From e6918187568dbd01842d8d1d2c808ce16a894239 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 21 Apr 2024 13:54:28 +0200
Subject: Adding upstream version 18.2.2.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/c-ares/m4/ax_check_user_namespace.m4 | 54 ++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 src/c-ares/m4/ax_check_user_namespace.m4

(limited to 'src/c-ares/m4/ax_check_user_namespace.m4')

diff --git a/src/c-ares/m4/ax_check_user_namespace.m4 b/src/c-ares/m4/ax_check_user_namespace.m4
new file mode 100644
index 000000000..27ba69821
--- /dev/null
+++ b/src/c-ares/m4/ax_check_user_namespace.m4
@@ -0,0 +1,54 @@
+# -*- Autoconf -*-
+
+# SYNOPSIS
+#
+#   AX_CHECK_USER_NAMESPACE
+#
+# DESCRIPTION
+#
+#   This macro checks whether the local system supports Linux user namespaces.
+#   If so, it calls AC_DEFINE(HAVE_USER_NAMESPACE).
+
+AC_DEFUN([AX_CHECK_USER_NAMESPACE],[dnl
+ AC_CACHE_CHECK([whether user namespaces are supported],
+  ax_cv_user_namespace,[
+  AC_LANG_PUSH([C])
+  AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int userfn(void *d) {
+  usleep(100000);  /* synchronize by sleep */
+  return (getuid() != 0);
+}
+char userst[1024*1024];
+int main() {
+  char buffer[1024];
+  int rc, status, fd;
+  pid_t child = clone(userfn, userst + 1024*1024, CLONE_NEWUSER|SIGCHLD, 0);
+  if (child < 0) return 1;
+
+  sprintf(buffer, "/proc/%d/uid_map", child);
+  fd = open(buffer, O_CREAT|O_WRONLY|O_TRUNC, 0755);
+  sprintf(buffer, "0 %d 1\n", getuid());
+  write(fd, buffer, strlen(buffer));
+  close(fd);
+
+  rc = waitpid(child, &status, 0);
+  if (rc <= 0) return 1;
+  if (!WIFEXITED(status)) return 1;
+  return WEXITSTATUS(status);
+}
+  ]])],[ax_cv_user_namespace=yes],[ax_cv_user_namespace=no],[ax_cv_user_namespace=no])
+ AC_LANG_POP([C])
+ ])
+ if test "$ax_cv_user_namespace" = yes; then
+   AC_DEFINE([HAVE_USER_NAMESPACE],[1],[Whether user namespaces are available])
+ fi
+]) # AX_CHECK_USER_NAMESPACE
-- 
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