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 #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
  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
  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
  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 static int bpf_mt_check(const struct xt_mtchk_param *par)
  66 {
  67         struct xt_bpf_info *info = par->matchinfo;
  68
  69         return __bpf_mt_check_bytecode(info->bpf_program,
  70                                        info->bpf_program_num_elem,
  71                                        &info->filter);
  72 }
  73
  74 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
  75 {
  76         struct xt_bpf_info_v1 *info = par->matchinfo;
  77
  78         if (info->mode == XT_BPF_MODE_BYTECODE)
  79                 return __bpf_mt_check_bytecode(info->bpf_program,
  80                                                info->bpf_program_num_elem,
  81                                                &info->filter);
  82         else if (info->mode == XT_BPF_MODE_FD_ELF)
  83                 return __bpf_mt_check_fd(info->fd, &info->filter);
  84         else if (info->mode == XT_BPF_MODE_PATH_PINNED)
  85                 return __bpf_mt_check_path(info->path, &info->filter);
  86         else
  87                 return -EINVAL;
  88 }
  89
  90 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
  91 {
  92         const struct xt_bpf_info *info = par->matchinfo;
  93
  94         return BPF_PROG_RUN(info->filter, skb);
  95 }
  96
  97 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
  98 {
  99         const struct xt_bpf_info_v1 *info = par->matchinfo;
 100
 101         return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 102 }
 103
 104 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 105 {
 106         const struct xt_bpf_info *info = par->matchinfo;
 107
 108         bpf_prog_destroy(info->filter);
 109 }
 110
 111 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 112 {
 113         const struct xt_bpf_info_v1 *info = par->matchinfo;
 114
 115         bpf_prog_destroy(info->filter);
 116 }
 117
 118 static struct xt_match bpf_mt_reg[] __read_mostly = {
 119         {
 120                 .name           = "bpf",
 121                 .revision       = 0,
 122                 .family         = NFPROTO_UNSPEC,
 123                 .checkentry     = bpf_mt_check,
 124                 .match          = bpf_mt,
 125                 .destroy        = bpf_mt_destroy,
 126                 .matchsize      = sizeof(struct xt_bpf_info),
 127                 .usersize       = offsetof(struct xt_bpf_info, filter),
 128                 .me             = THIS_MODULE,
 129         },
 130         {
 131                 .name           = "bpf",
 132                 .revision       = 1,
 133                 .family         = NFPROTO_UNSPEC,
 134                 .checkentry     = bpf_mt_check_v1,
 135                 .match          = bpf_mt_v1,
 136                 .destroy        = bpf_mt_destroy_v1,
 137                 .matchsize      = sizeof(struct xt_bpf_info_v1),
 138                 .usersize       = offsetof(struct xt_bpf_info_v1, filter),
 139                 .me             = THIS_MODULE,
 140         },
 141 };
 142
 143 static int __init bpf_mt_init(void)
 144 {
 145         return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 146 }
 147
 148 static void __exit bpf_mt_exit(void)
 149 {
 150         xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 151 }
 152
 153 module_init(bpf_mt_init);
 154 module_exit(bpf_mt_exit);