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/* Copyright (C) 1999, 2001, 2002 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, write to the Free

   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA

   02111-1307 USA.  */

#include <assert.h>

#include <errno.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <sys/socket.h>

#include "libc-symbols.h"

/* Return a socket of any type.  The socket can be used in subsequent

   ioctl calls to talk to the kernel.  */

int internal_function

__opensock (void)

{

  static int last_family;       /* Available socket family we will use.  */

  static int last_type;

  static const struct

  {

    int family;

    const char procname[15];

  } afs[] =

    {

      /* The 2.2 kernels cannot handle ioctl(SIOCGIFCONF) on AF_UNIX sockets.

         Give the kernel a chance to user inet sockets on old kernels.  */

#if __LINUX_KERNEL_VERSION < 132096

      { AF_INET, "" },

      { AF_UNIX, "net/unix" },

#else

      { AF_UNIX, "net/unix" },

      { AF_INET, "" },

#endif

      { AF_INET6, "net/if_inet6" },

      { AF_AX25, "net/ax25" },

      { AF_NETROM, "net/nr" },

      { AF_ROSE, "net/rose" },

      { AF_IPX, "net/ipx" },

      { AF_APPLETALK, "net/appletalk" },

      { AF_ECONET, "sys/net/econet" },

      { AF_ASH, "sys/net/ash" },

      { AF_X25, "net/x25" }

    };

#define nafs (sizeof (afs) / sizeof (afs[0]))

  char fname[sizeof "/proc/" + 14];

  int result;

  int has_proc;

  size_t cnt;

  /* We already know which family to use from the last call.  Use it

     again.  */

  if (last_family != 0)

    {

      assert (last_type != 0);

      result = socket (last_family, last_type, 0);

      if (result != -1 || errno != EAFNOSUPPORT)

        /* Maybe the socket type isn't supported anymore (module is

           unloaded).  In this case again try to find the type.  */

        return result;

      /* Reset the values.  They seem not valid anymore.  */

      last_family = 0;

      last_type = 0;

    }

  /* Check whether the /proc filesystem is available.  */

  has_proc = access ("/proc/net", R_OK) != -1;

  strcpy (fname, "/proc/");

  /* Iterate over the interface families and find one which is

     available.  */

  for (cnt = 0; cnt < nafs; ++cnt)

    {

      int type = SOCK_DGRAM;

      if (has_proc && afs[cnt].procname[0] != '\0')

        {

          strcpy (fname + 6, afs[cnt].procname);

          if (access (fname, R_OK) == -1)

            /* The /proc entry is not available.  I.e., we cannot

               create a socket of this type (without loading the

               module).  Don't look for it since this might trigger

               loading the module.  */

            continue;

        }

      if (afs[cnt].family == AF_NETROM || afs[cnt].family == AF_X25)

        type = SOCK_SEQPACKET;

      result = socket (afs[cnt].family, type, 0);

      if (result != -1)

        {

          /* Found an available family.  */

          last_type = type;

          last_family = afs[cnt].family;

          return result;

        }

    }

  /* None of the protocol families is available.  It is unclear what kind

     of error is returned.  ENOENT seems like a reasonable choice.  */

  __set_errno (ENOENT);

  return -1;

}