PyLink/protocols/ts6.py

"""
ts6.py: PyLink protocol module for TS6-based IRCds (charybdis, elemental-ircd).
"""

import time
import re

from pylinkirc import utils, conf
from pylinkirc.classes import *
from pylinkirc.log import log
from pylinkirc.protocols.ts6_common import *

class TS6Protocol(TS6BaseProtocol):

    SUPPORTED_IRCDS = ('charybdis', 'elemental', 'chatircd', 'ratbox')
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self._ircd = self.serverdata.get('ircd', 'elemental' if self.serverdata.get('use_elemental_modes')
                                                             else 'charybdis')
        self._ircd = self._ircd.lower()
        if self._ircd not in self.SUPPORTED_IRCDS:
            log.warning("(%s) Unsupported IRCd %r; falling back to 'charybdis' instead", self.name, target_ircd)
            self._ircd = 'charybdis'

        self._can_chghost = False
        if self._ircd in ('charybdis', 'elemental', 'chatircd'):
            # Charybdis and derivatives allow slashes in hosts. Ratbox does not.
            self.protocol_caps |= {'slash-in-hosts'}
            self._can_chghost = True

        self.casemapping = 'rfc1459'
        self.hook_map = {'SJOIN': 'JOIN', 'TB': 'TOPIC', 'TMODE': 'MODE', 'BMASK': 'MODE',
                         'EUID': 'UID', 'RSFNC': 'SVSNICK', 'ETB': 'TOPIC',
                         # ENCAP LOGIN is used on burst for EUID-less servers
                         'USERMODE': 'MODE', 'LOGIN': 'CLIENT_SERVICES_LOGIN'}

        self.required_caps = {'TB', 'ENCAP', 'QS', 'CHW'}

        # From ChatIRCd: https://github.com/ChatLounge/ChatIRCd/blob/master/doc/technical/ChatIRCd-extra.txt
        # Our command handler rewrites ENCAP so that this is the exact same syntax as MODE.
        # <- :101AAAAAB ENCAP test.hub2 USERMODE 111AAAAAB :+Qw
        self.handle_usermode = self.handle_mode

    ### OUTGOING COMMANDS

    def spawn_client(self, nick, ident='null', host='null', realhost=None, modes=set(),
            server=None, ip='0.0.0.0', realname=None, ts=None, opertype='IRC Operator',
            manipulatable=False):
        """
        Spawns a new client with the given options.

        Note: No nick collision / valid nickname checks are done here; it is
        up to plugins to make sure they don't introduce anything invalid.
        """
        server = server or self.sid

        if not self.is_internal_server(server):
            raise ValueError('Server %r is not a PyLink server!' % server)

        uid = self.uidgen[server].next_uid()

        # EUID:
        # parameters: nickname, hopcount, nickTS, umodes, username,
        # visible hostname, IP address, UID, real hostname, account name, gecos
        ts = ts or int(time.time())
        realname = realname or conf.conf['bot']['realname']
        raw_modes = self.join_modes(modes)
        u = self.users[uid] = User(self, nick, ts, uid, server, ident=ident, host=host,
                                   realname=realname, realhost=realhost or host, ip=ip,
                                   manipulatable=manipulatable, opertype=opertype)

        self.apply_modes(uid, modes)
        self.servers[server].users.add(uid)

        if 'EUID' in self._caps:
            # charybdis-style EUID
            self._send_with_prefix(server, "EUID {nick} {hopcount} {ts} {modes} {ident} {host} {ip} {uid} "
                                           "{realhost} * :{realname}".format(ts=ts, host=host,
                                           nick=nick, ident=ident, uid=uid,
                                           modes=raw_modes, ip=ip, realname=realname,
                                           realhost=realhost or host,
                                           hopcount=self.servers[server].hopcount))
        else:
            # Basic ratbox UID
            self._send_with_prefix(server, "UID {nick} {hopcount} {ts} {modes} {ident} {host} {ip} {uid} "
                                           ":{realname}".format(ts=ts, host=host,
                                           nick=nick, ident=ident, uid=uid,
                                           modes=raw_modes, ip=ip, realname=realname,
                                           hopcount=self.servers[server].hopcount))

