClientHandler,
                              interface=server_settings[u"interface"],
                              use_ipv6=use_ipv6,
                              gnutls_priority=
                              server_settings[u"priority"],
                              use_dbus=use_dbus)
    pidfilename = u"/var/run/mandos.pid"
    try:
        pidfile = open(pidfilename, u"w")
    except IOError:
        logger.error(u"Could not open file %r", pidfilename)
    
    try:
        uid = pwd.getpwnam(u"_mandos").pw_uid
        gid = pwd.getpwnam(u"_mandos").pw_gid
    except KeyError:
        try:
            uid = pwd.getpwnam(u"mandos").pw_uid
            gid = pwd.getpwnam(u"mandos").pw_gid
        except KeyError:
            try:
                uid = pwd.getpwnam(u"nobody").pw_uid
                gid = pwd.getpwnam(u"nobody").pw_gid
            except KeyError:
                uid = 65534
                gid = 65534
    try:
        os.setgid(gid)
        os.setuid(uid)
    except OSError, error:
        if error[0] != errno.EPERM:
            raise error
    
    # Enable all possible GnuTLS debugging
    if debug:
        # "Use a log level over 10 to enable all debugging options."
        # - GnuTLS manual
        gnutls.library.functions.gnutls_global_set_log_level(11)
        
        @gnutls.library.types.gnutls_log_func
        def debug_gnutls(level, string):
            logger.debug(u"GnuTLS: %s", string[:-1])
        
        (gnutls.library.functions
         .gnutls_global_set_log_function(debug_gnutls))
    
    global main_loop
    # From the Avahi example code
    DBusGMainLoop(set_as_default=True )
    main_loop = gobject.MainLoop()
    bus = dbus.SystemBus()
    # End of Avahi example code
    if use_dbus:
        bus_name = dbus.service.BusName(u"se.bsnet.fukt.Mandos", bus)
    protocol = avahi.PROTO_INET6 if use_ipv6 else avahi.PROTO_INET
    service = AvahiService(name = server_settings[u"servicename"],
                           servicetype = u"_mandos._tcp",
                           protocol = protocol, bus = bus)
    if server_settings["interface"]:
        service.interface = (if_nametoindex
                             (str(server_settings[u"interface"])))
    
    client_class = Client
    if use_dbus:
        client_class = functools.partial(ClientDBus, bus = bus)
    tcp_server.clients.update(set(
            client_class(name = section,
                         config= dict(client_config.items(section)))
            for section in client_config.sections()))
    if not tcp_server.clients:
        logger.warning(u"No clients defined")
    
    if debug:
        # Redirect stdin so all checkers get /dev/null
        null = os.open(os.path.devnull, os.O_NOCTTY | os.O_RDWR)
        os.dup2(null, sys.stdin.fileno())
        if null > 2:
            os.close(null)
    else:
        # No console logging
        logger.removeHandler(console)
        # Close all input and output, do double fork, etc.
        daemon()
    
    try:
        with closing(pidfile):
            pid = os.getpid()
            pidfile.write(str(pid) + "\n")
        del pidfile
    except IOError:
        logger.error(u"Could not write to file %r with PID %d",
                     pidfilename, pid)
    except NameError:
        # "pidfile" was never created
        pass
    del pidfilename
    
    def cleanup():
        "Cleanup function; run on exit"
        service.cleanup()
        
        while tcp_server.clients:
            client = tcp_server.clients.pop()
            client.disable_hook = None
            client.disable()
    
    atexit.register(cleanup)
    
    if not debug:
        signal.signal(signal.SIGINT, signal.SIG_IGN)
    signal.signal(signal.SIGHUP, lambda signum, frame: sys.exit())
    signal.signal(signal.SIGTERM, lambda signum, frame: sys.exit())
    
    if use_dbus:
        class MandosDBusService(dbus.service.Object):
            """A D-Bus proxy object"""
            def __init__(self):
                dbus.service.Object.__init__(self, bus, u"/")
            _interface = u"se.bsnet.fukt.Mandos"
            
            @dbus.service.signal(_interface, signature=u"oa{sv}")
            def ClientAdded(self, objpath, properties):
                "D-Bus signal"
                pass
            
            @dbus.service.signal(_interface, signature=u"s")
            def ClientNotFound(self, fingerprint):
                "D-Bus signal"
                pass
            
            @dbus.service.signal(_interface, signature=u"os")
            def ClientRemoved(self, objpath, name):
                "D-Bus signal"
                pass
            
            @dbus.service.method(_interface, out_signature=u"ao")
            def GetAllClients(self):
                "D-Bus method"
                return dbus.Array(c.dbus_object_path
                                  for c in tcp_server.clients)
            
            @dbus.service.method(_interface,
                                 out_signature=u"a{oa{sv}}")
            def GetAllClientsWithProperties(self):
                "D-Bus method"
                return dbus.Dictionary(
                    ((c.dbus_object_path, c.GetAllProperties())
                     for c in tcp_server.clients),
                    signature=u"oa{sv}")
            
            @dbus.service.method(_interface, in_signature=u"o")
            def RemoveClient(self, object_path):
                "D-Bus method"
                for c in tcp_server.clients:
                    if c.dbus_object_path == object_path:
                        tcp_server.clients.remove(c)
                        c.remove_from_connection()
                        # Don't signal anything except ClientRemoved
                        c.disable(signal=False)
                        # Emit D-Bus signal
                        self.ClientRemoved(object_path, c.name)
                        return
                raise KeyError
            
            del _interface
        
        mandos_dbus_service = MandosDBusService()
    
    for client in tcp_server.clients:
        if use_dbus:
            # Emit D-Bus signal
            mandos_dbus_service.ClientAdded(client.dbus_object_path,
                                            client.GetAllProperties())
        client.enable()
    
    tcp_server.enable()
    tcp_server.server_activate()
    
    # Find out what port we got
    service.port = tcp_server.socket.getsockname()[1]
    if use_ipv6:
        logger.info(u"Now listening on address %r, port %d,"
                    " flowinfo %d, scope_id %d"
                    % tcp_server.socket.getsockname())
    else:                       # IPv4
        logger.info(u"Now listening on address %r, port %d"
                    % tcp_server.socket.getsockname())
    
    #service.interface = tcp_server.socket.getsockname()[3]
    
    try:
        # From the Avahi example code
        try:
            service.activate()
        except dbus.exceptions.DBusException, error:
            logger.critical(u"DBusException: %s", error)
            sys.exit(1)
        # End of Avahi example code
        
        gobject.io_add_watch(tcp_server.fileno(), gobject.IO_IN,
                             lambda *args, **kwargs:
                             (tcp_server.handle_request
                              (*args[2:], **kwargs) or True))
        
        logger.debug(u"Starting main loop")
        main_loop.run()
    except AvahiError, error:
        logger.critical(u"AvahiError: %s", error)
        sys.exit(1)
    except KeyboardInterrupt:
        if debug:
            print >> sys.stderr
        logger.debug(u"Server received KeyboardInterrupt")
    logger.debug(u"Server exiting")

if __name__ == '__main__':
    main()