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/syscalls.h>
12 #include <linux/skbuff.h>
13 #include <linux/filter.h>
14 #include <linux/bpf.h>
15
16 #include <linux/netfilter/xt_bpf.h>
17 #include <linux/netfilter/x_tables.h>
18
19 MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
20 MODULE_DESCRIPTION("Xtables: BPF filter match");
21 MODULE_LICENSE("GPL");
22 MODULE_ALIAS("ipt_bpf");
23 MODULE_ALIAS("ip6t_bpf");
24
__bpf_mt_check_bytecode(struct sock_filter * insns,__u16 len,struct bpf_prog ** ret)25 static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
26 struct bpf_prog **ret)
27 {
28 struct sock_fprog_kern program;
29
30 if (len > XT_BPF_MAX_NUM_INSTR)
31 return -EINVAL;
32
33 program.len = len;
34 program.filter = insns;
35
36 if (bpf_prog_create(ret, &program)) {
37 pr_info("bpf: check failed: parse error\n");
38 return -EINVAL;
39 }
40
41 return 0;
42 }
43
__bpf_mt_check_fd(int fd,struct bpf_prog ** ret)44 static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
45 {
46 struct bpf_prog *prog;
47
48 prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
49 if (IS_ERR(prog))
50 return PTR_ERR(prog);
51
52 *ret = prog;
53 return 0;
54 }
55
__bpf_mt_check_path(const char * path,struct bpf_prog ** ret)56 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
57 {
58 if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
59 return -EINVAL;
60
61 *ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
62 return PTR_ERR_OR_ZERO(*ret);
63
64 }
65
bpf_mt_check(const struct xt_mtchk_param * par)66 static int bpf_mt_check(const struct xt_mtchk_param *par)
67 {
68 struct xt_bpf_info *info = par->matchinfo;
69
70 return __bpf_mt_check_bytecode(info->bpf_program,
71 info->bpf_program_num_elem,
72 &info->filter);
73 }
74
bpf_mt_check_v1(const struct xt_mtchk_param * par)75 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
76 {
77 struct xt_bpf_info_v1 *info = par->matchinfo;
78
79 if (info->mode == XT_BPF_MODE_BYTECODE)
80 return __bpf_mt_check_bytecode(info->bpf_program,
81 info->bpf_program_num_elem,
82 &info->filter);
83 else if (info->mode == XT_BPF_MODE_FD_ELF)
84 return __bpf_mt_check_fd(info->fd, &info->filter);
85 else if (info->mode == XT_BPF_MODE_PATH_PINNED)
86 return __bpf_mt_check_path(info->path, &info->filter);
87 else
88 return -EINVAL;
89 }
90
bpf_mt(const struct sk_buff * skb,struct xt_action_param * par)91 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
92 {
93 const struct xt_bpf_info *info = par->matchinfo;
94
95 return BPF_PROG_RUN(info->filter, skb);
96 }
97
bpf_mt_v1(const struct sk_buff * skb,struct xt_action_param * par)98 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
99 {
100 const struct xt_bpf_info_v1 *info = par->matchinfo;
101
102 return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
103 }
104
bpf_mt_destroy(const struct xt_mtdtor_param * par)105 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
106 {
107 const struct xt_bpf_info *info = par->matchinfo;
108
109 bpf_prog_destroy(info->filter);
110 }
111
bpf_mt_destroy_v1(const struct xt_mtdtor_param * par)112 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
113 {
114 const struct xt_bpf_info_v1 *info = par->matchinfo;
115
116 bpf_prog_destroy(info->filter);
117 }
118
119 static struct xt_match bpf_mt_reg[] __read_mostly = {
120 {
121 .name = "bpf",
122 .revision = 0,
123 .family = NFPROTO_UNSPEC,
124 .checkentry = bpf_mt_check,
125 .match = bpf_mt,
126 .destroy = bpf_mt_destroy,
127 .matchsize = sizeof(struct xt_bpf_info),
128 .usersize = offsetof(struct xt_bpf_info, filter),
129 .me = THIS_MODULE,
130 },
131 {
132 .name = "bpf",
133 .revision = 1,
134 .family = NFPROTO_UNSPEC,
135 .checkentry = bpf_mt_check_v1,
136 .match = bpf_mt_v1,
137 .destroy = bpf_mt_destroy_v1,
138 .matchsize = sizeof(struct xt_bpf_info_v1),
139 .usersize = offsetof(struct xt_bpf_info_v1, filter),
140 .me = THIS_MODULE,
141 },
142 };
143
bpf_mt_init(void)144 static int __init bpf_mt_init(void)
145 {
146 return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
147 }
148
bpf_mt_exit(void)149 static void __exit bpf_mt_exit(void)
150 {
151 xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
152 }
153
154 module_init(bpf_mt_init);
155 module_exit(bpf_mt_exit);
156