Adding upstream version 2.19+dfsg.upstream/2.19+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1058 insertions, 0 deletions

diff --git a/irkerd b/irkerd
new file mode 100755
index 0000000..d42f56e
--- /dev/null
+++ b/irkerd
@@ -0,0 +1,1058 @@
+#!/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.
+
+Design and code by Eric S. Raymond <esr@thyrsus.com>. See the project
+resource page at <http://www.catb.org/~esr/irker/>.
+
+Requires Python 2.7, or:
+* 2.6 with the argparse package installed.
+* Any 3.x
+
+"""
+# SPDX-License-Identifier: BSD-2-Clause
+
+# These things might need tuning
+
+HOST = "localhost"
+PORT = 6659
+
+PROXY_TYPE = None # Use proxy if set 1: SOCKS4, 2: SOCKS5, 3: HTTP
+PROXY_HOST = ""
+PROXY_PORT = 1080
+
+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
+RECONNECT_DELAY = 3		# Don't spam servers with connection attempts
+
+# No user-serviceable parts below this line
+
+version = "2.19"
+
+import argparse
+import logging
+import logging.handlers
+import json
+import os
+import os.path
+try:  # Python 3
+    import queue
+except ImportError:  # Python 2
+    import Queue as queue
+import random
+import re
+import select
+import signal
+import socket
+try:
+    import socks
+    socks_on = True
+except ImportError:
+    socks_on = False
+try:  # Python 3
+    import socketserver
+except ImportError:  # Python 2
+    import SocketServer as socketserver
+import ssl
+import sys
+import threading
+import time
+import traceback
+try:  # Python 3
+    import urllib.parse as urllib_parse
+except ImportError:  # Python 2
+    import urlparse as urllib_parse
+
+
+LOG = logging.getLogger(__name__)
+LOG.setLevel(logging.ERROR)
+LOG_LEVELS = ['critical', 'error', 'warning', 'info', 'debug']
+
+try:  # Python 2
+    UNICODE_TYPE = unicode
+except NameError:  # Python 3
+    UNICODE_TYPE = str
+
+
+# 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(BaseException):
+    "An IRC exception"
+    pass
+
+class InvalidRequest(ValueError):
+    "An invalid JSON request"
+    pass
+
+class IRCClient():
+    "An IRC client session to one or more servers."
+    def __init__(self):
+        self.mutex = threading.RLock()
+        self.server_connections = []
+        self.event_handlers = {}
+        self.add_event_handler("ping",
+                               lambda c, e: c.ship("PONG %s" % e.target))
+
+    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:
+            nextsleep = 0
+            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:
+                        try:
+                            connmap[s.fileno()].consume()
+                        except UnicodeDecodeError as e:
+                            LOG.warn('{0}: invalid encoding ({1})'.format(
+                                self, e))
+                else:
+                    nextsleep = timeout
+            time.sleep(nextsleep)
+
+    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 = 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)
+
+
+class LineBufferedStream():
+    "Line-buffer a read stream."
+    _crlf_re = re.compile(b'\r?\n')
+
+    def __init__(self):
+        self.buffer = b''
+
+    def append(self, newbytes):
+        self.buffer += newbytes
+
+    def lines(self):
+        "Iterate over lines in the buffer."
+        lines = self._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
+
+    # PROTOCOL_SSLv23 selects the highest version that both client and server support
+    def _wrap_socket(self, socket, target, certfile=None, cafile=None,
+                     protocol=ssl.PROTOCOL_SSLv23):
+        try:  # Python 3.2 and greater
+            ssl_context = ssl.SSLContext(protocol)
+        except AttributeError:  # Python < 3.2
+            self.socket = ssl.wrap_socket(
+                socket, certfile=certfile, cert_reqs=ssl.CERT_REQUIRED,
+                ssl_version=protocol, ca_certs=cafile)
+        else:
+            ssl_context.verify_mode = ssl.CERT_REQUIRED
+            if certfile:
+                ssl_context.load_cert_chain(certfile)
+            if cafile:
+                ssl_context.load_verify_locations(cafile=cafile)
+            else:
+                ssl_context.set_default_verify_paths()
+            kwargs = {}
+            if ssl.HAS_SNI:
+                kwargs['server_hostname'] = target.servername
+            self.socket = ssl_context.wrap_socket(socket, **kwargs)
+        return self.socket
+
+    def _check_hostname(self, target):
+        if hasattr(ssl, 'match_hostname'):  # Python >= 3.2
+            cert = self.socket.getpeercert()
+            try:
+                ssl.match_hostname(cert, target.servername)
+            except ssl.CertificateError as e:
+                raise IRCServerConnectionError(
+                    'Invalid SSL/TLS certificate: %s' % e)
+        else:  # Python < 3.2
+            LOG.warning(
+                'cannot check SSL/TLS hostname with Python %s' % sys.version)
+
+    def connect(self, target, nickname, username=None, realname=None,
+                **kwargs):
+        LOG.debug("connect(server=%r, port=%r, nickname=%r, ...)" % (
+            target.servername, target.port, nickname))
+        if self.socket is not None:
+            self.disconnect("Changing servers")
+
+        self.buffer = LineBufferedStream()
+        self.event_handlers = {}
+        self.real_server_name = ""
+        self.target = target
+        self.nickname = nickname
+        try:
+            if socks_on and PROXY_TYPE:
+                self.socket = socks.socksocket(socket.AF_INET,socket.SOCK_STREAM)
