| /* Kernel module to match packet length. */ |
| /* (C) 1999-2001 James Morris <jmorros@intercode.com.au> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/ipv6.h> |
| #include <net/ip.h> |
| |
| #include <linux/netfilter/xt_length.h> |
| #include <linux/netfilter/x_tables.h> |
| |
| MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>"); |
| MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match"); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS("ipt_length"); |
| MODULE_ALIAS("ip6t_length"); |
| |
| static bool |
| length_mt(const struct sk_buff *skb, const struct xt_action_param *par) |
| { |
| const struct xt_length_info *info = par->matchinfo; |
| u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len); |
| |
| return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| } |
| |
| static bool |
| length_mt6(const struct sk_buff *skb, const struct xt_action_param *par) |
| { |
| const struct xt_length_info *info = par->matchinfo; |
| const u_int16_t pktlen = ntohs(ipv6_hdr(skb)->payload_len) + |
| sizeof(struct ipv6hdr); |
| |
| return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; |
| } |
| |
| static struct xt_match length_mt_reg[] __read_mostly = { |
| { |
| .name = "length", |
| .family = NFPROTO_IPV4, |
| .match = length_mt, |
| .matchsize = sizeof(struct xt_length_info), |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "length", |
| .family = NFPROTO_IPV6, |
| .match = length_mt6, |
| .matchsize = sizeof(struct xt_length_info), |
| .me = THIS_MODULE, |
| }, |
| }; |
| |
| static int __init length_mt_init(void) |
| { |
| return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| } |
| |
| static void __exit length_mt_exit(void) |
| { |
| xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
| } |
| |
| module_init(length_mt_init); |
| module_exit(length_mt_exit); |