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/* Kernel module to match AH parameters. */
/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
*
* 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/in.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/netfilter_ipv4/ipt_ah.h>
#include <linux/netfilter/x_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
#ifdef DEBUG_CONNTRACK
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif
/* Returns 1 if the spi is matched by the range, 0 otherwise */
static inline bool
spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
{
bool r;
duprintf("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
min,spi,max);
r=(spi >= min && spi <= max) ^ invert;
duprintf(" result %s\n",r? "PASS" : "FAILED");
return r;
}
static bool
ah_mt(const struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, const struct xt_match *match,
const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
{
struct ip_auth_hdr _ahdr;
const struct ip_auth_hdr *ah;
const struct ipt_ah *ahinfo = matchinfo;
/* Must not be a fragment. */
if (offset)
return false;
ah = skb_header_pointer(skb, protoff,
sizeof(_ahdr), &_ahdr);
if (ah == NULL) {
/* We've been asked to examine this packet, and we
* can't. Hence, no choice but to drop.
*/
duprintf("Dropping evil AH tinygram.\n");
*hotdrop = true;
return 0;
}
return spi_match(ahinfo->spis[0], ahinfo->spis[1],
ntohl(ah->spi),
!!(ahinfo->invflags & IPT_AH_INV_SPI));
}
/* Called when user tries to insert an entry of this type. */
static bool
ah_mt_check(const char *tablename, const void *ip_void,
const struct xt_match *match, void *matchinfo,
unsigned int hook_mask)
{
const struct ipt_ah *ahinfo = matchinfo;
/* Must specify no unknown invflags */
if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
duprintf("ipt_ah: unknown flags %X\n", ahinfo->invflags);
return false;
}
return true;
}
static struct xt_match ah_mt_reg __read_mostly = {
.name = "ah",
.family = AF_INET,
.match = ah_mt,
.matchsize = sizeof(struct ipt_ah),
.proto = IPPROTO_AH,
.checkentry = ah_mt_check,
.me = THIS_MODULE,
};
static int __init ah_mt_init(void)
{
return xt_register_match(&ah_mt_reg);
}
static void __exit ah_mt_exit(void)
{
xt_unregister_match(&ah_mt_reg);
}
module_init(ah_mt_init);
module_exit(ah_mt_exit);
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