+                self.socket.set_proxy(PROXY_TYPE, PROXY_HOST, PROXY_PORT)
+            else:
+                self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            if target.ssl:
+                self.socket = self._wrap_socket(
+                    socket=self.socket, target=target, **kwargs)
+            self.socket.bind(('', 0))
+            self.socket.connect((target.servername, target.port))
+        except socket.error as err:
+            raise IRCServerConnectionError("Couldn't connect to socket: %s" % err)
+
+        if target.ssl:
+            self._check_hostname(target=target)
+        if target.password:
+            self.ship("PASS " + target.password)
+        self.nick(self.nickname)
+        self.user(
+            username=target.username or username or 'irker',
+            realname=realname or 'irker relaying client')
+        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:
+            if not isinstance(line, UNICODE_TYPE):
+                line = UNICODE_TYPE(line, 'utf-8')
+                LOG.debug("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:]
+
+            LOG.debug("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.target.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=""):
+        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')
+            LOG.debug("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, irker, target, nick_template, nick_needs_number=False,
+                 password=None, **kwargs):
+        self.irker = irker
+        self.target = target
+        self.nick_template = nick_template
+        self.nick_needs_number = nick_needs_number
+        self.password = password
+        self.kwargs = kwargs
+        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 self.nick_needs_number:
+            return self.nick_template % n
+        else:
+            return self.nick_template
+    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"
+        LOG.info("nick %s accepted" % self.nickname())
+        if self.password:
+            self.connection.privmsg("nickserv", "identify %s" % self.password)
+    def handle_badnick(self):
+        "The server says our nick is ill-formed or has a conflict."
+        LOG.info("nick %s rejected" % self.nickname())
+        if self.nick_needs_number:
+            # 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"
+        # Avoid flooding the server if it disconnects
+        # immediately on sucessful login.
+        time.sleep(RECONNECT_DELAY)
+    def handle_kick(self, outof):
+        "We've been kicked."
+        self.status = "handshaking"
+        try:
+            del self.channels_joined[outof]
+        except KeyError:
+            LOG.error("irkerd: kicked by %s from %s that's not joined" % (
+                self.target, 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, quit_after=False):
+        "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))
+        if quit_after:
+            self.queue.put((channel, None, 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:
+                        LOG.info((
+                            "timing out connection to %s at %s "
+                            "(ping_timeout=%s, xmit_timeout=%s)") % (
+                            self.target, 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(
+                                target=self.target,
+                                nickname=self.nickname(),
+                                **self.kwargs)
+                            self.status = "handshaking"
+                            LOG.info("XMIT_TTL bump (%s connection) at %s" % (
+                                self.target, time.asctime()))
+                            self.last_xmit = time.time()
+                            self.last_ping = time.time()
+                        except IRCServerConnectionError as e:
+                            LOG.error("irkerd: %s" % e)
+                            self.status = "expired"
+                            break
+                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)
+                        LOG.info("joining %s on %s." % (channel, self.target))
+                    # None is magic - it's a request to quit the server
+                    if message is None:
+                        self.connection.quit()
+                    # 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.
+                    elif 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:
+                                LOG.warning((
+                                    "rejected a message to %s on %s "
+                                    "because: %s") % (
+                                    channel, self.target, UNICODE_TYPE(err)))
+                                LOG.debug(traceback.format_exc())
+                            time.sleep(ANTI_FLOOD_DELAY)
+                    self.last_xmit = self.channels_joined[channel] = time.time()
+                    LOG.info("XMIT_TTL bump (%s transmission) at %s" % (
+                        self.target, time.asctime()))
+                    self.queue.task_done()
+                elif self.status == "expired":
+                    LOG.error(
+                        "irkerd: we're expired but still running! This is a bug.")
+                    break
+        except Exception as e:
+            LOG.error("irkerd: exception %s in thread for %s" % (e, self.target))
+            # Maybe this should have its own status?
