Index: Makefile.inc1
===================================================================
--- Makefile.inc1
+++ Makefile.inc1
@@ -2742,6 +2742,7 @@
 		lib/libelf lib/libexpat \
 		lib/libfigpar \
 		${_lib_libgssapi} \
+		lib/libjail \
 		lib/libkiconv lib/libkvm lib/liblzma lib/libmd lib/libnv \
 		lib/libzstd \
 		${_lib_casper} \
Index: lib/Makefile
===================================================================
--- lib/Makefile
+++ lib/Makefile
@@ -138,6 +138,11 @@
 SUBDIR_DEPEND_libpcap= ofed
 .endif
 
+.if !defined(COMPAT_32BIT)
+SUBDIR+=	flua
+SUBDIR_DEPEND_flua=	libjail
+.endif
+
 # NB: keep these sorted by MK_* knobs
 
 SUBDIR.${MK_ATM}+=	libngatm
Index: lib/flua/Makefile
===================================================================
--- /dev/null
+++ lib/flua/Makefile
@@ -0,0 +1,5 @@
+# $FreeBSD$
+
+SUBDIR=	libjail
+
+.include <bsd.subdir.mk>
Index: lib/flua/libjail/Makefile
===================================================================
--- /dev/null
+++ lib/flua/libjail/Makefile
@@ -0,0 +1,15 @@
+#! $FreeBSD$
+
+SHLIB_NAME=	jail.so
+SHLIBDIR=	${LIBDIR}/flua
+
+SRCS+=		lua_jail.c
+
+CFLAGS+= \
+	-I${.CURDIR} \
+	-I${SRCTOP}/contrib/lua/src \
+	-I${SRCTOP}/lib/liblua \
+
+LIBADD+=	jail
+
+.include <bsd.lib.mk>
Index: lib/flua/libjail/lua_jail.c
===================================================================
--- /dev/null
+++ lib/flua/libjail/lua_jail.c
@@ -0,0 +1,384 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2020, Ryan Moeller <freqlabs@FreeBSD.org>
+ *
+ * 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 REGENTS 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 REGENTS 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.
+ */
+
+#include <sys/param.h>
+#include <sys/jail.h>
+#include <errno.h>
+#include <jail.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+
+static int
+l_getid(lua_State *L)
+{
+	const char *name;
+	int jid;
+
+	name = luaL_checkstring(L, 1);
+	jid = jail_getid(name);
+	if (jid == -1) {
+		lua_pushnil(L);
+		lua_pushstring(L, jail_errmsg);
+		return (2);
+	}
+	lua_pushinteger(L, jid);
+	return (1);
+}
+
+static int
+l_getname(lua_State *L)
+{
+	char *name;
+	int jid;
+
+	jid = luaL_checkinteger(L, 1);
+	name = jail_getname(jid);
+	if (name == NULL) {
+		lua_pushnil(L);
+		lua_pushstring(L, jail_errmsg);
+		return (2);
+	}
+	lua_pushstring(L, name);
+	free(name);
+	return (1);
+}
+
+static int
+l_allparams(lua_State *L)
+{
+	struct jailparam *params;
+	int params_count;
+
+	params_count = jailparam_all(&params);
+	if (params_count == -1) {
+		lua_pushnil(L);
+		lua_pushstring(L, jail_errmsg);
+		return (2);
+	}
+	lua_newtable(L);
+	for (int i = 0; i < params_count; ++i) {
+		lua_pushstring(L, params[i].jp_name);
+		lua_rawseti(L, -2, i + 1);
+	}
+	jailparam_free(params, params_count);
+	free(params);
+	return (1);
+}
+
+static int
+l_getparams(lua_State *L)
+{
+	const char *name;
+	struct jailparam *params;
+	size_t params_count, skipped;
+	int flags, jid, type;
+
+	type = lua_type(L, 1);
+	luaL_argcheck(L, type == LUA_TSTRING || type == LUA_TNUMBER, 1,
+	    "expected a jail name (string) or id (integer)");
+	luaL_checktype(L, 2, LUA_TTABLE);
+	params_count = 1 + lua_rawlen(L, 2);
+	luaL_argcheck(L, params_count > 1, 2, "expected #params > 0");
+	flags = luaL_optinteger(L, 3, 0);
+
+	params = malloc(params_count * sizeof(struct jailparam));
+	if (params == NULL)
+		return (luaL_error(L, "malloc: %s", strerror(errno)));
+
+	/*
+	 * Set the jail name or id param as determined by the first arg.
