Synchronize support/ infrastructure with master

This commit updates the support/ subdirectory to
commit 2714c5f3c95f90977167c1d21326d907fb76b419
on the master branch and modifies Makeconfig,
Rules, and extra-lib.mk accordingly.

119 files changed, 7306 insertions, 3 deletions

diff --git a/Makeconfig b/Makeconfig
index 03fd89c..ee379f5 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -394,6 +394,9 @@ ifndef after-link
 after-link =
 endif
 
+# Additional libraries to link into every test.
+link-extra-libs-tests = $(libsupport)
+
 # Command for linking PIE programs with the C library.
 ifndef +link-pie
 +link-pie-before-libc = $(CC) -pie -Wl,-O1 -nostdlib -nostartfiles -o $@ \
@@ -503,7 +506,7 @@ link-libc = $(link-libc-rpath-link) $(link-libc-before-gnulib) $(gnulib)
 link-libc-tests = $(link-libc-tests-rpath-link) \
 		  $(link-libc-before-gnulib) $(gnulib-tests)
 # This is how to find at build-time things that will be installed there.
-rpath-dirs = math elf dlfcn nss nis rt resolv crypt mathvec
+rpath-dirs = math elf dlfcn nss nis rt resolv crypt mathvec support
 rpath-link = \
 $(common-objdir):$(subst $(empty) ,:,$(patsubst ../$(subdir),.,$(rpath-dirs:%=$(common-objpfx)%)))
 else
@@ -850,7 +853,7 @@ libio-include = -I$(..)libio
 # List of non-library modules that we build.
 built-modules = iconvprogs iconvdata ldconfig lddlibc4 libmemusage \
 		libSegFault libpcprofile librpcsvc locale-programs \
-		memusagestat nonlib nscd extramodules libnldbl
+		memusagestat nonlib nscd extramodules libnldbl libsupport
 
 in-module = $(subst -,_,$(firstword $(libof-$(basename $(@F))) \
 				    $(libof-$(<F)) \
@@ -1089,6 +1092,12 @@ libm = $(common-objpfx)math/libm.a
 libmvec = $(common-objpfx)mathvec/libmvec.a
 endif
 
+ifeq ($(build-shared),yes)
+libsupport = $(common-objpfx)support/libsupport_nonshared.a
+else
+libsupport = $(common-objpfx)support/libsupport.a
+endif
+
 # These are the subdirectories containing the library source.  The order
 # is more or less arbitrary.  The sorting step will take care of the
 # dependencies.
@@ -1096,7 +1105,7 @@ all-subdirs = csu assert ctype locale intl catgets math setjmp signal	    \
 	      stdlib stdio-common libio malloc string wcsmbs time dirent    \
 	      grp pwd posix io termios resource misc socket sysvipc gmon    \
 	      gnulib iconv iconvdata wctype manual shadow gshadow po argp   \
-	      crypt localedata timezone rt conform debug mathvec	    \
+	      crypt localedata timezone rt conform debug mathvec support    \
 	      $(add-on-subdirs) dlfcn elf
 
 ifndef avoid-generated
diff --git a/Rules b/Rules
index 8306d36..a981965 100644
--- a/Rules
+++ b/Rules
@@ -149,6 +149,7 @@ endif
 
 ifneq "$(strip $(binaries-shared-tests))" ""
 $(addprefix $(objpfx),$(binaries-shared-tests)): %: %.o \
+  $(link-extra-libs-tests) \
   $(sort $(filter $(common-objpfx)lib%,$(link-libc))) \
   $(addprefix $(csu-objpfx),start.o) $(+preinit) $(+postinit)
 	$(+link-tests)
@@ -156,6 +157,7 @@ endif
 
 ifneq "$(strip $(binaries-pie-tests))" ""
 $(addprefix $(objpfx),$(binaries-pie-tests)): %: %.o \
+  $(link-extra-libs-tests) \
   $(sort $(filter $(common-objpfx)lib%,$(link-libc))) \
   $(addprefix $(csu-objpfx),start.o) $(+preinit) $(+postinit)
 	$(+link-pie-tests)
@@ -177,6 +179,7 @@ endif
 
 ifneq "$(strip $(binaries-static-tests))" ""
 $(addprefix $(objpfx),$(binaries-static-tests)): %: %.o \
+  $(link-extra-libs-tests) \
   $(sort $(filter $(common-objpfx)lib%,$(link-libc-static-tests))) \
   $(addprefix $(csu-objpfx),start.o) $(+preinit) $(+postinit)
 	$(+link-static-tests)
diff --git a/extra-lib.mk b/extra-lib.mk
index b10748d..2552049 100644
--- a/extra-lib.mk
+++ b/extra-lib.mk
@@ -5,6 +5,9 @@
 # The variable $($(lib)-routines) defines the list of modules
 # to be included in that library.  A sysdep Makefile can add to
 # $(lib)-sysdep_routines to include additional modules.
+#
+# Libraries listed in $(extra-libs-noinstall) are built, but not
+# installed.
 
 lib := $(firstword $(extra-libs-left))
 extra-libs-left := $(filter-out $(lib),$(extra-libs-left))
@@ -28,7 +31,9 @@ extra-objs := $(extra-objs)
 all-$(lib)-routines := $($(lib)-routines) $($(lib)-sysdep_routines)
 
 # Add each flavor of library to the lists of things to build and install.
+ifeq (,$(filter $(lib), $(extra-libs-noinstall)))
 install-lib += $(foreach o,$(object-suffixes-$(lib)),$(lib:lib%=$(libtype$o)))
+endif
 extra-objs += $(foreach o,$(filter-out .os .oS,$(object-suffixes-$(lib))),\
 			$(patsubst %,%$o,$(filter-out \
 					   $($(lib)-shared-only-routines),\
diff --git a/scripts/backport-support.sh b/scripts/backport-support.sh
new file mode 100644
index 0000000..2ece7ce
--- /dev/null
+++ b/scripts/backport-support.sh
@@ -0,0 +1,110 @@
+#!/bin/bash
+# Create a patch which backports the support/ subdirectory.
+# Copyright (C) 2017 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
+# <http://www.gnu.org/licenses/>.
+
+# This script does not backport the Makefile tweaks outside the
+# support/ directory (which need to be backported separately), or the
+# changes to test-skeleton.c (which should not be backported).
+
+set -e
+
+export LC_ALL=C
+export GIT_CONFIG=/dev/null
+export GTT_CONFIG_NOSYSTEM=0
+export GIT_PAGER=
+
+usage () {
+    cat >&2 <<EOF
+usage: $0 {patch|commit}
+EOF
+    exit 1
+}
+
+if test $# -ne 1 ; then
+    usage
+fi
+
+command="$1"
+
+case "$command" in
+    patch|commit)
+    ;;
+    *)
+	usage
+	;;
+esac
+
+# The upstream branch to work on.
+branch=origin/master
+
+# The commit which added the support/ directory.
+initial_commit=c23de0aacbeaa7a091609b35764bed931475a16d
+
+# We backport the support directory and this script.  Directories need
+# to end in a /.
+patch_targets="support/ scripts/backport-support.sh"
+
+latest_commit="$(git log --max-count=1 --pretty=format:%H "$branch" -- \
+  $patch_targets)"
+
+# Simplify the branch name somewhat for reporting.
+branch_name="$(echo "$branch" | sed s,^origin/,,)"
+
+command_patch () {
+    cat <<EOF
+This patch creates the contents of the support/ directory up to this
+upstream commit on the $branch_name branch:
+
+EOF
+    git log --max-count=1 "$latest_commit"
+    echo
+    git diff "$initial_commit"^.."$latest_commit" $patch_targets
+    echo "# Before applying the patch, run this command:" >&2
+    echo "# rm -rf $patch_targets" >&2
+}
+
+command_commit () {
+    git status --porcelain | while read line ; do
+	echo "error: working copy is not clean, cannot commit" >&2
+	exit 1
+    done
+    for path in $patch_targets; do
+	echo "# Processing $path" >&2
+	case "$path" in
+	    [a-zA-Z0-9]*/)
+		# Directory.
+		git rm --cached --ignore-unmatch -r "$path"
+		rm -rf "$path"
+		git read-tree --prefix="$path" "$latest_commit":"$path"
+		git checkout "$path"
+		;;
+	    *)
+		# File.
+		git show "$latest_commit":"$path" > "$path"
+		git add "$path"
+	esac
+    done
+    git commit -m "Synchronize support/ infrastructure with $branch_name
+
+This commit updates the support/ subdirectory to
+commit $latest_commit
+on the $branch_name branch.
+"
+}
+
+command_$command
diff --git a/support/Makefile b/support/Makefile
new file mode 100644
index 0000000..20b0343
--- /dev/null
+++ b/support/Makefile
@@ -0,0 +1,146 @@
+# Makefile for support library, used only at build and test time
+# Copyright (C) 2016-2017 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
+# <http://www.gnu.org/licenses/>.
+
+subdir := support
+
+include ../Makeconfig
+
+extra-libs := libsupport
+extra-libs-others = $(extra-libs)
+extra-libs-noinstall := $(extra-libs)
+
+libsupport-routines = \
+  check \
+  check_addrinfo \
+  check_dns_packet \
+  check_hostent \
+  check_netent \
+  delayed_exit \
+  ignore_stderr \
+  oom_error \
+  resolv_test \
+  set_fortify_handler \
+  support-xstat \
+  support_become_root \
+  support_can_chroot \
+  support_capture_subprocess \
+  support_capture_subprocess_check \
+  support_enter_network_namespace \
+  support_format_address_family \
+  support_format_addrinfo \
+  support_format_dns_packet \
+  support_format_herrno \
+  support_format_hostent \
+  support_format_netent \
+  support_isolate_in_subprocess \
+  support_record_failure \
+  support_run_diff \
+  support_shared_allocate \
+  support_write_file_string \
+  support_test_main \
+  support_test_verify_impl \
+  temp_file \
+  write_message \
+  xaccept \
+  xaccept4 \
+  xasprintf \
+  xbind \
+  xcalloc \
+  xchroot \
+  xclose \
+  xconnect \
+  xdup2 \
+  xfclose \
+  xfopen \
+  xfork \
+  xgetsockname \
+  xlisten \
+  xmalloc \
+  xmemstream \
+  xmkdir \
+  xmmap \
+  xmunmap \
+  xopen \
+  xpipe \
+  xpoll \
+  xpthread_attr_destroy \
+  xpthread_attr_init \
+  xpthread_attr_setdetachstate \
+  xpthread_attr_setstacksize \
+  xpthread_barrier_destroy \
+  xpthread_barrier_init \
+  xpthread_barrier_wait \
+  xpthread_cancel \
+  xpthread_check_return \
+  xpthread_cond_wait \
+  xpthread_create \
+  xpthread_detach \
+  xpthread_join \
+  xpthread_mutex_consistent \
+  xpthread_mutex_destroy \
+  xpthread_mutex_init \
+  xpthread_mutex_lock \
+  xpthread_mutex_unlock \
+  xpthread_mutexattr_destroy \
+  xpthread_mutexattr_init \
+  xpthread_mutexattr_setprotocol \
+  xpthread_mutexattr_setpshared \
+  xpthread_mutexattr_setrobust \
+  xpthread_mutexattr_settype \
+  xpthread_once \
+  xpthread_sigmask \
+  xpthread_spin_lock \
+  xpthread_spin_unlock \
+  xrealloc \
+  xrecvfrom \
+  xsendto \
+  xsetsockopt \
+  xsocket \
+  xstrdup \
+  xwaitpid \
+  xwrite \
+
+libsupport-static-only-routines := $(libsupport-routines)
+# Only build one variant of the library.
+libsupport-inhibit-o := .os
+ifeq ($(build-shared),yes)
+libsupport-inhibit-o += .o
+endif
+
+tests = \
+  README-testing \
+  tst-support-namespace \
+  tst-support_capture_subprocess \
+  tst-support_format_dns_packet \
+  tst-support_record_failure \
+
+ifeq ($(run-built-tests),yes)
+tests-special = \
+  $(objpfx)tst-support_record_failure-2.out
+
+$(objpfx)tst-support_record_failure-2.out: tst-support_record_failure-2.sh \
+  $(objpfx)tst-support_record_failure
+	$(SHELL) $< $(common-objpfx) '$(test-program-prefix-before-env)' \
+	  '$(run-program-env)' '$(test-program-prefix-after-env)' \
+	  > $@; \
+	$(evaluate-test)
+endif
+
+$(objpfx)tst-support_format_dns_packet: $(common-objpfx)resolv/libresolv.so
+
+include ../Rules
diff --git a/support/README b/support/README
new file mode 100644
index 0000000..476cfcd
--- /dev/null
+++ b/support/README
@@ -0,0 +1,29 @@
+This subdirectory contains infrastructure which is not put into
+installed libraries, but may be linked into programs (installed or
+not) and tests.
+
+# Error-checking wrappers
+
+These wrappers test for error return codes an terminate the process on
+error.  They are declared in these header files:
+
+* support.h
+* xsignal.h
+* xthread.h
+
+In general, new wrappers should be added to support.h if possible.
+However, support.h must remain fully compatible with C90 and therefore
+cannot include headers which use identifers not reserved in C90.  If
+the wrappers need additional types, additional headers such as
+signal.h need to be introduced.
+
+# Test framework
+
+The test framework provides a main program for tests, including a
+timeout for hanging tests.  See README-testing.c for a minimal
+example, and test-driver.c for details how to use it.  The following
+header files provide related declarations:
+
+* check.h
+* temp_file.h
+* test-driver.h
diff --git a/support/README-testing.c b/support/README-testing.c
new file mode 100644
index 0000000..9d289c3
--- /dev/null
+++ b/support/README-testing.c
@@ -0,0 +1,19 @@
+/* This file contains an example test case which shows minimal use of
+   the test framework.  Additional testing hooks are described in
+   <support/test-driver.c>.  */
+
+/* This function will be called from the test driver.  */
+static int
+do_test (void)
+{
+  if (3 == 5)
+    /* Indicate failure.  */
+    return 1;
+  else
+    /* Indicate success.  */
+    return 0;
+}
+
+/* This file references do_test above and contains the definition of
+   the main function.  */
+#include <support/test-driver.c>
diff --git a/support/capture_subprocess.h b/support/capture_subprocess.h
new file mode 100644
index 0000000..43caf9b
--- /dev/null
+++ b/support/capture_subprocess.h
@@ -0,0 +1,61 @@
+/* Capture output from a subprocess.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_CAPTURE_SUBPROCESS_H
+#define SUPPORT_CAPTURE_SUBPROCESS_H
+
+#include <support/xmemstream.h>
+
+struct support_capture_subprocess
+{
+  struct xmemstream out;
+  struct xmemstream err;
+  int status;
+};
+
+/* Invoke CALLBACK (CLOSURE) in a subprocess and capture standard
+   output, standard error, and the exit status.  The out.buffer and
+   err.buffer members in the result are null-terminated strings which
+   can be examined by the caller (out.out and err.out are NULL).  */
+struct support_capture_subprocess support_capture_subprocess
+  (void (*callback) (void *), void *closure);
+
+/* Deallocate the subprocess data captured by
+   support_capture_subprocess.  */
+void support_capture_subprocess_free (struct support_capture_subprocess *);
+
+enum support_capture_allow
+{
+  /* No output is allowed.  */
+  sc_allow_none = 0x01,
+  /* Output to stdout is permitted.  */
+  sc_allow_stdout = 0x02,
+  /* Output to standard error is permitted.  */
+  sc_allow_stderr = 0x04,
+};
+
+/* Check that the subprocess exited with STATUS and that only the
+   allowed outputs happened.  ALLOWED is a combination of
+   support_capture_allow flags.  Report errors under the CONTEXT
+   message.  */
+void support_capture_subprocess_check (struct support_capture_subprocess *,
+                                       const char *context, int status,
+                                       int allowed)
+  __attribute__ ((nonnull (1, 2)));
+
+#endif /* SUPPORT_CAPTURE_SUBPROCESS_H */
diff --git a/support/check.c b/support/check.c
new file mode 100644
index 0000000..592f2bc
--- /dev/null
+++ b/support/check.c
@@ -0,0 +1,57 @@
+/* Support code for reporting test results.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/test-driver.h>
+
+static void
+print_failure (const char *file, int line, const char *format, va_list ap)
+{
+  printf ("error: %s:%d: ", file, line);
+  vprintf (format, ap);
+  puts ("");
+}
+
+int
+support_print_failure_impl (const char *file, int line,
+                            const char *format, ...)
+{
+  support_record_failure ();
+  va_list ap;
+  va_start (ap, format);
+  print_failure (file, line, format, ap);
+  va_end (ap);
+  return 1;
+}
+
+void
+support_exit_failure_impl (int status, const char *file, int line,
+                           const char *format, ...)
+{
+  if (status != EXIT_SUCCESS && status != EXIT_UNSUPPORTED)
+    support_record_failure ();
+  va_list ap;
+  va_start (ap, format);
+  print_failure (file, line, format, ap);
+  va_end (ap);
+  exit (status);
+}
diff --git a/support/check.h b/support/check.h
new file mode 100644
index 0000000..1d244a3
--- /dev/null
+++ b/support/check.h
@@ -0,0 +1,94 @@
+/* Functionality for reporting test results.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_CHECK_H
+#define SUPPORT_CHECK_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Record a test failure, print the failure message to standard output
+   and return 1.  */
+#define FAIL_RET(...) \
+  return support_print_failure_impl (__FILE__, __LINE__, __VA_ARGS__)
+
+/* Print the failure message and terminate the process with STATUS.
+   Record a the process as failed if STATUS is neither EXIT_SUCCESS
+   nor EXIT_UNSUPPORTED.  */
+#define FAIL_EXIT(status, ...) \
+  support_exit_failure_impl (status, __FILE__, __LINE__, __VA_ARGS__)
+
+/* Record a test failure, print the failure message and terminate with
+   exit status 1.  */
+#define FAIL_EXIT1(...) \
+  support_exit_failure_impl (1, __FILE__, __LINE__, __VA_ARGS__)
+
+/* Print failure message and terminate with as unsupported test (exit
+   status of 77).  */
+#define FAIL_UNSUPPORTED(...) \
+  support_exit_failure_impl (77, __FILE__, __LINE__, __VA_ARGS__)
+
+/* Record a test failure (but continue executing) if EXPR evaluates to
+   false.  */
+#define TEST_VERIFY(expr)                                       \
+  ({                                                            \
+    if (expr)                                                   \
+      ;                                                         \
+    else                                                        \
+      support_test_verify_impl (-1, __FILE__, __LINE__, #expr); \
+  })
+
+/* Record a test failure and exit if EXPR evaluates to false.  */
+#define TEST_VERIFY_EXIT(expr)                                  \
+  ({                                                            \
+    if (expr)                                                   \
+      ;                                                         \
+    else                                                        \
+      support_test_verify_impl (1, __FILE__, __LINE__, #expr);  \
+  })
+
+int support_print_failure_impl (const char *file, int line,
+                                const char *format, ...)
+  __attribute__ ((nonnull (1), format (printf, 3, 4)));
+void support_exit_failure_impl (int exit_status,
+                                const char *file, int line,
+                                const char *format, ...)
+  __attribute__ ((noreturn, nonnull (2), format (printf, 4, 5)));
+void support_test_verify_impl (int status, const char *file, int line,
+                               const char *expr);
+
+/* Record a test failure.  This function returns and does not
+   terminate the process.  The failure counter is stored in a shared
+   memory mapping, so that failures reported in child processes are
+   visible to the parent process and test driver.  This function
+   depends on initialization by an ELF constructor, so it can only be
+   invoked after the test driver has run.  Note that this function
+   does not support reporting failures from a DSO.  */
+void support_record_failure (void);
+
+/* Internal function called by the test driver.  */
+int support_report_failure (int status)
+  __attribute__ ((weak, warn_unused_result));
+
+/* Internal function used to test the failure recording framework.  */
+void support_record_failure_reset (void);
+
+__END_DECLS
+
+#endif /* SUPPORT_CHECK_H */
diff --git a/support/check_addrinfo.c b/support/check_addrinfo.c
new file mode 100644
index 0000000..55895ac
--- /dev/null
+++ b/support/check_addrinfo.c
@@ -0,0 +1,42 @@
+/* Compare struct addrinfo values against a formatted string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check_nss.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/run_diff.h>
+
+void
+check_addrinfo (const char *query_description, struct addrinfo *ai, int ret,
+                const char *expected)
+{
+  char *formatted = support_format_addrinfo (ai, ret);
+  if (strcmp (formatted, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: addrinfo comparison failure\n");
+      if (query_description != NULL)
+        printf ("query: %s\n", query_description);
+      support_run_diff ("expected", expected,
+                        "actual", formatted);
+    }
+  free (formatted);
+}
diff --git a/support/check_dns_packet.c b/support/check_dns_packet.c
new file mode 100644
index 0000000..d2a31be
--- /dev/null
+++ b/support/check_dns_packet.c
@@ -0,0 +1,42 @@
+/* Check that a DNS packet buffer has the expected contents.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check_nss.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/run_diff.h>
+
+void
+check_dns_packet (const char *query_description,
+                  const unsigned char *buffer, size_t length,
+                  const char *expected)
+{
+  char *formatted = support_format_dns_packet (buffer, length);
+  if (strcmp (formatted, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: packet comparison failure\n");
+      if (query_description != NULL)
+        printf ("query: %s\n", query_description);
+      support_run_diff ("expected", expected, "actual", formatted);
+    }
+  free (formatted);
+}
diff --git a/support/check_hostent.c b/support/check_hostent.c
new file mode 100644
index 0000000..890d672
--- /dev/null
+++ b/support/check_hostent.c
@@ -0,0 +1,42 @@
+/* Compare struct hostent values against a formatted string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check_nss.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/run_diff.h>
+
+void
+check_hostent (const char *query_description, struct hostent *h,
+               const char *expected)
+{
+  char *formatted = support_format_hostent (h);
+  if (strcmp (formatted, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: hostent comparison failure\n");
+      if (query_description != NULL)
+        printf ("query: %s\n", query_description);
+      support_run_diff ("expected", expected,
+                        "actual", formatted);
+    }
+  free (formatted);
+}
diff --git a/support/check_netent.c b/support/check_netent.c
new file mode 100644
index 0000000..daa3083
--- /dev/null
+++ b/support/check_netent.c
@@ -0,0 +1,42 @@
+/* Compare struct netent values against a formatted string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check_nss.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/run_diff.h>
+
+void
+check_netent (const char *query_description, struct netent *e,
+              const char *expected)
+{
+  char *formatted = support_format_netent (e);
+  if (strcmp (formatted, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: netent comparison failure\n");
+      if (query_description != NULL)
+        printf ("query: %s\n", query_description);
+      support_run_diff ("expected", expected,
+                        "actual", formatted);
+    }
+  free (formatted);
+}
diff --git a/support/check_nss.h b/support/check_nss.h
new file mode 100644
index 0000000..2893f2c
--- /dev/null
+++ b/support/check_nss.h
@@ -0,0 +1,42 @@
+/* Test verification functions for NSS- and DNS-related data.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_CHECK_NSS_H
+#define SUPPORT_CHECK_NSS_H
+
+#include <netdb.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Compare the data structures against the expected values (which have
+   to be formatted according to the support_format_* functions in
+   <support/format_nss.h>).  If there is a difference, a delayed test
+   failure is recorded, and a diff is written to standard output.  */
+void check_addrinfo (const char *query_description,
+                     struct addrinfo *, int ret, const char *expected);
+void check_dns_packet (const char *query_description,
+                       const unsigned char *, size_t, const char *expected);
+void check_hostent (const char *query_description,
+                    struct hostent *, const char *expected);
+void check_netent (const char *query_description,
+                   struct netent *, const char *expected);
+
+__END_DECLS
+
+#endif  /* SUPPORT_CHECK_NSS_H */
diff --git a/support/delayed_exit.c b/support/delayed_exit.c
new file mode 100644
index 0000000..67442f9
--- /dev/null
+++ b/support/delayed_exit.c
@@ -0,0 +1,55 @@
+/* Time-triggered process termination.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+#include <support/xsignal.h>
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <time.h>
+
+static void *
+delayed_exit_thread (void *seconds_as_ptr)
+{
+  int seconds = (uintptr_t) seconds_as_ptr;
+  struct timespec delay = { seconds, 0 };
+  struct timespec remaining = { 0 };
+  if (nanosleep (&delay, &remaining) != 0)
+    FAIL_EXIT1 ("nanosleep: %m");
+  /* Exit the process sucessfully.  */
+  exit (0);
+  return NULL;
+}
+
+void
+delayed_exit (int seconds)
+{
+  /* Create the new thread with all signals blocked.  */
+  sigset_t all_blocked;
+  sigfillset (&all_blocked);
+  sigset_t old_set;
+  xpthread_sigmask (SIG_SETMASK, &all_blocked, &old_set);
+  /* Create a detached thread. */
+  pthread_t thr = xpthread_create
+    (NULL, delayed_exit_thread, (void *) (uintptr_t) seconds);
+  xpthread_detach (thr);
+  /* Restore the original signal mask.  */
+  xpthread_sigmask (SIG_SETMASK, &old_set, NULL);
+}
diff --git a/support/format_nss.h b/support/format_nss.h
new file mode 100644
index 0000000..fb4597c
--- /dev/null
+++ b/support/format_nss.h
@@ -0,0 +1,41 @@
+/* String formatting functions for NSS- and DNS-related data.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_FORMAT_NSS_H
+#define SUPPORT_FORMAT_NSS_H
+
+#include <netdb.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* The following functions format their arguments as human-readable
+   strings (which can span multiple lines).  The caller must free the
+   returned buffer.  For NULL pointers or failure status arguments,
+   error variables such as h_errno and errno are included in the
+   result.  */
+char *support_format_address_family (int);
+char *support_format_addrinfo (struct addrinfo *, int ret);
+char *support_format_dns_packet (const unsigned char *buffer, size_t length);
+char *support_format_herrno (int);
+char *support_format_hostent (struct hostent *);
+char *support_format_netent (struct netent *);
+
+__END_DECLS
+
+#endif  /* SUPPORT_FORMAT_NSS_H */
diff --git a/support/ignore_stderr.c b/support/ignore_stderr.c
new file mode 100644
index 0000000..7b77a2c
--- /dev/null
+++ b/support/ignore_stderr.c
@@ -0,0 +1,38 @@
+/* Avoid all the buffer overflow messages on stderr.