+            self.status = "expired"
+            LOG.debug(traceback.format_exc())
+        finally:
+            # Make sure we don't leave any zombies behind
+            if self.connection:
+                self.connection.close()
+    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):
+        self.url = url
+        parsed = urllib_parse.urlparse(url)
+        self.ssl = parsed.scheme == 'ircs'
+        if self.ssl:
+            default_ircport = 6697
+        else:
+            default_ircport = 6667
+        self.username = parsed.username
+        self.password = parsed.password
+        self.servername = parsed.hostname
+        self.port = parsed.port or default_ircport
+        # 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)
+
+    def __str__(self):
+        "Represent this instance as a string"
+        return self.servername or self.url or repr(self)
+
+    def validate(self):
+        "Raise InvalidRequest if the URL is missing a critical component"
+        if not self.servername:
+            raise InvalidRequest(
+                'target URL missing a servername: %r' % self.url)
+        if not self.channel:
+            raise InvalidRequest(
+                'target URL missing a channel: %r' % self.url)
+    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, irker, **kwargs):
+        self.irker = irker
+        self.kwargs = kwargs
+        self.connections = []
+    def dispatch(self, channel, message, key, quit_after=False):
+        "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, quit_after)
+            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, quit_after)
+            return
+        # All existing channels had recent activity
+        newconn = Connection(self.irker, **self.kwargs)
+        self.connections.append(newconn)
+        newconn.enqueue(channel, message, key, quit_after)
+    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 pending(self):
+        "Return all connections with pending traffic."
+        return [x for x in self.connections if not x.queue.empty()]
+    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, logfile=None, **kwargs):
+        self.logfile = logfile
+        self.kwargs = kwargs
+        self.irc = IRCClient()
+        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)
+        self.servers = {}
+    def thread_launch(self):
+        thread = threading.Thread(target=self.irc.spin)
+        thread.setDaemon(True)
+        self.irc._thread = thread
+        thread.start()
+    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 self.logfile:
+                        connection.mode(cxt.nickname(), "+"+lump[5:])
+                elif lump.startswith("MAXCHANNELS="):
+                    m = int(lump[12:])
+                    for pref in "#&+":
+                        cxt.channel_limits[pref] = m
+                    LOG.info("%s maxchannels is %d" % (connection.target, 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
+                        LOG.info("%s channel limit map is %s" % (
+                            connection.target, cxt.channel_limits))
+                    except ValueError:
+                        LOG.error("irkerd: ill-formed CHANLIMIT property")
+    def _handle_disconnect(self, connection, _event):
+        "Server hung up the connection."
+        LOG.info("server %s disconnected" % connection.target)
+        connection.close()
+        if connection.context:
+            connection.context.handle_disconnect()
+    def _handle_kick(self, connection, event):
+        "Server hung up the connection."
+        target = event.target
+        LOG.info("irker has been kicked from %s on %s" % (
+            target, connection.target))
+        if connection.context:
+            connection.context.handle_kick(target)
+    def _handle_every_raw_message(self, _connection, event):
+        "Log all messages when in watcher mode."
+        if self.logfile:
+            with open(self.logfile, "ab") as logfp:
+                message = u"%03f|%s|%s\n" % \
+                          (time.time(), event.source, event.arguments[0])
+                logfp.write(message.encode('utf-8'))
+
+    def pending(self):
+        "Do we have any pending message traffic?"
+        return [k for (k, v) in self.servers.items() if v.pending()]
+
+    def _parse_request(self, line):
+        "Request-parsing helper for the handle() method"
+        request = json.loads(line.strip())
+        if not isinstance(request, dict):
+            raise InvalidRequest(
+                "request is not a JSON dictionary: %r" % request)
+        if "to" not in request or "privmsg" not in request:
+            raise InvalidRequest(
+                "malformed request - 'to' or 'privmsg' missing: %r" % request)
+        channels = request['to']
+        message = request['privmsg']
+        if not isinstance(channels, (list, UNICODE_TYPE)):
+            raise InvalidRequest(
+                "malformed request - unexpected channel type: %r" % channels)
+        if not isinstance(message, UNICODE_TYPE):
+            raise InvalidRequest(
+                "malformed request - unexpected message type: %r" % message)
+        if not isinstance(channels, list):
+            channels = [channels]
+        targets = []
+        for url in channels:
+            try:
+                if not isinstance(url, UNICODE_TYPE):
+                    raise InvalidRequest(
+                        "malformed request - URL has unexpected type: %r" %
+                        url)
+                target = Target(url)
+                target.validate()
+            except InvalidRequest as e:
+                LOG.error("irkerd: " + UNICODE_TYPE(e))
+            else:
+                targets.append(target)
+        return (targets, message)
+
+    def handle(self, line, quit_after=False):
+        "Perform a JSON relay request."
