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);