diff --git a/configure.ac b/configure.ac
index 07f590b390..e31d122713 100644
--- a/configure.ac
+++ b/configure.ac
@@ -240,6 +240,7 @@ AC_CONFIG_FILES([
 	tests/zfs-tests/tests/Makefile
 	tests/zfs-tests/tests/functional/Makefile
 	tests/zfs-tests/tests/functional/acl/Makefile
+	tests/zfs-tests/tests/functional/acl/off/Makefile
 	tests/zfs-tests/tests/functional/acl/posix/Makefile
 	tests/zfs-tests/tests/functional/acl/posix-sa/Makefile
 	tests/zfs-tests/tests/functional/alloc_class/Makefile
diff --git a/tests/runfiles/freebsd.run b/tests/runfiles/freebsd.run
index c7ca1d769f..153b204b49 100644
--- a/tests/runfiles/freebsd.run
+++ b/tests/runfiles/freebsd.run
@@ -22,6 +22,10 @@ failsafe = callbacks/zfs_failsafe
 outputdir = /var/tmp/test_results
 tags = ['functional']
 
+[tests/functional/acl/off:FreeBSD]
+tests = ['dosmode']
+tags = ['functional', 'acl']
+
 [tests/functional/cli_root/zfs_jail:FreeBSD]
 tests = ['zfs_jail_001_pos']
 tags = ['functional', 'cli_root', 'zfs_jail']
diff --git a/tests/zfs-tests/tests/functional/acl/Makefile.am b/tests/zfs-tests/tests/functional/acl/Makefile.am
index 382bb5f064..d752f63744 100644
--- a/tests/zfs-tests/tests/functional/acl/Makefile.am
+++ b/tests/zfs-tests/tests/functional/acl/Makefile.am
@@ -3,4 +3,4 @@ dist_pkgdata_DATA = \
 	acl.cfg \
 	acl_common.kshlib
 
-SUBDIRS = posix posix-sa
+SUBDIRS = off posix posix-sa
diff --git a/tests/zfs-tests/tests/functional/acl/off/.gitignore b/tests/zfs-tests/tests/functional/acl/off/.gitignore
new file mode 100644
index 0000000000..f3c93191ce
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/.gitignore
@@ -0,0 +1 @@
+/dosmode_readonly_write
diff --git a/tests/zfs-tests/tests/functional/acl/off/Makefile.am b/tests/zfs-tests/tests/functional/acl/off/Makefile.am
new file mode 100644
index 0000000000..df8adcafef
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/Makefile.am
@@ -0,0 +1,15 @@
+include $(top_srcdir)/config/Rules.am
+
+pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/acl/off
+
+dist_pkgdata_SCRIPTS = \
+	dosmode.ksh \
+	cleanup.ksh \
+	setup.ksh
+
+pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/acl/off
+
+if BUILD_FREEBSD
+pkgexec_PROGRAMS = dosmode_readonly_write
+dosmode_readonly_write_SOURCES = dosmode_readonly_write.c
+endif
diff --git a/tests/zfs-tests/tests/functional/acl/off/cleanup.ksh b/tests/zfs-tests/tests/functional/acl/off/cleanup.ksh
new file mode 100755
index 0000000000..bb58a8cf2e
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/cleanup.ksh
@@ -0,0 +1,33 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/acl/acl_common.kshlib
+
+cleanup_user_group
+
+default_cleanup
diff --git a/tests/zfs-tests/tests/functional/acl/off/dosmode.ksh b/tests/zfs-tests/tests/functional/acl/off/dosmode.ksh
new file mode 100755
index 0000000000..e232dfd525
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/dosmode.ksh
@@ -0,0 +1,199 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Portions Copyright 2021 iXsystems, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/acl/acl_common.kshlib
+
+#
+# DESCRIPTION:
+#	Verify that DOS mode flags function correctly.
