85 lines
2.1 KiB
C
85 lines
2.1 KiB
C
/* 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/ipv6.h>
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#include <net/ip.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("IP tables packet length matching module");
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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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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 struct xt_match *match,
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const void *matchinfo,
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int offset,
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unsigned int protoff,
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int *hotdrop)
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{
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const struct xt_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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match6(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 struct xt_match *match,
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const void *matchinfo,
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int offset,
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unsigned int protoff,
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int *hotdrop)
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{
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const struct xt_length_info *info = matchinfo;
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u_int16_t pktlen = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr);
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return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
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}
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static struct xt_match xt_length_match[] = {
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{
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.name = "length",
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.family = AF_INET,
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.match = match,
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.matchsize = sizeof(struct xt_length_info),
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.me = THIS_MODULE,
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},
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{
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.name = "length",
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.family = AF_INET6,
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.match = match6,
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.matchsize = sizeof(struct xt_length_info),
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.me = THIS_MODULE,
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},
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};
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static int __init xt_length_init(void)
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{
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return xt_register_matches(xt_length_match,
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ARRAY_SIZE(xt_length_match));
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}
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static void __exit xt_length_fini(void)
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{
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xt_unregister_matches(xt_length_match, ARRAY_SIZE(xt_length_match));
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}
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module_init(xt_length_init);
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module_exit(xt_length_fini);
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