            if realhost:
                # If real host is specified, send it using ENCAP REALHOST
                self._send_with_prefix(uid, "ENCAP * REALHOST %s" % realhost)

        return u

    def join(self, client, channel):
        """Joins a PyLink client to a channel."""
        # JOIN:
        # parameters: channelTS, channel, '+' (a plus sign)
        if not self.is_internal_client(client):
            log.error('(%s) Error trying to join %r to %r (no such client exists)', self.name, client, channel)
            raise LookupError('No such PyLink client exists.')
        self._send_with_prefix(client, "JOIN {ts} {channel} +".format(ts=self._channels[channel].ts, channel=channel))
        self._channels[channel].users.add(client)
        self.users[client].channels.add(channel)

    def sjoin(self, server, channel, users, ts=None, modes=set()):
        """Sends an SJOIN for a group of users to a channel.

        The sender should always be a Server ID (SID). TS is optional, and defaults
        to the one we've stored in the channel state if not given.
        <users> is a list of (prefix mode, UID) pairs:

        Example uses:
            sjoin('100', '#test', [('', '100AAABBC'), ('o', 100AAABBB'), ('v', '100AAADDD')])
            sjoin(self.sid, '#test', [('o', self.pseudoclient.uid)])
        """
        # https://github.com/grawity/irc-docs/blob/master/server/ts6.txt#L821
        # parameters: channelTS, channel, simple modes, opt. mode parameters..., nicklist

        # Broadcasts a channel creation or bursts a channel.

        # The nicklist consists of users joining the channel, with status prefixes for
        # their status ('@+', '@', '+' or ''), for example:
        # '@+1JJAAAAAB +2JJAAAA4C 1JJAAAADS'. All users must be behind the source server
        # so it is not possible to use this message to force users to join a channel.
        server = server or self.sid
        assert users, "sjoin: No users sent?"
        log.debug('(%s) sjoin: got %r for users', self.name, users)
        if not server:
            raise LookupError('No such PyLink client exists.')

        modes = set(modes or self._channels[channel].modes)
        orig_ts = self._channels[channel].ts
        ts = ts or orig_ts

        # Get all the ban modes in a separate list. These are bursted using a separate BMASK
        # command.
        banmodes = {k: [] for k in self.cmodes['*A']}
        regularmodes = []
        log.debug('(%s) Unfiltered SJOIN modes: %s', self.name, modes)
        for mode in modes:
            modechar = mode[0][-1]
            if modechar in self.cmodes['*A']:
                # Mode character is one of 'beIq'
                if (modechar, mode[1]) in self._channels[channel].modes:
                    # Don't reset modes that are already set.
                    continue

                banmodes[modechar].append(mode[1])
            else:
                regularmodes.append(mode)
        log.debug('(%s) Filtered SJOIN modes to be regular modes: %s, banmodes: %s', self.name, regularmodes, banmodes)

        changedmodes = modes
        while users[:12]:
            uids = []
            namelist = []
            # We take <users> as a list of (prefixmodes, uid) pairs.
            for userpair in users[:12]:
                assert len(userpair) == 2, "Incorrect format of userpair: %r" % userpair
                prefixes, user = userpair
                prefixchars = ''
                for prefix in prefixes:
                    pr = self.prefixmodes.get(prefix)
                    if pr:
                        prefixchars += pr
                        changedmodes.add(('+%s' % prefix, user))
                namelist.append(prefixchars+user)
                uids.append(user)
                try:
                    self.users[user].channels.add(channel)
                except KeyError:  # Not initialized yet?
                    log.debug("(%s) sjoin: KeyError trying to add %r to %r's channel list?", self.name, channel, user)
            users = users[12:]
            namelist = ' '.join(namelist)
            self._send_with_prefix(server, "SJOIN {ts} {channel} {modes} :{users}".format(
                    ts=ts, users=namelist, channel=channel,
                    modes=self.join_modes(regularmodes)))
            self._channels[channel].users.update(uids)