+   Copyright (C) 2015-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <fcntl.h>
+#include <paths.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+void
+ignore_stderr (void)
+{
+  int fd = open (_PATH_DEVNULL, O_WRONLY);
+  if (fd == -1)
+    close (STDERR_FILENO);
+  else
+    {
+      dup2 (fd, STDERR_FILENO);
+      close (fd);
+    }
+  setenv ("LIBC_FATAL_STDERR_", "1", 1);
+}
diff --git a/support/namespace.h b/support/namespace.h
new file mode 100644
index 0000000..e1ccaa1
--- /dev/null
+++ b/support/namespace.h
@@ -0,0 +1,65 @@
+/* Entering namespaces for test case isolation.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_NAMESPACE_H
+#define SUPPORT_NAMESPACE_H
+
+#include <stdbool.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Attempts to become root (or acquire root-like privileges), possibly
+   with the help of user namespaces.  Return true if (restricted) root
+   privileges could be attained in some way.  Print diagnostics to
+   standard output.
+
+   Note that this function generally has to be called before a process
+   becomes multi-threaded, otherwise it may fail with insufficient
+   privileges on systems which would support this operation for
+   single-threaded processes.  */
+bool support_become_root (void);
+
+/* Return true if this process can perform a chroot operation.  In
+   general, this is only possible if support_become_root has been
+   called.  Note that the actual test is performed in a subprocess,
+   after fork, so that the file system root of the original process is
+   not changed.  */
+bool support_can_chroot (void);
+
+/* Enter a network namespace (and a UTS namespace if possible) and
+   configure the loopback interface.  Return true if a network
+   namespace could be created.  Print diagnostics to standard output.
+   If a network namespace could be created, but networking in it could
+   not be configured, terminate the process.  It is recommended to
+   call support_become_root before this function so that the process
+   has sufficient privileges.  */
+bool support_enter_network_namespace (void);
+
+/* Return true if support_enter_network_namespace managed to enter a
+   UTS namespace.  */
+bool support_in_uts_namespace (void);
+
+/* Invoke CALLBACK (CLOSURE) in a subprocess created using fork.
+   Terminate the calling process if the subprocess exits with a
+   non-zero exit status.  */
+void support_isolate_in_subprocess (void (*callback) (void *), void *closure);
+
+__END_DECLS
+
+#endif
diff --git a/support/oom_error.c b/support/oom_error.c
new file mode 100644
index 0000000..7816978
--- /dev/null
+++ b/support/oom_error.c
@@ -0,0 +1,29 @@
+/* Reporting out-of-memory errors.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+void
+oom_error (const char *function, size_t size)
+{
+  printf ("%s: unable to allocate %zu bytes: %m\n", function, size);
+  exit (1);
+}
diff --git a/support/resolv_test.c b/support/resolv_test.c
new file mode 100644
index 0000000..050cd71
--- /dev/null
+++ b/support/resolv_test.c
@@ -0,0 +1,1202 @@
+/* DNS test framework and libresolv redirection.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/resolv_test.h>
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <nss.h>
+#include <resolv.h>
+#include <search.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/xsocket.h>
+#include <support/xthread.h>
+#include <support/xunistd.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+/* Response builder.  */
+
+enum
+  {
+    max_response_length = 65536
+  };
+
+/* List of pointers to be freed.  The hash table implementation
+   (struct hsearch_data) does not provide a way to deallocate all
+   objects, so this approach is used to avoid memory leaks.  */
+struct to_be_freed
+{
+  struct to_be_freed *next;
+  void *ptr;
+};
+
+struct resolv_response_builder
+{
+  const unsigned char *query_buffer;
+  size_t query_length;
+
+  size_t offset;                /* Bytes written so far in buffer.  */
+  ns_sect section;              /* Current section in the DNS packet.  */
+  unsigned int truncate_bytes;  /* Bytes to remove at end of response. */
+  bool drop;                    /* Discard generated response.  */
+  bool close;                   /* Close TCP client connection.  */
+
+  /* Offset of the two-byte RDATA length field in the currently
+     written RDATA sub-structure.  0 if no RDATA is being written.  */
+  size_t current_rdata_offset;
+
+  /* Hash table for locating targets for label compression.  */
+  struct hsearch_data compression_offsets;
+  /* List of pointers which need to be freed.  Used for domain names
+     involved in label compression.  */
+  struct to_be_freed *to_be_freed;
+
+  /* Must be last.  Not zeroed for performance reasons.  */
+  unsigned char buffer[max_response_length];
+};
+
+/* Response builder. */
+
+/* Add a pointer to the list of pointers to be freed when B is
+   deallocated.  */
+static void
+response_push_pointer_to_free (struct resolv_response_builder *b, void *ptr)
+{
+  if (ptr == NULL)
+    return;
+  struct to_be_freed *e = xmalloc (sizeof (*e));
+  *e = (struct to_be_freed) {b->to_be_freed, ptr};
+  b->to_be_freed = e;
+}
+
+void
+resolv_response_init (struct resolv_response_builder *b,
+                      struct resolv_response_flags flags)
+{
+  if (b->offset > 0)
+    FAIL_EXIT1 ("response_init: called at offset %zu", b->offset);
+  if (b->query_length < 12)
+    FAIL_EXIT1 ("response_init called for a query of size %zu",
+                b->query_length);
+  if (flags.rcode > 15)
+    FAIL_EXIT1 ("response_init: invalid RCODE %u", flags.rcode);
+
+  /* Copy the transaction ID.  */
+  b->buffer[0] = b->query_buffer[0];
+  b->buffer[1] = b->query_buffer[1];
+
+  /* Initialize the flags.  */
+  b->buffer[2] = 0x80;                       /* Mark as response.   */
+  b->buffer[2] |= b->query_buffer[2] & 0x01; /* Copy the RD bit.  */
+  if (flags.tc)
+    b->buffer[2] |= 0x02;
+  b->buffer[3] = 0x80 | flags.rcode; /* Always set RA.  */
+
+  /* Fill in the initial section count values.  */
+  b->buffer[4] = flags.qdcount >> 8;
+  b->buffer[5] = flags.qdcount;
+  b->buffer[6] = flags.ancount >> 8;
+  b->buffer[7] = flags.ancount;
+  b->buffer[8] = flags.nscount >> 8;
+  b->buffer[9] = flags.nscount;
+  b->buffer[10] = flags.adcount >> 8;
+  b->buffer[11] = flags.adcount;
+
+  b->offset = 12;
+}
+
+void
+resolv_response_section (struct resolv_response_builder *b, ns_sect section)
+{
+  if (b->offset == 0)
+    FAIL_EXIT1 ("resolv_response_section: response_init not called before");
+  if (section < b->section)
+    FAIL_EXIT1 ("resolv_response_section: cannot go back to previous section");
+  b->section = section;
+}
+
+/* Add a single byte to B.  */
+static inline void
+response_add_byte (struct resolv_response_builder *b, unsigned char ch)
+{
+  if (b->offset == max_response_length)
+    FAIL_EXIT1 ("DNS response exceeds 64 KiB limit");
+  b->buffer[b->offset] = ch;
+  ++b->offset;
+}
+
+/* Add a 16-bit word VAL to B, in big-endian format.  */
+static void
+response_add_16 (struct resolv_response_builder *b, uint16_t val)
+{
+  response_add_byte (b, val >> 8);
+  response_add_byte (b, val);
+}
+
+/* Increment the pers-section record counter in the packet header.  */
+static void
+response_count_increment (struct resolv_response_builder *b)
+{
+  unsigned int offset = b->section;
+  offset = 4 + 2 * offset;
+  ++b->buffer[offset + 1];
+  if (b->buffer[offset + 1] == 0)
+    {
+      /* Carry.  */
+      ++b->buffer[offset];
+      if (b->buffer[offset] == 0)
+        /* Overflow.  */
+        FAIL_EXIT1 ("too many records in section");
+    }
+}
+
+void
+resolv_response_add_question (struct resolv_response_builder *b,
+                              const char *name, uint16_t class, uint16_t type)
+{
+  if (b->offset == 0)
+    FAIL_EXIT1 ("resolv_response_add_question: "
+                "resolv_response_init not called");
+  if (b->section != ns_s_qd)
+    FAIL_EXIT1 ("resolv_response_add_question: "
+                "must be called in the question section");
+
+  resolv_response_add_name (b, name);
+  response_add_16 (b, type);
+  response_add_16 (b, class);
+
+  response_count_increment (b);
+}
+
+void
+resolv_response_add_name (struct resolv_response_builder *b,
+                          const char *const origname)
+{
+  /* Normalized name.  */
+  char *name;
+  /* Normalized name with case preserved.  */
+  char *name_case;
+  {
+    size_t namelen = strlen (origname);
+    /* Remove trailing dots.  FIXME: Handle trailing quoted dots.  */
+    while (namelen > 0 && origname[namelen - 1] == '.')
+      --namelen;
+    name = xmalloc (namelen + 1);
+    name_case = xmalloc (namelen + 1);
+    /* Copy and convert to lowercase.  FIXME: This needs to normalize
+       escaping as well.  */
+    for (size_t i = 0; i < namelen; ++i)
+      {
+        char ch = origname[i];
+        name_case[i] = ch;
+        if ('A' <= ch && ch <= 'Z')
+          ch = ch - 'A' + 'a';
+        name[i] = ch;
+      }
+    name[namelen] = 0;
+    name_case[namelen] = 0;
+  }
+  char *name_start = name;
+  char *name_case_start = name_case;
+
+  bool compression = false;
+  while (*name)
+    {
+      /* Search for a previous name we can reference.  */
+      ENTRY new_entry =
+        {
+          .key = name,
+          .data = (void *) (uintptr_t) b->offset,
+        };
+
+      /* If the label can be a compression target because it is at a
+         reachable offset, add it to the hash table.  */
+      ACTION action;
+      if (b->offset < (1 << 12))
+        action = ENTER;
+      else
+        action = FIND;
+
+      /* Search for known compression offsets in the hash table.  */
+      ENTRY *e;
+      if (hsearch_r (new_entry, action, &e, &b->compression_offsets) == 0)
+        {
+          if (action == FIND && errno == ESRCH)
+            /* Fall through.  */
+            e = NULL;
+          else
+            FAIL_EXIT1 ("hsearch_r failure in name compression: %m");
+        }
+
+      /* The name is known.  Reference the previous location.  */
+      if (e != NULL && e->data != new_entry.data)
+        {
+          size_t old_offset = (uintptr_t) e->data;
+          response_add_byte (b, 0xC0 | (old_offset >> 8));
+          response_add_byte (b, old_offset);
+          compression = true;
+          break;
+        }
+
+      /* The name does not exist yet.  Write one label.  First, add
+         room for the label length.  */
+      size_t buffer_label_offset = b->offset;
+      response_add_byte (b, 0);
+
+      /* Copy the label.  */
+      while (true)
+        {
+          char ch = *name_case;
+          if (ch == '\0')
+            break;
+          ++name;
+          ++name_case;
+          if (ch == '.')
+            break;
+          /* FIXME: Handle escaping.  */
+          response_add_byte (b, ch);
+        }
+
+      /* Patch in the label length.  */
+      size_t label_length = b->offset - buffer_label_offset - 1;
+      if (label_length == 0)
+        FAIL_EXIT1 ("empty label in name compression: %s", origname);
+      if (label_length > 63)
+        FAIL_EXIT1 ("label too long in name compression: %s", origname);
+      b->buffer[buffer_label_offset] = label_length;
+
+      /* Continue with the tail of the name and the next label.  */
+    }
+
+  if (compression)
+    {
+      /* If we found an immediate match for the name, we have not put
+         it into the hash table, and can free it immediately.  */
+      if (name == name_start)
+        free (name_start);
+      else
+        response_push_pointer_to_free (b, name_start);
+    }
+  else
+    {
+      /* Terminate the sequence of labels.  With compression, this is
+         implicit in the compression reference.  */
+      response_add_byte (b, 0);
+      response_push_pointer_to_free (b, name_start);
+    }
+
+  free (name_case_start);
+}
+
+void
+resolv_response_open_record (struct resolv_response_builder *b,
+                             const char *name,
+                             uint16_t class, uint16_t type, uint32_t ttl)
+{
+  if (b->section == ns_s_qd)
+    FAIL_EXIT1 ("resolv_response_open_record called in question section");
+  if (b->current_rdata_offset != 0)
+    FAIL_EXIT1 ("resolv_response_open_record called with open record");
+
+  resolv_response_add_name (b, name);
+  response_add_16 (b, type);
+  response_add_16 (b, class);
+  response_add_16 (b, ttl >> 16);
+  response_add_16 (b, ttl);
+
+  b->current_rdata_offset = b->offset;
+  /* Add room for the RDATA length.  */
+  response_add_16 (b, 0);
+}
+
+
+void
+resolv_response_close_record (struct resolv_response_builder *b)
+{
+  size_t rdata_offset = b->current_rdata_offset;
+  if (rdata_offset == 0)
+    FAIL_EXIT1 ("response_close_record called without open record");
+  size_t rdata_length = b->offset - rdata_offset - 2;
+  if (rdata_length > 65535)
+    FAIL_EXIT1 ("RDATA length %zu exceeds limit", rdata_length);
+  b->buffer[rdata_offset] = rdata_length >> 8;
+  b->buffer[rdata_offset + 1] = rdata_length;
+  response_count_increment (b);
+  b->current_rdata_offset = 0;
+}
+
+void
+resolv_response_add_data (struct resolv_response_builder *b,
+                          const void *data, size_t length)
+{
+  size_t remaining = max_response_length - b->offset;
+  if (remaining < length)
+    FAIL_EXIT1 ("resolv_response_add_data: not enough room for %zu bytes",
+                length);
+  memcpy (b->buffer + b->offset, data, length);
+  b->offset += length;
+}
+
+void
+resolv_response_drop (struct resolv_response_builder *b)
+{
+  b->drop = true;
+}
+
+void
+resolv_response_close (struct resolv_response_builder *b)
+{
+  b->close = true;
+}
+
+void
+resolv_response_truncate_data (struct resolv_response_builder *b, size_t count)
+{
+  if (count > 65535)
+    FAIL_EXIT1 ("resolv_response_truncate_data: argument too large: %zu",
+                count);
+  b->truncate_bytes = count;
+}
+
+
+size_t
+resolv_response_length (const struct resolv_response_builder *b)
+{
+  return b->offset;
+}
+
+unsigned char *
+resolv_response_buffer (const struct resolv_response_builder *b)
+{
+  unsigned char *result = xmalloc (b->offset);
+  memcpy (result, b->buffer, b->offset);
+  return result;
+}
+
+static struct resolv_response_builder *
+response_builder_allocate
+  (const unsigned char *query_buffer, size_t query_length)
+{
+  struct resolv_response_builder *b = xmalloc (sizeof (*b));
+  memset (b, 0, offsetof (struct resolv_response_builder, buffer));
+  b->query_buffer = query_buffer;
+  b->query_length = query_length;
+  TEST_VERIFY_EXIT (hcreate_r (10000, &b->compression_offsets) != 0);
+  return b;
+}
+
+static void
+response_builder_free (struct resolv_response_builder *b)
+{
+  struct to_be_freed *current = b->to_be_freed;
+  while (current != NULL)
+    {
+      struct to_be_freed *next = current->next;
+      free (current->ptr);
+      free (current);
+      current = next;
+    }
+  hdestroy_r (&b->compression_offsets);
+  free (b);
+}
+
+/* DNS query processing. */
+
+/* Data extracted from the question section of a DNS packet.  */
+struct query_info
+{
+  char qname[MAXDNAME];
+  uint16_t qclass;
+  uint16_t qtype;
+  struct resolv_edns_info edns;
+};
+
+/* Update *INFO from the specified DNS packet.  */
+static void
+parse_query (struct query_info *info,
+             const unsigned char *buffer, size_t length)
+{
+  HEADER hd;
+  _Static_assert (sizeof (hd) == 12, "DNS header size");
+  if (length < sizeof (hd))
+    FAIL_EXIT1 ("malformed DNS query: too short: %zu bytes", length);
+  memcpy (&hd, buffer, sizeof (hd));
+
+  if (ntohs (hd.qdcount) != 1)
+    FAIL_EXIT1 ("malformed DNS query: wrong question count: %d",
+                (int) ntohs (hd.qdcount));
+  if (ntohs (hd.ancount) != 0)
+    FAIL_EXIT1 ("malformed DNS query: wrong answer count: %d",
+                (int) ntohs (hd.ancount));
+  if (ntohs (hd.nscount) != 0)
+    FAIL_EXIT1 ("malformed DNS query: wrong authority count: %d",
+                (int) ntohs (hd.nscount));
+  if (ntohs (hd.arcount) > 1)
+    FAIL_EXIT1 ("malformed DNS query: wrong additional count: %d",
+                (int) ntohs (hd.arcount));
+
+  int ret = dn_expand (buffer, buffer + length, buffer + sizeof (hd),
+                       info->qname, sizeof (info->qname));
+  if (ret < 0)
+    FAIL_EXIT1 ("malformed DNS query: cannot uncompress QNAME");
+
+  /* Obtain QTYPE and QCLASS.  */
+  size_t remaining = length - (12 + ret);
+  struct
+  {
+    uint16_t qtype;
+    uint16_t qclass;
+  } qtype_qclass;
+  if (remaining < sizeof (qtype_qclass))
+    FAIL_EXIT1 ("malformed DNS query: "
+                "query lacks QCLASS/QTYPE, QNAME: %s", info->qname);
+  memcpy (&qtype_qclass, buffer + 12 + ret, sizeof (qtype_qclass));
+  info->qclass = ntohs (qtype_qclass.qclass);
+  info->qtype = ntohs (qtype_qclass.qtype);
+
+  memset (&info->edns, 0, sizeof (info->edns));
+  if (ntohs (hd.arcount) > 0)
+    {
+      /* Parse EDNS record.  */
+      struct __attribute__ ((packed, aligned (1)))
+      {
+        uint8_t root;
+        uint16_t rtype;
+        uint16_t payload;
+        uint8_t edns_extended_rcode;
+        uint8_t edns_version;
+        uint16_t flags;
+        uint16_t rdatalen;
+      } rr;
+      _Static_assert (sizeof (rr) == 11, "EDNS record size");
+
+      if (remaining < 4 + sizeof (rr))
+        FAIL_EXIT1 ("mailformed DNS query: no room for EDNS record");
+      memcpy (&rr, buffer + 12 + ret + 4, sizeof (rr));
+      if (rr.root != 0)
+        FAIL_EXIT1 ("malformed DNS query: invalid OPT RNAME: %d\n", rr.root);
+      if (rr.rtype != htons (41))
+        FAIL_EXIT1 ("malformed DNS query: invalid OPT type: %d\n",
+                    ntohs (rr.rtype));
+      info->edns.active = true;
+      info->edns.extended_rcode = rr.edns_extended_rcode;
+      info->edns.version = rr.edns_version;
+      info->edns.flags = ntohs (rr.flags);
+      info->edns.payload_size = ntohs (rr.payload);
+    }
+}
+
+
+/* Main testing framework.  */
+
+/* Per-server information.  One struct is allocated for each test
+   server.  */
+struct resolv_test_server
+{
+  /* Local address of the server.  UDP and TCP use the same port.  */
+  struct sockaddr_in address;
+
+  /* File descriptor of the UDP server, or -1 if this server is
+     disabled.  */
+  int socket_udp;
+
+  /* File descriptor of the TCP server, or -1 if this server is
+     disabled.  */
+  int socket_tcp;
+
+  /* Counter of the number of responses processed so far.  */
+  size_t response_number;
+
+  /* Thread handles for the server threads (if not disabled in the
+     configuration).  */
+  pthread_t thread_udp;
+  pthread_t thread_tcp;
+};
+
+/* Main struct for keeping track of libresolv redirection and
+   testing.  */
+struct resolv_test
+{
+  /* After initialization, any access to the struct must be performed
+     while this lock is acquired.  */
+  pthread_mutex_t lock;
+
+  /* Data for each test server. */
+  struct resolv_test_server servers[resolv_max_test_servers];
+
+  /* Used if config.single_thread_udp is true.  */
+  pthread_t thread_udp_single;
+
+  struct resolv_redirect_config config;
+  bool termination_requested;
+};
+
+/* Function implementing a server thread.  */
+typedef void (*thread_callback) (struct resolv_test *, int server_index);
+
+/* Storage for thread-specific data, for passing to the
+   thread_callback function.  */
+struct thread_closure
+{
+  struct resolv_test *obj;      /* Current test object.  */
+  thread_callback callback;     /* Function to call.  */
+  int server_index;             /* Index of the implemented server.  */
+};
+
+/* Wrap response_callback as a function which can be passed to
+   pthread_create.  */
+static void *
+thread_callback_wrapper (void *arg)
+{
+  struct thread_closure *closure = arg;
+  closure->callback (closure->obj, closure->server_index);
+  free (closure);
+  return NULL;
+}
+
+/* Start a server thread for the specified SERVER_INDEX, implemented
+   by CALLBACK.  */
+static pthread_t
+start_server_thread (struct resolv_test *obj, int server_index,
+                     thread_callback callback)
+{
+  struct thread_closure *closure = xmalloc (sizeof (*closure));
+  *closure = (struct thread_closure)
+    {
+      .obj = obj,
+      .callback = callback,
+      .server_index = server_index,
+    };
+  return xpthread_create (NULL, thread_callback_wrapper, closure);
+}
+
+/* Process one UDP query.  Return false if a termination requested has
+   been detected.  */
+static bool
+server_thread_udp_process_one (struct resolv_test *obj, int server_index)
+{
+  unsigned char query[512];
+  struct sockaddr_storage peer;
+  socklen_t peerlen = sizeof (peer);
+  size_t length = xrecvfrom (obj->servers[server_index].socket_udp,
+                             query, sizeof (query), 0,
+                             (struct sockaddr *) &peer, &peerlen);
+  /* Check for termination.  */
+  {
+    bool termination_requested;
+    xpthread_mutex_lock (&obj->lock);
+    termination_requested = obj->termination_requested;
+    xpthread_mutex_unlock (&obj->lock);
+    if (termination_requested)
+      return false;
+  }
+
+
+  struct query_info qinfo;
+  parse_query (&qinfo, query, length);
+  if (test_verbose > 0)
+    {
+      if (test_verbose > 1)
+        printf ("info: UDP server %d: incoming query:"
+                " %zd bytes, %s/%u/%u, tnxid=0x%02x%02x\n",
