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xwords/xwords4/relay/states.cpp
ehouse fc17df2a7e When guest connects, check if providing too many players before 
reponding to connection request so that we just deny the request (with
new error code) rather than revoking it later.
2009-12-14 04:10:23 +00:00

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/* -*-mode: C; fill-column: 78; c-basic-offset: 4; -*- */
/*
* Copyright 2005-2009 by Eric House (xwords@eehouse.org). All rights
* reserved.
*
* This program 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; either version 2
* of the License, or (at your option) any later version.
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include "assert.h"
#include "string.h"
#include "states.h"
#include "xwrelay_priv.h"
typedef struct StateTable {
XW_RELAY_STATE stateStart;
XW_RELAY_EVENT stateEvent;
XW_RELAY_ACTION stateAction;
XW_RELAY_STATE stateEnd; /* Do I need this? Or does the code that
performs the action determine the state? */
} StateTable;
/* Connecting. The problem is that we don't know how many devices to expect.
So hosts connect and get a response. Hosts send messages to be forwarded.
We may or may not have an ID for the recipient host. If we do, we forward.
If we don't, we drop. No big deal. So is there any difference between
CONNECTING and CONNECTED? I don't think so. Messages come in and we try
to forward. Connection requests come in and we accept them if the host in
question is unknown. NOT QUITE. There's a DOS vulnerability there. It's
best if we can put the game in a state where others can't connect, if the
window where new devices can sign in using a given cookie is fairly small.
New rules on accepting connections and reconnections:
- Connect and reconnect messages contain nPlayersHere (local) and
nPlayersTotal params.
- On connect action, we either note the total expected, or increase the
total we have. Ditto on reconnect. On disconnect, we take the departing
hosts marbles away from the game.
- We only accept [re]connections when we're missing players, and we only
forward messages when all devices/players are accounted for. There's a
notification sent when the last shows up, so devices can send pending
messages at that time.
- There's at least one bug with this scheme: we don't know how many players
to expect until the server shows up, so we'll keep accepting clients
until that happens. Probably need a config variable that sets an upper
bound on the number of players.
*/
StateTable g_stateTable[] = {
{ XWS_INITED, XWE_HOSTCONNECT, XWA_SEND_HOST_RSP, XWS_WAITGUESTS },
{ XWS_INITED, XWE_GUESTCONNECT, XWA_SEND_NO_ROOM, XWS_DEAD },
{ XWS_WAITGUESTS, XWE_GUESTCONNECT, XWA_CHECK_HAVE_ROOM,XWS_ROOMCHK },
{ XWS_ROOMCHK, XWE_HAVE_ROOM, XWA_SEND_GUEST_RSP, XWS_CHK_ALLHERE },
{ XWS_ROOMCHK, XWE_TOO_MANY, XWA_SEND_TOO_MANY, XWS_WAITGUESTS },
{ XWS_CHK_ALLHERE, XWE_ALLHERE, XWA_SENDALLHERE, XWS_ALLCONND },
{ XWS_CHK_ALLHERE, XWE_SOMEMISSING, XWA_NONE, XWS_WAITGUESTS },
{ XWS_WAITGUESTS, XWE_HOSTCONNECT, XWA_SEND_DUP_ROOM, XWS_WAITGUESTS },
{ XWS_ALLCONND, XWE_DISCONN, XWA_DISCONNECT, XWS_MISSING },
{ XWS_WAITGUESTS, XWE_DISCONN, XWA_DISCONNECT, XWS_WAITGUESTS },
{ XWS_MISSING, XWE_DISCONN, XWA_DISCONNECT, XWS_MISSING },
/* EMPTY means have messages to send but no connections. Time out and free
memory after a while. BUT: don't I really want to keep these forever and
free the oldest ones if memory usage realy does become a problem.