        # Now, burst bans.
        # <- :42X BMASK 1424222769 #dev b :*!test@*.isp.net *!badident@*
        for bmode, bans in banmodes.items():
            # Max 15-3 = 12 bans per line to prevent cut off. (TS6 allows a max of 15 parameters per
            # line)
            if bans:
                log.debug('(%s) sjoin: bursting mode %s with bans %s, ts:%s', self.name, bmode, bans, ts)
                msgprefix = ':{sid} BMASK {ts} {channel} {bmode} :'.format(sid=server, ts=ts,
                                                                          channel=channel, bmode=bmode)
                # Actually, we cut off at 17 arguments/line, since the prefix and command name don't count.
                for msg in utils.wrapArguments(msgprefix, bans, self.S2S_BUFSIZE, max_args_per_line=17):
                    self.send(msg)

        self.updateTS(server, channel, ts, changedmodes)

    def mode(self, numeric, target, modes, ts=None):
        """Sends mode changes from a PyLink client/server."""
        # c <- :0UYAAAAAA TMODE 0 #a +o 0T4AAAAAC
        # u <- :0UYAAAAAA MODE 0UYAAAAAA :-Facdefklnou

        if (not self.is_internal_client(numeric)) and \
                (not self.is_internal_server(numeric)):
            raise LookupError('No such PyLink client/server exists.')

        self.apply_modes(target, modes)
        modes = list(modes)

        if self.is_channel(target):
            ts = ts or self._channels[target].ts
            # TMODE:
            # parameters: channelTS, channel, cmode changes, opt. cmode parameters...

            # On output, at most ten cmode parameters should be sent; if there are more,
            # multiple TMODE messages should be sent.
            msgprefix = ':%s TMODE %s %s ' % (numeric, ts, target)
            bufsize = self.S2S_BUFSIZE - len(msgprefix)

            for modestr in self.wrap_modes(modes, bufsize, max_modes_per_msg=10):
                self.send(msgprefix + modestr)
        else:
            joinedmodes = self.join_modes(modes)
            self._send_with_prefix(numeric, 'MODE %s %s' % (target, joinedmodes))

    def topic_burst(self, numeric, target, text):
        """Sends a topic change from a PyLink server. This is usually used on burst."""
        if not self.is_internal_server(numeric):
            raise LookupError('No such PyLink server exists.')
        # TB
        # capab: TB
        # source: server
        # propagation: broadcast
        # parameters: channel, topicTS, opt. topic setter, topic
        ts = self._channels[target].ts
        servername = self.servers[numeric].name
        self._send_with_prefix(numeric, 'TB %s %s %s :%s' % (target, ts, servername, text))
        self._channels[target].topic = text
        self._channels[target].topicset = True

    def invite(self, numeric, target, channel):
        """Sends an INVITE from a PyLink client.."""
        if not self.is_internal_client(numeric):
            raise LookupError('No such PyLink client exists.')
        self._send_with_prefix(numeric, 'INVITE %s %s %s' % (target, channel, self._channels[channel].ts))

    def knock(self, numeric, target, text):
        """Sends a KNOCK from a PyLink client."""
        if 'KNOCK' not in self._caps:
            log.debug('(%s) knock: Dropping KNOCK to %r since the IRCd '
                      'doesn\'t support it.', self.name, target)
            return
        if not self.is_internal_client(numeric):
            raise LookupError('No such PyLink client exists.')
        # No text value is supported here; drop it.
        self._send_with_prefix(numeric, 'KNOCK %s' % target)

    def set_server_ban(self, source, duration, user='*', host='*', reason='User banned'):
        """
        Sets a server ban.
        """
        # source: user
        # parameters: target server mask, duration, user mask, host mask, reason
        assert not (user == host == '*'), "Refusing to set ridiculous ban on *@*"

        if not source in self.users:
            log.debug('(%s) Forcing KLINE sender to %s as TS6 does not allow KLINEs from servers', self.name, self.pseudoclient.uid)
            source = self.pseudoclient.uid

        self._send_with_prefix(source, 'ENCAP * KLINE %s %s %s :%s' % (duration, user, host, reason))

    def update_client(self, target, field, text):
        """Updates the hostname of any connected client."""
        field = field.upper()
        if field == 'HOST' and self._can_chghost:
            self.users[target].host = text
            self._send_with_prefix(self.sid, 'CHGHOST %s :%s' % (target, text))
            if not self.is_internal_client(target):
                # If the target isn't one of our clients, send hook payload
                # for other plugins to listen to.
                self.call_hooks([self.sid, 'CHGHOST',
                                   {'target': target, 'newhost': text}])
        else:
            raise NotImplementedError("Changing field %r of a client is "
                                      "unsupported by this IRCd." % field)