+                server_index, length, qinfo.qname, qinfo.qclass, qinfo.qtype,
+                query[0], query[1]);
+      else
+        printf ("info: UDP server %d: incoming query:"
+                " %zd bytes, %s/%u/%u\n",
+                server_index, length, qinfo.qname, qinfo.qclass, qinfo.qtype);
+    }
+
+  struct resolv_response_context ctx =
+    {
+      .query_buffer = query,
+      .query_length = length,
+      .server_index = server_index,
+      .tcp = false,
+      .edns = qinfo.edns,
+    };
+  struct resolv_response_builder *b = response_builder_allocate (query, length);
+  obj->config.response_callback
+    (&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
+
+  if (b->drop)
+    {
+      if (test_verbose)
+        printf ("info: UDP server %d: dropping response to %s/%u/%u\n",
+                server_index, qinfo.qname, qinfo.qclass, qinfo.qtype);
+    }
+  else
+    {
+      if (test_verbose)
+        {
+          if (b->offset >= 12)
+            printf ("info: UDP server %d: sending response:"
+                    " %zu bytes, RCODE %d (for %s/%u/%u)\n",
+                    server_index, b->offset, b->buffer[3] & 0x0f,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype);
+          else
+            printf ("info: UDP server %d: sending response: %zu bytes"
+                    " (for %s/%u/%u)\n",
+                    server_index, b->offset,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype);
+          if (b->truncate_bytes > 0)
+            printf ("info:    truncated by %u bytes\n", b->truncate_bytes);
+        }
+      size_t to_send = b->offset;
+      if (to_send < b->truncate_bytes)
+        to_send = 0;
+      else
+        to_send -= b->truncate_bytes;
+
+      /* Ignore most errors here because the other end may have closed
+         the socket. */
+      if (sendto (obj->servers[server_index].socket_udp,
+                  b->buffer, to_send, 0,
+                  (struct sockaddr *) &peer, peerlen) < 0)
+        TEST_VERIFY_EXIT (errno != EBADF);
+    }
+  response_builder_free (b);
+  return true;
+}
+
+/* UDP thread_callback function.  Variant for one thread per
+   server.  */
+static void
+server_thread_udp (struct resolv_test *obj, int server_index)
+{
+  while (server_thread_udp_process_one (obj, server_index))
+    ;
+}
+
+/* Single-threaded UDP processing function, for the single_thread_udp
+   case.  */
+static void *
+server_thread_udp_single (void *closure)
+{
+  struct resolv_test *obj = closure;
+
+  struct pollfd fds[resolv_max_test_servers];
+  for (int server_index = 0; server_index < resolv_max_test_servers;
+       ++server_index)
+    if (obj->config.servers[server_index].disable_udp)
+      fds[server_index] = (struct pollfd) {.fd = -1};
+    else
+      {
+        fds[server_index] = (struct pollfd)
+          {
+            .fd = obj->servers[server_index].socket_udp,
+            .events = POLLIN
+          };
+
+        /* Make the socket non-blocking.  */
+        int flags = fcntl (obj->servers[server_index].socket_udp, F_GETFL, 0);
+        if (flags < 0)
+          FAIL_EXIT1 ("fcntl (F_GETFL): %m");
+        flags |= O_NONBLOCK;
+        if (fcntl (obj->servers[server_index].socket_udp, F_SETFL, flags) < 0)
+          FAIL_EXIT1 ("fcntl (F_SETFL): %m");
+      }
+
+  while (true)
+    {
+      xpoll (fds, resolv_max_test_servers, -1);
+      for (int server_index = 0; server_index < resolv_max_test_servers;
+           ++server_index)
+        if (fds[server_index].revents != 0)
+          {
+            if (!server_thread_udp_process_one (obj, server_index))
+              goto out;
+            fds[server_index].revents = 0;
+          }
+    }
+
+ out:
+  return NULL;
+}
+
+/* Start the single UDP handler thread (for the single_thread_udp
+   case).  */
+static void
+start_server_thread_udp_single (struct resolv_test *obj)
+{
+  obj->thread_udp_single
+    = xpthread_create (NULL, server_thread_udp_single, obj);
+}
+
+/* Data describing a TCP client connect.  */
+struct tcp_thread_closure
+{
+  struct resolv_test *obj;
+  int server_index;
+  int client_socket;
+};
+
+/* Read a complete DNS query packet.  If EOF_OK, an immediate
+   end-of-file condition is acceptable.  */
+static bool
+read_fully (int fd, void *buf, size_t len, bool eof_ok)
+{
+  const void *const end = buf + len;
+  while (buf < end)
+    {
+      ssize_t ret = read (fd, buf, end - buf);
+      if (ret == 0)
+        {
+          if (!eof_ok)
+            {
+              support_record_failure ();
+              printf ("error: unexpected EOF on TCP connection\n");
+            }
+          return false;
+        }
+      else if (ret < 0)
+        {
+          if (!eof_ok || errno != ECONNRESET)
+            {
+              support_record_failure ();
+              printf ("error: TCP read: %m\n");
+            }
+          return false;
+        }
+      buf += ret;
+      eof_ok = false;
+    }
+  return true;
+}
+
+/* Write an array of iovecs.  Terminate the process on failure.  */
+static void
+writev_fully (int fd, struct iovec *buffers, size_t count)
+{
+  while (count > 0)
+    {
+      /* Skip zero-length write requests.  */
+      if (buffers->iov_len == 0)
+        {
+          ++buffers;
+          --count;
+          continue;
+        }
+      /* Try to rewrite the remaing buffers.  */
+      ssize_t ret = writev (fd, buffers, count);
+      if (ret < 0)
+        FAIL_EXIT1 ("writev: %m");
+      if (ret == 0)
+        FAIL_EXIT1 ("writev: invalid return value zero");
+      /* Find the buffers that were successfully written.  */
+      while (ret > 0)
+        {
+          if (count == 0)
+            FAIL_EXIT1 ("internal writev consistency failure");
+          /* Current buffer was partially written.  */
+          if (buffers->iov_len > (size_t) ret)
+            {
+              buffers->iov_base += ret;
+              buffers->iov_len -= ret;
+              ret = 0;
+            }
+          else
+            {
+              ret -= buffers->iov_len;
+              buffers->iov_len = 0;
+              ++buffers;
+              --count;
+            }
+        }
+    }
+}
+
+/* Thread callback for handling a single established TCP connection to
+   a client.  */
+static void *
+server_thread_tcp_client (void *arg)
+{
+  struct tcp_thread_closure *closure = arg;
+
+  while (true)
+    {
+      /* Read packet length.  */
+      uint16_t query_length;
+      if (!read_fully (closure->client_socket,
+                       &query_length, sizeof (query_length), true))
+        break;
+      query_length = ntohs (query_length);
+
+      /* Read the packet.  */
+      unsigned char *query_buffer = xmalloc (query_length);
+      read_fully (closure->client_socket, query_buffer, query_length, false);
+
+      struct query_info qinfo;
+      parse_query (&qinfo, query_buffer, query_length);
+      if (test_verbose > 0)
+        {
+          if (test_verbose > 1)
+            printf ("info: UDP server %d: incoming query:"
+                    " %d bytes, %s/%u/%u, tnxid=0x%02x%02x\n",
+                    closure->server_index, query_length,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype,
+                    query_buffer[0], query_buffer[1]);
+          else
+            printf ("info: TCP server %d: incoming query:"
+                    " %u bytes, %s/%u/%u\n",
+                    closure->server_index, query_length,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype);
+        }
+
+      struct resolv_response_context ctx =
+        {
+          .query_buffer = query_buffer,
+          .query_length = query_length,
+          .server_index = closure->server_index,
+          .tcp = true,
+          .edns = qinfo.edns,
+        };
+      struct resolv_response_builder *b = response_builder_allocate
+        (query_buffer, query_length);
+      closure->obj->config.response_callback
+        (&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
+
+      if (b->drop)
+        {
+          if (test_verbose)
+            printf ("info: TCP server %d: dropping response to %s/%u/%u\n",
+                    closure->server_index,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype);
+        }
+      else
+        {
+          if (test_verbose)
+            printf ("info: TCP server %d: sending response: %zu bytes"
+                    " (for %s/%u/%u)\n",
+                    closure->server_index, b->offset,
+                    qinfo.qname, qinfo.qclass, qinfo.qtype);
+          uint16_t length = htons (b->offset);
+          size_t to_send = b->offset;
+          if (to_send < b->truncate_bytes)
+            to_send = 0;
+          else
+            to_send -= b->truncate_bytes;
+          struct iovec buffers[2] =
+            {
+              {&length, sizeof (length)},
+              {b->buffer, to_send}
+            };
+          writev_fully (closure->client_socket, buffers, 2);
+        }
+      bool close_flag = b->close;
+      response_builder_free (b);
+      free (query_buffer);
+      if (close_flag)
+        break;
+    }
+
+  xclose (closure->client_socket);
+  free (closure);
+  return NULL;
+}
+
+/* thread_callback for the TCP case.  Accept connections and create a
+   new thread for each client.  */
+static void
+server_thread_tcp (struct resolv_test *obj, int server_index)
+{
+  while (true)
+    {
+      /* Get the client conenction.  */
+      int client_socket = xaccept
+        (obj->servers[server_index].socket_tcp, NULL, NULL);
+
+      /* Check for termination.  */
+      xpthread_mutex_lock (&obj->lock);
+      if (obj->termination_requested)
+        {
+          xpthread_mutex_unlock (&obj->lock);
+          xclose (client_socket);
+          break;
+        }
+      xpthread_mutex_unlock (&obj->lock);
+
+      /* Spawn a new thread for handling this connection.  */
+      struct tcp_thread_closure *closure = xmalloc (sizeof (*closure));
+      *closure = (struct tcp_thread_closure)
+        {
+          .obj = obj,
+          .server_index = server_index,
+          .client_socket = client_socket,
+        };
+
+      pthread_t thr
+        = xpthread_create (NULL, server_thread_tcp_client, closure);
+      /* TODO: We should keep track of this thread so that we can
+         block in resolv_test_end until it has exited.  */
+      xpthread_detach (thr);
+    }
+}
+
+/* Create UDP and TCP server sockets.  */
+static void
+make_server_sockets (struct resolv_test_server *server)
+{
+  while (true)
+    {
+      server->socket_udp = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+      server->socket_tcp = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
+
+      /* Pick the address for the UDP socket.  */
+      server->address = (struct sockaddr_in)
+        {
+          .sin_family = AF_INET,
+          .sin_addr = {.s_addr = htonl (INADDR_LOOPBACK)}
+        };
+      xbind (server->socket_udp,
+             (struct sockaddr *)&server->address, sizeof (server->address));
+
+      /* Retrieve the address. */
+      socklen_t addrlen = sizeof (server->address);
+      xgetsockname (server->socket_udp,
+                    (struct sockaddr *)&server->address, &addrlen);
+
+      /* Bind the TCP socket to the same address.  */
+      {
+        int on = 1;
+        xsetsockopt (server->socket_tcp, SOL_SOCKET, SO_REUSEADDR,
+                     &on, sizeof (on));
+      }
+      if (bind (server->socket_tcp,
+                (struct sockaddr *)&server->address,
+                sizeof (server->address)) != 0)
+        {
+          /* Port collision.  The UDP bind succeeded, but the TCP BIND
+             failed.  We assume here that the kernel will pick the
+             next local UDP address randomly.  */
+          if (errno == EADDRINUSE)
+            {
+              xclose (server->socket_udp);
+              xclose (server->socket_tcp);
+              continue;
+            }
+          FAIL_EXIT1 ("TCP bind: %m");
+        }
+      xlisten (server->socket_tcp, 5);
+      break;
+    }
+}
+
+/* One-time initialization of NSS.  */
+static void
+resolv_redirect_once (void)
+{
+  /* Only use nss_dns.  */
+  __nss_configure_lookup ("hosts", "dns");
+  __nss_configure_lookup ("networks", "dns");
+  /* Enter a network namespace for isolation and firewall state
+     cleanup.  The tests will still work if these steps fail, but they
+     may be less reliable.  */
+  support_become_root ();
+  support_enter_network_namespace ();
+}
+pthread_once_t resolv_redirect_once_var = PTHREAD_ONCE_INIT;
+
+void
+resolv_test_init (void)
+{
+  /* Perform one-time initialization of NSS.  */
+  xpthread_once (&resolv_redirect_once_var, resolv_redirect_once);
+}
+
+/* Copy the search path from CONFIG.search to the _res object.  */
+static void
+set_search_path (struct resolv_redirect_config config)
+{
+  memset (_res.defdname, 0, sizeof (_res.defdname));
+  memset (_res.dnsrch, 0, sizeof (_res.dnsrch));
+
+  char *current = _res.defdname;
+  char *end = current + sizeof (_res.defdname);
+
+  for (unsigned int i = 0;
+       i < sizeof (config.search) / sizeof (config.search[0]); ++i)
+    {
+      if (config.search[i] == NULL)
+        continue;
+
+      size_t length = strlen (config.search[i]) + 1;
+      size_t remaining = end - current;
+      TEST_VERIFY_EXIT (length <= remaining);
+      memcpy (current, config.search[i], length);
+      _res.dnsrch[i] = current;
+      current += length;
+    }
+}
+
+struct resolv_test *
+resolv_test_start (struct resolv_redirect_config config)
+{
+  /* Apply configuration defaults.  */
+  if (config.nscount == 0)
+    config.nscount = resolv_max_test_servers;
+
+  struct resolv_test *obj = xmalloc (sizeof (*obj));
+  *obj = (struct resolv_test) {
+    .config = config,
+    .lock = PTHREAD_MUTEX_INITIALIZER,
+  };
+
+  resolv_test_init ();
+
+  /* Create all the servers, to reserve the necessary ports.  */
+  for (int server_index = 0; server_index < config.nscount; ++server_index)
+    make_server_sockets (obj->servers + server_index);
+
+  /* Start server threads.  Disable the server ports, as
+     requested.  */
+  for (int server_index = 0; server_index < config.nscount; ++server_index)
+    {
+      struct resolv_test_server *server = obj->servers + server_index;
+      if (config.servers[server_index].disable_udp)
+        {
+          xclose (server->socket_udp);
+          server->socket_udp = -1;
+        }
+      else if (!config.single_thread_udp)
+        server->thread_udp = start_server_thread (obj, server_index,
+                                                  server_thread_udp);
+      if (config.servers[server_index].disable_tcp)
+        {
+          xclose (server->socket_tcp);
+          server->socket_tcp = -1;
+        }
+      else
+        server->thread_tcp = start_server_thread (obj, server_index,
+                                                  server_thread_tcp);
+    }
+  if (config.single_thread_udp)
+    start_server_thread_udp_single (obj);
+
+  int timeout = 1;
+
+  /* Initialize libresolv.  */
+  TEST_VERIFY_EXIT (res_init () == 0);
+
+  /* Disable IPv6 name server addresses.  The code below only
+     overrides the IPv4 addresses.  */
+  __res_iclose (&_res, true);
+  _res._u._ext.nscount = 0;
+
+  /* Redirect queries to the server socket.  */
+  if (test_verbose)
+    {
+      printf ("info: old timeout value: %d\n", _res.retrans);
+      printf ("info: old retry attempt value: %d\n", _res.retry);
+      printf ("info: old _res.options: 0x%lx\n", _res.options);
+      printf ("info: old _res.nscount value: %d\n", _res.nscount);
+      printf ("info: old _res.ndots value: %d\n", _res.ndots);
+    }
+  _res.retrans = timeout;
+  _res.retry = 4;
+  _res.nscount = config.nscount;
+  _res.options = RES_INIT | RES_RECURSE | RES_DEFNAMES | RES_DNSRCH;
+  _res.ndots = 1;
+  if (test_verbose)
+    {
+      printf ("info: new timeout value: %d\n", _res.retrans);
+      printf ("info: new retry attempt value: %d\n", _res.retry);
+      printf ("info: new _res.options: 0x%lx\n", _res.options);
+      printf ("info: new _res.nscount value: %d\n", _res.nscount);
+      printf ("info: new _res.ndots value: %d\n", _res.ndots);
+    }
+  for (int server_index = 0; server_index < config.nscount; ++server_index)
+    {
+      _res.nsaddr_list[server_index] = obj->servers[server_index].address;
+      if (test_verbose)
+        {
+          char buf[256];
+          TEST_VERIFY_EXIT
+            (inet_ntop (AF_INET, &obj->servers[server_index].address.sin_addr,
+                        buf, sizeof (buf)) != NULL);
+          printf ("info: server %d: %s/%u\n",
+                  server_index, buf,
+                  htons (obj->servers[server_index].address.sin_port));
+        }
+    }
+
+  set_search_path (config);
+
+  return obj;
+}
+
+void
+resolv_test_end (struct resolv_test *obj)
+{
+  res_close ();
+
+  xpthread_mutex_lock (&obj->lock);
+  obj->termination_requested = true;
+  xpthread_mutex_unlock (&obj->lock);
+
+  /* Send trigger packets to unblock the server threads.  */
+  for (int server_index = 0; server_index < obj->config.nscount;
+       ++server_index)
+    {
+      if (!obj->config.servers[server_index].disable_udp)
+        {
+          int sock = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+          xsendto (sock, "", 1, 0,
+                   (struct sockaddr *) &obj->servers[server_index].address,
+                   sizeof (obj->servers[server_index].address));
+          xclose (sock);
+        }
+      if (!obj->config.servers[server_index].disable_tcp)
+        {
+          int sock = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
+          xconnect (sock,
+                    (struct sockaddr *) &obj->servers[server_index].address,
+                    sizeof (obj->servers[server_index].address));
+          xclose (sock);
+        }
+    }
+
+  if (obj->config.single_thread_udp)
+    xpthread_join (obj->thread_udp_single);
+
+  /* Wait for the server threads to terminate.  */
+  for (int server_index = 0; server_index < obj->config.nscount;
+       ++server_index)
+    {
+      if (!obj->config.servers[server_index].disable_udp)
+        {
+          if (!obj->config.single_thread_udp)
+            xpthread_join (obj->servers[server_index].thread_udp);
+          xclose (obj->servers[server_index].socket_udp);
+        }
+      if (!obj->config.servers[server_index].disable_tcp)
+        {
+          xpthread_join (obj->servers[server_index].thread_tcp);
+          xclose (obj->servers[server_index].socket_tcp);
+        }
+    }
+
+  free (obj);
+}
diff --git a/support/resolv_test.h b/support/resolv_test.h
new file mode 100644
index 0000000..6498751
--- /dev/null
+++ b/support/resolv_test.h
@@ -0,0 +1,180 @@
+/* DNS test framework and libresolv redirection.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_RESOLV_TEST_H
+#define SUPPORT_RESOLV_TEST_H
+
+#include <arpa/nameser.h>
+#include <stdbool.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Information about EDNS properties of a DNS query.  */
+struct resolv_edns_info
+{
+  bool active;
+  uint8_t extended_rcode;
+  uint8_t version;
+  uint16_t flags;
+  uint16_t payload_size;
+};
+
+/* This struct provides context information when the response callback
+   specified in struct resolv_redirect_config is invoked. */
+struct resolv_response_context
+{
+  const unsigned char *query_buffer;
+  size_t query_length;
+  int server_index;
+  bool tcp;
+  struct resolv_edns_info edns;
+};
+
+/* This opaque struct is used to construct responses from within the
+   response callback function.  */
+struct resolv_response_builder;
+
+/* This opaque struct collects information about the resolver testing
+   currently in progress.  */
+struct resolv_test;
+
+enum
+  {
+    /* Maximum number of test servers supported by the framework.  */
+    resolv_max_test_servers = 3,
+  };
+
+/* Configuration settings specific to individual test servers.  */
+struct resolv_redirect_server_config
+{
+  bool disable_tcp;             /* If true, no TCP server is listening.  */
+  bool disable_udp;             /* If true, no UDP server is listening.  */
+};
+
+/* Instructions for setting up the libresolv redirection.  */
+struct resolv_redirect_config
+{
+  /* The response_callback function is called for every incoming DNS
+     packet, over UDP or TCP.  It must be specified, the other
+     configuration settings are optional.  */
+  void (*response_callback) (const struct resolv_response_context *,
+                             struct resolv_response_builder *,
+                             const char *qname,
+                             uint16_t qclass, uint16_t qtype);
+
+  /* Per-server configuration.  */
+  struct resolv_redirect_server_config servers[resolv_max_test_servers];
+
+  /* Search path entries.  The first entry serves as the default
+     domain name as well.  */
+  const char *search[7];
+
+  /* Number of servers to activate in resolv.  0 means the default,
+     resolv_max_test_servers.  */
+  int nscount;
+
+  /* If true, use a single thread to process all UDP queries.  This
+     may results in more predictable ordering of queries and
+     responses.  */
+  bool single_thread_udp;
+};
+
+/* Configure NSS to use, nss_dns only for aplicable databases, and try
+   to put the process into a network namespace for better isolation.
