/* * Support the max connections option. * * Copyright (C) 1998 Andrew Tridgell * Copyright (C) 2006-2020 Wayne Davison * * 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 3 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, visit the http://fsf.org website. */ #include "rsync.h" /* A simple routine to do connection counting.  This returns 1 on success * and 0 on failure, with errno also being set if the open() failed (errno * will be 0 if the lock request failed). */int claim_connection(char *fname, int max_connections){	int fd, i; 	if (max_connections == 0)		return 1; 	/* 'lock file = PATH': refuse symlinks not owned by uid 0 or our euid so	 * a planted parent can't redirect the root daemon's O_CREAT open. */	if ((fd = open_no_attacker_symlinks(fname, O_RDWR|O_CREAT, 0600)) < 0)		return 0; 	/* Find a free spot. */	for (i = 0; i < max_connections; i++) {		if (lock_range(fd, i*4, 4))			return 1;	} 	close(fd); 	/* A lock failure needs to return an errno of 0. */	errno = 0;	return 0;}