Fix buggy config string transmitting ('bcsN')

The bcs0, bcs1, and bcs2 commands are used to transmit an info string
that has more than a certain length. The old code chopped them into
pieces based on the original length rather than the escaped length and
provided only a fixed amount of overhead for escape characters. Turns
out the overhead wasn't enough for real-life use cases (there are a lot
of backslashes due to infostring separators) and so the command to send
the serverinfo configstring would sometimes overflow and be silently
dropped.

Fix this by chopping up the string based on the escaped length.

Author: slipher

src/engine/server/sv_init.cpp

@@ -82,11 +82,49 @@ void SV_SetConfigstring( int index, const char *val )
 	sv.configstringsmodified[ index ] = true;
 }
 
+static void SendConfigStringToClient( int cs, client_t *cl )
+{
+	char buf[ 1024 ]; // escaped characters, in a quoted context
+	// max command size for SV_SendServerCommand is 1022, leave a little overhead for the command
+	char *limit = buf + 990;
+
+	char *out = buf;
+	bool first = true;
+	
+	for ( const char *in = sv.configstrings[ cs ]; ; )
+	{
+		char c = *in++;
+
+		// '$' does not need to be escaped as it is not interpreted in the context of a server command
+		if ( c == '\\' || c == '"' )
+		{
+			*out++ = '\\';
+		}
+
+		*out++ = c;
+
+		if ( !*in )
+		{
+			break;
+		}
+
+		if ( out >= limit )
+		{
+			*out = '\0';
+			SV_SendServerCommand( cl, "%s %d \"%s\"", first ? "bcs0" : "bcs1", cs, buf );
+			first = false;
+			out = buf;
+		}
+	}
+
+	*out = '\0';
+	SV_SendServerCommand( cl, "%s %d \"%s\"", first ? "cs" : "bcs2", cs, buf );
+}
+
 void SV_UpdateConfigStrings()
 {
-	int      len, i, index;
+	int i, index;
 	client_t *client;
-	int      maxChunkSize = MAX_STRING_CHARS - 64;
 
 	for ( index = 0; index < MAX_CONFIGSTRINGS; index++ )
 	{
@@ -101,8 +139,6 @@ void SV_UpdateConfigStrings()
 		// spawning a new server
 		if ( sv.state == serverState_t::SS_GAME || sv.restarting )
 		{
-			len = strlen( sv.configstrings[ index ] );
-
 			// send the data to all relevent clients
 			for ( i = 0, client = svs.clients; i < sv_maxclients->integer; i++, client++ )
 			{
@@ -117,41 +153,7 @@ void SV_UpdateConfigStrings()
 					continue;
 				}
 
-				if ( len >= maxChunkSize )
-				{
-					int  sent = 0;
-					int  remaining = len;
-					const char *cmd;
-					char buf[ MAX_STRING_CHARS ];
-
-					while ( remaining > 0 )
-					{
-						if ( sent == 0 )
-						{
-							cmd = "bcs0";
-						}
-						else if ( remaining < maxChunkSize )
-						{
-							cmd = "bcs2";
-						}
-						else
-						{
-							cmd = "bcs1";
-						}
-
-						Q_strncpyz( buf, &sv.configstrings[ index ][ sent ], maxChunkSize );
-
-						SV_SendServerCommand( client, "%s %i %s\n", cmd, index, Cmd_QuoteString( buf ) );
-
-						sent += ( maxChunkSize - 1 );
-						remaining -= ( maxChunkSize - 1 );
-					}
-				}
-				else
-				{
-					// standard cs, just send it
-					SV_SendServerCommand( client, "cs %i %s\n", index, Cmd_QuoteString( sv.configstrings[ index ] ) );
-				}
+				SendConfigStringToClient( index, client );
 			}
 		}
 	}