| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* Kernel module to match packet length. */ |
| 3 | /* (C) 1999-2001 James Morris <jmorros@intercode.com.au> |
| 4 | */ |
| 5 | |
| 6 | #include <linux/module.h> |
| 7 | #include <linux/skbuff.h> |
| 8 | #include <linux/ipv6.h> |
| 9 | #include <net/ip.h> |
| 10 | |
| 11 | #include <linux/netfilter/xt_length.h> |
| 12 | #include <linux/netfilter/x_tables.h> |
| 13 | |
| 14 | MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>"); |
| 15 | MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match"); |
| 16 | MODULE_LICENSE("GPL"); |
| 17 | MODULE_ALIAS("ipt_length"); |
| 18 | MODULE_ALIAS("ip6t_length"); |
| 19 | |
| 20 | static bool |
| 21 | length_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| 22 | { |
| 23 | const struct xt_length_info *info = par->matchinfo; |
| 24 | u32 pktlen = skb_ip_totlen(skb); |
| 25 | |
| 26 | return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| 27 | } |
| 28 | |
| 29 | static bool |
| 30 | length_mt6(const struct sk_buff *skb, struct xt_action_param *par) |
| 31 | { |
| 32 | const struct xt_length_info *info = par->matchinfo; |
| 33 | u32 pktlen = skb->len; |
| 34 | |
| 35 | return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| 36 | } |
| 37 | |
| 38 | static struct xt_match length_mt_reg[] __read_mostly = { |
| 39 | { |
| 40 | .name = "length", |
| 41 | .family = NFPROTO_IPV4, |
| 42 | .match = length_mt, |
| 43 | .matchsize = sizeof(struct xt_length_info), |
| 44 | .me = THIS_MODULE, |
| 45 | }, |
| 46 | { |
| 47 | .name = "length", |
| 48 | .family = NFPROTO_IPV6, |
| 49 | .match = length_mt6, |
| 50 | .matchsize = sizeof(struct xt_length_info), |
| 51 | .me = THIS_MODULE, |
| 52 | }, |
| 53 | }; |
| 54 | |
| 55 | static int __init length_mt_init(void) |
| 56 | { |
| 57 | return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| 58 | } |
| 59 | |
| 60 | static void __exit length_mt_exit(void) |
| 61 | { |
| 62 | xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| 63 | } |
| 64 | |
| 65 | module_init(length_mt_init); |
| 66 | module_exit(length_mt_exit); |