+   This may have to be called before resolv_test_start, before the
+   process creates any threads.  Otherwise, initialization is
+   performed by resolv_test_start implicitly.  */
+void resolv_test_init (void);
+
+/* Initiate resolver testing.  This updates the _res variable as
+   needed.  As a side effect, NSS is reconfigured to use nss_dns only
+   for aplicable databases, and the process may enter a network
+   namespace for better isolation.  */
+struct resolv_test *resolv_test_start (struct resolv_redirect_config);
+
+/* Call this function at the end of resolver testing, to free
+   resources and report pending errors (if any).  */
+void resolv_test_end (struct resolv_test *);
+
+/* The remaining facilities in this file are used for constructing
+   response packets from the response_callback function.  */
+
+/* Special settings for constructing responses from the callback.  */
+struct resolv_response_flags
+{
+  /* 4-bit response code to incorporate into the response. */
+  unsigned char rcode;
+
+  /* If true, the TC (truncation) flag will be set.  */
+  bool tc;
+
+  /* Initial section count values.  Can be used to artificially
+     increase the counts, for malformed packet testing.*/
+  unsigned short qdcount;
+  unsigned short ancount;
+  unsigned short nscount;
+  unsigned short adcount;
+};
+
+/* Begin a new response with the requested flags.  Must be called
+   first.  */
+void resolv_response_init (struct resolv_response_builder *,
+                           struct resolv_response_flags);
+
+/* Switches to the section in the response packet.  Only forward
+   movement is supported.  */
+void resolv_response_section (struct resolv_response_builder *, ns_sect);
+
+/* Add a question record to the question section.  */
+void resolv_response_add_question (struct resolv_response_builder *,
+                                   const char *name, uint16_t class,
+                                   uint16_t type);
+/* Starts a new resource record with the specified owner name, class,
+   type, and TTL.  Data is supplied with resolv_response_add_data or
+   resolv_response_add_name.  */
+void resolv_response_open_record (struct resolv_response_builder *,
+                                  const char *name, uint16_t class,
+                                  uint16_t type, uint32_t ttl);
+
+/* Add unstructed bytes to the RDATA part of a resource record.  */
+void resolv_response_add_data (struct resolv_response_builder *,
+                               const void *, size_t);
+
+/* Add a compressed domain name to the RDATA part of a resource
+   record.  */
+void resolv_response_add_name (struct resolv_response_builder *,
+                               const char *name);
+
+/* Mark the end of the constructed record.  Must be called last.  */
+void resolv_response_close_record (struct resolv_response_builder *);
+
+/* Drop this query packet (that is, do not send a response, not even
+   an empty packet).  */
+void resolv_response_drop (struct resolv_response_builder *);
+
+/* In TCP mode, close the connection after this packet (if a response
+   is sent).  */
+void resolv_response_close (struct resolv_response_builder *);
+
+/* The size of the response packet built so far.  */
+size_t resolv_response_length (const struct resolv_response_builder *);
+
+__END_DECLS
+
+#endif /* SUPPORT_RESOLV_TEST_H */
diff --git a/support/run_diff.h b/support/run_diff.h
new file mode 100644
index 0000000..f65b5dd
--- /dev/null
+++ b/support/run_diff.h
@@ -0,0 +1,31 @@
+/* Invoke the system diff tool to compare two strings.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_RUN_DIFF_H
+#define SUPPORT_RUN_DIFF_H
+
+/* Compare the two NUL-terminated strings LEFT and RIGHT using the
+   diff tool.  Label the sides of the diff with LEFT_LABEL and
+   RIGHT_LABEL, respectively.
+
+   This function assumes that LEFT and RIGHT are different
+   strings.  */
+void support_run_diff (const char *left_label, const char *left,
+                       const char *right_label, const char *right);
+
+#endif /* SUPPORT_RUN_DIFF_H */
diff --git a/support/set_fortify_handler.c b/support/set_fortify_handler.c
new file mode 100644
index 0000000..f434a80
--- /dev/null
+++ b/support/set_fortify_handler.c
@@ -0,0 +1,34 @@
+/* Set signal handler for use in fortify tests.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <signal.h>
+
+void
+set_fortify_handler (void (*handler) (int sig))
+{
+  struct sigaction sa;
+
+  sa.sa_handler = handler;
+  sa.sa_flags = 0;
+  sigemptyset (&sa.sa_mask);
+
+  sigaction (SIGABRT, &sa, NULL);
+  ignore_stderr ();
+}
diff --git a/support/support-xstat.c b/support/support-xstat.c
new file mode 100644
index 0000000..86a81ec
--- /dev/null
+++ b/support/support-xstat.c
@@ -0,0 +1,30 @@
+/* stat64 with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* NB: Non-standard file name to avoid sysdeps override for xstat.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/stat.h>
+
+void
+xstat (const char *path, struct stat64 *result)
+{
+  if (stat64 (path, result) != 0)
+    FAIL_EXIT1 ("stat64 (\"%s\"): %m", path);
+}
diff --git a/support/support.h b/support/support.h
new file mode 100644
index 0000000..4b5f04c
--- /dev/null
+++ b/support/support.h
@@ -0,0 +1,74 @@
+/* Common extra functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* This header file should only contain definitions compatible with
+   C90.  (Using __attribute__ is fine because <features.h> provides a
+   fallback.)  */
+
+#ifndef SUPPORT_H
+#define SUPPORT_H
+
+#include <stddef.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Write a message to standard output.  Can be used in signal
+   handlers.  */
+void write_message (const char *message) __attribute__ ((nonnull (1)));
+
+/* Avoid all the buffer overflow messages on stderr.  */
+void ignore_stderr (void);
+
+/* Set fortification error handler.  Used when tests want to verify that bad
+   code is caught by the library.  */
+void set_fortify_handler (void (*handler) (int sig));
+
+/* Report an out-of-memory error for the allocation of SIZE bytes in
+   FUNCTION, terminating the process.  */
+void oom_error (const char *function, size_t size)
+  __attribute__ ((nonnull (1)));
+
+/* Return a pointer to a memory region of SIZE bytes.  The memory is
+   initialized to zero and will be shared with subprocesses (across
+   fork).  The returned pointer must be freed using
+   support_shared_free; it is not compatible with the malloc
+   functions.  */
+void *support_shared_allocate (size_t size);
+
+/* Deallocate a pointer returned by support_shared_allocate.  */
+void support_shared_free (void *);
+
+/* Write CONTENTS to the file PATH.  Create or truncate the file as
+   needed.  The file mode is 0666 masked by the umask.  Terminate the
+   process on error.  */
+void support_write_file_string (const char *path, const char *contents);
+
+/* Error-checking wrapper functions which terminate the process on
+   error.  */
+
+void *xmalloc (size_t) __attribute__ ((malloc));
+void *xcalloc (size_t n, size_t s) __attribute__ ((malloc));
+void *xrealloc (void *p, size_t n);
+char *xasprintf (const char *format, ...)
+  __attribute__ ((format (printf, 1, 2), malloc));
+char *xstrdup (const char *);
+
+__END_DECLS
+
+#endif /* SUPPORT_H */
diff --git a/support/support_become_root.c b/support/support_become_root.c
new file mode 100644
index 0000000..3fa0bd4
--- /dev/null
+++ b/support/support_become_root.c
@@ -0,0 +1,40 @@
+/* Acquire root privileges.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/namespace.h>
+
+#include <sched.h>
+#include <stdio.h>
+#include <unistd.h>
+
+bool
+support_become_root (void)
+{
+#ifdef CLONE_NEWUSER
+  if (unshare (CLONE_NEWUSER | CLONE_NEWNS) == 0)
+    /* Even if we do not have UID zero, we have extended privileges at
+       this point.  */
+    return true;
+#endif
+  if (setuid (0) != 0)
+    {
+      printf ("warning: could not become root outside namespace (%m)\n");
+      return false;
+    }
+  return true;
+}
diff --git a/support/support_can_chroot.c b/support/support_can_chroot.c
new file mode 100644
index 0000000..0dfd2de
--- /dev/null
+++ b/support/support_can_chroot.c
@@ -0,0 +1,65 @@
+/* Return true if the process can perform a chroot operation.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/support.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <xunistd.h>
+
+static void
+callback (void *closure)
+{
+  int *result = closure;
+  struct stat64 before;
+  xstat ("/dev", &before);
+  if (chroot ("/dev") != 0)
+    {
+      *result = errno;
+      return;
+    }
+  struct stat64 after;
+  xstat ("/", &after);
+  TEST_VERIFY (before.st_dev == after.st_dev);
+  TEST_VERIFY (before.st_ino == after.st_ino);
+  *result = 0;
+}
+
+bool
+support_can_chroot (void)
+{
+  int *result = support_shared_allocate (sizeof (*result));
+  *result = 0;
+  support_isolate_in_subprocess (callback, result);
+  bool ok = *result == 0;
+  if (!ok)
+    {
+      static bool already_warned;
+      if (!already_warned)
+        {
+          already_warned = true;
+          errno = *result;
+          printf ("warning: this process does not support chroot: %m\n");
+        }
+    }
+  support_shared_free (result);
+  return ok;
+}
diff --git a/support/support_capture_subprocess.c b/support/support_capture_subprocess.c
new file mode 100644
index 0000000..030f124
--- /dev/null
+++ b/support/support_capture_subprocess.c
@@ -0,0 +1,108 @@
+/* Capture output from a subprocess.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/capture_subprocess.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <support/xsocket.h>
+
+static void
+transfer (const char *what, struct pollfd *pfd, struct xmemstream *stream)
+{
+  if (pfd->revents != 0)
+    {
+      char buf[1024];
+      ssize_t ret = TEMP_FAILURE_RETRY (read (pfd->fd, buf, sizeof (buf)));
+      if (ret < 0)
+        {
+          support_record_failure ();
+          printf ("error: reading from subprocess %s: %m", what);
+          pfd->events = 0;
+          pfd->revents = 0;
+        }
+      else if (ret == 0)
+        {
+          /* EOF reached.  Stop listening.  */
+          pfd->events = 0;
+          pfd->revents = 0;
+        }
+      else
+        /* Store the data just read.   */
+        TEST_VERIFY (fwrite (buf, ret, 1, stream->out) == 1);
+    }
+}
+
+struct support_capture_subprocess
+support_capture_subprocess (void (*callback) (void *), void *closure)
+{
+  struct support_capture_subprocess result;
+  xopen_memstream (&result.out);
+  xopen_memstream (&result.err);
+
+  int stdout_pipe[2];
+  xpipe (stdout_pipe);
+  int stderr_pipe[2];
+  xpipe (stderr_pipe);
+
+  TEST_VERIFY (fflush (stdout) == 0);
+  TEST_VERIFY (fflush (stderr) == 0);
+
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      xclose (stdout_pipe[0]);
+      xclose (stderr_pipe[0]);
+      xdup2 (stdout_pipe[1], STDOUT_FILENO);
+      xdup2 (stderr_pipe[1], STDERR_FILENO);
+      callback (closure);
+      _exit (0);
+    }
+  xclose (stdout_pipe[1]);
+  xclose (stderr_pipe[1]);
+
+  struct pollfd fds[2] =
+    {
+      { .fd = stdout_pipe[0], .events = POLLIN },
+      { .fd = stderr_pipe[0], .events = POLLIN },
+    };
+
+  do
+    {
+      xpoll (fds, 2, -1);
+      transfer ("stdout", &fds[0], &result.out);
+      transfer ("stderr", &fds[1], &result.err);
+    }
+  while (fds[0].events != 0 || fds[1].events != 0);
+  xclose (stdout_pipe[0]);
+  xclose (stderr_pipe[0]);
+
+  xfclose_memstream (&result.out);
+  xfclose_memstream (&result.err);
+  xwaitpid (pid, &result.status, 0);
+  return result;
+}
+
+void
+support_capture_subprocess_free (struct support_capture_subprocess *p)
+{
+  free (p->out.buffer);
+  free (p->err.buffer);
+}
diff --git a/support/support_capture_subprocess_check.c b/support/support_capture_subprocess_check.c
new file mode 100644
index 0000000..708c89f
--- /dev/null
+++ b/support/support_capture_subprocess_check.c
@@ -0,0 +1,67 @@
+/* Verify capture output from a subprocess.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+
+static void
+print_context (const char *context, bool *failed)
+{
+  if (*failed)
+    /* Do not duplicate message.  */
+    return;
+  support_record_failure ();
+  printf ("error: subprocess failed: %s\n", context);
+}
+
+void
+support_capture_subprocess_check (struct support_capture_subprocess *proc,
+                                  const char *context, int status,
+                                  int allowed)
+{
+  TEST_VERIFY ((allowed & sc_allow_none)
+               || (allowed & sc_allow_stdout)
+               || (allowed & sc_allow_stderr));
+  TEST_VERIFY (!((allowed & sc_allow_none)
+                 && ((allowed & sc_allow_stdout)
+                     || (allowed & sc_allow_stderr))));
+
+  bool failed = false;
+  if (proc->status != status)
+    {
+      print_context (context, &failed);
+      printf ("error:   expected exit status: %d\n", status);
+      printf ("error:   actual exit status:   %d\n", status);
+    }
+  if (!(allowed & sc_allow_stdout) && proc->out.length != 0)
+    {
+      print_context (context, &failed);
+      printf ("error:   unexpected output from subprocess\n");
+      fwrite (proc->out.buffer, proc->out.length, 1, stdout);
+      puts ("\n");
+    }
+  if (!(allowed & sc_allow_stderr) && proc->err.length != 0)
+    {
+      print_context (context, &failed);
+      printf ("error:   unexpected error output from subprocess\n");
+      fwrite (proc->err.buffer, proc->err.length, 1, stdout);
+      puts ("\n");
+    }
+}
diff --git a/support/support_enter_network_namespace.c b/support/support_enter_network_namespace.c
new file mode 100644
index 0000000..28b0ee2
--- /dev/null
+++ b/support/support_enter_network_namespace.c
@@ -0,0 +1,75 @@
+/* Enter a network namespace.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/namespace.h>
+
+#include <net/if.h>
+#include <sched.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+static bool in_uts_namespace;
+
+bool
+support_enter_network_namespace (void)
+{
+#ifdef CLONE_NEWUTS
+  if (unshare (CLONE_NEWUTS) == 0)
+    in_uts_namespace = true;
+  else
+    printf ("warning: unshare (CLONE_NEWUTS) failed: %m\n");
+#endif
+
+#ifdef CLONE_NEWNET
+  if (unshare (CLONE_NEWNET) == 0)
+    {
+      /* Bring up the loopback interface.  */
+      int fd = xsocket (AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+      struct ifreq req;
+      strcpy (req.ifr_name, "lo");
+      TEST_VERIFY_EXIT (ioctl (fd, SIOCGIFFLAGS, &req) == 0);
+      bool already_up = req.ifr_flags & IFF_UP;
+      if (already_up)
+        /* This means that we likely have not achieved isolation from
+           the parent namespace.  */
+        printf ("warning: loopback interface already exists"
+                " in new network namespace\n");
+      else
+        {
+          req.ifr_flags |= IFF_UP | IFF_RUNNING;
+          TEST_VERIFY_EXIT (ioctl (fd, SIOCSIFFLAGS, &req) == 0);
+        }
+      xclose (fd);
+
+      return !already_up;
+    }
+#endif
+  printf ("warning: could not enter network namespace\n");
+  return false;
+}
+
+bool
+support_in_uts_namespace (void)
+{
+  return in_uts_namespace;
+}
diff --git a/support/support_format_address_family.c b/support/support_format_address_family.c
new file mode 100644
index 0000000..5d42c42
--- /dev/null
+++ b/support/support_format_address_family.c
@@ -0,0 +1,35 @@
+/* Convert an address family to a string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <support/support.h>
+
+char *
+support_format_address_family (int family)
+{
+  switch (family)
+    {
+    case AF_INET:
+      return xstrdup ("INET");
+    case AF_INET6:
+      return xstrdup ("INET6");
+    default:
+      return xasprintf ("<unknown address family %d>", family);
+    }
+}
diff --git a/support/support_format_addrinfo.c b/support/support_format_addrinfo.c
new file mode 100644
index 0000000..eedb030
--- /dev/null
+++ b/support/support_format_addrinfo.c
@@ -0,0 +1,239 @@
+/* Convert struct addrinfo values to a string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <stdio.h>
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+static size_t
+socket_address_length (int family)
+{
+  switch (family)
+    {
+    case AF_INET:
+      return sizeof (struct sockaddr_in);
+    case AF_INET6:
+      return sizeof (struct sockaddr_in6);
+    default:
+      return -1;
+    }
+}
+
+static void
+format_ai_flags_1 (FILE *out, struct addrinfo *ai, int flag, const char *name,
+                   int * flags_printed)
+{
+  if ((ai->ai_flags & flag) != 0)
+    fprintf (out, " %s", name);
+  *flags_printed |= flag;
+}
+
+static void
+format_ai_flags (FILE *out, struct addrinfo *ai)
+{
+  if (ai == NULL)
+    return;
+
+  if (ai->ai_flags != 0)
+    {
+      fprintf (out, "flags:");
+      int flags_printed = 0;
+#define FLAG(flag) format_ai_flags_1 (out, ai, flag, #flag, &flags_printed)
+      FLAG (AI_PASSIVE);
+      FLAG (AI_CANONNAME);
+      FLAG (AI_NUMERICHOST);
+      FLAG (AI_V4MAPPED);
+      FLAG (AI_ALL);
+      FLAG (AI_ADDRCONFIG);
+      FLAG (AI_IDN);
+      FLAG (AI_CANONIDN);
+      FLAG (AI_IDN_ALLOW_UNASSIGNED);
+      FLAG (AI_IDN_USE_STD3_ASCII_RULES);
+      FLAG (AI_NUMERICSERV);
+#undef FLAG
+      int remaining = ai->ai_flags & ~flags_printed;
+      if (remaining != 0)
+        fprintf (out, " %08x", remaining);
+      fprintf (out, "\n");
+    }
+
+  /* Report flag mismatches within the list.  */
+  int flags = ai->ai_flags;
+  int index = 1;
+  ai = ai->ai_next;
+  while (ai != NULL)
+    {
+      if (ai->ai_flags != flags)
+        fprintf (out, "error: flags at %d: 0x%x expected, 0x%x actual\n",
+                 index, flags, ai->ai_flags);
+      ai = ai->ai_next;
+      ++index;
+    }
+}
+
+static void
+format_ai_canonname (FILE *out, struct addrinfo *ai)
+{
+  if (ai == NULL)
+    return;
+  if (ai->ai_canonname != NULL)
+    fprintf (out, "canonname: %s\n", ai->ai_canonname);
+
+  /* Report incorrectly set ai_canonname fields on subsequent list
+     entries.  */
+  int index = 1;
+  ai = ai->ai_next;
+  while (ai != NULL)
+    {
+      if (ai->ai_canonname != NULL)
+        fprintf (out, "error: canonname set at %d: %s\n",
+                 index, ai->ai_canonname);
+      ai = ai->ai_next;
+      ++index;
+    }
+}
+
+static void
+format_ai_one (FILE *out, struct addrinfo *ai)
+{
+  {
+    char type_buf[32];
+    const char *type_str;
+    char proto_buf[32];
+    const char *proto_str;
+
+    /* ai_socktype */
+    switch (ai->ai_socktype)
+      {
+      case SOCK_RAW:
+        type_str = "RAW";
+        break;
+      case SOCK_DGRAM:
+        type_str = "DGRAM";
+        break;
+      case SOCK_STREAM:
+        type_str = "STREAM";
+        break;
+      default:
+        snprintf (type_buf, sizeof (type_buf), "%d", ai->ai_socktype);
+        type_str = type_buf;
+      }
+
+    /* ai_protocol */
+    switch (ai->ai_protocol)
+      {
+      case IPPROTO_IP:
+        proto_str = "IP";
+        break;
+      case IPPROTO_UDP:
+        proto_str = "UDP";
+        break;
+      case IPPROTO_TCP:
+        proto_str = "TCP";
+        break;
+      default:
+        snprintf (proto_buf, sizeof (proto_buf), "%d", ai->ai_protocol);
+        proto_str = proto_buf;
+      }
+    fprintf (out, "address: %s/%s", type_str, proto_str);
+  }
+
+  /* ai_addrlen */
+  if (ai->ai_addrlen != socket_address_length (ai->ai_family))
+    {
+      char *family = support_format_address_family (ai->ai_family);
+      fprintf (out, "error: invalid address length %d for %s\n",
+               ai->ai_addrlen, family);
+      free (family);
+    }
+
+  /* ai_addr */
+  {
+    char buf[128];
+    uint16_t port;
+    const char *ret;
+    switch (ai->ai_family)
+      {
+      case AF_INET:
+        {
+          struct sockaddr_in *sin = (struct sockaddr_in *) ai->ai_addr;
+          ret = inet_ntop (AF_INET, &sin->sin_addr, buf, sizeof (buf));
+          port = sin->sin_port;
+        }
+        break;
+      case AF_INET6:
+        {
+          struct sockaddr_in6 *sin = (struct sockaddr_in6 *) ai->ai_addr;
+          ret = inet_ntop (AF_INET6, &sin->sin6_addr, buf, sizeof (buf));
+          port = sin->sin6_port;
+        }
+        break;
+      default:
+        errno = EAFNOSUPPORT;
+        ret = NULL;
+      }
+    if (ret == NULL)
+        fprintf (out, "error: inet_top failed: %m\n");
+    else
+      fprintf (out, " %s %u\n", buf, ntohs (port));
+  }
+}
+
+/* Format all the addresses in one address family.  */
+static void
+format_ai_family (FILE *out, struct addrinfo *ai, int family)
+{
+  while (ai)
+    {
+      if (ai->ai_family == family)
+        format_ai_one (out, ai);
+      ai = ai->ai_next;
+    }
+}
+
+char *
+support_format_addrinfo (struct addrinfo *ai, int ret)
+{
+  int errno_copy = errno;
+
+  struct xmemstream mem;
+  xopen_memstream (&mem);
+  if (ret != 0)
+    {
+      fprintf (mem.out, "error: %s\n", gai_strerror (ret));
+      if (ret == EAI_SYSTEM)
+        {
+          errno = errno_copy;
+          fprintf (mem.out, "error: %m\n");
+        }
+    }
+  else
+    {
+      format_ai_flags (mem.out, ai);
+      format_ai_canonname (mem.out, ai);
+      format_ai_family (mem.out, ai, AF_INET);
+      format_ai_family (mem.out, ai, AF_INET6);
+    }
+
+  xfclose_memstream (&mem);
+  return mem.buffer;
+}
diff --git a/support/support_format_dns_packet.c b/support/support_format_dns_packet.c
