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irkerd

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    irkerd 37.21 KiB
    #!/usr/bin/env python
    """
    irkerd - a simple IRC multiplexer daemon
    
    Listens for JSON objects of the form {'to':<irc-url>, 'privmsg':<text>}
    and relays messages to IRC channels. Each request must be followed by
    a newline.
    
    The <text> must be a string.  The value of the 'to' attribute can be a
    string containing an IRC URL (e.g. 'irc://chat.freenet.net/botwar') or
    a list of such strings; in the latter case the message is broadcast to
    all listed channels.  Note that the channel portion of the URL need
    *not* have a leading '#' unless the channel name itself does.
    
    Options: -d sets the debug-message level (probably only of interest to
    developers). -l sets a logfile to capture message traffic from
    channels.  -n sets the nick and -p the nickserv password. The -V
    option prints the program version and exits.
    
    Design and code by Eric S. Raymond <esr@thyrsus.com>. See the project
    resource page at <http://www.catb.org/~esr/irker/>.
    
    Requires Python 2.6 or 2.5 with the simplejson library installed.
    """
    
    from __future__ import with_statement
    
    # These things might need tuning
    
    HOST = "localhost"
    PORT = 6659
    
    XMIT_TTL = (3 * 60 * 60)	# Time to live, seconds from last transmit
    PING_TTL = (15 * 60)		# Time to live, seconds from last PING
    HANDSHAKE_TTL = 60		# Time to live, seconds from nick transmit
    CHANNEL_TTL = (3 * 60 * 60)	# Time to live, seconds from last transmit
    DISCONNECT_TTL = (24 * 60 * 60)	# Time to live, seconds from last connect
    UNSEEN_TTL = 60			# Time to live, seconds since first request
    CHANNEL_MAX = 18		# Max channels open per socket (default)
    ANTI_FLOOD_DELAY = 1.0		# Anti-flood delay after transmissions, seconds
    ANTI_BUZZ_DELAY = 0.09		# Anti-buzz delay after queue-empty check
    CONNECTION_MAX = 200		# To avoid hitting a thread limit
    
    # No user-serviceable parts below this line
    
    version = "2.1"
    
    import sys, getopt, urlparse, time, random, socket, signal, re
    import threading, Queue, SocketServer, select
    try:
        import simplejson as json	# Faster, also makes us Python-2.4-compatible
    except ImportError:
        import json
    
    # Sketch of implementation:
    #
    # One Irker object manages multiple IRC sessions.  It holds a map of
    # Dispatcher objects, one per (server, port) combination, which are
    # responsible for routing messages to one of any number of Connection
    # objects that do the actual socket conversations.  The reason for the
    # Dispatcher layer is that IRC daemons limit the number of channels a
    # client (that is, from the daemon's point of view, a socket) can be
    # joined to, so each session to a server needs a flock of Connection
    # instances each with its own socket.
    #
    # Connections are timed out and removed when either they haven't seen a
    # PING for a while (indicating that the server may be stalled or down)
    # or there has been no message traffic to them for a while, or
    # even if the queue is nonempty but efforts to connect have failed for
    # a long time.
    #
    # There are multiple threads. One accepts incoming traffic from all
    # servers.  Each Connection also has a consumer thread and a
    # thread-safe message queue.  The program main appends messages to
    # queues as JSON requests are received; the consumer threads try to
    # ship them to servers.  When a socket write stalls, it only blocks an
    # individual consumer thread; if it stalls long enough, the session
    # will be timed out. This solves the biggest problem with a
    # single-threaded implementation, which is that you can't count on a
    # single stalled write not hanging all other traffic - you're at the
    # mercy of the length of the buffers in the TCP/IP layer.
    #
    # Message delivery is thus not reliable in the face of network stalls,
    # but this was considered acceptable because IRC (notoriously) has the
    # same problem - there is little point in reliable delivery to a relay
    # that is down or unreliable.
    #
    # This code uses only NICK, JOIN, PART, MODE, PRIVMSG, USER, and QUIT. 
    # It is strictly compliant to RFC1459, except for the interpretation and
    # use of the DEAF and CHANLIMIT and (obsolete) MAXCHANNELS features.
    #
    # CHANLIMIT is as described in the Internet RFC draft
    # draft-brocklesby-irc-isupport-03 at <http://www.mirc.com/isupport.html>.
    # The ",isnick" feature is as described in
    # <http://ftp.ics.uci.edu/pub/ietf/uri/draft-mirashi-url-irc-01.txt>.
    
