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); 157