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         program.len = len;
  31         program.filter = insns;
  32
  33         if (bpf_prog_create(ret, &program)) {
  34                 pr_info("bpf: check failed: parse error\n");
  35                 return -EINVAL;
  36         }
  37
  38         return 0;
  39 }
  40
  41 static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
  42 {
  43         struct bpf_prog *prog;
  44
  45         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
  46         if (IS_ERR(prog))
  47                 return PTR_ERR(prog);
  48
  49         *ret = prog;
  50         return 0;
  51 }
  52
  53 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
  54 {
  55         mm_segment_t oldfs = get_fs();
  56         int retval, fd;
  57
  58         set_fs(KERNEL_DS);
  59         fd = bpf_obj_get_user(path, 0);
  60         set_fs(oldfs);
  61         if (fd < 0)
  62                 return fd;
  63
  64         retval = __bpf_mt_check_fd(fd, ret);
  65         sys_close(fd);
  66         return retval;
  67 }
  68
  69 static int bpf_mt_check(const struct xt_mtchk_param *par)
  70 {
  71         struct xt_bpf_info *info = par->matchinfo;
  72
  73         return __bpf_mt_check_bytecode(info->bpf_program,
  74                                        info->bpf_program_num_elem,
  75                                        &info->filter);
  76 }
  77
  78 static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
  79 {
  80         struct xt_bpf_info_v1 *info = par->matchinfo;
  81
  82         if (info->mode == XT_BPF_MODE_BYTECODE)
  83                 return __bpf_mt_check_bytecode(info->bpf_program,
  84                                                info->bpf_program_num_elem,
  85                                                &info->filter);
  86         else if (info->mode == XT_BPF_MODE_FD_ELF)
  87                 return __bpf_mt_check_fd(info->fd, &info->filter);
  88         else if (info->mode == XT_BPF_MODE_PATH_PINNED)
  89                 return __bpf_mt_check_path(info->path, &info->filter);
  90         else
  91                 return -EINVAL;
  92 }
  93
  94 static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
  95 {
  96         const struct xt_bpf_info *info = par->matchinfo;
  97
  98         return BPF_PROG_RUN(info->filter, skb);
  99 }
 100
 101 static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 102 {
 103         const struct xt_bpf_info_v1 *info = par->matchinfo;
 104
 105         return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
 106 }
 107
 108 static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
 109 {
 110         const struct xt_bpf_info *info = par->matchinfo;
 111
 112         bpf_prog_destroy(info->filter);
 113 }
 114
 115 static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
 116 {
 117         const struct xt_bpf_info_v1 *info = par->matchinfo;
 118
 119         bpf_prog_destroy(info->filter);
 120 }
 121
 122 static struct xt_match bpf_mt_reg[] __read_mostly = {
 123         {
 124                 .name           = "bpf",
 125                 .revision       = 0,
 126                 .family         = NFPROTO_UNSPEC,
 127                 .checkentry     = bpf_mt_check,
 128                 .match          = bpf_mt,
 129                 .destroy        = bpf_mt_destroy,
 130                 .matchsize      = sizeof(struct xt_bpf_info),
 131                 .usersize       = offsetof(struct xt_bpf_info, filter),
 132                 .me             = THIS_MODULE,
 133         },
 134         {
 135                 .name           = "bpf",
 136                 .revision       = 1,
 137                 .family         = NFPROTO_UNSPEC,
 138                 .checkentry     = bpf_mt_check_v1,
 139                 .match          = bpf_mt_v1,
 140                 .destroy        = bpf_mt_destroy_v1,
 141                 .matchsize      = sizeof(struct xt_bpf_info_v1),
 142                 .usersize       = offsetof(struct xt_bpf_info_v1, filter),
 143                 .me             = THIS_MODULE,
 144         },
 145 };
 146
 147 static int __init bpf_mt_init(void)
 148 {
 149         return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 150 }
 151
 152 static void __exit bpf_mt_exit(void)
 153 {
 154         xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
 155 }
 156
 157 module_init(bpf_mt_init);
 158 module_exit(bpf_mt_exit);