Update copyright headers.

[user/henk/code/inspircd.git] / src / modules / m_spanningtree / fjoin.cpp

/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2015, 2018-2019 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2012-2016 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2009-2010 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2008, 2012 Robin Burchell <robin+git@viroteck.net>
 *   Copyright (C) 2008, 2010 Craig Edwards <brain@inspircd.org>
 *
 * This file is part of InspIRCd.  InspIRCd is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "inspircd.h"
#include "commands.h"
#include "treeserver.h"
#include "treesocket.h"

/** FJOIN builder for rebuilding incoming FJOINs and splitting them up into multiple messages if necessary
 */
class FwdFJoinBuilder : public CommandFJoin::Builder
{
        TreeServer* const sourceserver;

 public:
        FwdFJoinBuilder(Channel* chan, TreeServer* server)
                : CommandFJoin::Builder(chan, server)
                , sourceserver(server)
        {
        }

        void add(Membership* memb, std::string::const_iterator mbegin, std::string::const_iterator mend);
};

/** FJOIN, almost identical to TS6 SJOIN, except for nicklist handling. */
CmdResult CommandFJoin::Handle(User* srcuser, Params& params)
{
        /* 1.1+ FJOIN works as follows:
         *
         * Each FJOIN is sent along with a timestamp, and the side with the lowest
         * timestamp 'wins'. From this point on we will refer to this side as the
         * winner. The side with the higher timestamp loses, from this point on we
         * will call this side the loser or losing side. This should be familiar to
         * anyone who's dealt with dreamforge or TS6 before.
         *
         * When two sides of a split heal and this occurs, the following things
         * will happen:
         *
         * If the timestamps are exactly equal, both sides merge their privilages
         * and users, as in InspIRCd 1.0 and ircd2.8. The channels have not been
         * re-created during a split, this is safe to do.
         *
         * If the timestamps are NOT equal, the losing side removes all of its
         * modes from the channel, before introducing new users into the channel
         * which are listed in the FJOIN command's parameters. The losing side then
         * LOWERS its timestamp value of the channel to match that of the winning
         * side, and the modes of the users of the winning side are merged in with
         * the losing side.
         *
         * The winning side on the other hand will ignore all user modes from the
         * losing side, so only its own modes get applied. Life is simple for those
         * who succeed at internets. :-)
         *
         * Outside of netbursts, the winning side also resyncs the losing side if it
         * detects that the other side recreated the channel.
         *
         * Syntax:
         * :<sid> FJOIN <chan> <TS> <modes> :[<member> [<member> ...]]
         * The last parameter is a list consisting of zero or more channel members
         * (permanent channels may have zero users). Each entry on the list is in the
         * following format:
         * [[<modes>,]<uuid>[:<membid>]
         * <modes> is a concatenation of the mode letters the user has on the channel
         * (e.g.: "ov" if the user is opped and voiced). The order of the mode letters
         * are not important but if a server ecounters an unknown mode letter, it will
         * drop the link to avoid desync.
         *
         * InspIRCd 2.0 and older required a comma before the uuid even if the user
         * had no prefix modes on the channel, InspIRCd 3.0 and later does not require
         * a comma in this case anymore.
         *
         * <membid> is a positive integer representing the id of the membership.
         * If not present (in FJOINs coming from pre-1205 servers), 0 is assumed.
         *
         * Forwarding:
         * FJOIN messages are forwarded with the new TS and modes. Prefix modes of
         * members on the losing side are not forwarded.
         * This is required to only have one server on each side of the network who
         * decides the fate of a channel during a network merge. Otherwise, if the
         * clock of a server is slightly off it may make a different decision than
         * the rest of the network and desync.
         * The prefix modes are always forwarded as-is, or not at all.
         * One incoming FJOIN may result in more than one FJOIN being generated
         * and forwarded mainly due to compatibility reasons with non-InspIRCd
         * servers that don't handle more than 512 char long lines.
         *
         * Forwarding examples:
         * Existing channel #chan with TS 1000, modes +n.
         * Incoming:  :220 FJOIN #chan 1000 +t :o,220AAAAAB:0
         * Forwarded: :220 FJOIN #chan 1000 +nt :o,220AAAAAB:0
         * Merge modes and forward the result. Forward their prefix modes as well.
         *
         * Existing channel #chan with TS 1000, modes +nt.
         * Incoming:  :220 FJOIN #CHAN 2000 +i :ov,220AAAAAB:0 o,220AAAAAC:20
         * Forwarded: :220 FJOIN #chan 1000 +nt :,220AAAAAB:0 ,220AAAAAC:20
         * Drop their modes, forward our modes and TS, use our channel name
         * capitalization. Don't forward prefix modes.
         *
         */