    # Historical note: the IRCClient and IRCServerConnection classes
    # (~270LOC) replace the overweight, overcomplicated 3KLOC mass of
    # irclib code that irker formerly used as a service library.  They
    # still look similar to parts of irclib because I contributed to that
    # code before giving up on it.
    
    class IRCError(Exception):
        "An IRC exception"
        pass
    
    class IRCClient():
        "An IRC client session to one or more servers."
        def __init__(self, debuglevel):
            self.mutex = threading.RLock()
            self.server_connections = []
            self.event_handlers = {}
            self.add_event_handler("ping",
                                   lambda c, e: c.ship("PONG %s" % e.target))
            self.debuglevel = debuglevel
    
        def newserver(self):
            "Initialize a new server-connection object."
            conn = IRCServerConnection(self)
            with self.mutex:
                self.server_connections.append(conn)
            return conn
    
        def spin(self, timeout=0.2):
            "Spin processing data from connections forever."
            # Outer loop should specifically *not* be mutex-locked.
            # Otherwise no other thread would ever be able to change
            # the shared state of an IRC object running this function.
            while True:
                with self.mutex:
                    connected = [x for x in self.server_connections
                                 if x is not None and x.socket is not None]
                    sockets = [x.socket for x in connected]
                    if sockets:
                        connmap = dict([(c.socket.fileno(), c) for c in connected])
                        (insocks, _o, _e) = select.select(sockets, [], [], timeout)
                        for s in insocks:
                            connmap[s.fileno()].consume()
    
                    else:
                        time.sleep(timeout)
    
        def add_event_handler(self, event, handler):
            "Set a handler to be called later."
            with self.mutex:
                event_handlers = self.event_handlers.setdefault(event, [])
                event_handlers.append(handler)
    
        def handle_event(self, connection, event):
            with self.mutex:
                h = self.event_handlers
                th = sorted(h.get("all_events", []) + h.get(event.type, []))
                for handler in th:
                    handler(connection, event)
    
        def drop_connection(self, connection):
            with self.mutex:
                self.server_connections.remove(connection)
    
        def debug(self, level, errmsg):
            "Debugging information."
            if self.debuglevel >= level:
                sys.stderr.write("irkerd: %s\n" % errmsg)
    
    class LineBufferedStream():
        "Line-buffer a read stream."
        crlf_re = re.compile(b'\r?\n')
    
        def __init__(self):
            self.buffer = ''
    
        def append(self, newbytes):
            self.buffer += newbytes
    
        def lines(self):
            "Iterate over lines in the buffer."
            lines = LineBufferedStream.crlf_re.split(self.buffer)
            self.buffer = lines.pop()
            return iter(lines)
    
        def __iter__(self):
            return self.lines()
    
    class IRCServerConnectionError(IRCError):
        pass
    
    class IRCServerConnection():
        command_re = re.compile("^(:(?P<prefix>[^ ]+) +)?(?P<command>[^ ]+)( *(?P<argument> .+))?")
        # The full list of numeric-to-event mappings is in Perl's Net::IRC.
        # We only need to ensure that if some ancient server throws numerics
        # for the ones we actually want to catch, they're mapped.
        codemap = {
            "001": "welcome",
            "005": "featurelist",
            "432": "erroneusnickname",
            "433": "nicknameinuse",
            "436": "nickcollision",
            "437": "unavailresource",
        }
    
        def __init__(self, master):
            self.master = master
            self.socket = None
    
        def connect(self, server, port, nickname,
                    password=None, username=None, ircname=None):
            self.master.debug(2, "connect(server=%r, port=%r, nickname=%r, ...)" %
                              (server, port, nickname))
            if self.socket is not None:
                self.disconnect("Changing servers")
    
