| 1 | /* Kernel module to match packet length. */ |
| 2 | /* (C) 1999-2001 James Morris <jmorros@intercode.com.au> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License version 2 as |
| 6 | * published by the Free Software Foundation. |
| 7 | */ |
| 8 | |
| 9 | #include <linux/module.h> |
| 10 | #include <linux/skbuff.h> |
| 11 | #include <linux/ipv6.h> |
| 12 | #include <net/ip.h> |
| 13 | |
| 14 | #include <linux/netfilter/xt_length.h> |
| 15 | #include <linux/netfilter/x_tables.h> |
| 16 | |
| 17 | MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>"); |
| 18 | MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match"); |
| 19 | MODULE_LICENSE("GPL"); |
| 20 | MODULE_ALIAS("ipt_length"); |
| 21 | MODULE_ALIAS("ip6t_length"); |
| 22 | |
| 23 | static bool |
| 24 | length_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| 25 | { |
| 26 | const struct xt_length_info *info = par->matchinfo; |
| 27 | u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len); |
| 28 | |
| 29 | return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| 30 | } |
| 31 | |
| 32 | static bool |
| 33 | length_mt6(const struct sk_buff *skb, struct xt_action_param *par) |
| 34 | { |
| 35 | const struct xt_length_info *info = par->matchinfo; |
| 36 | const u_int16_t pktlen = ntohs(ipv6_hdr(skb)->payload_len) + |
| 37 | sizeof(struct ipv6hdr); |
| 38 | |
| 39 | return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| 40 | } |
| 41 | |
| 42 | static struct xt_match length_mt_reg[] __read_mostly = { |
| 43 | { |
| 44 | .name = "length", |
| 45 | .family = NFPROTO_IPV4, |
| 46 | .match = length_mt, |
| 47 | .matchsize = sizeof(struct xt_length_info), |
| 48 | .me = THIS_MODULE, |
| 49 | }, |
| 50 | { |
| 51 | .name = "length", |
| 52 | .family = NFPROTO_IPV6, |
| 53 | .match = length_mt6, |
| 54 | .matchsize = sizeof(struct xt_length_info), |
| 55 | .me = THIS_MODULE, |
| 56 | }, |
| 57 | }; |
| 58 | |
| 59 | static int __init length_mt_init(void) |
| 60 | { |
| 61 | return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| 62 | } |
| 63 | |
| 64 | static void __exit length_mt_exit(void) |
| 65 | { |
| 66 | xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| 67 | } |
| 68 | |
| 69 | module_init(length_mt_init); |
| 70 | module_exit(length_mt_exit); |