        time_t TS = ServerCommand::ExtractTS(params[1]);

        const std::string& channel = params[0];
        Channel* chan = ServerInstance->FindChan(channel);
        bool apply_other_sides_modes = true;
        TreeServer* const sourceserver = TreeServer::Get(srcuser);

        if (!chan)
        {
                chan = new Channel(channel, TS);
        }
        else
        {
                time_t ourTS = chan->age;
                if (TS != ourTS)
                {
                        ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Merge FJOIN received for %s, ourTS: %lu, TS: %lu, difference: %ld",
                                chan->name.c_str(), (unsigned long)ourTS, (unsigned long)TS, (long)(ourTS - TS));
                        /* If our TS is less than theirs, we dont accept their modes */
                        if (ourTS < TS)
                        {
                                // If the source server isn't bursting then this FJOIN is the result of them recreating the channel with a higher TS.
                                // This happens if the last user on the channel hops and before the PART propagates a user on another server joins. Fix it by doing a resync.
                                // Servers behind us won't react this way because the forwarded FJOIN will have the correct TS.
                                if (!sourceserver->IsBursting())
                                {
                                        ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Server %s recreated channel %s with higher TS, resyncing", sourceserver->GetName().c_str(), chan->name.c_str());
                                        sourceserver->GetSocket()->SyncChannel(chan);
                                }
                                apply_other_sides_modes = false;
                        }
                        else if (ourTS > TS)
                        {
                                // Our TS is greater than theirs, remove all modes, extensions, etc. from the channel
                                LowerTS(chan, TS, channel);

                                // XXX: If the channel does not exist in the chan hash at this point, create it so the remote modes can be applied on it.
                                // This happens to 0-user permanent channels on the losing side, because those are removed (from the chan hash, then
                                // deleted later) as soon as the permchan mode is removed from them.
                                if (ServerInstance->FindChan(channel) == NULL)
                                {
                                        chan = new Channel(channel, TS);
                                }
                        }
                }
        }

        // Apply their channel modes if we have to
        Modes::ChangeList modechangelist;
        if (apply_other_sides_modes)
        {
                ServerInstance->Modes.ModeParamsToChangeList(srcuser, MODETYPE_CHANNEL, params, modechangelist, 2, params.size() - 1);
                ServerInstance->Modes->Process(srcuser, chan, NULL, modechangelist, ModeParser::MODE_LOCALONLY | ModeParser::MODE_MERGE);
                // Reuse for prefix modes
                modechangelist.clear();
        }

        // Build a new FJOIN for forwarding. Put the correct TS in it and the current modes of the channel
        // after applying theirs. If they lost, the prefix modes from their message are not forwarded.
        FwdFJoinBuilder fwdfjoin(chan, sourceserver);

        // Process every member in the message
        irc::spacesepstream users(params.back());
        std::string item;
        Modes::ChangeList* modechangelistptr = (apply_other_sides_modes ? &modechangelist : NULL);
        while (users.GetToken(item))
        {
                ProcessModeUUIDPair(item, sourceserver, chan, modechangelistptr, fwdfjoin);
        }

        fwdfjoin.finalize();
        fwdfjoin.Forward(sourceserver->GetRoute());

        // Set prefix modes on their users if we lost the FJOIN or had equal TS
        if (apply_other_sides_modes)
                ServerInstance->Modes->Process(srcuser, chan, NULL, modechangelist, ModeParser::MODE_LOCALONLY);

        return CMD_SUCCESS;
}

void CommandFJoin::ProcessModeUUIDPair(const std::string& item, TreeServer* sourceserver, Channel* chan, Modes::ChangeList* modechangelist, FwdFJoinBuilder& fwdfjoin)
{
        std::string::size_type comma = item.find(',');

        // Comma not required anymore if the user has no modes
        const std::string::size_type ubegin = (comma == std::string::npos ? 0 : comma+1);
        std::string uuid(item, ubegin, UIDGenerator::UUID_LENGTH);
        User* who = ServerInstance->FindUUID(uuid);
        if (!who)
        {
                // Probably KILLed, ignore
                return;
        }

        TreeSocket* src_socket = sourceserver->GetSocket();
        /* Check that the user's 'direction' is correct */
        TreeServer* route_back_again = TreeServer::Get(who);
        if (route_back_again->GetSocket() != src_socket)
        {
                return;
        }

        std::string::const_iterator modeendit = item.begin(); // End of the "ov" mode string
        /* Check if the user received at least one mode */
        if ((modechangelist) && (comma != std::string::npos))
        {
                modeendit += comma;
                /* Iterate through the modes and see if they are valid here, if so, apply */
                for (std::string::const_iterator i = item.begin(); i != modeendit; ++i)
                {
                        ModeHandler* mh = ServerInstance->Modes->FindMode(*i, MODETYPE_CHANNEL);
                        if (!mh)
                                throw ProtocolException("Unrecognised mode '" + std::string(1, *i) + "'");