            self.buffer = LineBufferedStream()
            self.event_handlers = {}
            self.real_server_name = ""
            self.server = server
            self.port = port
            self.server_address = (server, port)
            self.nickname = nickname
            self.username = username or nickname
            self.ircname = ircname or nickname
            self.password = password
            try:
                self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                self.socket.bind(('', 0))
                self.socket.connect(self.server_address)
            except socket.error as err:
                raise IRCServerConnectionError("Couldn't connect to socket: %s" % err)
    
            if self.password:
                self.ship("PASS " + self.password)
            self.nick(self.nickname)
            self.user(self.username, self.ircname)
            return self
    
        def close(self):
            # Without this thread lock, there is a window during which
            # select() can find a closed socket, leading to an EBADF error.
            with self.master.mutex:
                self.disconnect("Closing object")
                self.master.drop_connection(self)
    
        def consume(self):
            try:
                incoming = self.socket.recv(16384)
            except socket.error:
                # Server hung up on us.
                self.disconnect("Connection reset by peer")
                return
            if not incoming:
                # Dead air also indicates a connection reset.
                self.disconnect("Connection reset by peer")
                return
    
            self.buffer.append(incoming)
    
            for line in self.buffer:
                self.master.debug(2, "FROM: %s" % line)
    
                if not line:
                    continue
    
                prefix = None
                command = None
                arguments = None
                self.handle_event(Event("every_raw_message",
                                         self.real_server_name,
                                         None,
                                         [line]))
    
                m = IRCServerConnection.command_re.match(line)
                if m.group("prefix"):
                    prefix = m.group("prefix")
                    if not self.real_server_name:
                        self.real_server_name = prefix
                if m.group("command"):
                    command = m.group("command").lower()
                if m.group("argument"):
                    a = m.group("argument").split(" :", 1)
                    arguments = a[0].split()
                    if len(a) == 2:
                        arguments.append(a[1])
    
                command = IRCServerConnection.codemap.get(command, command)
                if command in ["privmsg", "notice"]:
                    target = arguments.pop(0)
                else:
                    target = None
    
                    if command == "quit":
                        arguments = [arguments[0]]
                    elif command == "ping":
                        target = arguments[0]
                    else:
                        target = arguments[0]
                        arguments = arguments[1:]
    
                self.master.debug(2,
                                  "command: %s, source: %s, target: %s, arguments: %s" % (command, prefix, target, arguments))
                self.handle_event(Event(command, prefix, target, arguments))
    
        def handle_event(self, event):
            self.master.handle_event(self, event)
            if event.type in self.event_handlers:
                for fn in self.event_handlers[event.type]:
                    fn(self, event)
    
        def is_connected(self):
            return self.socket is not None
    
        def disconnect(self, message=""):
            if self.socket is None:
                return
            # Don't send a QUIT here - causes infinite loop!
            try:
                self.socket.shutdown(socket.SHUT_WR)
                self.socket.close()
            except socket.error:
                pass
            del self.socket
            self.socket = None
            self.handle_event(Event("disconnect", self.server, "", [message]))
    
        def join(self, channel, key=""):
            self.ship("JOIN %s%s" % (channel, (key and (" " + key))))
    
        def mode(self, target, command):
            self.ship("MODE %s %s" % (target, command))
    
        def nick(self, newnick):
            self.ship("NICK " + newnick)
    
        def part(self, channel, message=""):
            cmd_parts = ['PART', channel]
            if message:
                cmd_parts.append(message)
            self.ship(' '.join(cmd_parts))
    
        def privmsg(self, target, text):
            self.ship("PRIVMSG %s :%s" % (target, text))
    
        def quit(self, message=""):
            # Triggers an error that forces a disconnect.
            self.ship("QUIT" + (message and (" :" + message)))
    
        def user(self, username, realname):
            self.ship("USER %s 0 * :%s" % (username, realname))
    
        def ship(self, string):
            "Ship a command to the server, appending CR/LF"
            try:
                self.socket.send(string.encode('utf-8') + b'\r\n')
                self.master.debug(2, "TO: %s" % string)
            except socket.error:
                self.disconnect("Connection reset by peer.")
    
