connection.c

   1 /*
   2  * Support the max connections option.
   3  *
   4  * Copyright (C) 1998 Andrew Tridgell
   5  * Copyright (C) 2006-2020 Wayne Davison
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 3 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, visit the http://fsf.org website.
  19  */
  20
  21 #include "rsync.h"
  22
  23 /* A simple routine to do connection counting.  This returns 1 on success
  24  * and 0 on failure, with errno also being set if the open() failed (errno
  25  * will be 0 if the lock request failed). */
  26 int claim_connection(char *fname, int max_connections)
  27 {
  28         int fd, i;
  29
  30         if (max_connections == 0)
  31                 return 1;
  32
  33         if ((fd = open(fname, O_RDWR|O_CREAT, 0600)) < 0)
  34                 return 0;
  35
  36         /* Find a free spot. */
  37         for (i = 0; i < max_connections; i++) {
  38                 if (lock_range(fd, i*4, 4))
  39                         return 1;
  40         }
  41
  42         close(fd);
  43
  44         /* A lock failure needs to return an errno of 0. */
  45         errno = 0;
  46         return 0;
  47 }