+#
+#	These flags are not currently exposed on Linux, so the test is
+#	only useful on FreeBSD.
+#
+# STRATEGY:
+#	1. ARCHIVE
+#	2. HIDDEN
+#	3. OFFLINE
+#	4. READONLY
+#	5. REPARSE
+#	6. SPARSE
+#	7. SYSTEM
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	rm -f $testfile
+}
+
+function hasflag
+{
+	typeset flag=$1
+	typeset path=$2
+
+	ls -lo $path | awk '{ gsub(",", "\n", $5); print $5 }' | grep -qxF $flag
+}
+
+log_assert "Verify DOS mode flags function correctly"
+log_onexit cleanup
+
+tests_base=$STF_SUITE/tests/functional/acl/off
+testfile=$TESTDIR/testfile
+owner=$ZFS_ACL_STAFF1
+other=$ZFS_ACL_STAFF2
+
+#
+# ARCHIVE
+#
+# This flag is set by ZFS when a file has been updated to indicate that
+# the file needs to be archived.
+#
+log_must touch $testfile
+log_must hasflag uarch $testfile
+log_must chflags nouarch $testfile
+log_must hasflag - $testfile
+log_must touch $testfile
+log_must hasflag uarch $testfile
+log_must rm $testfile
+log_must user_run $owner touch $testfile
+log_must hasflag uarch $testfile
+log_must user_run $owner chflags nouarch $testfile
+log_mustnot user_run $other chflags uarch $testfile
+log_must hasflag - $testfile
+log_must user_run $owner touch $testfile
+log_mustnot user_run $other chflags nouarch $testfile
+log_must hasflag uarch $testfile
+log_must user_run $owner rm $testfile
+
+#
+# HIDDEN
+#
+log_must touch $testfile
+log_must chflags hidden $testfile
+log_must hasflag hidden $testfile
+log_must chflags 0 $testfile
+log_must hasflag - $testfile
+log_must rm $testfile
+log_must user_run $owner touch $testfile
+log_must user_run $owner chflags hidden $testfile
+log_mustnot user_run $other chflags nohidden $testfile
+log_must hasflag hidden $testfile
+log_must user_run $owner chflags 0 $testfile
+log_mustnot user_run $other chflags hidden $testfile
+log_must hasflag - $testfile
+log_must user_run $owner rm $testfile
+
+
+#
+# OFFLINE
+#
+log_must touch $testfile
+log_must chflags offline $testfile
+log_must hasflag offline $testfile
+log_must chflags 0 $testfile
+log_must hasflag - $testfile
+log_must rm $testfile
+log_must user_run $owner touch $testfile
+log_must user_run $owner chflags offline $testfile
+log_mustnot user_run $other chflags nooffline $testfile
+log_must hasflag offline $testfile
+log_must user_run $owner chflags 0 $testfile
+log_mustnot user_run $other chflags offline $testfile
+log_must hasflag - $testfile
+log_must user_run $owner rm $testfile
+
+#
+# READONLY
+#
+# This flag prevents users from writing or appending to the file,
+# but root is always allowed the operation.
+#
+log_must touch $testfile
+log_must chflags rdonly $testfile
+log_must hasflag rdonly $testfile
+log_must eval "echo 'root write allowed' >> $testfile"
+log_must cat $testfile
+log_must chflags 0 $testfile
+log_must hasflag - $tesfile
+log_must rm $testfile
+# It is required to still be able to write to an fd that was opened RW before
+# READONLY is set.  We have a special test program for that.
+log_must user_run $owner touch $testfile
+log_mustnot user_run $other chflags rdonly $testfile
+log_must user_run $owner $tests_base/dosmode_readonly_write $testfile
+log_mustnot user_run $other chflags nordonly $testfile
+log_must hasflag rdonly $testfile
+log_mustnot user_run $owner "echo 'user write forbidden' >> $testfile"
+log_must eval "echo 'root write allowed' >> $testfile"
+# We are still allowed to read and remove the file when READONLY is set.
