[PATCH v5 1/3] support: Add support_socket_so_timestamp_time64

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

Check if the socket support 64-bit network packages timestamps
(SO_TIMESTAMP and SO_TIMESTAMPNS).  This will be used on recvmsg
and recvmmsg tests to check if the timestamp should be generated.
---
 support/Makefile                             |  1 +
 support/support.h                            |  4 ++
 support/support_socket_so_timestamp_time64.c | 48 ++++++++++++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 support/support_socket_so_timestamp_time64.c

diff --git a/support/Makefile b/support/Makefile
index 6dc6c9d49a..5ddcb8d158 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -80,6 +80,7 @@ libsupport-routines = \
   support_set_small_thread_stack_size \
   support_shared_allocate \
   support_small_stack_thread_attribute \
+  support_socket_so_timestamp_time64 \
   support_stat_nanoseconds \
   support_subprocess \
   support_test_compare_blob \
diff --git a/support/support.h b/support/support.h
index ee27149d98..73b9fc48f0 100644
--- a/support/support.h
+++ b/support/support.h
@@ -183,6 +183,10 @@ extern bool support_select_modifies_timeout (void);
    tv_usec larger than 1000000.  */
 extern bool support_select_normalizes_timeout (void);
 
+/* Return true if socket FD supports 64-bit timestamps with the SOL_SOCKET
+   and SO_TIMESTAMP/SO_TIMESTAMPNS.  */
+extern bool support_socket_so_timestamp_time64 (int fd);
+
 /* Create a timer that trigger after SEC seconds and NSEC nanoseconds.  If
    REPEAT is true the timer will repeat indefinitely.  If CALLBACK is not
    NULL, the function will be called when the timer expires; otherwise a
diff --git a/support/support_socket_so_timestamp_time64.c b/support/support_socket_so_timestamp_time64.c
new file mode 100644
index 0000000000..54bf3f4272
--- /dev/null
+++ b/support/support_socket_so_timestamp_time64.c
@@ -0,0 +1,48 @@
+/* Return whether socket supports 64-bit timestamps.
+   Copyright (C) 2022 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 <unistd.h>
+#include <sys/syscall.h>
+#include <sys/socket.h>
+#include <support/support.h>
+#ifdef __linux__
+# include <socket-constants-time64.h>
+#endif
+
+bool
+support_socket_so_timestamp_time64 (int fd)
+{
+#ifdef __linux__
+# if __LINUX_KERNEL_VERSION >= 0x050100                          \
+   || __WORDSIZE == 64                                           \
+   || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
+  return true;
+# else
+  int level = SOL_SOCKET;
+  int optname = COMPAT_SO_TIMESTAMP_NEW;
+  int optval;
+  socklen_t len = sizeof (optval);
+
+  int r = syscall (__NR_getsockopt, fd, level, optname, &optval, &len);
+  return r != -1;
+# endif
+#else
+  return false;
+#endif
+}
-- 
2.32.0