new file mode 100644
index 0000000..2992c57
--- /dev/null
+++ b/support/support_format_dns_packet.c
@@ -0,0 +1,222 @@
+/* Convert a DNS packet to a human-readable representation.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <arpa/inet.h>
+#include <resolv.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+struct in_buffer
+{
+  const unsigned char *data;
+  size_t size;
+};
+
+static inline bool
+extract_8 (struct in_buffer *in, unsigned char *value)
+{
+  if (in->size == 0)
+    return false;
+  *value = in->data[0];
+  ++in->data;
+  --in->size;
+  return true;
+}
+
+static inline bool
+extract_16 (struct in_buffer *in, unsigned short *value)
+{
+  if (in->size < 2)
+    return false;
+  *value = (in->data[0] << 8) | in->data[1];
+  in->data += 2;
+  in->size -= 2;
+  return true;
+}
+
+static inline bool
+extract_32 (struct in_buffer *in, unsigned *value)
+{
+  if (in->size < 4)
+    return false;
+  unsigned a = in->data[0];
+  unsigned b = in->data[1];
+  unsigned c = in->data[2];
+  unsigned d = in->data[3];
+  *value = (a << 24) | (b << 16) | (c << 8) | d;
+  in->data += 4;
+  in->size -= 4;
+  return true;
+}
+
+static inline bool
+extract_bytes (struct in_buffer *in, size_t length, struct in_buffer *value)
+{
+  if (in->size < length)
+    return false;
+  *value = (struct in_buffer) {in->data, length};
+  in->data += length;
+  in->size -= length;
+  return true;
+}
+
+struct dname
+{
+  char name[MAXDNAME + 1];
+};
+
+static bool
+extract_name (struct in_buffer full, struct in_buffer *in, struct dname *value)
+{
+  const unsigned char *full_end = full.data + full.size;
+  /* Sanity checks; these indicate buffer misuse.  */
+  TEST_VERIFY_EXIT
+    (!(in->data < full.data || in->data > full_end
+       || in->size > (size_t) (full_end - in->data)));
+  int ret = dn_expand (full.data, full_end, in->data,
+                       value->name, sizeof (value->name));
+  if (ret < 0)
+    return false;
+  in->data += ret;
+  in->size -= ret;
+  return true;
+}
+
+char *
+support_format_dns_packet (const unsigned char *buffer, size_t length)
+{
+  struct in_buffer full = { buffer, length };
+  struct in_buffer in = full;
+  struct xmemstream mem;
+  xopen_memstream (&mem);
+
+  unsigned short txnid;
+  unsigned short flags;
+  unsigned short qdcount;
+  unsigned short ancount;
+  unsigned short nscount;
+  unsigned short adcount;
+  if (!(extract_16 (&in, &txnid)
+        && extract_16 (&in, &flags)
+        && extract_16 (&in, &qdcount)
+        && extract_16 (&in, &ancount)
+        && extract_16 (&in, &nscount)
+        && extract_16 (&in, &adcount)))
+    {
+      fprintf (mem.out, "error: could not parse DNS header\n");
+      goto out;
+    }
+  if (qdcount != 1)
+    {
+      fprintf (mem.out, "error: question count is %d, not 1\n", qdcount);
+      goto out;
+    }
+  struct dname qname;
+  if (!extract_name (full, &in, &qname))
+    {
+      fprintf (mem.out, "error: malformed QNAME\n");
+      goto out;
+    }
+  unsigned short qtype;
+  unsigned short qclass;
+  if (!(extract_16 (&in, &qtype)
+        && extract_16 (&in, &qclass)))
+    {
+      fprintf (mem.out, "error: malformed question\n");
+      goto out;
+    }
+  if (qtype != T_A && qtype != T_AAAA && qtype != T_PTR)
+    {
+      fprintf (mem.out, "error: unsupported QTYPE %d\n", qtype);
+      goto out;
+    }
+
+  fprintf (mem.out, "name: %s\n", qname.name);
+
+  for (int i = 0; i < ancount; ++i)
+    {
+      struct dname rname;
+      if (!extract_name (full, &in, &rname))
+        {
+          fprintf (mem.out, "error: malformed record name\n");
+          goto out;
+        }
+      unsigned short rtype;
+      unsigned short rclass;
+      unsigned ttl;
+      unsigned short rdlen;
+      struct in_buffer rdata;
+      if (!(extract_16 (&in, &rtype)
+            && extract_16 (&in, &rclass)
+            && extract_32 (&in, &ttl)
+            && extract_16 (&in, &rdlen)
+            && extract_bytes (&in, rdlen, &rdata)))
+        {
+          fprintf (mem.out, "error: malformed record header\n");
+          goto out;
+        }
+      /* Skip non-matching record types.  */
+      if ((rtype != qtype && rtype != T_CNAME) || rclass != qclass)
+        continue;
+      switch (rtype)
+        {
+        case T_A:
+          if (rdlen == 4)
+              fprintf (mem.out, "address: %d.%d.%d.%d\n",
+                       rdata.data[0],
+                       rdata.data[1],
+                       rdata.data[2],
+                       rdata.data[3]);
+          else
+            fprintf (mem.out, "error: A record of size %d: %s\n",
+                     rdlen, rname.name);
+          break;
+        case T_AAAA:
+          {
+            if (rdlen == 16)
+              {
+                char buf[100];
+                if (inet_ntop (AF_INET6, rdata.data, buf, sizeof (buf)) == NULL)
+                  fprintf (mem.out, "error: AAAA record decoding failed: %m\n");
+                else
+                  fprintf (mem.out, "address: %s\n", buf);
+              }
+            else
+              fprintf (mem.out, "error: AAAA record of size %d: %s\n",
+                       rdlen, rname.name);
+          }
+          break;
+        case T_CNAME:
+        case T_PTR:
+          {
+            struct dname name;
+            if (extract_name (full, &rdata, &name))
+              fprintf (mem.out, "name: %s\n", name.name);
+            else
+              fprintf (mem.out, "error: malformed CNAME/PTR record\n");
+          }
+        }
+    }
+
+ out:
+  xfclose_memstream (&mem);
+  return mem.buffer;
+}
diff --git a/support/support_format_herrno.c b/support/support_format_herrno.c
new file mode 100644
index 0000000..493d6ae
--- /dev/null
+++ b/support/support_format_herrno.c
@@ -0,0 +1,45 @@
+/* Convert a h_errno error code to a string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <support/support.h>
+
+char *
+support_format_herrno (int code)
+{
+  const char *errstr;
+  switch (code)
+    {
+    case HOST_NOT_FOUND:
+      errstr = "HOST_NOT_FOUND";
+      break;
+    case NO_ADDRESS:
+      errstr = "NO_ADDRESS";
+      break;
+    case NO_RECOVERY:
+      errstr = "NO_RECOVERY";
+      break;
+    case TRY_AGAIN:
+      errstr = "TRY_AGAIN";
+      break;
+    default:
+      return xasprintf ("<invalid h_errno value %d>\n", code);
+    }
+  return xstrdup (errstr);
+}
diff --git a/support/support_format_hostent.c b/support/support_format_hostent.c
new file mode 100644
index 0000000..5b5f260
--- /dev/null
+++ b/support/support_format_hostent.c
@@ -0,0 +1,75 @@
+/* Convert a struct hostent object to a string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+static int
+address_length (int family)
+{
+  switch (family)
+    {
+    case AF_INET:
+      return 4;
+    case AF_INET6:
+      return 16;
+    }
+  return -1;
+}
+
+char *
+support_format_hostent (struct hostent *h)
+{
+  if (h == NULL)
+    {
+      char *value = support_format_herrno (h_errno);
+      char *result = xasprintf ("error: %s\n", value);
+      free (value);
+      return result;
+    }
+
+  struct xmemstream mem;
+  xopen_memstream (&mem);
+
+  fprintf (mem.out, "name: %s\n", h->h_name);
+  for (char **alias = h->h_aliases; *alias != NULL; ++alias)
+    fprintf (mem.out, "alias: %s\n", *alias);
+  for (unsigned i = 0; h->h_addr_list[i] != NULL; ++i)
+    {
+      char buf[128];
+      if (inet_ntop (h->h_addrtype, h->h_addr_list[i],
+                     buf, sizeof (buf)) == NULL)
+        fprintf (mem.out, "error: inet_ntop failed: %m\n");
+      else
+        fprintf (mem.out, "address: %s\n", buf);
+    }
+  if (h->h_length != address_length (h->h_addrtype))
+    {
+      char *family = support_format_address_family (h->h_addrtype);
+      fprintf (mem.out, "error: invalid address length %d for %s\n",
+               h->h_length, family);
+      free (family);
+    }
+
+  xfclose_memstream (&mem);
+  return mem.buffer;
+}
diff --git a/support/support_format_netent.c b/support/support_format_netent.c
new file mode 100644
index 0000000..020f572
--- /dev/null
+++ b/support/support_format_netent.c
@@ -0,0 +1,52 @@
+/* Convert a struct netent object to a string.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/format_nss.h>
+
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+char *
+support_format_netent (struct netent *e)
+{
+  if (e == NULL)
+    {
+      char *value = support_format_herrno (h_errno);
+      char *result = xasprintf ("error: %s\n", value);
+      free (value);
+      return result;
+    }
+
+  struct xmemstream mem;
+  xopen_memstream (&mem);
+
+  if (e->n_name != NULL)
+    fprintf (mem.out, "name: %s\n", e->n_name);
+  for (char **ap = e->n_aliases; *ap != NULL; ++ap)
+    fprintf (mem.out, "alias: %s\n", *ap);
+  if (e->n_addrtype != AF_INET)
+    fprintf (mem.out, "addrtype: %d\n", e->n_addrtype);
+  /* On alpha, e->n_net is an unsigned long.  */
+  unsigned int n_net = e->n_net;
+  fprintf (mem.out, "net: 0x%08x\n", n_net);
+
+  xfclose_memstream (&mem);
+  return mem.buffer;
+}
diff --git a/support/support_isolate_in_subprocess.c b/support/support_isolate_in_subprocess.c
new file mode 100644
index 0000000..cf48614
--- /dev/null
+++ b/support/support_isolate_in_subprocess.c
@@ -0,0 +1,38 @@
+/* Run a function in a subprocess.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+
+void
+support_isolate_in_subprocess (void (*callback) (void *), void *closure)
+{
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      /* Child process.  */
+      callback (closure);
+      _exit (0);
+    }
+
+  /* Parent process.  */
+  int status;
+  xwaitpid (pid, &status, 0);
+  if (status != 0)
+    FAIL_EXIT1 ("child process exited with status %d", status);
+}
diff --git a/support/support_record_failure.c b/support/support_record_failure.c
new file mode 100644
index 0000000..684055c
--- /dev/null
+++ b/support/support_record_failure.c
@@ -0,0 +1,106 @@
+/* Global test failure counter.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+/* This structure keeps track of test failures.  The counter is
+   incremented on each failure.  The failed member is set to true if a
+   failure is detected, so that even if the counter wraps around to
+   zero, the failure of a test can be detected.
+
+   The init constructor function below puts *state on a shared
+   annonymous mapping, so that failure reports from subprocesses
+   propagate to the parent process.  */
+struct test_failures
+{
+  unsigned int counter;
+  unsigned int failed;
+};
+static struct test_failures *state;
+
+static __attribute__ ((constructor)) void
+init (void)
+{
+  void *ptr = mmap (NULL, sizeof (*state), PROT_READ | PROT_WRITE,
+                    MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+  if (ptr == MAP_FAILED)
+    {
+      printf ("error: could not map %zu bytes: %m\n", sizeof (*state));
+      exit (1);
+    }
+  /* Zero-initialization of the struct is sufficient.  */
+  state = ptr;
+}
+
+void
+support_record_failure (void)
+{
+  if (state == NULL)
+    {
+      write_message
+        ("error: support_record_failure called without initialization\n");
+      _exit (1);
+    }
+  /* Relaxed MO is sufficient because we are only interested in the
+     values themselves, in isolation.  */
+  __atomic_store_n (&state->failed, 1, __ATOMIC_RELEASE);
+  __atomic_add_fetch (&state->counter, 1, __ATOMIC_RELEASE);
+}
+
+int
+support_report_failure (int status)
+{
+  if (state == NULL)
+    {
+      write_message
+        ("error: support_report_failure called without initialization\n");
+      return 1;
+    }
+
+  /* Relaxed MO is sufficient because acquire test result reporting
+     assumes that exiting from the main thread happens before the
+     error reporting via support_record_failure, which requires some
+     form of external synchronization.  */
+  bool failed = __atomic_load_n (&state->failed, __ATOMIC_RELAXED);
+  if (failed)
+    printf ("error: %u test failures\n",
+            __atomic_load_n (&state->counter, __ATOMIC_RELAXED));
+
+  if ((status == 0 || status == EXIT_UNSUPPORTED) && failed)
+    /* If we have a recorded failure, it overrides a non-failure
+       report from the test function.  */
+    status = 1;
+  return status;
+}
+
+void
+support_record_failure_reset (void)
+{
+  /* Only used for testing the test framework, with external
+     synchronization, but use release MO for consistency.  */
+  __atomic_store_n (&state->failed, 0, __ATOMIC_RELAXED);
+  __atomic_add_fetch (&state->counter, 0, __ATOMIC_RELAXED);
+}
diff --git a/support/support_run_diff.c b/support/support_run_diff.c
new file mode 100644
index 0000000..f5155de
--- /dev/null
+++ b/support/support_run_diff.c
@@ -0,0 +1,76 @@
+/* Invoke the system diff tool to compare two strings.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/run_diff.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+#include <sys/wait.h>
+
+static char *
+write_to_temp_file (const char *prefix, const char *str)
+{
+  char *template = xasprintf ("run_diff-%s", prefix);
+  char *name = NULL;
+  int fd = create_temp_file (template, &name);
+  TEST_VERIFY_EXIT (fd >= 0);
+  free (template);
+  xwrite (fd, str, strlen (str));
+  xclose (fd);
+  return name;
+}
+
+void
+support_run_diff (const char *left_label, const char *left,
+                  const char *right_label, const char *right)
+{
+  /* Ensure that the diff command output is ordered properly with
+     standard output.  */
+  TEST_VERIFY_EXIT (fflush (stdout) == 0);
+
+  char *left_path = write_to_temp_file ("left-diff", left);
+  char *right_path = write_to_temp_file ("right-diff", right);
+
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      execlp ("diff", "diff", "-u",
+              "--label", left_label, "--label", right_label,
+              "--", left_path, right_path,
+              NULL);
+      _exit (17);
+    }
+  else
+    {
+      int status;
+      xwaitpid (pid, &status, 0);
+      if (!WIFEXITED (status) || WEXITSTATUS (status) != 1)
+        printf ("warning: could not run diff, exit status: %d\n"
+                "*** %s ***\n%s\n"
+                "*** %s ***\n%s\n",
+                status, left_label, left, right_label, right);
+    }
+
+  free (right_path);
+  free (left_path);
+}
diff --git a/support/support_shared_allocate.c b/support/support_shared_allocate.c
new file mode 100644
index 0000000..61d088e
--- /dev/null
+++ b/support/support_shared_allocate.c
@@ -0,0 +1,57 @@
+/* Allocate a memory region shared across processes.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <stddef.h>
+#include <support/support.h>
+#include <support/xunistd.h>
+#include <sys/mman.h>
+
+/* Header for the allocation.  It contains the size of the allocation
+   for subsequent unmapping.  */
+struct header
+{
+  size_t total_size;
+  char data[] __attribute__ ((aligned (__alignof__ (max_align_t))));
+};
+
+void *
+support_shared_allocate (size_t size)
+{
+  size_t total_size = size + offsetof (struct header, data);
+  if (total_size < size)
+    {
+      errno = ENOMEM;
+      oom_error (__func__, size);
+      return NULL;
+    }
+  else
+    {
+      struct header *result = xmmap (NULL, total_size, PROT_READ | PROT_WRITE,
+                                     MAP_ANONYMOUS | MAP_SHARED, -1);
+      result->total_size = total_size;
+      return &result->data;
+    }
+}
+
+void
+support_shared_free (void *data)
+{
+  struct header *header = data - offsetof (struct header, data);
+  xmunmap (header, header->total_size);
+}
diff --git a/support/support_test_main.c b/support/support_test_main.c
new file mode 100644
index 0000000..914d64f
--- /dev/null
+++ b/support/support_test_main.c
@@ -0,0 +1,423 @@
+/* Main worker function for the test driver.
+   Copyright (C) 1998-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/test-driver.h>
+#include <support/check.h>
+#include <support/temp_file-internal.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <getopt.h>
+#include <malloc.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <unistd.h>
+
+static const struct option default_options[] =
+{
+  TEST_DEFAULT_OPTIONS
+  { NULL, 0, NULL, 0 }
+};
+
+/* Show people how to run the program.  */
+static void
+usage (const struct option *options)
+{
+  size_t i;
+
+  printf ("Usage: %s [options]\n"
+          "\n"
+          "Environment Variables:\n"
+          "  TIMEOUTFACTOR          An integer used to scale the timeout\n"
+          "  TMPDIR                 Where to place temporary files\n"
+          "  TEST_COREDUMPS         Do not disable coredumps if set\n"
+          "\n",
+          program_invocation_short_name);
+  printf ("Options:\n");
+  for (i = 0; options[i].name; ++i)
+    {
+      int indent;
+
+      indent = printf ("  --%s", options[i].name);
+      if (options[i].has_arg == required_argument)
+        indent += printf (" <arg>");
+      printf ("%*s", 25 - indent, "");
+      switch (options[i].val)
+        {
+        case 'v':
+          printf ("Increase the output verbosity");
+          break;
+        case OPT_DIRECT:
+          printf ("Run the test directly (instead of forking & monitoring)");
+          break;
+        case OPT_TESTDIR:
+          printf ("Override the TMPDIR env var");
+          break;
+        }
+      printf ("\n");
+    }
+}
+
+/* The PID of the test process.  */
+static pid_t test_pid;
+
+/* The cleanup handler passed to test_main.  */
+static void (*cleanup_function) (void);
+
+/* Timeout handler.  We kill the child and exit with an error.  */
+static void
+__attribute__ ((noreturn))
+signal_handler (int sig)
+{
+  int killed;
+  int status;
+
+  assert (test_pid > 1);
+  /* Kill the whole process group.  */
+  kill (-test_pid, SIGKILL);
+  /* In case setpgid failed in the child, kill it individually too.  */
+  kill (test_pid, SIGKILL);
+
+  /* Wait for it to terminate.  */
+  int i;
+  for (i = 0; i < 5; ++i)
+    {
+      killed = waitpid (test_pid, &status, WNOHANG|WUNTRACED);
+      if (killed != 0)
+        break;
+
+      /* Delay, give the system time to process the kill.  If the
+         nanosleep() call return prematurely, all the better.  We
+         won't restart it since this probably means the child process
+         finally died.  */
+      struct timespec ts;
+      ts.tv_sec = 0;
+      ts.tv_nsec = 100000000;
+      nanosleep (&ts, NULL);
+    }
+  if (killed != 0 && killed != test_pid)
+    {
+      printf ("Failed to kill test process: %m\n");
+      exit (1);
+    }
+
+  if (cleanup_function != NULL)
+    cleanup_function ();
+
+  if (sig == SIGINT)
+    {
+      signal (sig, SIG_DFL);
+      raise (sig);
+    }
+
+  if (killed == 0 || (WIFSIGNALED (status) && WTERMSIG (status) == SIGKILL))
+    puts ("Timed out: killed the child process");
+  else if (WIFSTOPPED (status))
+    printf ("Timed out: the child process was %s\n",
+            strsignal (WSTOPSIG (status)));
+  else if (WIFSIGNALED (status))
+    printf ("Timed out: the child process got signal %s\n",
+            strsignal (WTERMSIG (status)));
+  else
+    printf ("Timed out: killed the child process but it exited %d\n",
+            WEXITSTATUS (status));
+
+  /* Exit with an error.  */
+  exit (1);
+}
+
+/* Run test_function or test_function_argv.  */
+static int
+run_test_function (int argc, char **argv, const struct test_config *config)
+{
+  if (config->test_function != NULL)
+    return config->test_function ();
+  else if (config->test_function_argv != NULL)
+    return config->test_function_argv (argc, argv);
+  else
+    {
+      printf ("error: no test function defined\n");
+      exit (1);
+    }
+}
+
+static bool test_main_called;
+
+const char *test_dir = NULL;
+unsigned int test_verbose = 0;
+
+/* If test failure reporting has been linked in, it may contribute
+   additional test failures.  */
+static int
+adjust_exit_status (int status)
+{
+  if (support_report_failure != NULL)
+    return support_report_failure (status);
+  return status;
+}
+
+int
+support_test_main (int argc, char **argv, const struct test_config *config)
+{
+  if (test_main_called)
+    {
+      printf ("error: test_main called for a second time\n");
+      exit (1);
+    }
+  test_main_called = true;
+  const struct option *options;
+  if (config->options != NULL)
+    options = config->options;
+  else
+    options = default_options;
+
+  cleanup_function = config->cleanup_function;
+
+  int direct = 0;       /* Directly call the test function?  */
+  int status;
+  int opt;
+  unsigned int timeoutfactor = 1;
+  pid_t termpid;
+
+  if (!config->no_mallopt)
+    {
+      /* Make uses of freed and uninitialized memory known.  Do not
+         pull in a definition for mallopt if it has not been defined
+         already.  */
+      extern __typeof__ (mallopt) mallopt __attribute__ ((weak));
+      if (mallopt != NULL)
+        mallopt (M_PERTURB, 42);
+    }
+
+  while ((opt = getopt_long (argc, argv, "+", options, NULL)) != -1)
+    switch (opt)
+      {
+      case '?':
+        usage (options);
+        exit (1);
+      case 'v':
+        ++test_verbose;
+        break;
+      case OPT_DIRECT:
+        direct = 1;
+        break;
+      case OPT_TESTDIR:
+        test_dir = optarg;
+        break;
+      default:
+        if (config->cmdline_function != NULL)
+          config->cmdline_function (opt);
+      }
+
+  /* If set, read the test TIMEOUTFACTOR value from the environment.
