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/* Kernel module to match ESP 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/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/netfilter_ipv4/ipt_esp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
MODULE_DESCRIPTION("iptables ESP SPI match module");
#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 int
spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
{
int r=0;
duprintf("esp 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 int
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const void *matchinfo,
int offset,
unsigned int protoff,
int *hotdrop)
{
struct ip_esp_hdr _esp, *eh;
const struct ipt_esp *espinfo = matchinfo;
/* Must not be a fragment. */
if (offset)
return 0;
eh = skb_header_pointer(skb, protoff,
sizeof(_esp), &_esp);
if (eh == NULL) {
/* We've been asked to examine this packet, and we
* can't. Hence, no choice but to drop.
*/
duprintf("Dropping evil ESP tinygram.\n");
*hotdrop = 1;
return 0;
}
return spi_match(espinfo->spis[0], espinfo->spis[1],
ntohl(eh->spi),
!!(espinfo->invflags & IPT_ESP_INV_SPI));
}
/* Called when user tries to insert an entry of this type. */
static int
checkentry(const char *tablename,
const void *ip_void,
void *matchinfo,
unsigned int matchinfosize,
unsigned int hook_mask)
{
const struct ipt_esp *espinfo = matchinfo;
/* Must specify no unknown invflags */
if (espinfo->invflags & ~IPT_ESP_INV_MASK) {
duprintf("ipt_esp: unknown flags %X\n", espinfo->invflags);
return 0;
}
return 1;
}
static struct ipt_match esp_match = {
.name = "esp",
.match = match,
.matchsize = sizeof(struct ipt_esp),
.proto = IPPROTO_ESP,
.checkentry = checkentry,
.me = THIS_MODULE,
};
static int __init init(void)
{
return ipt_register_match(&esp_match);
}
static void __exit cleanup(void)
{
ipt_unregister_match(&esp_match);
}
module_init(init);
module_exit(cleanup);
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