socket/opensock.c

   1 /* Copyright (C) 1999-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdio.h>
  19 #include <sys/socket.h>
  20 #include <libc-lock.h>
  21
  22 /* Return a socket of any type.  The socket can be used in subsequent
  23    ioctl calls to talk to the kernel.  */
  24 int
  25 __opensock (void)
  26 {
  27   /* Cache the last AF that worked, to avoid many redundant calls to
  28      socket().  */
  29   static int sock_af = -1;
  30   int fd = -1;
  31   __libc_lock_define_initialized (static, lock);
  32
  33   if (sock_af != -1)
  34     {
  35       fd = __socket (sock_af, SOCK_DGRAM, 0);
  36       if (fd != -1)
  37         return fd;
  38     }
  39
  40   __libc_lock_lock (lock);
  41
  42   if (sock_af != -1)
  43     fd = __socket (sock_af, SOCK_DGRAM, 0);
  44
  45   if (fd == -1)
  46     {
  47 #ifdef AF_INET
  48       fd = __socket (sock_af = AF_INET, SOCK_DGRAM, 0);
  49 #endif
  50 #ifdef AF_INET6
  51       if (fd < 0)
  52         fd = __socket (sock_af = AF_INET6, SOCK_DGRAM, 0);
  53 #endif
  54 #ifdef AF_IPX
  55       if (fd < 0)
  56         fd = __socket (sock_af = AF_IPX, SOCK_DGRAM, 0);
  57 #endif
  58 #ifdef AF_AX25
  59       if (fd < 0)
  60         fd = __socket (sock_af = AF_AX25, SOCK_DGRAM, 0);
  61 #endif
  62 #ifdef AF_APPLETALK
  63       if (fd < 0)
  64         fd = __socket (sock_af = AF_APPLETALK, SOCK_DGRAM, 0);
  65 #endif
  66     }
  67
  68   __libc_lock_unlock (lock);
  69   return fd;
  70 }