+     This value is used to scale the default test timeout values. */
+  char *envstr_timeoutfactor = getenv ("TIMEOUTFACTOR");
+  if (envstr_timeoutfactor != NULL)
+    {
+      char *envstr_conv = envstr_timeoutfactor;
+      unsigned long int env_fact;
+
+      env_fact = strtoul (envstr_timeoutfactor, &envstr_conv, 0);
+      if (*envstr_conv == '\0' && envstr_conv != envstr_timeoutfactor)
+        timeoutfactor = MAX (env_fact, 1);
+    }
+
+  /* Set TMPDIR to specified test directory.  */
+  if (test_dir != NULL)
+    {
+      setenv ("TMPDIR", test_dir, 1);
+
+      if (chdir (test_dir) < 0)
+        {
+          printf ("chdir: %m\n");
+          exit (1);
+        }
+    }
+  else
+    {
+      test_dir = getenv ("TMPDIR");
+      if (test_dir == NULL || test_dir[0] == '\0')
+        test_dir = "/tmp";
+    }
+  if (support_set_test_dir != NULL)
+    support_set_test_dir (test_dir);
+
+  int timeout = config->timeout;
+  if (timeout == 0)
+    timeout =  DEFAULT_TIMEOUT;
+
+  /* Make sure we see all message, even those on stdout.  */
+  setvbuf (stdout, NULL, _IONBF, 0);
+
+  /* Make sure temporary files are deleted.  */
+  if (support_delete_temp_files != NULL)
+      atexit (support_delete_temp_files);
+
+  /* Correct for the possible parameters.  */
+  argv[optind - 1] = argv[0];
+  argv += optind - 1;
+  argc -= optind - 1;
+
+  /* Call the initializing function, if one is available.  */
+  if (config->prepare_function != NULL)
+    config->prepare_function (argc, argv);
+
+  const char *envstr_direct = getenv ("TEST_DIRECT");
+  if (envstr_direct != NULL)
+    {
+      FILE *f = fopen (envstr_direct, "w");
+      if (f == NULL)
+        {
+          printf ("cannot open TEST_DIRECT output file '%s': %m\n",
+                  envstr_direct);
+          exit (1);
+        }
+
+      fprintf (f, "timeout=%u\ntimeoutfactor=%u\n",
+               config->timeout, timeoutfactor);
+      if (config->expected_status != 0)
+        fprintf (f, "exit=%u\n", config->expected_status);
+      if (config->expected_signal != 0)
+        fprintf (f, "signal=%s\n", strsignal (config->expected_signal));
+
+      if (support_print_temp_files != NULL)
+        support_print_temp_files (f);
+
+      fclose (f);
+      direct = 1;
+    }
+
+  bool disable_coredumps;
+  {
+    const char *coredumps = getenv ("TEST_COREDUMPS");
+    disable_coredumps = coredumps == NULL || coredumps[0] == '\0';
+  }
+
+  /* If we are not expected to fork run the function immediately.  */
+  if (direct)
+    return adjust_exit_status (run_test_function (argc, argv, config));
+
+  /* Set up the test environment:
+     - prevent core dumps
+     - set up the timer
+     - fork and execute the function.  */
+
+  test_pid = fork ();
+  if (test_pid == 0)
+    {
+      /* This is the child.  */
+      if (disable_coredumps)
+        {
+          /* Try to avoid dumping core.  This is necessary because we
+             run the test from the source tree, and the coredumps
+             would end up there (and not in the build tree).  */
+          struct rlimit core_limit;
+          core_limit.rlim_cur = 0;
+          core_limit.rlim_max = 0;
+          setrlimit (RLIMIT_CORE, &core_limit);
+        }
+
+      /* We put the test process in its own pgrp so that if it bogusly
+         generates any job control signals, they won't hit the whole build.  */
+      if (setpgid (0, 0) != 0)
+        printf ("Failed to set the process group ID: %m\n");
+
+      /* Execute the test function and exit with the return value.   */
+      exit (run_test_function (argc, argv, config));
+    }
+  else if (test_pid < 0)
+    {
+      printf ("Cannot fork test program: %m\n");
+      exit (1);
+    }
+
+  /* Set timeout.  */
+  signal (SIGALRM, signal_handler);
+  alarm (timeout * timeoutfactor);
+
+  /* Make sure we clean up if the wrapper gets interrupted.  */
+  signal (SIGINT, signal_handler);
+
+  /* Wait for the regular termination.  */
+  termpid = TEMP_FAILURE_RETRY (waitpid (test_pid, &status, 0));
+  if (termpid == -1)
+    {
+      printf ("Waiting for test program failed: %m\n");
+      exit (1);
+    }
+  if (termpid != test_pid)
+    {
+      printf ("Oops, wrong test program terminated: expected %ld, got %ld\n",
+              (long int) test_pid, (long int) termpid);
+      exit (1);
+    }
+
+  /* Process terminated normaly without timeout etc.  */
+  if (WIFEXITED (status))
+    {
+      if (config->expected_status == 0)
+        {
+          if (config->expected_signal == 0)
+            /* Exit with the return value of the test.  */
+            return adjust_exit_status (WEXITSTATUS (status));
+          else
+            {
+              printf ("Expected signal '%s' from child, got none\n",
+                      strsignal (config->expected_signal));
+              exit (1);
+            }
+        }
+      else
+        {
+          /* Non-zero exit status is expected */
+          if (WEXITSTATUS (status) != config->expected_status)
+            {
+              printf ("Expected status %d, got %d\n",
+                      config->expected_status, WEXITSTATUS (status));
+              exit (1);
+            }
+        }
+      return adjust_exit_status (0);
+    }
+  /* Process was killed by timer or other signal.  */
+  else
+    {
+      if (config->expected_signal == 0)
+        {
+          printf ("Didn't expect signal from child: got `%s'\n",
+                  strsignal (WTERMSIG (status)));
+          exit (1);
+        }
+      else if (WTERMSIG (status) != config->expected_signal)
+        {
+          printf ("Incorrect signal from child: got `%s', need `%s'\n",
+                  strsignal (WTERMSIG (status)),
+                  strsignal (config->expected_signal));
+          exit (1);
+        }
+
+      return adjust_exit_status (0);
+    }
+}
diff --git a/support/support_test_verify_impl.c b/support/support_test_verify_impl.c
new file mode 100644
index 0000000..5bae38f
--- /dev/null
+++ b/support/support_test_verify_impl.c
@@ -0,0 +1,33 @@
+/* Implementation of the TEST_VERIFY and TEST_VERIFY_EXIT macros.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+void
+support_test_verify_impl (int status, const char *file, int line,
+                          const char *expr)
+{
+  support_record_failure ();
+  printf ("error: %s:%d: not true: %s\n", file, line, expr);
+  if (status >= 0)
+    exit (status);
+
+}
diff --git a/support/support_write_file_string.c b/support/support_write_file_string.c
new file mode 100644
index 0000000..48e8959
--- /dev/null
+++ b/support/support_write_file_string.c
@@ -0,0 +1,39 @@
+/* Write a string to a file.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <fcntl.h>
+#include <string.h>
+#include <support/check.h>
+#include <xunistd.h>
+
+void
+support_write_file_string (const char *path, const char *contents)
+{
+  int fd = xopen (path, O_CREAT | O_TRUNC | O_WRONLY, 0666);
+  const char *end = contents + strlen (contents);
+  for (const char *p = contents; p < end; )
+    {
+      ssize_t ret = write (fd, p, end - p);
+      if (ret < 0)
+        FAIL_EXIT1 ("cannot write to \"%s\": %m", path);
+      if (ret == 0)
+        FAIL_EXIT1 ("zero-length write to \"%s\"", path);
+      p += ret;
+    }
+  xclose (fd);
+}
diff --git a/support/temp_file-internal.h b/support/temp_file-internal.h
new file mode 100644
index 0000000..fb6cceb
--- /dev/null
+++ b/support/temp_file-internal.h
@@ -0,0 +1,31 @@
+/* Internal weak declarations for temporary file handling.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_TEMP_FILE_INTERNAL_H
+#define SUPPORT_TEMP_FILE_INTERNAL_H
+
+/* These functions are called by the test driver if they are
+   defined.  Tests should not call them directly.  */
+
+#include <stdio.h>
+
+void support_set_test_dir (const char *name) __attribute__ ((weak));
+void support_delete_temp_files (void) __attribute__ ((weak));
+void support_print_temp_files (FILE *) __attribute__ ((weak));
+
+#endif /* SUPPORT_TEMP_FILE_INTERNAL_H */
diff --git a/support/temp_file.c b/support/temp_file.c
new file mode 100644
index 0000000..fdb2477
--- /dev/null
+++ b/support/temp_file.c
@@ -0,0 +1,132 @@
+/* Temporary file handling for tests.
+   Copyright (C) 1998-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* This is required to get an mkstemp which can create large files on
+   some 32-bit platforms. */
+#define _FILE_OFFSET_BITS 64
+
+#include <support/temp_file.h>
+#include <support/temp_file-internal.h>
+#include <support/support.h>
+
+#include <paths.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* List of temporary files.  */
+static struct temp_name_list
+{
+  struct temp_name_list *next;
+  char *name;
+  pid_t owner;
+} *temp_name_list;
+
+/* Location of the temporary files.  Set by the test skeleton via
+   support_set_test_dir.  The string is not be freed.  */
+static const char *test_dir = _PATH_TMP;
+
+void
+add_temp_file (const char *name)
+{
+  struct temp_name_list *newp
+    = (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
+  char *newname = strdup (name);
+  if (newname != NULL)
+    {
+      newp->name = newname;
+      newp->next = temp_name_list;
+      newp->owner = getpid ();
+      temp_name_list = newp;
+    }
+  else
+    free (newp);
+}
+
+int
+create_temp_file (const char *base, char **filename)
+{
+  char *fname;
+  int fd;
+
+  fname = (char *) xmalloc (strlen (test_dir) + 1 + strlen (base)
+			    + sizeof ("XXXXXX"));
+  strcpy (stpcpy (stpcpy (stpcpy (fname, test_dir), "/"), base), "XXXXXX");
+
+  fd = mkstemp (fname);
+  if (fd == -1)
+    {
+      printf ("cannot open temporary file '%s': %m\n", fname);
+      free (fname);
+      return -1;
+    }
+
+  add_temp_file (fname);
+  if (filename != NULL)
+    *filename = fname;
+  else
+    free (fname);
+
+  return fd;
+}
+
+/* Helper functions called by the test skeleton follow.  */
+
+void
+support_set_test_dir (const char *path)
+{
+  test_dir = path;
+}
+
+void
+support_delete_temp_files (void)
+{
+  pid_t pid = getpid ();
+  while (temp_name_list != NULL)
+    {
+      /* Only perform the removal if the path was registed in the same
+	 process, as identified by the PID.  (This assumes that the
+	 parent process which registered the temporary file sticks
+	 around, to prevent PID reuse.)  */
+      if (temp_name_list->owner == pid)
+	{
+	  if (remove (temp_name_list->name) != 0)
+	    printf ("warning: could not remove temporary file: %s: %m\n",
+		    temp_name_list->name);
+	}
+      free (temp_name_list->name);
+
+      struct temp_name_list *next = temp_name_list->next;
+      free (temp_name_list);
+      temp_name_list = next;
+    }
+}
+
+void
+support_print_temp_files (FILE *f)
+{
+  if (temp_name_list != NULL)
+    {
+      struct temp_name_list *n;
+      fprintf (f, "temp_files=(\n");
+      for (n = temp_name_list; n != NULL; n = n->next)
+        fprintf (f, "  '%s'\n", n->name);
+      fprintf (f, ")\n");
+    }
+}
diff --git a/support/temp_file.h b/support/temp_file.h
new file mode 100644
index 0000000..6fed8df
--- /dev/null
+++ b/support/temp_file.h
@@ -0,0 +1,37 @@
+/* Declarations for temporary file handling.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_TEMP_FILE_H
+#define SUPPORT_TEMP_FILE_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Schedule a temporary file for deletion on exit.  */
+void add_temp_file (const char *name);
+
+/* Create a temporary file.  Return the opened file descriptor on
+   success, or -1 on failure.  Write the file name to *FILENAME if
+   FILENAME is not NULL.  In this case, the caller is expected to free
+   *FILENAME.  */
+int create_temp_file (const char *base, char **filename);
+
+__END_DECLS
+
+#endif /* SUPPORT_TEMP_FILE_H */
diff --git a/support/test-driver.c b/support/test-driver.c
new file mode 100644
index 0000000..482066d
--- /dev/null
+++ b/support/test-driver.c
@@ -0,0 +1,156 @@
+/* Main function for test programs.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* This file should be included from test cases.  It will define a
+   main function which provides the test wrapper.
+
+   It assumes that the test case defines a function
+
+     int do_test (void);
+
+   and arranges for that function being called under the test wrapper.
+   The do_test function should return 0 to indicate a passing test, 1
+   to indicate a failing test, or 77 to indicate an unsupported test.
+   Other result values could be used to indicate a failing test, but
+   the result of the expression is passed to exit and exit only
+   returns the lower 8 bits of its input.  A non-zero return with some
+   values could cause a test to incorrectly be considered passing when
+   it really failed.  For this reason, the function should always
+   return 0 (EXIT_SUCCESS), 1 (EXIT_FAILURE), or 77
+   (EXIT_UNSUPPORTED).
+
+   The test function may print out diagnostic or warning messages as well
+   as messages about failures.  These messages should be printed to stdout
+   and not stderr so that the output is properly ordered with respect to
+   the rest of the glibc testsuite run output.
+
+   Several preprocessors macros can be defined before including this
+   file.
+
+   The name of the do_test function can be changed with the
+   TEST_FUNCTION macro.  It must expand to the desired function name.
+
+   If the test case needs access to command line parameters, it must
+   define the TEST_FUNCTION_ARGV macro with the name of the test
+   function.  It must have the following type:
+
+     int TEST_FUNCTION_ARGV (int argc, char **argv);
+
+   This overrides the do_test default function and is incompatible
+   with the TEST_FUNCTION macro.
+
+   If PREPARE is defined, it must expand to the name of a function of
+   the type
+
+     void PREPARE (int argc, char **);
+
+   This function will be called early, after parsing the command line,
+   but before running the test, in the parent process which acts as
+   the test supervisor.
+
+   If CLEANUP_HANDLER is defined, it must expand to the name of a
+   function of the type
+
+     void CLEANUP_HANDLER (void);
+
+   This function will be called from the timeout (SIGALRM) signal
+   handler.
+
+   If EXPECTED_SIGNAL is defined, it must expanded to a constant which
+   denotes the expected signal number.
+
+   If EXPECTED_STATUS is defined, it must expand to the expected exit
+   status.
+
+   If TIMEOUT is defined, it must be positive constant.  It overrides
+   the default test timeout and is measured in seconds.
+
+   If TEST_NO_MALLOPT is defined, the test wrapper will not call
+   mallopt.
+
+   Custom command line handling can be implemented by defining the
+   CMDLINE_OPTION macro (after including the <getopt.h> header; this
+   requires _GNU_SOURCE to be defined).  This macro must expand to a
+   to a comma-separated list of braced initializers for struct option
+   from <getopt.h>, with a trailing comma.  CMDLINE_PROCESS can be
+   defined as the name of a function which is called to process these
+   options.  The function is passed the option character/number and
+   has this type:
+
+     void CMDLINE_PROCESS (int);
+*/
+
+#include <support/test-driver.h>
+
+#include <string.h>
+
+int
+main (int argc, char **argv)
+{
+  struct test_config test_config;
+  memset (&test_config, 0, sizeof (test_config));
+
+#ifdef PREPARE
+  test_config.prepare_function = (PREPARE);
+#endif
+
+#if defined (TEST_FUNCTION) && defined (TEST_FUNCTON_ARGV)
+# error TEST_FUNCTION and TEST_FUNCTION_ARGV cannot be defined at the same time
+#endif
+#if defined (TEST_FUNCTION)
+  test_config.test_function = TEST_FUNCTION;
+#elif defined (TEST_FUNCTION_ARGV)
+  test_config.test_function_argv = TEST_FUNCTION_ARGV;
+#else
+  test_config.test_function = do_test;
+#endif
+
+#ifdef CLEANUP_HANDLER
+  test_config.cleanup_function = CLEANUP_HANDLER;
+#endif
+
+#ifdef EXPECTED_SIGNAL
+  test_config.expected_signal = (EXPECTED_SIGNAL);
+#endif
+
+#ifdef EXPECTED_STATUS
+  test_config.expected_status = (EXPECTED_STATUS);
+#endif
+
+#ifdef TEST_NO_MALLOPT
+  test_config.no_mallopt = 1;
+#endif
+
+#ifdef TIMEOUT
+  test_config.timeout = TIMEOUT;
+#endif
+
+#ifdef CMDLINE_OPTIONS
+  struct option options[] =
+    {
+      CMDLINE_OPTIONS
+      TEST_DEFAULT_OPTIONS
+    };
+  test_config.options = &options;
+#endif
+#ifdef CMDLINE_PROCESS
+  test_config.cmdline_function = CMDLINE_PROCESS;
+#endif
+
+  return support_test_main (argc, argv, &test_config);
+}
diff --git a/support/test-driver.h b/support/test-driver.h
new file mode 100644
index 0000000..af1971a
--- /dev/null
+++ b/support/test-driver.h
@@ -0,0 +1,74 @@
+/* Interfaces for the test driver.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_TEST_DRIVER_H
+#define SUPPORT_TEST_DRIVER_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+struct test_config
+{
+  void (*prepare_function) (int argc, char **argv);
+  int (*test_function) (void);
+  int (*test_function_argv) (int argc, char **argv);
+  void (*cleanup_function) (void);
+  void (*cmdline_function) (int);
+  const void *options;   /* Custom options if not NULL.  */
+  int timeout;           /* Test timeout in seconds.  */
+  int expected_status;   /* Expected exit status.  */
+  int expected_signal;   /* If non-zero, expect termination by signal.  */
+  char no_mallopt;       /* Boolean flag to disable mallopt.  */
+};
+
+enum
+  {
+    /* Test exit status which indicates that the feature is
+       unsupported. */
+    EXIT_UNSUPPORTED = 77,
+
+    /* Default timeout is twenty seconds.  Tests should normally
+       complete faster than this, but if they don't, that's abnormal
+       (a bug) anyways.  */
+    DEFAULT_TIMEOUT = 20,
+
+    /* Used for command line argument parsing.  */
+    OPT_DIRECT = 1000,
+    OPT_TESTDIR,
+  };
+
+/* Options provided by the test driver.  */
+#define TEST_DEFAULT_OPTIONS                            \
+  { "verbose", no_argument, NULL, 'v' },                \
+  { "direct", no_argument, NULL, OPT_DIRECT },          \
+  { "test-dir", required_argument, NULL, OPT_TESTDIR }, \
+
+/* The directory the test should use for temporary files.  */
+extern const char *test_dir;
+
+/* The number of --verbose arguments specified during program
+   invocation.  This variable can be used to control the verbosity of
+   tests.  */
+extern unsigned int test_verbose;
+
+int support_test_main (int argc, char **argv, const struct test_config *);
+
+__END_DECLS
+
+#endif /* SUPPORT_TEST_DRIVER_H */
diff --git a/support/tst-support-namespace.c b/support/tst-support-namespace.c
new file mode 100644
index 0000000..a50b074
--- /dev/null
+++ b/support/tst-support-namespace.c
@@ -0,0 +1,34 @@
+/* Test entering namespaces.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <support/namespace.h>
+
+static int
+do_test (void)
+{
+  if (support_become_root ())
+    printf ("info: acquired root-like privileges\n");
+  if (support_enter_network_namespace ())
+    printf ("info: entered network namespace\n");
+  if (support_in_uts_namespace ())
+    printf ("info: also entered UTS namespace\n");
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/tst-support_capture_subprocess.c b/support/tst-support_capture_subprocess.c
new file mode 100644
index 0000000..5672fba
--- /dev/null
+++ b/support/tst-support_capture_subprocess.c
@@ -0,0 +1,188 @@
+/* Test capturing output from a subprocess.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+/* Write one byte at *P to FD and advance *P.  Do nothing if *P is
+   '\0'.  */
+static void
+transfer (const unsigned char **p, int fd)
+{
+  if (**p != '\0')
+    {
+      TEST_VERIFY (write (fd, *p, 1) == 1);
+      ++*p;
+    }
+}
+
+/* Determine the order in which stdout and stderr are written.  */
+enum write_mode { out_first, err_first, interleave,
+                  write_mode_last =  interleave };
+
+/* Describe what to write in the subprocess.  */
+struct test
+{
+  char *out;
+  char *err;
+  enum write_mode write_mode;
+  int signal;
+  int status;
+};
+
+/* For use with support_capture_subprocess.  */
+static void
+callback (void *closure)
+{
+  const struct test *test = closure;
+  bool mode_ok = false;
+  switch (test->write_mode)
+    {
+    case out_first:
+      TEST_VERIFY (fputs (test->out, stdout) >= 0);
+      TEST_VERIFY (fflush (stdout) == 0);
+      TEST_VERIFY (fputs (test->err, stderr) >= 0);
+      TEST_VERIFY (fflush (stderr) == 0);
+      mode_ok = true;
+      break;
+    case err_first:
+      TEST_VERIFY (fputs (test->err, stderr) >= 0);
+      TEST_VERIFY (fflush (stderr) == 0);
+      TEST_VERIFY (fputs (test->out, stdout) >= 0);
+      TEST_VERIFY (fflush (stdout) == 0);
+      mode_ok = true;
+      break;
+    case interleave:
+      {
+        const unsigned char *pout = (const unsigned char *) test->out;
+        const unsigned char *perr = (const unsigned char *) test->err;
+        do
+          {
+            transfer (&pout, STDOUT_FILENO);
+            transfer (&perr, STDERR_FILENO);
+          }
+        while (*pout != '\0' || *perr != '\0');
+      }
+      mode_ok = true;
+      break;
+    }
+  TEST_VERIFY (mode_ok);
+
+  if (test->signal != 0)
+    raise (test->signal);
+  exit (test->status);
+}
+
+/* Create a heap-allocated random string of letters.  */
+static char *
+random_string (size_t length)
+{
+  char *result = xmalloc (length + 1);
+  for (size_t i = 0; i < length; ++i)
+    result[i] = 'a' + (rand () % 26);
+  result[length] = '\0';
+  return result;
+}
+
+/* Check that the specific stream from the captured subprocess matches
+   expectations.  */
+static void
+check_stream (const char *what, const struct xmemstream *stream,
+              const char *expected)
+{
+  if (strcmp (stream->buffer, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: captured %s data incorrect\n"
+              "  expected: %s\n"
+              "  actual:   %s\n",
+              what, expected, stream->buffer);
+    }
+  if (stream->length != strlen (expected))
+    {
+      support_record_failure ();
+      printf ("error: captured %s data length incorrect\n"
+              "  expected: %zu\n"
+              "  actual:   %zu\n",
+              what, strlen (expected), stream->length);
+    }
+}
+
+static int
+do_test (void)
+{
+  const int lengths[] = {0, 1, 17, 512, 20000, -1};
+
+  /* Test multiple combinations of support_capture_subprocess.
+
+     length_idx_stdout: Index into the lengths array above,
+       controls how many bytes are written by the subprocess to
+       standard output.
+     length_idx_stderr: Same for standard error.
+     write_mode: How standard output and standard error writes are
+       ordered.
+     signal: Exit with no signal if zero, with SIGTERM if one.
