1// SPDX-License-Identifier: GPL-2.0-only
2/* Xtables module to match packets using a BPF filter.
3 * Copyright 2013 Google Inc.
4 * Written by Willem de Bruijn <willemb@google.com>
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <linux/module.h>
10#include <linux/syscalls.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	if (len > XT_BPF_MAX_NUM_INSTR)
30		return -EINVAL;
31
32	program.len = len;
33	program.filter = insns;
34
35	if (bpf_prog_create(ret, &program)) {
36		pr_info_ratelimited("check failed: parse error\n");
37		return -EINVAL;
38	}
39
40	return 0;
41}
42
43static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
44{
45	struct bpf_prog *prog;
46
47	prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
48	if (IS_ERR(prog))
49		return PTR_ERR(prog);
50
51	*ret = prog;
52	return 0;
53}
54
55static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
56{
57	if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
58		return -EINVAL;
59
60	*ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
61	return PTR_ERR_OR_ZERO(*ret);
62}
63
64static int bpf_mt_check(const struct xt_mtchk_param *par)
65{
66	struct xt_bpf_info *info = par->matchinfo;
67
68	return __bpf_mt_check_bytecode(info->bpf_program,
69				       info->bpf_program_num_elem,
70				       &info->filter);
71}
72
73static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
74{
75	struct xt_bpf_info_v1 *info = par->matchinfo;
76
77	if (info->mode == XT_BPF_MODE_BYTECODE)
78		return __bpf_mt_check_bytecode(info->bpf_program,
79					       info->bpf_program_num_elem,
80					       &info->filter);
81	else if (info->mode == XT_BPF_MODE_FD_ELF)
82		return __bpf_mt_check_fd(info->fd, &info->filter);
83	else if (info->mode == XT_BPF_MODE_PATH_PINNED)
84		return __bpf_mt_check_path(info->path, &info->filter);
85	else
86		return -EINVAL;
87}
88
89static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
90{
91	const struct xt_bpf_info *info = par->matchinfo;
92
93	return bpf_prog_run(info->filter, skb);
94}
95
96static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
97{
98	const struct xt_bpf_info_v1 *info = par->matchinfo;
99
100	return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
101}
102
103static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
104{
105	const struct xt_bpf_info *info = par->matchinfo;
106
107	bpf_prog_destroy(info->filter);
108}
109
110static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
111{
112	const struct xt_bpf_info_v1 *info = par->matchinfo;
113
114	bpf_prog_destroy(info->filter);
115}
116
117static struct xt_match bpf_mt_reg[] __read_mostly = {
118	{
119		.name		= "bpf",
120		.revision	= 0,
121		.family		= NFPROTO_UNSPEC,
122		.checkentry	= bpf_mt_check,
123		.match		= bpf_mt,
124		.destroy	= bpf_mt_destroy,
125		.matchsize	= sizeof(struct xt_bpf_info),
126		.usersize	= offsetof(struct xt_bpf_info, filter),
127		.me		= THIS_MODULE,
128	},
129	{
130		.name		= "bpf",
131		.revision	= 1,
132		.family		= NFPROTO_UNSPEC,
133		.checkentry	= bpf_mt_check_v1,
134		.match		= bpf_mt_v1,
135		.destroy	= bpf_mt_destroy_v1,
136		.matchsize	= sizeof(struct xt_bpf_info_v1),
137		.usersize	= offsetof(struct xt_bpf_info_v1, filter),
138		.me		= THIS_MODULE,
139	},
140};
141
142static int __init bpf_mt_init(void)
143{
144	return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
145}
146
147static void __exit bpf_mt_exit(void)
148{
149	xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
150}
151
152module_init(bpf_mt_init);
153module_exit(bpf_mt_exit);
154