    ### Core / handlers

    def post_connect(self):
        """Initializes a connection to a server."""
        ts = self.start_ts

        f = self.send

        # Base TS6 mode set from ratbox.
        self.cmodes.update({'sslonly': 'S', 'noknock': 'p',
                            '*A': 'beI',
                            '*B': 'k',
                            '*C': 'l',
                            '*D': 'imnpstrS'})

        # https://github.com/grawity/irc-docs/blob/master/server/ts6.txt#L80
        if self._ircd in ('charybdis', 'elemental', 'chatircd'):
            self.cmodes.update({
                'quiet': 'q', 'redirect': 'f', 'freetarget': 'F',
                'joinflood': 'j', 'largebanlist': 'L', 'permanent': 'P',
                'noforwards': 'Q', 'stripcolor': 'c', 'allowinvite':
                'g', 'opmoderated': 'z', 'noctcp': 'C', 'ssl': 'Z',
                # charybdis modes provided by extensions
                'operonly': 'O', 'adminonly': 'A', 'sslonly': 'S',
                'nonotice': 'T',
                '*A': 'beIq', '*B': 'k', '*C': 'lfj', '*D': 'mnprstFLPQcgzCZOAST'
            })
            self.umodes.update({
                'deaf': 'D', 'servprotect': 'S', 'admin': 'a',
                'invisible': 'i', 'oper': 'o', 'wallops': 'w',
                'snomask': 's', 'noforward': 'Q', 'regdeaf': 'R',
                'callerid': 'g', 'operwall': 'z', 'locops': 'l',
                'cloak': 'x', 'override': 'p',
                '*A': '', '*B': '', '*C': '', '*D': 'DSaiowsQRgzlxp'
            })

            # Charybdis extbans
            self.extbans_matching = {'ban_all_registered': '$a', 'ban_inchannel': '$c:', 'ban_account': '$a:',
                                     'ban_all_opers': '$o', 'ban_realname': '$r:', 'ban_server': '$s:',
                                     'ban_banshare': '$j:', 'ban_extgecos': '$x:', 'ban_all_ssl': '$z'}
        elif self._ircd == 'ratbox':
            self.umodes.update({
                'callerid': 'g', 'admin': 'a', 'sno_botfloods': 'b',
                'sno_clientconnections': 'c', 'sno_extclientconnections': 'C', 'sno_debug': 'd',
                'sno_fullauthblock': 'f', 'sno_skill': 'k', 'locops': 'l', 'sno_rejectedclients': 'r',
                'snomask': 's', 'sno_badclientconnections': 'u', 'sno_serverconnects': 'x',
                'sno_stats': 'y', 'operwall': 'z', 'sno_operspy': 'Z', 'deaf': 'D', 'servprotect': 'S',
                '*A': '', '*B': '', '*C': '', '*D': 'igoabcCdfklrsuwxyzZD'
            })

        # TODO: make these more flexible...
        if self.serverdata.get('use_owner'):
            self.cmodes['owner'] = 'y'
            self.prefixmodes['y'] = '~'
        if self.serverdata.get('use_admin'):
            self.cmodes['admin'] = 'a'
            self.prefixmodes['a'] = '!' if self._ircd != 'chatircd' else '&'
        if self.serverdata.get('use_halfop'):
            self.cmodes['halfop'] = 'h'
            self.prefixmodes['h'] = '%'

