The timestamps created by __convert_scm_timestamps only make sense for
64 bit time_t programs, 32 bit time_t programs will ignore 64 bit time_t
timestamps since SO_TIMESTAMP will be defined to old values (either by
glibc or kernel headers).

Worse, if the buffer is not suffice MSG_CTRUNC is set to indicate it
(which breaks some programs [1]).

This patch makes only 64 bit time_t recvmsg and recvmmsg to call
__convert_scm_timestamps.  Also, the assumption to called it is changed
from __ASSUME_TIME64_SYSCALLS to __TIMESIZE != 64 since the setsockopt
might be called by libraries built without __TIME_BITS=64.  The
MSG_CTRUNC is only set for the 64 bit symbols, it should happen only
if 64 bit time_t programs run older kernels.

Checked on x86_64-linux-gnu and i686-linux-gnu.

[1] https://github.com/systemd/systemd/pull/20567

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

The recvmsg handling is more complicated because it requires check the
returned kernel control message and make some convertions.  For
!__ASSUME_TIME64_SYSCALLS it converts the first 32-bit time SO_TIMESTAMP
or SO_TIMESTAMPNS and appends it to the control buffer if has extra
space or returns MSG_CTRUNC otherwise.  The 32-bit time field is kept
as-is.

Calls with __TIMESIZE=32 will see the converted 64-bit time control
messages as spurious control message of unknown type.  Calls with
__TIMESIZE=64 running on pre-time64 kernels will see the original
message as a spurious control ones of unknown typ while running on
kernel with native 64-bit time support will only see the time64 version
of the control message.

Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
kernel).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

The wire-up syscall __NR_recvmmsg_time64 (for 32-bit) or
__NR_recvmmsg (for 64-bit) is used as default.  The 32-bit fallback
is used iff __ASSUME_TIME64_SYSCALLS is not defined, which assumes the
kernel ABI provides either __NR_socketcall or __NR_recvmmsg
(32-bit time_t).

It does not handle the timestamps on ancillary data (SCM_TIMESTAMPING
records).

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Among other localplt test failures when building with -Os, there are
libc.so PLT references for __cmsg_nxthdr.  This is a simple case of a
function that is inlined for -O2 but not for -Os; this patch adds
libc_hidden_proto / libc_hidden_def for it to avoid a localplt failure
even when it is not inlined.

Tested for x86_64 (both that it removes this particular localplt
failure for -Os - but other such failures remain so the bug can't yet
be closed - and that the testsuite continues to pass without -Os).

	[BZ #15105]
	* include/sys/socket.h [!_ISOMAC] (__cmsg_nxthdr): Use
	libc_hidden_proto.
	* sysdeps/unix/sysv/linux/cmsg_nxthdr.c (__cmsg_nxthdr): Use
	libc_hidden_def.

This fixes (harmless) data races when accessing the various
__have_sock_cloexec variables.

mq_notify (in the 1996 edition of POSIX) brings in references to recv
and socket (not in POSIX until the 2001 edition).  This patch fixes
this by using __recv and __socket, exporting them from libc at version
GLIBC_PRIVATE.

Tested for x86_64 and x86 (testsuite and comparison of installed
stripped shared libraries; PLT / dynamic symbol table changes render
the comparison not particularly useful for libc).

	[BZ #18546]
	* socket/recv.c (__recv): Use libc_hidden_def.
	* socket/socket.c (__socket): Likewise.
	* sysdeps/mach/hurd/recv.c (__recv): Likewise.
	* sysdeps/mach/hurd/socket.c (__socket): Likewise.
	* sysdeps/unix/sysv/linux/generic/recv.c (__recv): Likewise.
	* sysdeps/unix/sysv/linux/recv.c (__recv): Use libc_hidden_weak.
	* sysdeps/unix/sysv/linux/socket.c (__socket): Use
	libc_hidden_def.
	* sysdeps/unix/sysv/linux/x86_64/recv.c (__recv): Use
	libc_hidden_weak.
	* include/sys/socket.h (__socket): Do not use attribute_hidden.
	Use libc_hidden_proto.
	(__recv): Likewise.
	* socket/Versions (libc): Export __recv and __socket at version
	GLIBC_PRIVATE.
	* sysdeps/unix/sysv/linux/mq_notify.c (helper_thread): Call __recv
	instead of recv.
	(init_mq_netlink): Call __socket instead of socket.
	* conform/Makefile (test-xfail-POSIX/mqueue.h/linknamespace):
	Remove variable.

Add __USE_GNU guards on 'socket/sys/socket.h' __sendmmsg prototype.