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