        # Toggles support of shadowircd/elemental-ircd specific channel modes:
        # +T (no notice), +u (hidden ban list), +E (no kicks), +J (blocks kickrejoin),
        # +K (no repeat messages), +d (no nick changes), and user modes:
        # +B (bot), +C (blocks CTCP), +V (no invites), +I (hides channel list)
        if self._ircd == 'elemental':
            elemental_cmodes = {'hiddenbans': 'u', 'nokick': 'E',
                                'kicknorejoin': 'J', 'repeat': 'K', 'nonick': 'd',
                                'blockcaps': 'G'}
            self.cmodes.update(elemental_cmodes)
            self.cmodes['*D'] += ''.join(elemental_cmodes.values())

            elemental_umodes = {'noctcp': 'C', 'bot': 'B', 'noinvite': 'V', 'hidechans': 'I'}
            self.umodes.update(elemental_umodes)
            self.umodes['*D'] += ''.join(elemental_umodes.values())

        elif self._ircd == 'chatircd':
            chatircd_cmodes = {'netadminonly': 'N'}
            self.cmodes.update(chatircd_cmodes)
            self.cmodes['*D'] += ''.join(chatircd_cmodes.values())

            chatircd_umodes = {'netadmin': 'n', 'bot': 'B', 'callerid_sslonly': 't'}
            self.umodes.update(chatircd_umodes)
            self.umodes['*D'] += ''.join(chatircd_umodes.values())

        # Add definitions for all the inverted versions of the extbans.
        if self.extbans_matching:
            for k, v in self.extbans_matching.copy().items():
                if k == 'ban_all_registered':
                    newk = 'ban_unregistered'
                else:
                    newk = k.replace('_all_', '_').replace('ban_', 'ban_not_')
                self.extbans_matching[newk] = '$~' + v[1:]

        # https://github.com/grawity/irc-docs/blob/master/server/ts6.txt#L55
        f('PASS %s TS 6 %s' % (self.serverdata["sendpass"], self.sid))

        # We request the following capabilities:

        # QS: SQUIT doesn't send recursive quits for each users; required
        # by charybdis (Source: https://github.com/grawity/irc-docs/blob/master/server/ts-capab.txt)
        # ENCAP: message encapsulation for certain commands
        # EX: Support for ban exemptions (+e)
        # IE: Support for invite exemptions (+e)
        # CHW: Allow sending messages to @#channel and the like.
        # KNOCK: support for /knock
        # SAVE: support for SAVE (forces user to UID in nick collision)
        # SERVICES: adds mode +r (only registered users can join a channel)
        # TB: topic burst command; we send this in topic_burst
        # EUID: extended UID command, which includes real hostname + account data info,
        #       and allows sending CHGHOST without ENCAP.
        # RSFNC: states that we support RSFNC (forced nick changed attempts). XXX: With atheme services,
        #        does this actually do anything?
        # EOPMOD: supports ETB (extended TOPIC burst) and =#channel messages for opmoderated +z
        # KLN: supports remote KLINEs
        f('CAPAB :QS ENCAP EX CHW IE KNOCK SAVE SERVICES TB EUID RSFNC EOPMOD SAVETS_100 KLN')

        f('SERVER %s 0 :%s' % (self.serverdata["hostname"],
                               self.serverdata.get('serverdesc') or conf.conf['bot']['serverdesc']))

        # Finally, end all the initialization with a PING - that's Charybdis'
        # way of saying end-of-burst :)
        self._ping_uplink()

    def handle_pass(self, numeric, command, args):
        """
        Handles the PASS command, used to send the server's SID and negotiate
        passwords on connect.
        """
        # <- PASS $somepassword TS 6 :42X

        if args[0] != self.serverdata['recvpass']:
            # Check if recvpass is correct
            raise ProtocolError('Recvpass from uplink server %s does not match configuration!' % servername)

        if args[1] != 'TS' and args[2] != '6':
            raise ProtocolError("Remote protocol version is too old! Is this even TS6?")

        numeric = args[-1]
        log.debug('(%s) Found uplink SID as %r', self.name, numeric)