    class Event(object):
        def __init__(self, evtype, source, target, arguments=None):
            self.type = evtype
            self.source = source
            self.target = target
            if arguments is None:
                arguments = []
            self.arguments = arguments
    
    def is_channel(string):
        return string and string[0] in "#&+!"
    
    class Connection:
        def __init__(self, irkerd, servername, port):
            self.irker = irkerd
            self.servername = servername
            self.port = port
            self.nick_trial = None
            self.connection = None
            self.status = None
            self.last_xmit = time.time()
            self.last_ping = time.time()
            self.channels_joined = {}
            self.channel_limits = {}
            # The consumer thread
            self.queue = Queue.Queue()
            self.thread = None
        def nickname(self, n=None):
            "Return a name for the nth server connection."
            if n is None:
                n = self.nick_trial
            if fallback:
                return (namestyle % n)
            else:
                return namestyle
        def handle_ping(self):
            "Register the fact that the server has pinged this connection."
            self.last_ping = time.time()
        def handle_welcome(self):
            "The server says we're OK, with a non-conflicting nick."
            self.status = "ready"
            self.irker.irc.debug(1, "nick %s accepted" % self.nickname())
            if password:
                self.connection.privmsg("nickserv", "identify %s" % password)
        def handle_badnick(self):
            "The server says our nick is ill-formed or has a conflict."
            self.irker.irc.debug(1, "nick %s rejected" % self.nickname())
            if fallback:
                # Randomness prevents a malicious user or bot from
                # anticipating the next trial name in order to block us
                # from completing the handshake.
                self.nick_trial += random.randint(1, 3)
                self.last_xmit = time.time()
                self.connection.nick(self.nickname())
            # Otherwise fall through, it might be possible to
            # recover manually.
        def handle_disconnect(self):
            "Server disconnected us for flooding or some other reason."
            self.connection = None
            if self.status != "expired":
                self.status = "disconnected"
        def handle_kick(self, outof):
            "We've been kicked."
            self.status = "handshaking"
            try:
                del self.channels_joined[outof]
            except KeyError:
                self.irker.logerr("kicked by %s from %s that's not joined"
                                  % (self.servername, outof))
            qcopy = []
            while not self.queue.empty():
                (channel, message, key) = self.queue.get()
                if channel != outof:
                    qcopy.append((channel, message, key))
            for (channel, message, key) in qcopy:
                self.queue.put((channel, message, key))
            self.status = "ready"
        def enqueue(self, channel, message, key):
            "Enque a message for transmission."
            if self.thread is None or not self.thread.is_alive():
                self.status = "unseen"
                self.thread = threading.Thread(target=self.dequeue)
                self.thread.setDaemon(True)
                self.thread.start()
            self.queue.put((channel, message, key))
        def dequeue(self):
            "Try to ship pending messages from the queue."
            try:
                while True:
                    # We want to be kind to the IRC servers and not hold unused
                    # sockets open forever, so they have a time-to-live.  The
                    # loop is coded this particular way so that we can drop
                    # the actual server connection when its time-to-live
                    # expires, then reconnect and resume transmission if the
                    # queue fills up again.
                    if self.queue.empty():
                        # Queue is empty, at some point we want to time out
                        # the connection rather than holding a socket open in
                        # the server forever.
                        now = time.time()
                        xmit_timeout = now > self.last_xmit + XMIT_TTL
                        ping_timeout = now > self.last_ping + PING_TTL
                        if self.status == "disconnected":
                            # If the queue is empty, we can drop this connection.
                            self.status = "expired"
                            break
                        elif xmit_timeout or ping_timeout:
                            self.irker.irc.debug(1, "timing out connection to %s at %s (ping_timeout=%s, xmit_timeout=%s)" % (self.servername, time.asctime(), ping_timeout, xmit_timeout))
                            with self.irker.irc.mutex:
                                self.connection.context = None
                                self.connection.quit("transmission timeout")
                                self.connection = None
                            self.status = "disconnected"
                        else:
