net/netfilter/xt_bpf.c

   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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/module.h>
  13 #include <linux/syscalls.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/filter.h>
  16 #include <linux/bpf.h>
  17
  18 #include <linux/netfilter/xt_bpf.h>
  19 #include <linux/netfilter/x_tables.h>
  20
  21 MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
  22 MODULE_DESCRIPTION("Xtables: BPF filter match");
  23 MODULE_LICENSE("GPL");
  24 MODULE_ALIAS("ipt_bpf");
  25 MODULE_ALIAS("ip6t_bpf");
  26
  27 static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
  28                                    struct bpf_prog **ret)
  29 {
  30         struct sock_fprog_kern program;
  31
  32         if (len > XT_BPF_MAX_NUM_INSTR)
  33                 return -EINVAL;
  34
  35         program.len = len;
  36         program.filter = insns;
  37
  38         if (bpf_prog_create(ret, &program)) {
  39                 pr_info_ratelimited("check failed: parse error\n");
  40                 return -EINVAL;
  41         }
  42
  43         return 0;
  44 }
  45
  46 static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
  47 {
  48         struct bpf_prog *prog;
  49
  50         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
  51         if (IS_ERR(prog))
  52                 return PTR_ERR(prog);
  53
  54         *ret = prog;
  55         return 0;
  56 }
  57
  58 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
  59 {
  60         if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
  61                 return -EINVAL;
  62
  63         *ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
  64         return PTR_ERR_OR_ZERO(*ret);
  65 }
  66
  67 static int bpf_mt_check(const struct xt_mtchk_param *par)
  68 {
  69         struct xt_bpf_info *info = par->matchinfo;
  70
  71         return __bpf_mt_check_bytecode(info->bpf_program,
  72                                        info->bpf_program_num_elem,
  73                                        &info->filter);
  74 }
  75
  76 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
  77 {
  78         struct xt_bpf_info_v1 *info = par->matchinfo;
  79
  80         if (info->mode == XT_BPF_MODE_BYTECODE)
  81                 return __bpf_mt_check_bytecode(info->bpf_program,
  82                                                info->bpf_program_num_elem,
  83                                                &info->filter);
  84         else if (info->mode == XT_BPF_MODE_FD_ELF)
  85                 return __bpf_mt_check_fd(info->fd, &info->filter);
  86         else if (info->mode == XT_BPF_MODE_PATH_PINNED)
  87                 return __bpf_mt_check_path(info->path, &info->filter);
  88         else
  89                 return -EINVAL;
  90 }
  91
  92 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
  93 {
  94         const struct xt_bpf_info *info = par->matchinfo;
  95
  96         return BPF_PROG_RUN(info->filter, skb);
  97 }
  98
  99 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 100 {
 101         const struct xt_bpf_info_v1 *info = par->matchinfo;
 102
 103         return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 104 }
 105
 106 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 107 {
 108         const struct xt_bpf_info *info = par->matchinfo;
 109
 110         bpf_prog_destroy(info->filter);
 111 }
 112
 113 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 114 {
 115         const struct xt_bpf_info_v1 *info = par->matchinfo;
 116
 117         bpf_prog_destroy(info->filter);
 118 }
 119
 120 static struct xt_match bpf_mt_reg[] __read_mostly = {
 121         {
 122                 .name           = "bpf",
 123                 .revision       = 0,
 124                 .family         = NFPROTO_UNSPEC,
 125                 .checkentry     = bpf_mt_check,
 126                 .match          = bpf_mt,
 127                 .destroy        = bpf_mt_destroy,
 128                 .matchsize      = sizeof(struct xt_bpf_info),
 129                 .usersize       = offsetof(struct xt_bpf_info, filter),
 130                 .me             = THIS_MODULE,
 131         },
 132         {
 133                 .name           = "bpf",
 134                 .revision       = 1,
 135                 .family         = NFPROTO_UNSPEC,
 136                 .checkentry     = bpf_mt_check_v1,
 137                 .match          = bpf_mt_v1,
 138                 .destroy        = bpf_mt_destroy_v1,
 139                 .matchsize      = sizeof(struct xt_bpf_info_v1),
 140                 .usersize       = offsetof(struct xt_bpf_info_v1, filter),
 141                 .me             = THIS_MODULE,
 142         },
 143 };
 144
 145 static int __init bpf_mt_init(void)
 146 {
 147         return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 148 }
 149
 150 static void __exit bpf_mt_exit(void)
 151 {
 152         xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 153 }
 154
 155 module_init(bpf_mt_init);
 156 module_exit(bpf_mt_exit);