        # Server name and SID are sent in different messages, so we fill this
        # with dummy information until we get the actual sid.
        self.servers[numeric] = Server(self, None, '')
        self.uplink = numeric

    def handle_capab(self, numeric, command, args):
        """
        Handles the CAPAB command, used for TS6 capability negotiation.
        """
        # We only get a list of keywords here. Charybdis obviously assumes that
        # we know what modes it supports (indeed, this is a standard list).
        # <- CAPAB :BAN CHW CLUSTER ENCAP EOPMOD EUID EX IE KLN KNOCK MLOCK QS RSFNC SAVE SERVICES TB UNKLN
        self._caps = caps = args[0].split()

        for required_cap in self.required_caps:
            if required_cap not in caps:
                raise ProtocolError('%s not found in TS6 capabilities list; this is required! (got %r)' % (required_cap, caps))

        if 'EX' in caps:
            self.cmodes['banexception'] = 'e'
        if 'IE' in caps:
            self.cmodes['invex'] = 'I'
        if 'SERVICES' in caps:
            self.cmodes['regonly'] = 'r'

    def handle_ping(self, source, command, args):
        """Handles incoming PING commands."""
        # PING:
        # source: any
        # parameters: origin, opt. destination server
        # PONG:
        # source: server
        # parameters: origin, destination

        # Sends a PING to the destination server, which will reply with a PONG. If the
        # destination server parameter is not present, the server receiving the message
        # must reply.
        try:
            destination = args[1]
        except IndexError:
            destination = self.sid
        if self.is_internal_server(destination):
            self._send_with_prefix(destination, 'PONG %s %s' % (destination, source), queue=False)

            if not self.servers[source].has_eob:
                # TS6 endburst is just sending a PING to the other server.
                # https://github.com/charybdis-ircd/charybdis/blob/dc336d1/modules/core/m_server.c#L484-L485
                self.servers[source].has_eob = True

                if source == self.uplink:
                    log.debug('(%s) self.connected set!', self.name)
                    self.connected.set()

                # Return the endburst hook.
                return {'parse_as': 'ENDBURST'}

    def handle_sjoin(self, servernumeric, command, args):
        """Handles incoming SJOIN commands."""
        # parameters: channelTS, channel, simple modes, opt. mode parameters..., nicklist
        # <- :0UY SJOIN 1451041566 #channel +nt :@0UYAAAAAB
        channel = args[1]
        chandata = self._channels[channel].deepcopy()
        userlist = args[-1].split()

        modestring = args[2:-1] or args[2]
        parsedmodes = self.parse_modes(channel, modestring)
        namelist = []

        # Keep track of other modes that are added due to prefix modes being joined too.
        changedmodes = set(parsedmodes)

        log.debug('(%s) handle_sjoin: got userlist %r for %r', self.name, userlist, channel)
        for userpair in userlist:
            # charybdis sends this in the form "@+UID1, +UID2, UID3, @UID4"
            r = re.search(r'([^\d]*)(.*)', userpair)
            user = r.group(2)
            modeprefix = r.group(1) or ''
            finalprefix = ''
            assert user, 'Failed to get the UID from %r; our regex needs updating?' % userpair
            log.debug('(%s) handle_sjoin: got modeprefix %r for user %r', self.name, modeprefix, user)

            # Don't crash when we get an invalid UID.
            if user not in self.users:
                log.debug('(%s) handle_sjoin: tried to introduce user %s not in our user list, ignoring...',
                          self.name, user)
                continue

            for m in modeprefix:
                # Iterate over the mapping of prefix chars to prefixes, and
                # find the characters that match.
                for char, prefix in self.prefixmodes.items():
                    if m == prefix:
                        finalprefix += char
            namelist.append(user)
            self.users[user].channels.add(channel)

            # Only save mode changes if the remote has lower TS than us.
            changedmodes |= {('+%s' % mode, user) for mode in finalprefix}
            self._channels[channel].users.add(user)

        # Statekeeping with timestamps
        their_ts = int(args[0])
        our_ts = self._channels[channel].ts
        self.updateTS(servernumeric, channel, their_ts, changedmodes)

        return {'channel': channel, 'users': namelist, 'modes': parsedmodes, 'ts': their_ts,
                'channeldata': chandata}

    def handle_join(self, numeric, command, args):
        """Handles incoming channel JOINs."""
        # parameters: channelTS, channel, '+' (a plus sign)
        # <- :0UYAAAAAF JOIN 0 #channel +
        ts = int(args[0])
        if args[0] == '0':
            # /join 0; part the user from all channels
            oldchans = self.users[numeric].channels.copy()
            log.debug('(%s) Got /join 0 from %r, channel list is %r',
                      self.name, numeric, oldchans)
            for channel in oldchans:
                self._channels[channel].users.discard(numeric)
                self.users[numeric].channels.discard(channel)
            return {'channels': oldchans, 'text': 'Left all channels.', 'parse_as': 'PART'}
        else:
            channel = args[1]
            self.updateTS(numeric, channel, ts)

            self.users[numeric].channels.add(channel)
            self._channels[channel].users.add(numeric)