                            # Prevent this thread from hogging the CPU by pausing
                            # for just a little bit after the queue-empty check.
                            # As long as this is less that the duration of a human
                            # reflex arc it is highly unlikely any human will ever
                            # notice.
                            time.sleep(ANTI_BUZZ_DELAY)
                    elif self.status == "disconnected" \
                             and time.time() > self.last_xmit + DISCONNECT_TTL:
                        # Queue is nonempty, but the IRC server might be
                        # down. Letting failed connections retain queue
                        # space forever would be a memory leak.
                        self.status = "expired"
                        break
                    elif not self.connection and self.status != "expired":
                        # Queue is nonempty but server isn't connected.
                        with self.irker.irc.mutex:
                            self.connection = self.irker.irc.newserver()
                            self.connection.context = self
                            # Try to avoid colliding with other instances
                            self.nick_trial = random.randint(1, 990)
                            self.channels_joined = {}
                            try:
                                # This will throw
                                # IRCServerConnectionError on failure
                                self.connection.connect(self.servername,
                                                    self.port,
                                                    nickname=self.nickname(),
                                                    username="irker",
                                                    ircname="irker relaying client")
                                self.status = "handshaking"
                                self.irker.irc.debug(1, "XMIT_TTL bump (%s connection) at %s" % (self.servername, time.asctime()))
                                self.last_xmit = time.time()
                                self.last_ping = time.time()
                            except IRCServerConnectionError:
                                self.status = "expired"
                    elif self.status == "handshaking":
                        if time.time() > self.last_xmit + HANDSHAKE_TTL:
                            self.status = "expired"
                            break
                        else:
                            # Don't buzz on the empty-queue test while we're
                            # handshaking
                            time.sleep(ANTI_BUZZ_DELAY)
                    elif self.status == "unseen" \
                             and time.time() > self.last_xmit + UNSEEN_TTL:
                        # Nasty people could attempt a denial-of-service
                        # attack by flooding us with requests with invalid
                        # servernames. We guard against this by rapidly
                        # expiring connections that have a nonempty queue but
                        # have never had a successful open.
                        self.status = "expired"
                        break
                    elif self.status == "ready":
                        (channel, message, key) = self.queue.get()
                        if channel not in self.channels_joined:
                            self.connection.join(channel, key=key)
                            self.irker.irc.debug(1, "joining %s on %s." % (channel, self.servername))
                        # An empty message might be used as a keepalive or
                        # to join a channel for logging, so suppress the
                        # privmsg send unless there is actual traffic.
                        if message:
                            for segment in message.split("\n"):
                                # Truncate the message if it's too long,
                                # but we're working with characters here,
                                # not bytes, so we could be off.
                                # 500 = 512 - CRLF - 'PRIVMSG ' - ' :'
                                maxlength = 500 - len(channel)
                                if len(segment) > maxlength:
                                    segment = segment[:maxlength]
                                try:
                                    self.connection.privmsg(channel, segment)
                                except ValueError as err:
                                    self.irker.irc.debug(1, "irclib rejected a message to %s on %s because: %s" % (channel, self.servername, str(err)))
                                    self.irker.irc.debug(50, err.format_exc())
                                time.sleep(ANTI_FLOOD_DELAY)
                        self.last_xmit = self.channels_joined[channel] = time.time()
                        self.irker.irc.debug(1, "XMIT_TTL bump (%s transmission) at %s" % (self.servername, time.asctime()))
                        self.queue.task_done()
            except:
                (exc_type, _exc_value, exc_traceback) = sys.exc_info()
                self.irker.logerr("exception %s in thread for %s" % \
                                  (exc_type, self.servername))
    
