(svn r19622) [1.0] -Backport from trunk:

- Fix: Desync when a command is received and in the queue while a client starts joining, i.e. save the game state. This can happen in two ways: with frame_freq > 1 a command received in a previous frame might not be executed yet or when a command is received in the same frame as the join but before the savegame is made. In both cases the joining client would not get all commands to get in-sync with the server (and the other clients) (r19620)
- Fix: [desync debug] Minor fixes; "join" pause could cause a crash as some command data was not properly initialised, state was logged multiple times (r19619, r19617, r19602)

src/network/network.cpp

@@ -1078,7 +1078,14 @@ void NetworkGameLoop()
 
 	if (_network_server) {
 		/* Log the sync state to check for in-syncedness of replays. */
-		if (_date_fract == 0) DEBUG(desync, 1, "sync: %08x; %02x; %08x; %08x", _date, _date_fract, _random.state[0], _random.state[1]);
+		if (_date_fract == 0) {
+			/* We don't want to log multiple times if paused. */
+			static Date last_log;
+			if (last_log != _date) {
+				DEBUG(desync, 1, "sync: %08x; %02x; %08x; %08x", _date, _date_fract, _random.state[0], _random.state[1]);
+				last_log = _date;
+			}
+		}
 
 #ifdef DEBUG_DUMP_COMMANDS
 		/* Loading of the debug commands from -ddesync>=1 */
@@ -1086,22 +1093,34 @@ void NetworkGameLoop()
 		static Date next_date = 0;
 		static uint32 next_date_fract;
 		static CommandPacket *cp = NULL;
+		static bool check_sync_state = false;
+		static uint32 sync_state[2];
 		if (f == NULL && next_date == 0) {
 			DEBUG(net, 0, "Cannot open commands.log");
 			next_date = 1;
 		}
 
 		while (f != NULL && !feof(f)) {
-			if (cp != NULL && _date == next_date && _date_fract == next_date_fract) {
-				_current_company = cp->company;
-				bool ret = DoCommandP(cp->tile, cp->p1, cp->p2, cp->cmd, NULL, cp->text);
-				DEBUG(net, 0, "injecting: %08x; %02x; %02x; %06x; %08x; %08x; %08x; \"%s\" (%s) -> %i", _date, _date_fract, (int)_current_company, cp->tile, cp->p1, cp->p2, cp->cmd, cp->text, GetCommandName(cp->cmd), (int)ret);
-				assert(ret);
-				free(cp);
-				cp = NULL;
+			if (_date == next_date && _date_fract == next_date_fract) {
+				if (cp != NULL) {
+					NetworkSend_Command(cp->tile, cp->p1, cp->p2, cp->cmd & ~CMD_FLAGS_MASK, NULL, cp->text, cp->company);
+					DEBUG(net, 0, "injecting: %08x; %02x; %02x; %06x; %08x; %08x; %08x; \"%s\" (%s)", _date, _date_fract, (int)_current_company, cp->tile, cp->p1, cp->p2, cp->cmd, cp->text, GetCommandName(cp->cmd));
+					free(cp);
+					cp = NULL;
+				}
+				if (check_sync_state) {
+					if (sync_state[0] == _random.state[0] && sync_state[1] == _random.state[1]) {
+						DEBUG(net, 0, "sync check: %08x; %02x; match", _date, _date_fract);
+					} else {
+						DEBUG(net, 0, "sync check: %08x; %02x; mismatch expected {%08x, %08x}, got {%08x, %08x}",
+									_date, _date_fract, sync_state[0], sync_state[1], _random.state[0], _random.state[1]);
+						NOT_REACHED();
+					}
+					check_sync_state = false;
+				}
 			}
 
-			if (cp != NULL) break;
+			if (cp != NULL || check_sync_state) break;
 
 			char buff[4096];
 			if (fgets(buff, lengthof(buff), f) == NULL) break;
@@ -1128,12 +1147,23 @@ void NetworkGameLoop()
 				int ret = sscanf(p + 6, "%x; %x", &next_date, &next_date_fract);
 				assert(ret == 2);
 				DEBUG(net, 0, "injecting pause for join at %08x:%02x; please join when paused", next_date, next_date_fract);
-				cp = MallocT<CommandPacket>(1);
+				cp = CallocT<CommandPacket>(1);
 				cp->company = COMPANY_SPECTATOR;
 				cp->cmd = CMD_PAUSE;
 				cp->p1 = PM_PAUSED_NORMAL;
 				cp->p2 = 1;
 				_ddc_fastforward = false;
+			} else if (strncmp(p, "sync: ", 6) == 0) {
+				int ret = sscanf(p + 6, "%x; %x; %x; %x", &next_date, &next_date_fract, &sync_state[0], &sync_state[1]);
+				assert(ret == 4);
+				check_sync_state = true;
+			} else if (strncmp(p, "msg: ", 5) == 0 || strncmp(p, "client: ", 8) == 0 ||
+						strncmp(p, "load: ", 6) == 0 || strncmp(p, "save: ", 6) == 0) {
+				/* A message that is not very important to the log playback, but part of the log. */
+			} else {
+				/* Can't parse a line; what's wrong here? */
+				DEBUG(net, 0, "trying to parse: %s", p);
+				NOT_REACHED();
 			}
 		}
 		if (f != NULL && feof(f)) {

src/network/network_command.cpp

@@ -127,6 +127,24 @@ void NetworkSend_Command(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, Comma
 	SEND_COMMAND(PACKET_CLIENT_COMMAND)(&c);
 }
 
+/**
+ * Sync our local command queue to the command queue of the given
+ * socket. This is needed for the case where we receive a command
+ * before saving the game for a joining client, but without the
+ * execution of those commands. Not syncing those commands means
+ * that the client will never get them and as such will be in a
+ * desynced state from the time it started with joining.
+ * @param cs The client to sync the queue to.
+ */
+void NetworkSyncCommandQueue(NetworkClientSocket *cs)
+{
+	for (CommandPacket *p = _local_command_queue; p != NULL; p = p->next) {
+		CommandPacket c = *p;
+		c.callback = 0;
+		NetworkAddCommandQueue(c, cs);
+	}
+}
+
 /**
  * Execute all commands on the local command queue that ought to be executed this frame.
  */

src/network/network_internal.h

@@ -163,6 +163,7 @@ struct CommandPacket : CommandContainer {
 void NetworkAddCommandQueue(CommandPacket cp, NetworkClientSocket *cs = NULL);
 void NetworkExecuteLocalCommandQueue();
 void NetworkFreeLocalCommandQueue();
+void NetworkSyncCommandQueue(NetworkClientSocket *cs);
 
 /* from network.c */
 NetworkRecvStatus NetworkCloseClient(NetworkClientSocket *cs, NetworkRecvStatus status);

src/network/network_server.cpp

@@ -336,6 +336,7 @@ DEF_SERVER_SEND_COMMAND(PACKET_SERVER_MAP)
 
 		sent_packets = 4; // We start with trying 4 packets
 
+		NetworkSyncCommandQueue(cs);
 		cs->status = STATUS_MAP;
 		/* Mark the start of download */
 		cs->last_frame = _frame_counter;