        # We send users and modes here because SJOIN and JOIN both use one hook,
        # for simplicity's sake (with plugins).
        return {'channel': channel, 'users': [numeric], 'modes':
                self._channels[channel].modes, 'ts': ts}

    def handle_euid(self, numeric, command, args):
        """Handles incoming EUID commands (user introduction)."""
        # <- :42X EUID GL 1 1437505322 +ailoswz ~gl 127.0.0.1 127.0.0.1 42XAAAAAB * * :realname
        nick = args[0]
        self._check_nick_collision(nick)
        ts, modes, ident, host, ip, uid, realhost, accountname, realname = args[2:11]
        if realhost == '*':
            realhost = host

        log.debug('(%s) handle_euid got args: nick=%s ts=%s uid=%s ident=%s '
                  'host=%s realname=%s realhost=%s ip=%s', self.name, nick, ts, uid,
                  ident, host, realname, realhost, ip)
        assert ts != 0, "Bad TS 0 for user %s" % uid

        if ip == '0':  # IP was invalid; something used for services.
            ip = '0.0.0.0'

        self.users[uid] = User(self,  nick, ts, uid, numeric, ident, host, realname, realhost, ip)

        parsedmodes = self.parse_modes(uid, [modes])
        log.debug('Applying modes %s for %s', parsedmodes, uid)
        self.apply_modes(uid, parsedmodes)
        self.servers[numeric].users.add(uid)

        # Call the OPERED UP hook if +o is being added to the mode list.
        self._check_oper_status_change(uid, parsedmodes)

        # Set the accountname if present
        if accountname != "*":
            self.call_hooks([uid, 'CLIENT_SERVICES_LOGIN', {'text': accountname}])

        return {'uid': uid, 'ts': ts, 'nick': nick, 'realhost': realhost, 'host': host, 'ident': ident, 'ip': ip}

    def handle_uid(self, numeric, command, args):
        """Handles legacy user introductions (UID)."""
        # tl;dr We want to convert the following UID parameters:
        #    nickname, hopcount, nickTS, umodes, username, visible hostname, IP address, UID, gecos
        # to EUID parameters when parsing:
        #    nickname, hopcount, nickTS, umodes, username, visible hostname, IP address, UID,
        #    real hostname, account name, gecos

        euid_args = args[:]

        # Insert a * to denote that the user is not logged in.
        euid_args.insert(8, '*')

        # Copy the visible hostname to the real hostname, as this data isn't sent yet.
        euid_args.insert(8, args[5])

        return self.handle_euid(numeric, command, euid_args)

    def handle_server(self, numeric, command, args):
        """
        Handles 1) incoming legacy (no SID) server introductions,
        2) Sending server data in initial connection.
        """
        if numeric == self.uplink and not self.servers[numeric].name:
            # <- SERVER charybdis.midnight.vpn 1 :charybdis test server
            sname = args[0].lower()

            log.debug('(%s) Found uplink server name as %r', self.name, sname)
            self.servers[numeric].name = sname
            self.servers[numeric].desc = args[-1]

