1/* Xtables module to match packets using a BPF filter.
  2 * Copyright 2013 Google Inc.
  3 * Written by Willem de Bruijn <willemb@google.com>
  4 *
  5 * This program is free software; you can redistribute it and/or modify
  6 * it under the terms of the GNU General Public License version 2 as
  7 * published by the Free Software Foundation.
  8 */
  9
 10#include <linux/module.h>
 11#include <linux/skbuff.h>
 12#include <linux/filter.h>
 13#include <linux/bpf.h>
 14
 15#include <linux/netfilter/xt_bpf.h>
 16#include <linux/netfilter/x_tables.h>
 17
 18MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
 19MODULE_DESCRIPTION("Xtables: BPF filter match");
 20MODULE_LICENSE("GPL");
 21MODULE_ALIAS("ipt_bpf");
 22MODULE_ALIAS("ip6t_bpf");
 23
 24static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
 25				   struct bpf_prog **ret)
 26{
 27	struct sock_fprog_kern program;
 28
 29	program.len = len;
 30	program.filter = insns;
 31
 32	if (bpf_prog_create(ret, &program)) {
 33		pr_info("bpf: check failed: parse error\n");
 34		return -EINVAL;
 35	}
 36
 37	return 0;
 38}
 39
 40static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
 41{
 42	struct bpf_prog *prog;
 43
 44	prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
 45	if (IS_ERR(prog))
 46		return PTR_ERR(prog);
 47
 48	*ret = prog;
 49	return 0;
 50}
 51
 52static int bpf_mt_check(const struct xt_mtchk_param *par)
 53{
 54	struct xt_bpf_info *info = par->matchinfo;
 55
 56	return __bpf_mt_check_bytecode(info->bpf_program,
 57				       info->bpf_program_num_elem,
 58				       &info->filter);
 59}
 60
 61static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
 62{
 63	struct xt_bpf_info_v1 *info = par->matchinfo;
 64
 65	if (info->mode == XT_BPF_MODE_BYTECODE)
 66		return __bpf_mt_check_bytecode(info->bpf_program,
 67					       info->bpf_program_num_elem,
 68					       &info->filter);
 69	else if (info->mode == XT_BPF_MODE_FD_PINNED ||
 70		 info->mode == XT_BPF_MODE_FD_ELF)
 71		return __bpf_mt_check_fd(info->fd, &info->filter);
 72	else
 73		return -EINVAL;
 74}
 75
 76static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
 77{
 78	const struct xt_bpf_info *info = par->matchinfo;
 79
 80	return BPF_PROG_RUN(info->filter, skb);
 81}
 82
 83static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 84{
 85	const struct xt_bpf_info_v1 *info = par->matchinfo;
 86
 87	return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 88}
 89
 90static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 91{
 92	const struct xt_bpf_info *info = par->matchinfo;
 93
 94	bpf_prog_destroy(info->filter);
 95}
 96
 97static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 98{
 99	const struct xt_bpf_info_v1 *info = par->matchinfo;
100
101	bpf_prog_destroy(info->filter);
102}
103
104static struct xt_match bpf_mt_reg[] __read_mostly = {
105	{
106		.name		= "bpf",
107		.revision	= 0,
108		.family		= NFPROTO_UNSPEC,
109		.checkentry	= bpf_mt_check,
110		.match		= bpf_mt,
111		.destroy	= bpf_mt_destroy,
112		.matchsize	= sizeof(struct xt_bpf_info),
113		.me		= THIS_MODULE,
114	},
115	{
116		.name		= "bpf",
117		.revision	= 1,
118		.family		= NFPROTO_UNSPEC,
119		.checkentry	= bpf_mt_check_v1,
120		.match		= bpf_mt_v1,
121		.destroy	= bpf_mt_destroy_v1,
122		.matchsize	= sizeof(struct xt_bpf_info_v1),
123		.me		= THIS_MODULE,
124	},
125};
126
127static int __init bpf_mt_init(void)
128{
129	return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
130}
131
132static void __exit bpf_mt_exit(void)
133{
134	xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
135}
136
137module_init(bpf_mt_init);
138module_exit(bpf_mt_exit);