                        /* Add any modes this user had to the mode stack */
                        modechangelist->push_add(mh, who->nick);
                }
        }

        Membership* memb = chan->ForceJoin(who, NULL, sourceserver->IsBursting());
        if (!memb)
        {
                // User was already on the channel, forward because of the modes they potentially got
                memb = chan->GetUser(who);
                if (memb)
                        fwdfjoin.add(memb, item.begin(), modeendit);
                return;
        }

        // Assign the id to the new Membership
        Membership::Id membid = 0;
        const std::string::size_type colon = item.rfind(':');
        if (colon != std::string::npos)
                membid = Membership::IdFromString(item.substr(colon+1));
        memb->id = membid;

        // Add member to fwdfjoin with prefix modes
        fwdfjoin.add(memb, item.begin(), modeendit);
}

void CommandFJoin::RemoveStatus(Channel* c)
{
        Modes::ChangeList changelist;

        const ModeParser::ModeHandlerMap& mhs = ServerInstance->Modes->GetModes(MODETYPE_CHANNEL);
        for (ModeParser::ModeHandlerMap::const_iterator i = mhs.begin(); i != mhs.end(); ++i)
        {
                ModeHandler* mh = i->second;

                // Add the removal of this mode to the changelist. This handles all kinds of modes, including prefix modes.
                mh->RemoveMode(c, changelist);
        }

        ServerInstance->Modes->Process(ServerInstance->FakeClient, c, NULL, changelist, ModeParser::MODE_LOCALONLY);
}

void CommandFJoin::LowerTS(Channel* chan, time_t TS, const std::string& newname)
{
        if (Utils->AnnounceTSChange)
        {
                // WriteNotice is not used here because the message only needs to go to the local server.
                const std::string tsmessage  = InspIRCd::Format("Creation time of %s changed from %s to %s", newname.c_str(),
                        InspIRCd::TimeString(chan->age).c_str(), InspIRCd::TimeString(TS).c_str());
                ClientProtocol::Messages::Privmsg privmsg(ClientProtocol::Messages::Privmsg::nocopy, ServerInstance->FakeClient, chan, tsmessage, MSG_NOTICE);
                chan->Write(ServerInstance->GetRFCEvents().privmsg, privmsg);
        }

        // While the name is equal in case-insensitive compare, it might differ in case; use the remote version
        chan->name = newname;
        chan->age = TS;

        // Clear all modes
        CommandFJoin::RemoveStatus(chan);

        // Unset all extensions
        chan->FreeAllExtItems();

        // Clear the topic
        chan->SetTopic(ServerInstance->FakeClient, std::string(), 0);
        chan->setby.clear();
}

CommandFJoin::Builder::Builder(Channel* chan, TreeServer* source)
        : CmdBuilder(source, "FJOIN")
{
        push(chan->name).push_int(chan->age).push_raw(" +");
        pos = str().size();
        push_raw(chan->ChanModes(true)).push_raw(" :");
}

void CommandFJoin::Builder::add(Membership* memb, std::string::const_iterator mbegin, std::string::const_iterator mend)
{
        push_raw(mbegin, mend).push_raw(',').push_raw(memb->user->uuid);
        push_raw(':').push_raw_int(memb->id);
        push_raw(' ');
}

bool CommandFJoin::Builder::has_room(std::string::size_type nummodes) const
{
        return ((str().size() + nummodes + UIDGenerator::UUID_LENGTH + 2 + membid_max_digits + 1) <= maxline);
}

void CommandFJoin::Builder::clear()
{
        content.erase(pos);
        push_raw(" :");
}

const std::string& CommandFJoin::Builder::finalize()
{
        if (*content.rbegin() == ' ')
                content.erase(content.size()-1);
        return str();
}

void FwdFJoinBuilder::add(Membership* memb, std::string::const_iterator mbegin, std::string::const_iterator mend)
{
        // Pseudoserver compatibility:
        // Some pseudoservers do not handle lines longer than 512 so we split long FJOINs into multiple messages.
        // The forwarded FJOIN can end up being longer than the original one if we have more modes set and won, for example.

        // Check if the member fits into the current message. If not, send it and prepare a new one.
        if (!has_room(std::distance(mbegin, mend)))
        {
                finalize();
                Forward(sourceserver);
                clear();
        }
        // Add the member and their modes exactly as they sent them
        CommandFJoin::Builder::add(memb, mbegin, mend);
}