                # Maybe this should have its own status?
                self.status = "expired"
    
                # This is so we can see tracebacks for errors inside the thread
                # when we need to be able to for debugging purposes.
                if debuglvl > 0:
                    raise exc_type, _exc_value, exc_traceback
            finally:
                try:
                    # Make sure we don't leave any zombies behind
                    self.connection.close()
                except:
                    # Irclib has a habit of throwing fresh exceptions here. Ignore that
                    pass
        def live(self):
            "Should this connection not be scavenged?"
            return self.status != "expired"
        def joined_to(self, channel):
            "Is this connection joined to the specified channel?"
            return channel in self.channels_joined
        def accepting(self, channel):
            "Can this connection accept a join of this channel?"
            if self.channel_limits:
                match_count = 0
                for already in self.channels_joined:
                    # This obscure code is because the RFCs allow separate limits
                    # by channel type (indicated by the first character of the name)
                    # a feature that is almost never actually used.
                    if already[0] == channel[0]:
                        match_count += 1
                return match_count < self.channel_limits.get(channel[0], CHANNEL_MAX)
            else:
                return len(self.channels_joined) < CHANNEL_MAX
    
    class Target():
        "Represent a transmission target."
        def __init__(self, url):
            # Pre-2.6 Pythons don't recognize irc: as a valid URL prefix.
            url = url.replace("irc://", "http://")
            parsed = urlparse.urlparse(url)
            irchost, _, ircport = parsed.netloc.partition(':')
            if not ircport:
                ircport = 6667
            self.servername = irchost
            # IRC channel names are case-insensitive.  If we don't smash
            # case here we may run into problems later. There was a bug
            # observed on irc.rizon.net where an irkerd user specified #Channel,
            # got kicked, and irkerd crashed because the server returned
            # "#channel" in the notification that our kick handler saw.
            self.channel = parsed.path.lstrip('/').lower()
            # This deals with a tweak in recent versions of urlparse.
            if parsed.fragment:
                self.channel += "#" + parsed.fragment
            isnick = self.channel.endswith(",isnick")
            if isnick:
                self.channel = self.channel[:-7]
            if self.channel and not isnick and self.channel[0] not in "#&+":
                self.channel = "#" + self.channel
            # support both channel?secret and channel?key=secret
            self.key = ""
            if parsed.query:
                self.key = re.sub("^key=", "", parsed.query)
            self.port = int(ircport)
        def valid(self):
            "Both components must be present for a valid target."
            return self.servername and self.channel
        def server(self):
            "Return a hashable tuple representing the destination server."
            return (self.servername, self.port)
    
    class Dispatcher:
        "Manage connections to a particular server-port combination."
        def __init__(self, irkerd, servername, port):
            self.irker = irkerd
            self.servername = servername
            self.port = port
            self.connections = []
        def dispatch(self, channel, message, key):
            "Dispatch messages for our server-port combination."
            # First, check if there is room for another channel
            # on any of our existing connections.
            connections = [x for x in self.connections if x.live()]
            eligibles = [x for x in connections if x.joined_to(channel)] \
                        or [x for x in connections if x.accepting(channel)]
            if eligibles:
                eligibles[0].enqueue(channel, message, key)
                return
            # All connections are full up. Look for one old enough to be
            # scavenged.
            ancients = []
            for connection in connections:
                for (chan, age) in connections.channels_joined.items():
                    if age < time.time() - CHANNEL_TTL:
                        ancients.append((connection, chan, age))
            if ancients:
                ancients.sort(key=lambda x: x[2]) 
                (found_connection, drop_channel, _drop_age) = ancients[0]
                found_connection.part(drop_channel, "scavenged by irkerd")
                del found_connection.channels_joined[drop_channel]
                #time.sleep(ANTI_FLOOD_DELAY)
                found_connection.enqueue(channel, message, key)
                return
            # Didn't find any channels with no recent activity
            newconn = Connection(self.irker,
                                 self.servername,
                                 self.port)
            self.connections.append(newconn)
            newconn.enqueue(channel, message, key)
        def live(self):
            "Does this server-port combination have any live connections?"
            self.connections = [x for x in self.connections if x.live()]
            return len(self.connections) > 0
        def last_xmit(self):
            "Return the time of the most recent transmission."
            return max(x.last_xmit for x in self.connections)
    