+	 */
+
+	if (type == LUA_TSTRING) {
+		if (jailparam_init(&params[0], "name") == -1) {
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+		name = lua_tostring(L, 1);
+		if (jailparam_import(&params[0], name) == -1) {
+			jailparam_free(params, 1);
+			free(params);
+			return (luaL_error(L, "jailparam_import: %s",
+			    jail_errmsg));
+		}
+	} else /* type == LUA_TNUMBER */ {
+		if (jailparam_init(&params[0], "jid") == -1) {
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+		jid = lua_tointeger(L, 1);
+		if (jailparam_import_raw(&params[0], &jid, sizeof(jid)) == -1) {
+			jailparam_free(params, 1);
+			free(params);
+			return (luaL_error(L, "jailparam_import_raw: %s",
+			    jail_errmsg));
+		}
+	}
+
+	/*
+	 * Set the remaining param names being requested.
+	 */
+
+	skipped = 0;
+	for (size_t i = 1; i < params_count; ++i) {
+		const char *param_name;
+
+		lua_rawgeti(L, -1, i);
+		param_name = lua_tostring(L, -1);
+		if (param_name == NULL) {
+			jailparam_free(params, i - skipped);
+			free(params);
+			return (luaL_argerror(L, 2,
+			    "param names must be strings"));
+		}
+		lua_pop(L, 1);
+		/* Skip name or jid, whichever was given. */
+		if (type == LUA_TSTRING) {
+			if (strcmp(param_name, "name") == 0) {
+				++skipped;
+				continue;
+			}
+		} else /* type == LUA_TNUMBER */ {
+			if (strcmp(param_name, "jid") == 0) {
+				++skipped;
+				continue;
+			}
+		}
+		if (jailparam_init(&params[i - skipped], param_name) == -1) {
+			jailparam_free(params, i - skipped);
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+	}
+	params_count -= skipped;
+
+	/*
+	 * Get the values and convert to a table.
+	 */
+
+	jid = jailparam_get(params, params_count, flags);
+	if (jid == -1) {
+		jailparam_free(params, params_count);
+		free(params);
+		lua_pushnil(L);
+		lua_pushstring(L, jail_errmsg);
+		return (2);
+	}
+	lua_pushinteger(L, jid);
+
+	lua_newtable(L);
+	for (size_t i = 0; i < params_count; ++i) {
+		const char *value;
+
+		value = jailparam_export(&params[i]);
+		lua_pushstring(L, value);
+		lua_setfield(L, -2, params[i].jp_name);
+	}
+
+	jailparam_free(params, params_count);
+	free(params);
+
+	return (2);
+}
+
+static int
+l_setparams(lua_State *L)
+{
+	const char *name;
+	struct jailparam *params;
+	size_t params_count;
+	int flags, jid, type;
+
+	type = lua_type(L, 1);
+	luaL_argcheck(L, type == LUA_TSTRING || type == LUA_TNUMBER, 1,
+	    "expected a jail name (string) or id (integer)");
+	luaL_checktype(L, 2, LUA_TTABLE);
+
+	params_count = 1;
+	lua_pushnil(L);
+	for (params_count = 1; lua_next(L, 2) != 0; ++params_count)
+		lua_pop(L, 1);
+	luaL_argcheck(L, params_count > 1, 2, "expected #params > 0");
+
+	flags = luaL_optinteger(L, 3, 0);
+
+	params = malloc(params_count * sizeof(struct jailparam));
+	if (params == NULL)
+		return (luaL_error(L, "malloc: %s", strerror(errno)));
+
+	/*
+	 * Set the jail name or id param as determined by the first arg.