            # According to the TS6 protocol documentation, we should send SVINFO
            # when we get our uplink's SERVER command.
            self.send('SVINFO 6 6 0 :%s' % int(time.time()))

            return

        # <- :services.int SERVER a.bc 2 :(H) [GL] a
        return super().handle_server(numeric, command, args)

    def handle_tmode(self, numeric, command, args):
        """Handles incoming TMODE commands (channel mode change)."""
        # <- :42XAAAAAB TMODE 1437450768 #test -c+lkC 3 agte4
        # <- :0UYAAAAAD TMODE 0 #a +h 0UYAAAAAD
        channel = args[1]
        oldobj = self._channels[channel].deepcopy()
        modes = args[2:]
        changedmodes = self.parse_modes(channel, modes)
        self.apply_modes(channel, changedmodes)
        ts = int(args[0])
        return {'target': channel, 'modes': changedmodes, 'ts': ts,
                'channeldata': oldobj}

    def handle_tb(self, numeric, command, args):
        """Handles incoming topic burst (TB) commands."""
        # <- :42X TB #chat 1467427448 GL!~gl@127.0.0.1 :test
        channel = args[0]
        ts = args[1]
        setter = args[2]
        topic = args[-1]
        self._channels[channel].topic = topic
        self._channels[channel].topicset = True
        return {'channel': channel, 'setter': setter, 'ts': ts, 'text': topic}

    def handle_etb(self, numeric, command, args):
        """Handles extended topic burst (ETB)."""
        # <- :00AAAAAAC ETB 0 #test 1470021157 GL :test | abcd
        # Same as TB, with extra TS and extensions arguments.
        channel = args[1]
        ts = args[2]
        setter = args[3]
        topic = args[-1]
        self._channels[channel].topic = topic
        self._channels[channel].topicset = True
        return {'channel': channel, 'setter': setter, 'ts': ts, 'text': topic}

    def handle_chghost(self, numeric, command, args):
        """Handles incoming CHGHOST commands."""
        target = self._get_UID(args[0])
        self.users[target].host = newhost = args[1]
        return {'target': target, 'newhost': newhost}

    def handle_bmask(self, numeric, command, args):
        """Handles incoming BMASK commands (ban propagation on burst)."""
        # <- :42X BMASK 1424222769 #dev b :*!test@*.isp.net *!badident@*
        # This is used for propagating bans, not TMODE!
        channel = args[1]
        mode = args[2]
        ts = int(args[0])
        modes = []
        for ban in args[-1].split():
            modes.append(('+%s' % mode, ban))
        self.apply_modes(channel, modes)
        return {'target': channel, 'modes': modes, 'ts': ts}

    def handle_472(self, numeric, command, args):
        """Handles the incoming 472 numeric.

        472 is sent to us when one of our clients tries to set a mode the uplink
        server doesn't support. In this case, we'll raise a warning to alert
        the administrator that certain extensions should be loaded for the best
        compatibility.
        """
        # <- :charybdis.midnight.vpn 472 GL|devel O :is an unknown mode char to me
        badmode = args[1]
        reason = args[-1]
        setter = args[0]
        charlist = {'A': 'chm_adminonly', 'O': 'chm_operonly', 'S': 'chm_sslonly',
                    'T': 'chm_nonotice'}
        if badmode in charlist:
            log.warning('(%s) User %r attempted to set channel mode %r, but the '
                        'extension providing it isn\'t loaded! To prevent possible'
                        ' desyncs, try adding the line "loadmodule "extensions/%s.so";" to '
                        'your IRCd configuration.', self.name, setter, badmode,
                        charlist[badmode])

    def handle_su(self, numeric, command, args):
        """
        Handles SU, which is used for setting login information.
        """
        # <- :00A ENCAP * SU 42XAAAAAC :GLolol
        # <- :00A ENCAP * SU 42XAAAAAC
        try:
            account = args[1]  # Account name is being set
        except IndexError:
            account = ''  # No account name means a logout

        uid = args[0]
        self.call_hooks([uid, 'CLIENT_SERVICES_LOGIN', {'text': account}])

    def handle_rsfnc(self, numeric, command, args):
        """
        Handles RSFNC, used for forced nick change attempts.
        """
        # <- :00A ENCAP somenet.relay RSFNC 801AAAAAB Guest75038 1468299643 :1468299675
        return {'target': args[0], 'newnick': args[1]}

    def handle_realhost(self, uid, command, args):
        """Handles real host propagation."""
        log.debug('(%s) Got REALHOST %s for %s', args[0], uid)
        self.users[uid].realhost = args[0]

    def handle_login(self, uid, command, args):
        """Handles login propagation on burst."""
        self.users[uid].services_account = args[0]
        return {'text': args[0]}

Class = TS6Protocol