    class Irker:
        "Persistent IRC multiplexer."
        def __init__(self, debuglevel=0):
            self.debuglevel = debuglevel
            self.irc = IRCClient(self.debuglevel)
            self.irc.add_event_handler("ping", self._handle_ping)
            self.irc.add_event_handler("welcome", self._handle_welcome)
            self.irc.add_event_handler("erroneusnickname", self._handle_badnick)
            self.irc.add_event_handler("nicknameinuse", self._handle_badnick)
            self.irc.add_event_handler("nickcollision", self._handle_badnick)
            self.irc.add_event_handler("unavailresource", self._handle_badnick)
            self.irc.add_event_handler("featurelist", self._handle_features)
            self.irc.add_event_handler("disconnect", self._handle_disconnect)
            self.irc.add_event_handler("kick", self._handle_kick)
            self.irc.add_event_handler("every_raw_message", self._handle_every_raw_message)
            thread = threading.Thread(target=self.irc.spin)
            thread.setDaemon(True)
            self.irc._thread = thread
            thread.start()
            self.servers = {}
        def logerr(self, errmsg):
            "Log a processing error."
            sys.stderr.write("irkerd: " + errmsg + "\n")
        def _handle_ping(self, connection, _event):
            "PING arrived, bump the last-received time for the connection."
            if connection.context:
                connection.context.handle_ping()
        def _handle_welcome(self, connection, _event):
            "Welcome arrived, nick accepted for this connection."
            if connection.context:
                connection.context.handle_welcome()
        def _handle_badnick(self, connection, _event):
            "Nick not accepted for this connection."
            if connection.context:
                connection.context.handle_badnick()
        def _handle_features(self, connection, event):
            "Determine if and how we can set deaf mode."
            if connection.context:
                cxt = connection.context
                arguments = event.arguments
                for lump in arguments:
                    if lump.startswith("DEAF="):
                        if not logfile:
                            connection.mode(cxt.nickname(), "+"+lump[5:])
                    elif lump.startswith("MAXCHANNELS="):
                        m = int(lump[12:])
                        for pref in "#&+":
                            cxt.channel_limits[pref] = m
                        self.irc.debug(1, "%s maxchannels is %d"
                                   % (connection.server, m))
                    elif lump.startswith("CHANLIMIT=#:"):
                        limits = lump[10:].split(",")
                        try:
                            for token in limits:
                                (prefixes, limit) = token.split(":")
                                limit = int(limit)
                                for c in prefixes:
                                    cxt.channel_limits[c] = limit
                            self.irc.debug(1, "%s channel limit map is %s"
                                       % (connection.server, cxt.channel_limits))
                        except ValueError:
                            self.logerr("ill-formed CHANLIMIT property")
        def _handle_disconnect(self, connection, _event):
            "Server hung up the connection."
            self.irc.debug(1, "server %s disconnected" % connection.server)
            connection.close()
            if connection.context:
                connection.context.handle_disconnect()
        def _handle_kick(self, connection, event):
            "Server hung up the connection."
            target = event.target
            self.irc.debug(1, "irker has been kicked from %s on %s" % (target, connection.server))
            if connection.context:
                connection.context.handle_kick(target)
        def _handle_every_raw_message(self, _connection, event):
            "Log all messages when in watcher mode."
            if logfile:
                with open(logfile, "a") as logfp:
                    logfp.write("%03f|%s|%s\n" % \
                                 (time.time(), event.source, event.arguments[0]))
        def handle(self, line):
            "Perform a JSON relay request."
            try:
                request = json.loads(line.strip())
                if not isinstance(request, dict):
                    self.logerr("request is not a JSON dictionary: %r" % request)
                elif "to" not in request or "privmsg" not in request:
                    self.logerr("malformed request - 'to' or 'privmsg' missing: %r" % request)
                else:
                    channels = request['to']
                    message = request['privmsg']
                    if not isinstance(channels, (list, basestring)):
                        self.logerr("malformed request - unexpected channel type: %r" % channels)
                    if not isinstance(message, basestring):
                        self.logerr("malformed request - unexpected message type: %r" % message)
                    else:
                        if not isinstance(channels, list):
                            channels = [channels]
                        for url in channels:
                            if not isinstance(url, basestring):
                                self.logerr("malformed request - URL has unexpected type: %r" % url)
                            else:
                                target = Target(url)
                                if not target.valid():
                                    return
                                if target.server() not in self.servers:
                                    self.servers[target.server()] = Dispatcher(self, target.servername, target.port)
                                self.servers[target.server()].dispatch(target.channel, message, target.key)
                                # GC dispatchers with no active connections
                                servernames = self.servers.keys()
                                for servername in servernames:
                                    if not self.servers[servername].live():
                                        del self.servers[servername]
                                # If we might be pushing a resource limit
                                # even after garbage collection, remove a
                                # session.  The goal here is to head off
                                # DoS attacks that aim at exhausting
                                # thread space or file descriptors.  The
                                # cost is that attempts to DoS this
                                # service will cause lots of join/leave
                                # spam as we scavenge old channels after
                                # connecting to new ones. The particular
                                # method used for selecting a session to
                                # be terminated doesn't matter much; we
                                # choose the one longest idle on the
                                # assumption that message activity is likely
                                # to be clumpy.
                                if len(self.servers) >= CONNECTION_MAX:
                                    oldest = min(self.servers.keys(), key=lambda name: self.servers[name].last_xmit())
                                    del self.servers[oldest]
            except ValueError:
                self.logerr("can't recognize JSON on input: %r" % line)
            except RuntimeError:
                self.logerr("wildly malformed JSON blew the parser stack.")
    