+     status: Process exit status: 0 if zero, 3 if one.  */
+  for (int length_idx_stdout = 0; lengths[length_idx_stdout] >= 0;
+       ++length_idx_stdout)
+    for (int length_idx_stderr = 0; lengths[length_idx_stderr] >= 0;
+         ++length_idx_stderr)
+      for (int write_mode = 0; write_mode < write_mode_last; ++write_mode)
+        for (int signal = 0; signal < 2; ++signal)
+          for (int status = 0; status < 2; ++status)
+            {
+              struct test test =
+                {
+                  .out = random_string (lengths[length_idx_stdout]),
+                  .err = random_string (lengths[length_idx_stderr]),
+                  .write_mode = write_mode,
+                  .signal = signal * SIGTERM, /* 0 or SIGTERM.  */
+                  .status = status * 3,       /* 0 or 3.  */
+                };
+              TEST_VERIFY (strlen (test.out) == lengths[length_idx_stdout]);
+              TEST_VERIFY (strlen (test.err) == lengths[length_idx_stderr]);
+
+              struct support_capture_subprocess result
+                = support_capture_subprocess (callback, &test);
+              check_stream ("stdout", &result.out, test.out);
+              check_stream ("stderr", &result.err, test.err);
+              if (test.signal != 0)
+                {
+                  TEST_VERIFY (WIFSIGNALED (result.status));
+                  TEST_VERIFY (WTERMSIG (result.status) == test.signal);
+                }
+              else
+                {
+                  TEST_VERIFY (WIFEXITED (result.status));
+                  TEST_VERIFY (WEXITSTATUS (result.status) == test.status);
+                }
+              support_capture_subprocess_free (&result);
+              free (test.out);
+              free (test.err);
+            }
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/tst-support_format_dns_packet.c b/support/tst-support_format_dns_packet.c
new file mode 100644
index 0000000..9c8589c
--- /dev/null
+++ b/support/tst-support_format_dns_packet.c
@@ -0,0 +1,101 @@
+/* Tests for the support_format_dns_packet function.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/format_nss.h>
+#include <support/run_diff.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void
+check_packet (const void *buffer, size_t length,
+              const char *name, const char *expected)
+{
+  char *actual = support_format_dns_packet (buffer, length);
+  if (strcmp (actual, expected) != 0)
+    {
+      support_record_failure ();
+      printf ("error: formatted packet does not match: %s\n", name);
+      support_run_diff ("expected", expected,
+                        "actual", actual);
+    }
+  free (actual);
+}
+
+static void
+test_aaaa_length (void)
+{
+  static const char packet[] =
+    /* Header: Response with two records.  */
+    "\x12\x34\x80\x00\x00\x01\x00\x02\x00\x00\x00\x00"
+    /* Question section.  www.example/IN/AAAA.  */
+    "\x03www\x07""example\x00\x00\x1c\x00\x01"
+    /* Answer section.  www.example AAAA [corrupted].  */
+    "\xc0\x0c"
+    "\x00\x1c\x00\x01\x00\x00\x00\x00\x00\x10"
+    "\x20\x01\x0d\xb8\x05\x06\x07\x08"
+    "\x11\x12\x13\x14\x15\x16\x17\x18"
+    /* www.example AAAA [corrupted].  */
+    "\xc0\x0c"
+    "\x00\x1c\x00\x01\x00\x00\x00\x00\x00\x11"
+    "\x01\x02\x03\x04\x05\x06\x07\x08"
+    "\x11\x12\x13\x14\x15\x16\x17\x18" "\xff";
+  check_packet (packet, sizeof (packet) - 1, __func__,
+                "name: www.example\n"
+                "address: 2001:db8:506:708:1112:1314:1516:1718\n"
+                "error: AAAA record of size 17: www.example\n");
+}
+
+static void
+test_multiple_cnames (void)
+{
+  static const char packet[] =
+    /* Header: Response with three records.  */
+    "\x12\x34\x80\x00\x00\x01\x00\x03\x00\x00\x00\x00"
+    /* Question section.  www.example/IN/A.  */
+    "\x03www\x07""example\x00\x00\x01\x00\x01"
+    /* Answer section.  www.example CNAME www1.example.  */
+    "\xc0\x0c"
+    "\x00\x05\x00\x01\x00\x00\x00\x00\x00\x07"
+    "\x04www1\xc0\x10"
+    /* www1 CNAME www2.  */
+    "\x04www1\xc0\x10"
+    "\x00\x05\x00\x01\x00\x00\x00\x00\x00\x07"
+    "\x04www2\xc0\x10"
+    /* www2 A 192.0.2.1.  */
+    "\x04www2\xc0\x10"
+    "\x00\x01\x00\x01\x00\x00\x00\x00\x00\x04"
+    "\xc0\x00\x02\x01";
+  check_packet (packet, sizeof (packet) - 1, __func__,
+                "name: www.example\n"
+                "name: www1.example\n"
+                "name: www2.example\n"
+                "address: 192.0.2.1\n");
+}
+
+static int
+do_test (void)
+{
+  test_aaaa_length ();
+  test_multiple_cnames ();
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/tst-support_record_failure-2.sh b/support/tst-support_record_failure-2.sh
new file mode 100644
index 0000000..2c9372c
--- /dev/null
+++ b/support/tst-support_record_failure-2.sh
@@ -0,0 +1,69 @@
+#!/bin/sh
+# Test failure recording (with and without --direct).
+# Copyright (C) 2016-2017 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
+# <http://www.gnu.org/licenses/>.  */
+
+set -e
+
+common_objpfx=$1; shift
+test_program_prefix_before_env=$1; shift
+run_program_env=$1; shift
+test_program_prefix_after_env=$1; shift
+
+run_test () {
+    expected_status="$1"
+    expected_output="$2"
+    shift 2
+    args="${common_objpfx}support/tst-support_record_failure $*"
+    echo "running: $args"
+    set +e
+    output="$(${test_program_prefix_before_env} \
+		 ${run_program} ${test_program_prefix_after_env} $args)"
+    status=$?
+    set -e
+    echo "  exit status: $status"
+    if test "$output" != "$expected_output" ; then
+	echo "error: unexpected output: $output"
+	exit 1
+    fi
+    if test "$status" -ne "$expected_status" ; then
+	echo "error: exit status $expected_status expected"
+	exit 1
+    fi
+}
+
+different_status () {
+    direct="$1"
+    run_test 1 "error: 1 test failures" $direct --status=0
+    run_test 1 "error: 1 test failures" $direct --status=1
+    run_test 2 "error: 1 test failures" $direct --status=2
+    run_test 1 "error: 1 test failures" $direct --status=77
+    run_test 2 "error: tst-support_record_failure.c:109: not true: false
+error: 1 test failures" $direct --test-verify
+    run_test 2 "error: tst-support_record_failure.c:109: not true: false
+info: execution passed failed TEST_VERIFY
+error: 1 test failures" $direct --test-verify --verbose
+}
+
+different_status
+different_status --direct
+
+run_test 1 "error: tst-support_record_failure.c:116: not true: false
+error: 1 test failures" --test-verify-exit
+# --direct does not print the summary error message if exit is called.
+run_test 1 "error: tst-support_record_failure.c:116: not true: false" \
+	 --direct --test-verify-exit
diff --git a/support/tst-support_record_failure.c b/support/tst-support_record_failure.c
new file mode 100644
index 0000000..e739e73
--- /dev/null
+++ b/support/tst-support_record_failure.c
@@ -0,0 +1,153 @@
+/* Test support_record_failure state sharing.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/xunistd.h>
+
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+static int exit_status_with_failure = -1;
+static bool test_verify;
+static bool test_verify_exit;
+enum
+  {
+    OPT_STATUS = 10001,
+    OPT_TEST_VERIFY,
+    OPT_TEST_VERIFY_EXIT,
+  };
+#define CMDLINE_OPTIONS                                                 \
+  { "status", required_argument, NULL, OPT_STATUS },                    \
+  { "test-verify", no_argument, NULL, OPT_TEST_VERIFY },                \
+  { "test-verify-exit", no_argument, NULL, OPT_TEST_VERIFY_EXIT },
+static void
+cmdline_process (int c)
+{
+  switch (c)
+    {
+    case OPT_STATUS:
+      exit_status_with_failure = atoi (optarg);
+      break;
+    case OPT_TEST_VERIFY:
+      test_verify = true;
+      break;
+    case OPT_TEST_VERIFY_EXIT:
+      test_verify_exit = true;
+      break;
+    }
+}
+#define CMDLINE_PROCESS cmdline_process
+
+static void
+check_failure_reporting (int phase, int zero, int unsupported)
+{
+  int status = support_report_failure (0);
+  if (status != zero)
+    {
+      printf ("real-error (phase %d): support_report_failure (0) == %d\n",
+              phase, status);
+      exit (1);
+    }
+  status = support_report_failure (1);
+  if (status != 1)
+    {
+      printf ("real-error (phase %d): support_report_failure (1) == %d\n",
+              phase, status);
+      exit (1);
+    }
+  status = support_report_failure (2);
+  if (status != 2)
+    {
+      printf ("real-error (phase %d): support_report_failure (2) == %d\n",
+              phase, status);
+      exit (1);
+    }
+  status = support_report_failure (EXIT_UNSUPPORTED);
+  if (status != unsupported)
+    {
+      printf ("real-error (phase %d): "
+              "support_report_failure (EXIT_UNSUPPORTED) == %d\n",
+              phase, status);
+      exit (1);
+    }
+}
+
+static int
+do_test (void)
+{
+  if (exit_status_with_failure >= 0)
+    {
+      /* External invocation with requested error status.  Used by
+         tst-support_report_failure-2.sh.  */
+      support_record_failure ();
+      return exit_status_with_failure;
+    }
+  TEST_VERIFY (true);
+  TEST_VERIFY_EXIT (true);
+  if (test_verify)
+    {
+      TEST_VERIFY (false);
+      if (test_verbose)
+        printf ("info: execution passed failed TEST_VERIFY\n");
+      return 2; /* Expected exit status.  */
+    }
+  if (test_verify_exit)
+    {
+      TEST_VERIFY_EXIT (false);
+      return 3; /* Not reached.  Expected exit status is 1.  */
+    }
+
+  printf ("info: This test tests the test framework.\n"
+          "info: It reports some expected errors on stdout.\n");
+
+  /* Check that the status is passed through unchanged.  */
+  check_failure_reporting (1, 0, EXIT_UNSUPPORTED);
+
+  /* Check state propagation from a subprocess.  */
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      support_record_failure ();
+      _exit (0);
+    }
+  int status;
+  xwaitpid (pid, &status, 0);
+  if (status != 0)
+    {
+      printf ("real-error: incorrect status from subprocess: %d\n", status);
+      return 1;
+    }
+  check_failure_reporting (2, 1, 1);
+
+  /* Also test directly in the parent process.  */
+  support_record_failure_reset ();
+  check_failure_reporting (3, 0, EXIT_UNSUPPORTED);
+  support_record_failure ();
+  check_failure_reporting (4, 1, 1);
+
+  /* We need to mask the failure above.  */
+  support_record_failure_reset ();
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/write_message.c b/support/write_message.c
new file mode 100644
index 0000000..f03ed93
--- /dev/null
+++ b/support/write_message.c
@@ -0,0 +1,29 @@
+/* Write a message to standard output.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <string.h>
+#include <unistd.h>
+
+void
+write_message (const char *message)
+{
+  ssize_t unused __attribute__ ((unused));
+  unused = write (STDOUT_FILENO, message, strlen (message));
+}
diff --git a/support/xaccept.c b/support/xaccept.c
new file mode 100644
index 0000000..7b25af3
--- /dev/null
+++ b/support/xaccept.c
@@ -0,0 +1,32 @@
+/* accept with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+int
+xaccept (int fd, struct sockaddr *sa, socklen_t *salen)
+{
+  int clientfd = accept (fd, sa, salen);
+  if (clientfd < 0)
+    FAIL_EXIT1 ("accept (%d): %m", fd);
+  return clientfd;
+}
diff --git a/support/xaccept4.c b/support/xaccept4.c
new file mode 100644
index 0000000..67dd95e
--- /dev/null
+++ b/support/xaccept4.c
@@ -0,0 +1,32 @@
+/* accept4 with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+int
+xaccept4 (int fd, struct sockaddr *sa, socklen_t *salen, int flags)
+{
+  int clientfd = accept4 (fd, sa, salen, flags);
+  if (clientfd < 0)
+    FAIL_EXIT1 ("accept4 (%d, 0x%x): %m", fd, flags);
+  return clientfd;
+}
diff --git a/support/xasprintf.c b/support/xasprintf.c
new file mode 100644
index 0000000..5157680
--- /dev/null
+++ b/support/xasprintf.c
@@ -0,0 +1,36 @@
+/* Error-checking wrapper for asprintf.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+char *
+xasprintf (const char *format, ...)
+{
+  va_list ap;
+  va_start (ap, format);
+  char *result;
+  if (vasprintf (&result, format, ap) < 0)
+    FAIL_EXIT1 ("asprintf: %m");
+  va_end (ap);
+  return result;
+}
diff --git a/support/xbind.c b/support/xbind.c
new file mode 100644
index 0000000..cfc6dd8
--- /dev/null
+++ b/support/xbind.c
@@ -0,0 +1,30 @@
+/* bind with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xbind (int fd, const struct sockaddr *sa, socklen_t sa_len)
+{
+  if (bind (fd, sa, sa_len) != 0)
+    FAIL_EXIT1 ("bind (%d), family %d: %m", fd, sa->sa_family);
+}
diff --git a/support/xcalloc.c b/support/xcalloc.c
new file mode 100644
index 0000000..135f42d
--- /dev/null
+++ b/support/xcalloc.c
@@ -0,0 +1,34 @@
+/* Error-checking wrapper for calloc.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void *
+xcalloc (size_t n, size_t s)
+{
+  void *p;
+
+  p = calloc (n, s);
+  if (p == NULL)
+    oom_error ("calloc", n * s);
+  return p;
+}
diff --git a/support/xchroot.c b/support/xchroot.c
new file mode 100644
index 0000000..abcc299
--- /dev/null
+++ b/support/xchroot.c
@@ -0,0 +1,28 @@
+/* chroot with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/stat.h>
+
+void
+xchroot (const char *path)
+{
+  if (chroot (path) != 0)
+    FAIL_EXIT1 ("chroot (\"%s\"): %m", path);
+}
diff --git a/support/xclose.c b/support/xclose.c
new file mode 100644
index 0000000..c931e08
--- /dev/null
+++ b/support/xclose.c
@@ -0,0 +1,28 @@
+/* close with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+#include <support/check.h>
+#include <errno.h>
+
+void
+xclose (int fd)
+{
+  if (close (fd) < 0 && errno != EINTR)
+    FAIL_EXIT1 ("close of descriptor %d failed: %m", fd);
+}
diff --git a/support/xconnect.c b/support/xconnect.c
new file mode 100644
index 0000000..0266dbc
--- /dev/null
+++ b/support/xconnect.c
@@ -0,0 +1,30 @@
+/* connect with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xconnect (int fd, const struct sockaddr *sa, socklen_t sa_len)
+{
+  if (connect (fd, sa, sa_len) != 0)
+    FAIL_EXIT1 ("connect (%d), family %d: %m", fd, sa->sa_family);
+}
diff --git a/support/xdup2.c b/support/xdup2.c
new file mode 100644
index 0000000..dc08c94
--- /dev/null
+++ b/support/xdup2.c
@@ -0,0 +1,28 @@
+/* dup2 with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+
+#include <support/check.h>
+
+void
+xdup2 (int from, int to)
+{
+  if (dup2 (from, to) < 0)
+    FAIL_EXIT1 ("dup2 (%d, %d): %m", from, to);
+}
diff --git a/support/xfclose.c b/support/xfclose.c
new file mode 100644
index 0000000..2737f05
--- /dev/null
+++ b/support/xfclose.c
@@ -0,0 +1,33 @@
+/* fclose with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xstdio.h>
+
+#include <support/check.h>
+#include <stdlib.h>
+
+void
+xfclose (FILE *fp)
+{
+  if (ferror (fp))
+    FAIL_EXIT1 ("stdio stream closed with pending errors");
+  if (fflush (fp) != 0)
+    FAIL_EXIT1 ("fflush: %m");
+  if (fclose (fp) != 0)
+    FAIL_EXIT1 ("fclose: %m");
+}
diff --git a/support/xfopen.c b/support/xfopen.c
new file mode 100644
index 0000000..14532a0
--- /dev/null
+++ b/support/xfopen.c
@@ -0,0 +1,31 @@
+/* fopen with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xstdio.h>
+
+#include <support/check.h>
+#include <stdlib.h>
+
+FILE *
+xfopen (const char *path, const char *mode)
+{
+  FILE *fp = fopen (path, mode);
+  if (fp == NULL)
+    FAIL_EXIT1 ("could not open %s (mode \"%s\"): %m", path, mode);
+  return fp;
+}
diff --git a/support/xfork.c b/support/xfork.c
new file mode 100644
index 0000000..aa52ba6
--- /dev/null
+++ b/support/xfork.c
@@ -0,0 +1,32 @@
+/* fork with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+pid_t
+xfork (void)
+{
+  pid_t result = fork ();
+  if (result < 0)
+    FAIL_EXIT1 ("fork: %m");
+  return result;
+}
diff --git a/support/xgetsockname.c b/support/xgetsockname.c
new file mode 100644
index 0000000..c3bd884
--- /dev/null
+++ b/support/xgetsockname.c
@@ -0,0 +1,30 @@
+/* getsockname with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xgetsockname (int fd, struct sockaddr *sa, socklen_t *plen)
+{
+  if (getsockname (fd, sa, plen) != 0)
+    FAIL_EXIT1 ("setsockopt (%d): %m", fd);
+}
diff --git a/support/xlisten.c b/support/xlisten.c
new file mode 100644
index 0000000..1953e59
--- /dev/null
+++ b/support/xlisten.c
@@ -0,0 +1,30 @@
+/* listen with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xlisten (int fd, int backlog)
+{
+  if (listen (fd, backlog) != 0)
+    FAIL_EXIT1 ("listen (%d, %d): %m", fd, backlog);
+}
diff --git a/support/xmalloc.c b/support/xmalloc.c
new file mode 100644
index 0000000..450f699
--- /dev/null
+++ b/support/xmalloc.c
@@ -0,0 +1,34 @@
+/* Error-checking wrapper for malloc.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void *
+xmalloc (size_t n)
+{
+  void *p;
+
+  p = malloc (n);
+  if (p == NULL)
+    oom_error ("malloc", n);
+  return p;
+}
diff --git a/support/xmemstream.c b/support/xmemstream.c
new file mode 100644
index 0000000..bce6dc9
--- /dev/null
+++ b/support/xmemstream.c
@@ -0,0 +1,42 @@
+/* Error-checking wrappers for memstream functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xmemstream.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xstdio.h>
+
+void
+xopen_memstream (struct xmemstream *stream)
+{
+  int old_errno = errno;
+  *stream = (struct xmemstream) {};
+  stream->out = open_memstream (&stream->buffer, &stream->length);
+  if (stream->out == NULL)
+    FAIL_EXIT1 ("open_memstream: %m");
+  errno = old_errno;
+}
+
+void
+xfclose_memstream (struct xmemstream *stream)
+{
+  xfclose (stream->out);
+  stream->out = NULL;
+}
diff --git a/support/xmemstream.h b/support/xmemstream.h
new file mode 100644
index 0000000..e5ba231
--- /dev/null
+++ b/support/xmemstream.h
@@ -0,0 +1,49 @@
+/* Error-checking wrappers for memstream functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_XMEMSTREAM_H
+#define SUPPORT_XMEMSTREAM_H
+
+#include <stdio.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Wrappers for other libc functions.  */
+struct xmemstream
+{
+  FILE *out;
+  char *buffer;
+  size_t length;
+};
+
+/* Create a new in-memory stream.  Initializes *STREAM.  After this
+   function returns, STREAM->out is a file descriptor open for
+   writing.  errno is preserved, so that the %m format specifier can
+   be used for writing to STREAM->out.  */
+void xopen_memstream (struct xmemstream *stream);
+
+/* Closes STREAM->OUT.  After this function returns, STREAM->buffer
+   and STREAM->length denote a memory range which contains the bytes
+   written to the output stream.  The caller should free
+   STREAM->buffer.  */
+void xfclose_memstream (struct xmemstream *stream);
+
+__END_DECLS
+
+#endif /* SUPPORT_XMEMSTREAM_H */
diff --git a/support/xmkdir.c b/support/xmkdir.c
new file mode 100644
index 0000000..ea17d49
--- /dev/null
+++ b/support/xmkdir.c
@@ -0,0 +1,28 @@
+/* mkdir with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/stat.h>
+
+void
+xmkdir (const char *path, mode_t mode)
+{
+  if (mkdir (path, mode) != 0)
+    FAIL_EXIT1 ("mkdir (\"%s\", 0%o): %m", path, mode);
+}
diff --git a/support/xmmap.c b/support/xmmap.c
new file mode 100644
index 0000000..435b1eb
--- /dev/null
+++ b/support/xmmap.c
@@ -0,0 +1,31 @@
+/* mmap with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/mman.h>
+
+void *
+xmmap (void *addr, size_t length, int prot, int flags, int fd)
+{
+  void *result = mmap (addr, length, prot, flags, fd, 0);
+  if (result == MAP_FAILED)
+    FAIL_EXIT1 ("mmap of %zu bytes, prot=0x%x, flags=0x%x: %m",
+                length, prot, flags);
+  return result;
+}
diff --git a/support/xmunmap.c b/support/xmunmap.c
new file mode 100644
index 0000000..6ef5a4a
--- /dev/null
+++ b/support/xmunmap.c
@@ -0,0 +1,28 @@
+/* munmap with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/mman.h>
+
+void
+xmunmap (void *addr, size_t length)
+{
+  if (munmap (addr, length) != 0)
+    FAIL_EXIT1 ("munmap of %zu bytes: %m", length);
+}
diff --git a/support/xopen.c b/support/xopen.c
new file mode 100644
index 0000000..7f033a0
--- /dev/null
+++ b/support/xopen.c
@@ -0,0 +1,30 @@
+/* open64 with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <fcntl.h>
+
+int
+xopen (const char *path, int flags, mode_t mode)
+{
+  int ret = open64 (path, flags, mode);
+  if (ret < 0)
+    FAIL_EXIT1 ("open64 (\"%s\", 0x%x, 0%o): %m", path, flags, mode);
+  return ret;
+}
diff --git a/support/xpipe.c b/support/xpipe.c
new file mode 100644
index 0000000..89a64a5
--- /dev/null
+++ b/support/xpipe.c
@@ -0,0 +1,28 @@
+/* pipe with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+
+#include <support/check.h>
+
+void
+xpipe (int fds[2])
+{
+  if (pipe (fds) < 0)
+    FAIL_EXIT1 ("pipe: %m");
+}
diff --git a/support/xpoll.c b/support/xpoll.c
new file mode 100644
index 0000000..bec2521
--- /dev/null
+++ b/support/xpoll.c
@@ -0,0 +1,32 @@
+/* poll with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+int
+xpoll (struct pollfd *fds, nfds_t nfds, int timeout)
+{
+  int ret = poll (fds, nfds, timeout);
+  if (ret < 0)
+    FAIL_EXIT1 ("poll: %m");
+  return ret;
+}
diff --git a/support/xpthread_attr_destroy.c b/support/xpthread_attr_destroy.c
new file mode 100644
index 0000000..664c809
--- /dev/null
+++ b/support/xpthread_attr_destroy.c
@@ -0,0 +1,26 @@
+/* pthread_attr_destroy with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_attr_destroy (pthread_attr_t *attr)
+{
+  xpthread_check_return ("pthread_attr_destroy",
+			 pthread_attr_destroy (attr));
+}
diff --git a/support/xpthread_attr_init.c b/support/xpthread_attr_init.c
new file mode 100644
index 0000000..2e30ade
--- /dev/null
+++ b/support/xpthread_attr_init.c
@@ -0,0 +1,25 @@
+/* pthread_attr_init with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_attr_init (pthread_attr_t *attr)
+{