There's no problem now! */
{ XWS_MISSING, XWE_NOMORESOCKETS, XWA_NOTE_EMPTY, XWS_MSGONLY },
{ XWS_MSGONLY, XWE_NOMOREMSGS, XWA_NONE, XWS_DEAD },
{ XWS_ANY, XWE_NOMORESOCKETS, XWA_NONE, XWS_DEAD },
{ XWS_ANY, XWE_SHUTDOWN, XWA_SHUTDOWN, XWS_DEAD },
{ XWS_INITED, XWE_RECONNECT, XWA_SEND_RERSP, XWS_CHK_ALLHERE_2 },
{ XWS_MSGONLY, XWE_RECONNECT, XWA_SEND_RERSP, XWS_CHK_ALLHERE_2 },
{ XWS_MISSING, XWE_RECONNECT, XWA_SEND_RERSP, XWS_CHK_ALLHERE_2 },
{ XWS_CHK_ALLHERE_2, XWE_ALLHERE, XWA_SNDALLHERE_2, XWS_ALLCONND },
{ XWS_CHK_ALLHERE_2, XWE_SOMEMISSING, XWA_NONE, XWS_MISSING },
{ XWS_WAITGUESTS, XWE_REMOVESOCKET, XWA_REMOVESOCK_1, XWS_WAITGUESTS },
{ XWS_ALLCONND, XWE_REMOVESOCKET, XWA_REMOVESOCK_2, XWS_MISSING },
{ XWS_MISSING, XWE_REMOVESOCKET, XWA_REMOVESOCK_2, XWS_MISSING },
#ifdef RELAY_HEARTBEAT
{ XWS_ALLCONND, XWE_HEARTFAILED, XWA_HEARTDISCONN, XWS_MISSING },
{ XWS_WAITGUESTS, XWE_HEARTFAILED, XWA_HEARTDISCONN, XWS_WAITGUESTS },
{ XWS_MISSING, XWE_HEARTFAILED, XWA_HEARTDISCONN, XWS_MISSING },
/* Heartbeat arrived */
{ XWS_WAITGUESTS, XWE_HEARTRCVD, XWA_NOTEHEART, XWS_WAITGUESTS },
{ XWS_ALLCONND, XWE_HEARTRCVD, XWA_NOTEHEART, XWS_ALLCONND },
{ XWS_MISSING, XWE_HEARTRCVD, XWA_NOTEHEART, XWS_MISSING },
#endif
/* Connect timer */
{ XWS_WAITGUESTS, XWE_CONNTIMER, XWA_TIMERDISCONN, XWS_DEAD },
{ XWS_MISSING, XWE_CONNTIMER, XWA_NONE, XWS_MISSING },
{ XWS_ALLCONND, XWE_CONNTIMER, XWA_NONE, XWS_ALLCONND },
{ XWS_WAITGUESTS, XWE_NOTIFYDISCON, XWA_NOTIFYDISCON, XWS_WAITGUESTS },
{ XWS_ALLCONND, XWE_NOTIFYDISCON, XWA_NOTIFYDISCON, XWS_MISSING },
{ XWS_MISSING, XWE_NOTIFYDISCON, XWA_NOTIFYDISCON, XWS_MISSING },
{ XWS_DEAD, XWE_NOTIFYDISCON, XWA_NOTIFYDISCON, XWS_DEAD },
/* This is our bread-n-butter */
{ XWS_ALLCONND, XWE_FORWARDMSG, XWA_FWD, XWS_ALLCONND },
{ XWS_MISSING, XWE_FORWARDMSG, XWA_FWD, XWS_MISSING },
{ XWS_DEAD, XWE_REMOVESOCKET, XWA_REMOVESOCK_1, XWS_DEAD }
};
bool
getFromTable( XW_RELAY_STATE curState, XW_RELAY_EVENT curEvent,
XW_RELAY_ACTION* takeAction, XW_RELAY_STATE* nextState )
{
bool found = false;
StateTable* stp = g_stateTable;
const StateTable* end = stp + sizeof(g_stateTable)/sizeof(g_stateTable[0]);
while ( stp < end ) {
if ( stp->stateStart == curState || stp->stateStart == XWS_ANY ) {
