65 lines
1.5 KiB
C
65 lines
1.5 KiB
C
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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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*
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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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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter_ipv4/ipt_length.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
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MODULE_DESCRIPTION("IP tables packet length matching module");
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MODULE_LICENSE("GPL");
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static int
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match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const void *matchinfo,
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int offset,
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int *hotdrop)
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{
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const struct ipt_length_info *info = matchinfo;
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u_int16_t pktlen = ntohs(skb->nh.iph->tot_len);
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return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
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}
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static int
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checkentry(const char *tablename,
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const struct ipt_ip *ip,
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void *matchinfo,
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unsigned int matchsize,
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unsigned int hook_mask)
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{
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if (matchsize != IPT_ALIGN(sizeof(struct ipt_length_info)))
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return 0;
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return 1;
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}
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static struct ipt_match length_match = {
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.name = "length",
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.match = &match,
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.checkentry = &checkentry,
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.me = THIS_MODULE,
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};
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static int __init init(void)
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{
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return ipt_register_match(&length_match);
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}
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static void __exit fini(void)
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{
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ipt_unregister_match(&length_match);
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}
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module_init(init);
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module_exit(fini);
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