[PATCH v2 1/2] support: Add support_socket_time64_timestamp

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

Changes from previous version:

  - Use getsockopt instead of setsockopt.
  - Fixed socketcall fallback.

---

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                         |  3 ++
 support/support_socket_time64_timestamp.c | 64 +++++++++++++++++++++++
 3 files changed, 68 insertions(+)
 create mode 100644 support/support_socket_time64_timestamp.c

diff --git a/support/Makefile b/support/Makefile
index 5c69f0de4b..7659357b28 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -76,6 +76,7 @@ libsupport-routines = \
   support_set_small_thread_stack_size \
   support_shared_allocate \
   support_small_stack_thread_attribute \
+  support_socket_time64_timestamp \
   support_stat_nanoseconds \
   support_subprocess \
   support_test_compare_blob \
diff --git a/support/support.h b/support/support.h
index 9ec8ecb8d7..bf74a2584b 100644
--- a/support/support.h
+++ b/support/support.h
@@ -154,6 +154,9 @@ 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.  */
+extern bool support_socket_time64_timestamp (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_time64_timestamp.c b/support/support_socket_time64_timestamp.c
new file mode 100644
index 0000000000..a2b059a13d
--- /dev/null
+++ b/support/support_socket_time64_timestamp.c
@@ -0,0 +1,64 @@
+/* Return whether socket supports 64-bit timestamps.
+   Copyright (C) 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 <unistd.h>
+#include <sys/syscall.h>
+#include <sys/socket.h>
+#include <support/support.h>
+
+#ifdef __linux__
+# include <socket-constants-time64.h>
+
+static int
+__attribute_used__
+getsockopt_syscall (int fd)
+{
+  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);
+#  ifdef __NR_socketcall
+  if (r == -1 && errno == ENOSYS)
+    {
+      long int args[] = { fd, level, optname, (long int) &optval,
+			  sizeof (optval) };
+      r = syscall (__NR_socketcall, 15 /* SOCKOP_getsockopt  */ , args);
+    }
+#  endif
+  return r;
+}
+#endif
+
+bool
+support_socket_time64_timestamp (int fd)
+{
+#ifdef __linux__
+# if __LINUX_KERNEL_VERSION >= 0x050100                          \
+   || __WORDSIZE == 64                                           \
+   || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
+  return true;
+# else
+  return getsockopt_syscall (fd) != -1;
+# endif
+#else
+  return false;
+#endif
+}
-- 
2.30.2