+log_must user_run $owner cat $testfile
+log_must user_run $owner rm $testfile
+
+#
+# REPARSE
+#
+# FIXME: does not work, not sure if broken or testing wrong
+#
+
+#
+# SPARSE
+#
+log_must truncate -s 1m $testfile
+log_must chflags sparse $testfile
+log_must hasflag sparse $testfile
+log_must chflags 0 $testfile
+log_must hasflag - $testfile
+log_must rm $testfile
+log_must user_run $owner truncate -s 1m $testfile
+log_must user_run $owner chflags sparse $testfile
+log_mustnot user_run $other chflags nosparse $testfile
+log_must hasflag sparse $testfile
+log_must user_run $owner chflags 0 $testfile
+log_mustnot user_run $other chflags sparse $testfile
+log_must hasflag - $testfile
+log_must user_run $owner rm $testfile
+
+#
+# SYSTEM
+#
+log_must touch $testfile
+log_must chflags system $testfile
+log_must hasflag system $testfile
+log_must chflags 0 $testfile
+log_must hasflag - $testfile
+log_must rm $testfile
+log_must user_run $owner touch $testfile
+log_must user_run $owner chflags system $testfile
+log_mustnot user_run $other chflags nosystem $testfile
+log_must hasflag system $testfile
+log_must user_run $owner chflags 0 $testfile
+log_mustnot user_run $other chflags system $testfile
+log_must hasflag - $testfile
+log_must user_run $owner rm $testfile
+
+log_pass "DOS mode flags function correctly"
diff --git a/tests/zfs-tests/tests/functional/acl/off/dosmode_readonly_write.c b/tests/zfs-tests/tests/functional/acl/off/dosmode_readonly_write.c
new file mode 100644
index 0000000000..372c3f7f64
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/dosmode_readonly_write.c
@@ -0,0 +1,61 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 iXsystems, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * Test for correct behavior of DOS mode READONLY flag on a file.
+ * We should be able to open a file RW, set READONLY, and still write to the fd.
+ */
+
+#include <sys/stat.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int
+main(int argc, const char *argv[])
+{
+	const char *buf = "We should be allowed to write this to the fd.\n";
+	const char *path;
+	int fd;
+
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s PATH\n", argv[0]);
+		return (EXIT_FAILURE);
+	}
+	path = argv[1];
+	fd = open(path, O_CREAT|O_RDWR, 0777);
+	if (fd == -1)
+		err(EXIT_FAILURE, "%s: open failed", path);
+	if (chflags(path, UF_READONLY) == -1)
+		err(EXIT_FAILURE, "%s: chflags failed", path);
+	if (write(fd, buf, strlen(buf)) == -1)
+		err(EXIT_FAILURE, "%s: write failed", path);
+	if (close(fd) == -1)
+		err(EXIT_FAILURE, "%s: close failed", path);
+	return (EXIT_SUCCESS);
+}
diff --git a/tests/zfs-tests/tests/functional/acl/off/setup.ksh b/tests/zfs-tests/tests/functional/acl/off/setup.ksh
new file mode 100755
index 0000000000..9a5b598a59
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/acl/off/setup.ksh
@@ -0,0 +1,44 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Portions Copyright (c) 2021 iXsystems, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/acl/acl_common.kshlib
+
+DISK=${DISKS%% *}
+
+cleanup_user_group
+
+# Create staff group and add users to it
+log_must add_group $ZFS_ACL_STAFF_GROUP
+log_must add_user $ZFS_ACL_STAFF_GROUP $ZFS_ACL_STAFF1
+log_must add_user $ZFS_ACL_STAFF_GROUP $ZFS_ACL_STAFF2
+
+default_setup_noexit $DISK
+
+log_must zfs set acltype=off $TESTPOOL/$TESTFS
+log_must chmod 0777 $TESTDIR
+
+log_pass