+  xpthread_check_return ("pthread_attr_init", pthread_attr_init (attr));
+}
diff --git a/support/xpthread_attr_setdetachstate.c b/support/xpthread_attr_setdetachstate.c
new file mode 100644
index 0000000..b544dba
--- /dev/null
+++ b/support/xpthread_attr_setdetachstate.c
@@ -0,0 +1,27 @@
+/* pthread_attr_setdetachstate with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_attr_setdetachstate (pthread_attr_t *attr, int detachstate)
+{
+  xpthread_check_return ("pthread_attr_setdetachstate",
+			 pthread_attr_setdetachstate (attr,
+						      detachstate));
+}
diff --git a/support/xpthread_attr_setstacksize.c b/support/xpthread_attr_setstacksize.c
new file mode 100644
index 0000000..02d0631
--- /dev/null
+++ b/support/xpthread_attr_setstacksize.c
@@ -0,0 +1,26 @@
+/* pthread_attr_setstacksize with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_attr_setstacksize (pthread_attr_t *attr, size_t stacksize)
+{
+  xpthread_check_return ("pthread_attr_setstacksize",
+			 pthread_attr_setstacksize (attr, stacksize));
+}
diff --git a/support/xpthread_barrier_destroy.c b/support/xpthread_barrier_destroy.c
new file mode 100644
index 0000000..efc0719
--- /dev/null
+++ b/support/xpthread_barrier_destroy.c
@@ -0,0 +1,26 @@
+/* pthread_barrier_destroy with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_barrier_destroy (pthread_barrier_t *barrier)
+{
+  xpthread_check_return ("pthread_barrier_destroy",
+                         pthread_barrier_destroy (barrier));
+}
diff --git a/support/xpthread_barrier_init.c b/support/xpthread_barrier_init.c
new file mode 100644
index 0000000..b32dad1
--- /dev/null
+++ b/support/xpthread_barrier_init.c
@@ -0,0 +1,27 @@
+/* pthread_barrier_init with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_barrier_init (pthread_barrier_t *barrier,
+                       pthread_barrierattr_t *attr, unsigned int count)
+{
+  xpthread_check_return ("pthread_barrier_init",
+                         pthread_barrier_init (barrier, attr, count));
+}
diff --git a/support/xpthread_barrier_wait.c b/support/xpthread_barrier_wait.c
new file mode 100644
index 0000000..7cee44d
--- /dev/null
+++ b/support/xpthread_barrier_wait.c
@@ -0,0 +1,28 @@
+/* pthread_barrier_wait with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+int
+xpthread_barrier_wait (pthread_barrier_t *barrier)
+{
+  int ret = pthread_barrier_wait (barrier);
+  if (ret != 0 && ret != PTHREAD_BARRIER_SERIAL_THREAD)
+    xpthread_check_return ("pthread_barrier_wait", ret);
+  return ret == PTHREAD_BARRIER_SERIAL_THREAD;
+}
diff --git a/support/xpthread_cancel.c b/support/xpthread_cancel.c
new file mode 100644
index 0000000..3af16f9
--- /dev/null
+++ b/support/xpthread_cancel.c
@@ -0,0 +1,25 @@
+/* pthread_cancel with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_cancel (pthread_t thr)
+{
+  xpthread_check_return ("pthread_cancel", pthread_cancel (thr));
+}
diff --git a/support/xpthread_check_return.c b/support/xpthread_check_return.c
new file mode 100644
index 0000000..3094d82
--- /dev/null
+++ b/support/xpthread_check_return.c
@@ -0,0 +1,34 @@
+/* Return value checking for pthread functions, exit variant.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xpthread_check_return (const char *function, int value)
+{
+  if (value != 0)
+    {
+      errno = value;
+      FAIL_EXIT1 ("%s: %m", function);
+    }
+}
diff --git a/support/xpthread_cond_wait.c b/support/xpthread_cond_wait.c
new file mode 100644
index 0000000..b0e9b2a
--- /dev/null
+++ b/support/xpthread_cond_wait.c
@@ -0,0 +1,26 @@
+/* pthread_cond_wait with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
+{
+  xpthread_check_return
+    ("pthread_cond_wait", pthread_cond_wait (cond, mutex));
+}
diff --git a/support/xpthread_create.c b/support/xpthread_create.c
new file mode 100644
index 0000000..98c63e5
--- /dev/null
+++ b/support/xpthread_create.c
@@ -0,0 +1,29 @@
+/* pthread_create with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+pthread_t
+xpthread_create (pthread_attr_t *attr,
+                 void *(*thread_func) (void *), void *closure)
+{
+  pthread_t thr;
+  xpthread_check_return
+    ("pthread_create", pthread_create (&thr, attr, thread_func, closure));
+  return thr;
+}
diff --git a/support/xpthread_detach.c b/support/xpthread_detach.c
new file mode 100644
index 0000000..2088af2
--- /dev/null
+++ b/support/xpthread_detach.c
@@ -0,0 +1,25 @@
+/* pthread_detach with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_detach (pthread_t thr)
+{
+  xpthread_check_return ("pthread_detach", pthread_detach (thr));
+}
diff --git a/support/xpthread_join.c b/support/xpthread_join.c
new file mode 100644
index 0000000..f23bb9a
--- /dev/null
+++ b/support/xpthread_join.c
@@ -0,0 +1,27 @@
+/* pthread_join with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void *
+xpthread_join (pthread_t thr)
+{
+  void *result;
+  xpthread_check_return ("pthread_join", pthread_join (thr, &result));
+  return result;
+}
diff --git a/support/xpthread_mutex_consistent.c b/support/xpthread_mutex_consistent.c
new file mode 100644
index 0000000..52364be
--- /dev/null
+++ b/support/xpthread_mutex_consistent.c
@@ -0,0 +1,26 @@
+/* pthread_mutex_consistent with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutex_consistent (pthread_mutex_t *mutex)
+{
+  xpthread_check_return ("pthread_mutex_consistent",
+                         pthread_mutex_consistent (mutex));
+}
diff --git a/support/xpthread_mutex_destroy.c b/support/xpthread_mutex_destroy.c
new file mode 100644
index 0000000..f11f8f0
--- /dev/null
+++ b/support/xpthread_mutex_destroy.c
@@ -0,0 +1,26 @@
+/* pthread_mutex_destroy with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutex_destroy (pthread_mutex_t *mutex)
+{
+  xpthread_check_return ("pthread_mutex_destroy",
+                         pthread_mutex_destroy (mutex));
+}
diff --git a/support/xpthread_mutex_init.c b/support/xpthread_mutex_init.c
new file mode 100644
index 0000000..2d16d1b
--- /dev/null
+++ b/support/xpthread_mutex_init.c
@@ -0,0 +1,26 @@
+/* pthread_mutex_init with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutex_init (pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
+{
+  xpthread_check_return ("pthread_mutex_init",
+                         pthread_mutex_init (mutex, attr));
+}
diff --git a/support/xpthread_mutex_lock.c b/support/xpthread_mutex_lock.c
new file mode 100644
index 0000000..af727b4
--- /dev/null
+++ b/support/xpthread_mutex_lock.c
@@ -0,0 +1,25 @@
+/* pthread_mutex_lock with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutex_lock (pthread_mutex_t *mutex)
+{
+  xpthread_check_return ("pthread_mutex_lock", pthread_mutex_lock (mutex));
+}
diff --git a/support/xpthread_mutex_unlock.c b/support/xpthread_mutex_unlock.c
new file mode 100644
index 0000000..161b41e
--- /dev/null
+++ b/support/xpthread_mutex_unlock.c
@@ -0,0 +1,25 @@
+/* pthread_mutex_unlock with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutex_unlock (pthread_mutex_t *mutex)
+{
+  xpthread_check_return ("pthread_mutex_unlock", pthread_mutex_unlock (mutex));
+}
diff --git a/support/xpthread_mutexattr_destroy.c b/support/xpthread_mutexattr_destroy.c
new file mode 100644
index 0000000..c699e32
--- /dev/null
+++ b/support/xpthread_mutexattr_destroy.c
@@ -0,0 +1,26 @@
+/* pthread_mutexattr_destroy with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_destroy (pthread_mutexattr_t *attr)
+{
+  xpthread_check_return ("pthread_mutexattr_destroy",
+                         pthread_mutexattr_destroy (attr));
+}
diff --git a/support/xpthread_mutexattr_init.c b/support/xpthread_mutexattr_init.c
new file mode 100644
index 0000000..fa93fab
--- /dev/null
+++ b/support/xpthread_mutexattr_init.c
@@ -0,0 +1,25 @@
+/* pthread_mutexattr_init with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_init (pthread_mutexattr_t *attr)
+{
+  xpthread_check_return ("pthread_mutexattr_init", pthread_mutexattr_init (attr));
+}
diff --git a/support/xpthread_mutexattr_setprotocol.c b/support/xpthread_mutexattr_setprotocol.c
new file mode 100644
index 0000000..353f75e
--- /dev/null
+++ b/support/xpthread_mutexattr_setprotocol.c
@@ -0,0 +1,26 @@
+/* pthread_mutexattr_setprotocol with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_setprotocol (pthread_mutexattr_t *attr, int flag)
+{
+  xpthread_check_return ("pthread_mutexattr_setprotocol",
+                         pthread_mutexattr_setprotocol (attr, flag));
+}
diff --git a/support/xpthread_mutexattr_setpshared.c b/support/xpthread_mutexattr_setpshared.c
new file mode 100644
index 0000000..242da1a
--- /dev/null
+++ b/support/xpthread_mutexattr_setpshared.c
@@ -0,0 +1,26 @@
+/* pthread_mutexattr_setpshared with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_setpshared (pthread_mutexattr_t *attr, int flag)
+{
+  xpthread_check_return ("pthread_mutexattr_setpshared",
+                         pthread_mutexattr_setpshared (attr, flag));
+}
diff --git a/support/xpthread_mutexattr_setrobust.c b/support/xpthread_mutexattr_setrobust.c
new file mode 100644
index 0000000..d7d6fa8
--- /dev/null
+++ b/support/xpthread_mutexattr_setrobust.c
@@ -0,0 +1,26 @@
+/* pthread_mutexattr_setrobust with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_setrobust (pthread_mutexattr_t *attr, int flag)
+{
+  xpthread_check_return ("pthread_mutexattr_setrobust",
+                         pthread_mutexattr_setrobust (attr, flag));
+}
diff --git a/support/xpthread_mutexattr_settype.c b/support/xpthread_mutexattr_settype.c
new file mode 100644
index 0000000..cf22170
--- /dev/null
+++ b/support/xpthread_mutexattr_settype.c
@@ -0,0 +1,26 @@
+/* pthread_mutexattr_settype with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_mutexattr_settype (pthread_mutexattr_t *attr, int flag)
+{
+  xpthread_check_return ("pthread_mutexattr_settype",
+                         pthread_mutexattr_settype (attr, flag));
+}
diff --git a/support/xpthread_once.c b/support/xpthread_once.c
new file mode 100644
index 0000000..70d58db
--- /dev/null
+++ b/support/xpthread_once.c
@@ -0,0 +1,25 @@
+/* pthread_once with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_once (pthread_once_t *guard, void (*func) (void))
+{
+  xpthread_check_return ("pthread_once", pthread_once (guard, func));
+}
diff --git a/support/xpthread_sigmask.c b/support/xpthread_sigmask.c
new file mode 100644
index 0000000..0ba9ca0
--- /dev/null
+++ b/support/xpthread_sigmask.c
@@ -0,0 +1,34 @@
+/* pthread_sigmask with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsignal.h>
+#include <support/support.h>
+
+#include <unistd.h>
+
+void
+xpthread_sigmask (int how, const sigset_t *set, sigset_t *oldset)
+{
+  if (pthread_sigmask (how, set, oldset) != 0)
+    {
+      write_message ("error: pthread_setmask failed\n");
+      /* Do not use exit because pthread_sigmask can be called from a
+         signal handler.  */
+      _exit (1);
+    }
+}
diff --git a/support/xpthread_spin_lock.c b/support/xpthread_spin_lock.c
new file mode 100644
index 0000000..6975215
--- /dev/null
+++ b/support/xpthread_spin_lock.c
@@ -0,0 +1,25 @@
+/* pthread_spin_lock with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_spin_lock (pthread_spinlock_t *lock)
+{
+  xpthread_check_return ("pthread_spin_lock", pthread_spin_lock (lock));
+}
diff --git a/support/xpthread_spin_unlock.c b/support/xpthread_spin_unlock.c
new file mode 100644
index 0000000..4f19a44
--- /dev/null
+++ b/support/xpthread_spin_unlock.c
@@ -0,0 +1,25 @@
+/* pthread_spin_unlock with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xthread.h>
+
+void
+xpthread_spin_unlock (pthread_spinlock_t *lock)
+{
+  xpthread_check_return ("pthread_spin_unlock", pthread_spin_unlock (lock));
+}
diff --git a/support/xrealloc.c b/support/xrealloc.c
new file mode 100644
index 0000000..00c3138
--- /dev/null
+++ b/support/xrealloc.c
@@ -0,0 +1,32 @@
+/* Error-checking wrapper for realloc.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void *
+xrealloc (void *p, size_t n)
+{
+  void *result = realloc (p, n);
+  if (result == NULL && (n > 0 || p == NULL))
+    oom_error ("realloc", n);
+  return result;
+}
diff --git a/support/xrecvfrom.c b/support/xrecvfrom.c
new file mode 100644
index 0000000..17809c4
--- /dev/null
+++ b/support/xrecvfrom.c
@@ -0,0 +1,33 @@
+/* recvfrom with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+size_t
+xrecvfrom (int fd, void *buf, size_t buflen, int flags,
+           struct sockaddr *sa, socklen_t *salen)
+{
+  ssize_t ret = recvfrom (fd, buf, buflen, flags, sa, salen);
+  if (ret < 0)
+    FAIL_EXIT1 ("error: recvfrom (%d), %zu bytes buffer: %m", fd, buflen);
+  return ret;
+}
diff --git a/support/xsendto.c b/support/xsendto.c
new file mode 100644
index 0000000..20bddf6
--- /dev/null
+++ b/support/xsendto.c
@@ -0,0 +1,35 @@
+/* sendto with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xsendto (int fd, const void *buf, size_t buflen, int flags,
+         const struct sockaddr *sa, socklen_t salen)
+{
+  ssize_t ret = sendto (fd, buf, buflen, flags, sa, salen);
+  if (ret < 0)
+    FAIL_EXIT1 ("sendto (%d), %zu bytes, family %d: %m",
+                fd, buflen, sa->sa_family);
+  if (ret != buflen)
+    FAIL_EXIT1 ("sendto (%d) sent %zd bytes instead of %zu", fd, ret, buflen);
+}
diff --git a/support/xsetsockopt.c b/support/xsetsockopt.c
new file mode 100644
index 0000000..9931882
--- /dev/null
+++ b/support/xsetsockopt.c
@@ -0,0 +1,31 @@
+/* setsockopt with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+void
+xsetsockopt (int fd, int level, int name, const void *val, socklen_t vallen)
+{
+  if (setsockopt (fd, level, name, val, vallen) != 0)
+    FAIL_EXIT1 ("setsockopt (%d, %d, %d), %zu bytes: %m",
+                fd, level, name, (size_t) vallen);
+}
diff --git a/support/xsignal.h b/support/xsignal.h
new file mode 100644
index 0000000..3dc0d9d
--- /dev/null
+++ b/support/xsignal.h
@@ -0,0 +1,34 @@
+/* Support functionality for using signals.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_SIGNAL_H
+#define SUPPORT_SIGNAL_H
+
+#include <signal.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* The following functions call the corresponding libpthread functions
+   and terminate the process on error.  */
+
+void xpthread_sigmask (int how, const sigset_t *set, sigset_t *oldset);
+
+__END_DECLS
+
+#endif /* SUPPORT_SIGNAL_H */
diff --git a/support/xsocket.c b/support/xsocket.c
new file mode 100644
index 0000000..c1deaee
--- /dev/null
+++ b/support/xsocket.c
@@ -0,0 +1,32 @@
+/* socket with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+int
+xsocket (int domain, int type, int protocol)
+{
+  int fd = socket (domain, type, protocol);
+  if (fd < 0)
+    FAIL_EXIT1 ("socket (%d, %d, %d): %m\n", domain, type, protocol);
+  return fd;
+}
diff --git a/support/xsocket.h b/support/xsocket.h
new file mode 100644
index 0000000..d672494
--- /dev/null
+++ b/support/xsocket.h
@@ -0,0 +1,39 @@
+/* Error-checking wrappers for socket functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_XSOCKET_H
+#define SUPPORT_XSOCKET_H
+
+#include <poll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+int xsocket (int, int, int);
+void xsetsockopt (int, int, int, const void *, socklen_t);
+void xgetsockname (int, struct sockaddr *, socklen_t *);
+void xconnect (int, const struct sockaddr *, socklen_t);
+void xbind (int, const struct sockaddr *, socklen_t);
+void xlisten (int, int);
+int xaccept (int, struct sockaddr *, socklen_t *);
+int xaccept4 (int, struct sockaddr *, socklen_t *, int);
+void xsendto (int, const void *, size_t, int,
+              const struct sockaddr *, socklen_t);
+size_t xrecvfrom (int, void *, size_t, int, struct sockaddr *, socklen_t *);
+int xpoll (struct pollfd *, nfds_t, int);
+
+#endif /* SUPPORT_XSOCKET_H */
diff --git a/support/xstdio.h b/support/xstdio.h
new file mode 100644
index 0000000..bcc2e86
--- /dev/null
+++ b/support/xstdio.h
@@ -0,0 +1,32 @@
+/* Error-checking wrappers for stdio functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_XSTDIO_H
+#define SUPPORT_XSTDIO_H
+
+#include <stdio.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+FILE *xfopen (const char *path, const char *mode);
+void xfclose (FILE *);
+
+__END_DECLS
+
+#endif /* SUPPORT_XSTDIO_H */
diff --git a/support/xstrdup.c b/support/xstrdup.c
new file mode 100644
index 0000000..d6a8c04
--- /dev/null
+++ b/support/xstrdup.c
@@ -0,0 +1,30 @@
+/* strdup with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <string.h>
+
+char *
+xstrdup (const char *s)
+{
+  char *p = strdup (s);
+  if (p == NULL)
+    oom_error ("strdup", strlen (s));
+  return p;
+}
diff --git a/support/xthread.h b/support/xthread.h
new file mode 100644
index 0000000..6dd7e70
--- /dev/null
+++ b/support/xthread.h
@@ -0,0 +1,77 @@
+/* Support functionality for using threads.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_THREAD_H
+#define SUPPORT_THREAD_H
+
+#include <pthread.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/* Terminate the process (with exit status 0) after SECONDS have
+   elapsed, from a helper thread.  The process is terminated with the
+   exit function, so atexit handlers are executed.  */
+void delayed_exit (int seconds);
+
+/* Terminate the process (with exit status 1) if VALUE is not zero.
+   In that case, print a failure message to standard output mentioning
+   FUNCTION.  The process is terminated with the exit function, so
+   atexit handlers are executed.  */
+void xpthread_check_return (const char *function, int value);
+
+/* The following functions call the corresponding libpthread functions
+   and terminate the process on error.  */
+
+void xpthread_barrier_init (pthread_barrier_t *barrier,
+                            pthread_barrierattr_t *attr, unsigned int count);
+void xpthread_barrier_destroy (pthread_barrier_t *barrier);
+void xpthread_mutexattr_destroy (pthread_mutexattr_t *);
+void xpthread_mutexattr_init (pthread_mutexattr_t *);
+void xpthread_mutexattr_setprotocol (pthread_mutexattr_t *, int);
+void xpthread_mutexattr_setpshared (pthread_mutexattr_t *, int);
+void xpthread_mutexattr_setrobust (pthread_mutexattr_t *, int);
+void xpthread_mutexattr_settype (pthread_mutexattr_t *, int);
+void xpthread_mutex_init (pthread_mutex_t *, const pthread_mutexattr_t *);
+void xpthread_mutex_destroy (pthread_mutex_t *);
+void xpthread_mutex_lock (pthread_mutex_t *mutex);
+void xpthread_mutex_unlock (pthread_mutex_t *mutex);
+void xpthread_mutex_consistent (pthread_mutex_t *);
+void xpthread_spin_lock (pthread_spinlock_t *lock);
+void xpthread_spin_unlock (pthread_spinlock_t *lock);
+void xpthread_cond_wait (pthread_cond_t * cond, pthread_mutex_t * mutex);
+pthread_t xpthread_create (pthread_attr_t *attr,
+                           void *(*thread_func) (void *), void *closure);
+void xpthread_detach (pthread_t thr);
+void xpthread_cancel (pthread_t thr);
+void *xpthread_join (pthread_t thr);
+void xpthread_once (pthread_once_t *guard, void (*func) (void));
+void xpthread_attr_destroy (pthread_attr_t *attr);
+void xpthread_attr_init (pthread_attr_t *attr);
+void xpthread_attr_setdetachstate (pthread_attr_t *attr,
+				   int detachstate);
+void xpthread_attr_setstacksize (pthread_attr_t *attr,
+				 size_t stacksize);
+
+/* This function returns non-zero if pthread_barrier_wait returned
+   PTHREAD_BARRIER_SERIAL_THREAD.  */
+int xpthread_barrier_wait (pthread_barrier_t *barrier);
+
+__END_DECLS
+
+#endif /* SUPPORT_THREAD_H */
diff --git a/support/xunistd.h b/support/xunistd.h
new file mode 100644
index 0000000..151d743
--- /dev/null
+++ b/support/xunistd.h
@@ -0,0 +1,56 @@
+/* POSIX-specific extra functions.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* These wrapper functions use POSIX types and therefore cannot be
+   declared in <support/support.h>.  */
+
+#ifndef SUPPORT_XUNISTD_H
+#define SUPPORT_XUNISTD_H
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+__BEGIN_DECLS
+
+struct stat64;
+
+pid_t xfork (void);
+pid_t xwaitpid (pid_t, int *status, int flags);
+void xpipe (int[2]);
+void xdup2 (int, int);
+int xopen (const char *path, int flags, mode_t);
+void xstat (const char *path, struct stat64 *);
+void xmkdir (const char *path, mode_t);
+void xchroot (const char *path);
+
+/* Close the file descriptor.  Ignore EINTR errors, but terminate the
+   process on other errors.  */
+void xclose (int);
+
+/* Write the buffer.  Retry on short writes.  */
+void xwrite (int, const void *, size_t);
+
+/* Invoke mmap with a zero file offset.  */
+void *xmmap (void *addr, size_t length, int prot, int flags, int fd);
+
+void xmunmap (void *addr, size_t length);
+
+__END_DECLS
+
+#endif /* SUPPORT_XUNISTD_H */
diff --git a/support/xwaitpid.c b/support/xwaitpid.c
new file mode 100644
index 0000000..204795e
--- /dev/null
+++ b/support/xwaitpid.c
@@ -0,0 +1,33 @@
+/* waitpid with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <sys/wait.h>
+
+int
+xwaitpid (int pid, int *status, int flags)
+{
+  pid_t result = waitpid (pid, status, flags);
+  if (result < 0)
+    FAIL_EXIT1 ("waitpid: %m\n");
+  return result;
+}
diff --git a/support/xwrite.c b/support/xwrite.c
new file mode 100644
index 0000000..134e8ee
--- /dev/null
+++ b/support/xwrite.c
@@ -0,0 +1,39 @@
+/* write with error checking and retries.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xunistd.h>
+
+#include <support/check.h>
+
+void
+xwrite (int fd, const void *buffer, size_t length)
+{
+  const char *p = buffer;
+  const char *end = p + length;
+  while (p < end)
+    {
+      ssize_t ret = write (fd, p, end - p);
+      if (ret < 0)
+        FAIL_EXIT1 ("write of %zu bytes failed after %td: %m",
+                    length, p - (const char *) buffer);
+      if (ret == 0)
+        FAIL_EXIT1 ("write return 0 after writing %td bytes of %zu",
+                    p - (const char *) buffer, length);
+      p += ret;
+    }
+}