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/* Copyright (C) 1999-2020 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
<https://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;
}
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