    class IrkerTCPHandler(SocketServer.StreamRequestHandler):
        def handle(self):
            while True:
                line = self.rfile.readline()
                if not line:
                    break
                irker.handle(line.strip())
    
    class IrkerUDPHandler(SocketServer.BaseRequestHandler):
        def handle(self):
            data = self.request[0].strip()
            #socket = self.request[1]
            irker.handle(data)
    
    def usage():
        sys.stdout.write("""
    Usage:
      irkerd [-d debuglevel] [-l logfile] [-n nick] [-p password] [-V] [-h]
    
    Options
      -d    set debug level
      -l    set logfile
      -n    set nick-style
      -p    set nickserv password
      -V    return irkerd version
      -h    print this help dialog
    """)
    
    if __name__ == '__main__':
        debuglvl = 0
        namestyle = "irker%03d"
        password = None
        logfile = None
        try:
            (options, arguments) = getopt.getopt(sys.argv[1:], "d:l:n:p:Vh")
        except getopt.GetoptError as e:
            sys.stderr.write("%s" % e)
            usage()
            sys.exit(1)
        for (opt, val) in options:
            if opt == '-d':		# Enable debug/progress messages
                debuglvl = int(val)
            elif opt == '-l':	# Logfile mode - report traffic read in
                logfile = val
            elif opt == '-n':	# Force the nick
                namestyle = val
            elif opt == '-p':	# Set a nickserv password
                password = val
            elif opt == '-V':	# Emit version and exit
                sys.stdout.write("irkerd version %s\n" % version)
                sys.exit(0)
            elif opt == '-h':
                usage()
                sys.exit(0)
        fallback = re.search("%.*d", namestyle)
        irker = Irker(debuglevel=debuglvl)
        irker.irc.debug(1, "irkerd version %s" % version)
        try:
            tcpserver = SocketServer.TCPServer((HOST, PORT), IrkerTCPHandler)
            udpserver = SocketServer.UDPServer((HOST, PORT), IrkerUDPHandler)
            for server in [tcpserver, udpserver]:
                server = threading.Thread(target=server.serve_forever)
                server.setDaemon(True)
                server.start()
            try:
                signal.pause()
            except KeyboardInterrupt:
                raise SystemExit(1)
        except socket.error, e:
            sys.stderr.write("irkerd: server launch failed: %r\n" % e)
    
    # end