if ( stp->stateEvent == curEvent || stp->stateEvent == XWE_ANY ) {
*takeAction = stp->stateAction;
*nextState = stp->stateEnd;
found = true;
break;
}
}
++stp;
}
if ( !found ) {
logf( XW_LOGERROR, "==> ERROR :: unable to find transition from %s "
"on event %s",
stateString(curState), eventString(curEvent) );
}
return found;
} /* getFromTable */
#define CASESTR(s) case s: str = #s; break
const char*
stateString( XW_RELAY_STATE state )
{
const char* str = NULL;
switch( state ) {
CASESTR(XWS_NONE);
CASESTR(XWS_ANY);
CASESTR(XWS_INITED);
CASESTR(XWS_WAITGUESTS);
CASESTR(XWS_ALLCONND);
CASESTR(XWS_DEAD);
CASESTR(XWS_CHECKING_CONN);
CASESTR(XWS_MISSING);
CASESTR(XWS_MSGONLY);
CASESTR(XWS_CHK_ALLHERE);
CASESTR(XWS_CHK_ALLHERE_2);
CASESTR(XWS_CHKCOUNTS_INIT);
CASESTR(XWS_ROOMCHK);
default:
assert(0);
}
assert( 0 == strncmp( "XWS_", str, 4 ) );
str += 4;
return str;
}
const char*
eventString( XW_RELAY_EVENT evt )
{
const char* str = NULL;
switch( evt ) {
CASESTR(XWE_NONE);
CASESTR(XWE_GUESTCONNECT);
CASESTR(XWE_HOSTCONNECT);
CASESTR(XWE_RECONNECT);
CASESTR(XWE_DISCONN);
CASESTR(XWE_FORWARDMSG);
#ifdef RELAY_HEARTBEAT
CASESTR(XWE_HEARTRCVD);
CASESTR(XWE_HEARTFAILED);
#endif
CASESTR(XWE_CONNTIMER);
CASESTR(XWE_ANY);
CASESTR(XWE_REMOVESOCKET);
CASESTR(XWE_NOMORESOCKETS);
CASESTR(XWE_NOMOREMSGS);
CASESTR(XWE_NOTIFYDISCON);
CASESTR(XWE_ALLHERE);
CASESTR(XWE_SOMEMISSING);
CASESTR(XWE_TOO_MANY);
CASESTR(XWE_HAVE_ROOM);
CASESTR(XWE_SHUTDOWN);
default:
assert(0);
}
return str;
}
const char*
actString( XW_RELAY_ACTION act )
{
const char* str = NULL;
switch ( act ) {
CASESTR(XWA_NONE);
CASESTR(XWA_SEND_1ST_RERSP);
CASESTR(XWA_SEND_RERSP);
CASESTR(XWA_SENDALLHERE);
CASESTR(XWA_SEND_NO_ROOM);
CASESTR(XWA_SEND_TOO_MANY);
CASESTR(XWA_SEND_DUP_ROOM);
CASESTR(XWA_SEND_HOST_RSP);
CASESTR(XWA_SEND_GUEST_RSP);
CASESTR(XWA_SNDALLHERE_2);
CASESTR(XWA_FWD);
CASESTR(XWA_NOTEHEART);
CASESTR(XWA_TIMERDISCONN);
CASESTR(XWA_DISCONNECT);
CASESTR(XWA_NOTIFYDISCON);
CASESTR(XWA_REMOVESOCK_1);
CASESTR(XWA_REMOVESOCK_2);
CASESTR(XWA_HEARTDISCONN);
CASESTR(XWA_SHUTDOWN);
CASESTR(XWA_CHECK_HAVE_ROOM);
CASESTR(XWA_NOTE_EMPTY);
default:
assert(0);
}
return str;
}
#undef CASESTR
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