glibc/socket/opensock.c
Florian Weimer 5bf07e1b3a Linux: Simplify __opensock and fix race condition [BZ #28353]
AF_NETLINK support is not quite optional on modern Linux systems
anymore, so it is likely that the first attempt will always succeed.
Consequently, there is no need to cache the result.  Keep AF_UNIX
and the Internet address families as a fallback, for the rare case
that AF_NETLINK is missing.  The other address families previously
probed are totally obsolete be now, so remove them.

Use this simplified version as the generic implementation, disabling
Netlink support as needed.
2021-09-28 18:55:49 +02:00

50 lines
1.5 KiB
C

/* Create socket with an unspecified address family for use with ioctl.
Copyright (C) 1999-2021 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 <errno.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)
{
/* SOCK_DGRAM is supported by all address families. (Netlink does
not support SOCK_STREAM.) */
int type = SOCK_DGRAM | SOCK_CLOEXEC;
int fd;
#ifdef AF_NETLINK
fd = __socket (AF_NETLINK, type, 0);
if (fd >= 0)
return fd;
#endif
fd = __socket (AF_UNIX, type, 0);
if (fd >= 0)
return fd;
fd = __socket (AF_INET, type, 0);
if (fd >= 0)
return fd;
fd = __socket (AF_INET6, type, 0);
if (fd >= 0)
return fd;
__set_errno (ENOENT);
return fd;
}