/* Copyright (C) 1999-2018 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, see

   <http://www.gnu.org/licenses/>.  */

#include <assert.h>

#include <errno.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <sys/socket.h>

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

   ioctl calls to talk to the kernel.  */

int

__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[] =

    {

      { AF_UNIX, "net/unix" },

      { AF_INET, "" },

      { 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" },

#ifdef NEED_AF_IUCV

      { AF_IUCV, "net/iucv" }

#endif

    };

#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 | SOCK_CLOEXEC, 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 | SOCK_CLOEXEC, 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;

}