# -*- Autoconf -*-

# SYNOPSIS

#

#   AX_CHECK_UTS_NAMESPACE

#

# DESCRIPTION

#

#   This macro checks whether the local system supports Linux UTS namespaces.

#   Also requires user namespaces to be available, so that non-root users

#   can enter the namespace.

#   If so, it calls AC_DEFINE(HAVE_UTS_NAMESPACE).

AC_DEFUN([AX_CHECK_UTS_NAMESPACE],[dnl

 AC_CACHE_CHECK([whether UTS namespaces are supported],

  ax_cv_uts_namespace,[

  AC_LANG_PUSH([C])

  AC_RUN_IFELSE([AC_LANG_SOURCE([[

#define _GNU_SOURCE

#include <sched.h>

#include <signal.h>

#include <stdio.h>

#include <string.h>

#include <fcntl.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/wait.h>

int utsfn(void *d) {

  char buffer[1024];

  const char *name = "autoconftest";

  int rc = sethostname(name, strlen(name));

  if (rc != 0) return 1;

  gethostname(buffer, 1024);

  return (strcmp(buffer, name) != 0);

}

char st2[1024*1024];

int fn(void *d) {

  pid_t child;

  int rc, status;

  usleep(100000);  /* synchronize by sleep */

  if (getuid() != 0) return 1;

  child = clone(utsfn, st2 + 1024*1024, CLONE_NEWUTS|SIGCHLD, 0);

  if (child < 0) return 1;

  rc = waitpid(child, &status, 0);

  if (rc <= 0) return 1;

  if (!WIFEXITED(status)) return 1;

  return WEXITSTATUS(status);

}

char st[1024*1024];

int main() {

  char buffer[1024];

  int rc, status, fd;

  pid_t child = clone(fn, st + 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_uts_namespace=yes],[ax_cv_uts_namespace=no],[ax_cv_uts_namespace=no])

 AC_LANG_POP([C])

 ])

 if test "$ax_cv_uts_namespace" = yes; then

   AC_DEFINE([HAVE_UTS_NAMESPACE],[1],[Whether UTS namespaces are available])

 fi

]) # AX_CHECK_UTS_NAMESPACE