+	 */
+
+	if (type == LUA_TSTRING) {
+		if (jailparam_init(&params[0], "name") == -1) {
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+		name = lua_tostring(L, 1);
+		if (jailparam_import(&params[0], name) == -1) {
+			jailparam_free(params, 1);
+			free(params);
+			return (luaL_error(L, "jailparam_import: %s",
+			    jail_errmsg));
+		}
+	} else /* type == LUA_TNUMBER */ {
+		if (jailparam_init(&params[0], "jid") == -1) {
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+		jid = lua_tointeger(L, 1);
+		if (jailparam_import_raw(&params[0], &jid, sizeof(jid)) == -1) {
+			jailparam_free(params, 1);
+			free(params);
+			return (luaL_error(L, "jailparam_import_raw: %s",
+			    jail_errmsg));
+		}
+	}
+
+	/*
+	 * Set the rest of the provided params.
+	 */
+
+	lua_pushnil(L);
+	for (size_t i = 1; i < params_count && lua_next(L, 2) != 0; ++i) {
+		const char *value;
+
+		name = lua_tostring(L, -2);
+		if (name == NULL) {
+			jailparam_free(params, i);
+			free(params);
+			return (luaL_argerror(L, 2,
+			    "param names must be strings"));
+		}
+		if (jailparam_init(&params[i], name) == -1) {
+			jailparam_free(params, i);
+			free(params);
+			return (luaL_error(L, "jailparam_init: %s",
+			    jail_errmsg));
+		}
+
+		value = lua_tostring(L, -1);
+		if (value == NULL) {
+			jailparam_free(params, i + 1);
+			free(params);
+			return (luaL_argerror(L, 2,
+			    "param values must be strings"));
+		}
+		if (jailparam_import(&params[i], value) == -1) {
+			jailparam_free(params, i + 1);
+			free(params);
+			return (luaL_error(L, "jailparam_import: %s",
+			    jail_errmsg));
+		}
+
+		lua_pop(L, 1);
+	}
+
+	/*
+	 * Attempt to set the params.
+	 */
+
+	jid = jailparam_set(params, params_count, flags);
+	if (jid == -1) {
+		jailparam_free(params, params_count);
+		free(params);
+		lua_pushnil(L);
+		lua_pushstring(L, jail_errmsg);
+		return (2);
+	}
+	lua_pushinteger(L, jid);
+
+	jailparam_free(params, params_count);
+	free(params);
+	return (1);
+}
+
+static const struct luaL_Reg l_jail[] = {
+	/** Get id of a jail by name.
+	 * @param name	jail name (string)
+	 * @return	jail id (integer)
+	 *		or nil, error (string) on error
+	 */
+	{"getid", l_getid},
+	/** Get name of a jail by id.
+	 * @param jid	jail id (integer)
+	 * @return	jail name (string)
+	 *		or nil, error (string) on error
+	 */
+	{"getname", l_getname},
+	/** Get a list of all known jail parameters.
+	 * @return	list of jail parameter names (table of strings)
+	 *		or nil, error (string) on error
+	 */
+	{"allparams", l_allparams},
+	/** Get the listed params for a given jail.
+	 * @param jail	jail name (string) or id (integer)
+	 * @param params	list of parameter names (table of strings)
+	 * @param flags	optional flags (integer)
+	 * @return	jid (integer), params (table of [string] = string)
+	 *		or nil, error (string) on error
+	 */
+	{"getparams", l_getparams},
+	/** Set params for a given jail.
+	 * @param jail	jail name (string) or id (integer)
+	 * @param params	params and values (table of [string] = string)
+	 * @param flags	optional flags (integer)
+	 * @return	jid (integer)
+	 *		or nil, error (string) on error
+	 */
+	{"setparams", l_setparams},
+	{NULL, NULL}
+};
+
+int
+luaopen_jail(lua_State *L)
+{
+	lua_newtable(L);
+
+	luaL_setfuncs(L, l_jail, 0);
+
+	lua_pushinteger(L, JAIL_CREATE);
+	lua_setfield(L, -2, "CREATE");
+	lua_pushinteger(L, JAIL_UPDATE);
+	lua_setfield(L, -2, "UPDATE");
+	lua_pushinteger(L, JAIL_ATTACH);
+	lua_setfield(L, -2, "ATTACH");
+	lua_pushinteger(L, JAIL_DYING);
+	lua_setfield(L, -2, "DYING");
+
+	return (1);
+}