+        try:
+            targets, message = self._parse_request(line=line)
+            for target in targets:
+                if target.server() not in self.servers:
+                    self.servers[target.server()] = Dispatcher(
+                        self, target=target, **self.kwargs)
+                self.servers[target.server()].dispatch(
+                    target.channel, message, target.key, quit_after=quit_after)
+                # 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 InvalidRequest as e:
+            LOG.error("irkerd: " + UNICODE_TYPE(e))
+        except ValueError:
+            LOG.error("irkerd: " + "can't recognize JSON on input: %r" % line)
+        except RuntimeError:
+            LOG.error("irkerd: " + "wildly malformed JSON blew the parser stack.")
+
+class IrkerTCPHandler(socketserver.StreamRequestHandler):
+    def handle(self):
+        while True:
+            line = self.rfile.readline()
+            if not line:
+                break
+            if not isinstance(line, UNICODE_TYPE):
+                line = UNICODE_TYPE(line, 'utf-8')
+            irker.handle(line=line.strip())
+
+class IrkerUDPHandler(socketserver.BaseRequestHandler):
+    def handle(self):
+        line = self.request[0].strip()
+        #socket = self.request[1]
+        if not isinstance(line, UNICODE_TYPE):
+            line = UNICODE_TYPE(line, 'utf-8')
+        irker.handle(line=line.strip())
+
+def in_background():
+    "Is this process running in background?"
+    try:
+        return os.getpgrp() != os.tcgetpgrp(1)
+    except OSError:
+        return True
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(
+        description=__doc__.strip().splitlines()[0])
+    parser.add_argument(
+        '-c', '--ca-file', metavar='PATH',
+        help='file of trusted certificates for SSL/TLS')
+    parser.add_argument(
+        '-e', '--cert-file', metavar='PATH',
+        help='pem file used to authenticate to the server')
+    parser.add_argument(
+        '-d', '--log-level', metavar='LEVEL', choices=LOG_LEVELS,
+        help='how much to log to the log file (one of %(choices)s)')
+    parser.add_argument(
+        '-H', '--host', metavar='ADDRESS', default=HOST,
+        help='IP address to listen on')
+    parser.add_argument(
+        '-l', '--log-file', metavar='PATH',
+        help='file for saving captured message traffic')
+    parser.add_argument(
+        '-n', '--nick', metavar='NAME', default='irker%03d',
+        help="nickname (optionally with a '%%.*d' server connection marker)")
+    parser.add_argument(
+        '-p', '--password', metavar='PASSWORD',
+        help='NickServ password')
+    parser.add_argument(
+        '-i', '--immediate', metavar='IRC-URL',
+        help=(
+            'send a single message to IRC-URL and exit.  The message is the '
+            'first positional argument.'))
+    parser.add_argument(
+        '-V', '--version', action='version',
+        version='%(prog)s {0}'.format(version))
+    parser.add_argument(
+        'message', metavar='MESSAGE', nargs='?',
+        help='message for --immediate mode')
+    args = parser.parse_args()
+
+    if not args.log_file and in_background():
+        # There's a case for falling back to address = ('localhost', 514)
+        # But some systems (including OS X) disable this for security reasons.
+        handler = logging.handlers.SysLogHandler(facility='daemon')
+    else:
+        handler = logging.StreamHandler()
+
+    LOG.addHandler(handler)
+    if args.log_level:
+        log_level = getattr(logging, args.log_level.upper())
+        LOG.setLevel(log_level)
+
+    irker = Irker(
+        logfile=args.log_file,
+        nick_template=args.nick,
+        nick_needs_number=re.search('%.*d', args.nick),
+        password=args.password,
+        cafile=args.ca_file,
+        certfile=args.cert_file,
+        )
+    LOG.info("irkerd version %s" % version)
+    if args.immediate:
+        if not args.message:
+            # We want newline to become '\n' and tab to become '\t';
+            # the JSON decoder will undo these transformations.
+            # This will also encode backslash, backspace, formfeed,
+            # and high-half characters, which might produce unexpected
+            # results on output.
+            args.message = sys.stdin.read().encode("string_escape")
+        irker.irc.add_event_handler("quit", lambda _c, _e: sys.exit(0))
+        irker.handle('{"to":"%s","privmsg":"%s"}' % (
+            args.immediate, args.message), quit_after=True)
+        irker.irc.spin()
+    else:
+        if args.message:
+            LOG.error(
+                'irkerd: message argument given (%r), but --immediate not set' % (
+                args.message))
+            raise SystemExit(1)
+        irker.thread_launch()
+        try:
+            tcpserver = socketserver.TCPServer((args.host, PORT), IrkerTCPHandler)
+            udpserver = socketserver.UDPServer((args.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 as e:
+            LOG.error("irkerd: server launch failed: %r\n" % e)
+
+# end