ircd/m_destruct.c

   1 /*
   2  * IRC - Internet Relay Chat, ircd/m_destruct.c
   3  * Copyright (C) 1997 Carlo Wood.
   4  *
   5  * See file AUTHORS in IRC package for additional names of
   6  * the programmers.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 1, or (at your option)
  11  * any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  *
  22  * $Id: m_destruct.c,v 1.9 2005/03/20 16:06:18 entrope Exp $
  23  */
  24
  25 #include "config.h"
  26
  27 #include "client.h"
  28 #include "hash.h"
  29 #include "ircd.h"
  30 #include "ircd_log.h"
  31 #include "ircd_reply.h"
  32 #include "ircd_string.h"
  33 #include "msg.h"
  34 #include "numeric.h"
  35 #include "numnicks.h"
  36 #include "send.h"
  37 #include "channel.h"
  38 #include "destruct_event.h"
  39
  40 /* #include <assert.h> -- Now using assert in ircd_log.h */
  41 #include <stdlib.h>
  42
  43 /*
  44  * ms_destruct - server message handler
  45  *
  46  * Added 1997 by Run, actually coded and used since 2002.
  47  *
  48  * parv[0] = sender prefix
  49  * parv[1] = channel channelname
  50  * parv[2] = channel time stamp
  51  *
  52  * This message is intended to destruct _empty_ channels.
  53  *
  54  * The reason it is needed is to somehow add the notion
  55  * "I destructed information" to the networks state
  56  * (also messages that are still propagating are part
  57  *  of the global state).  Without it the network could
  58  * easily be desynced as a result of destructing a channel
  59  * on only a part of the network while keeping the modes
  60  * and creation time on others.
  61  * There are three possible ways a DESTRUCT message is
  62  * handled by remote servers:
  63  * 1) The channel is empty and has the same timestamp
  64  *    as on the message.  Conclusion: The channel has
  65  *    not been destructed and recreated in the meantime,
  66  *    this means that the normal synchronization rules
  67  *    account and we react as if we decided to destruct
  68  *    the channel ourselves: we destruct the channel and
  69  *    send a DESTRUCT in all directions.
  70  * 2) The channel is not empty.  In case we cannot remove
  71  *    it and do not propagate the DESTRUCT message. Instead
  72  *    a resynchronizing BURST message is sent upstream
  73  *    in order to restore the channel on that side (which
  74  *    will have a TS younger than the current channel if
  75  *    it was recreated and will thus be fully synced, just
  76  *    like in the case of a real net-junction).
  77  * 3) The channel is empty, but the creation time of the
  78  *    channel is older than the timestamp on the message.
  79  *    This can happen when there is more than one minute
  80  *    lag and remotely a channel was created slightly
  81  *    after we created the channel, being abandoned again
  82  *    and staying empty for a minute without that our
  83  *    CREATE reached that remote server.  The remote server
  84  *    then could have generated the DESTRUCT.  In the meantime
  85  *    our user also left the channel.  We can ignore the
  86  *    destruct because it comes from an 'area' that will
  87  *    be overridden by our own CREATE: the state that generated
  88  *    this DESTRUCT is 'history'.
  89  */
  90 int ms_destruct(struct Client* cptr, struct Client* sptr, int parc, char* parv[])
  91 {
  92   time_t chanTS;                /* Creation time of the channel */
  93   struct Channel* chptr;
  94
  95   assert(0 != cptr);
  96   assert(0 != sptr);
  97   assert(IsServer(cptr));
  98
  99   if (parc < 3 || EmptyString(parv[2]))
 100     return need_more_params(sptr,"DESTRUCT");
 101
 102   chanTS = atoi(parv[2]);
 103
 104   /* Ignore DESTRUCT messages for non-existing channels. */
 105   if (!(chptr = FindChannel(parv[1])))
 106     return 0;
 107
 108   /* Ignore DESTRUCT when the channel is older than the
 109      timestamp on the message. */
 110   if (chanTS > chptr->creationtime)
 111     return 0;
 112
 113   /* Don't pass on DESTRUCT messages for channels that
 114      are not empty, but instead send a BURST msg upstream. */
 115   if (chptr->users > 0) {
 116     send_channel_modes(cptr, chptr);
 117     return 0;
 118   }
 119
 120   /* Pass on DESTRUCT message and ALSO bounce it back! */
 121   sendcmdto_serv_butone(&me, CMD_DESTRUCT, 0, "%s %Tu", parv[1], chanTS);
 122
 123   /* Remove the empty channel. */
 124   remove_destruct_event(chptr);
 125   destruct_channel(chptr);
 126
 127   return 0;
 128 }