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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/in.h>
#include <linux/ip.h>
#include <linux/netfilter/xt_esp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
MODULE_DESCRIPTION("x_tables ESP SPI match module");
MODULE_ALIAS("ipt_esp");
MODULE_ALIAS("ip6t_esp");
#if 0
#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("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 bool
match(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_esp_hdr _esp, *eh;
const struct xt_esp *espinfo = matchinfo;
/* Must not be a fragment. */
if (offset)
return false;
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 = true;
return false;
}
return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
!!(espinfo->invflags & XT_ESP_INV_SPI));
}
/* Called when user tries to insert an entry of this type. */
static bool
checkentry(const char *tablename,
const void *ip_void,
const struct xt_match *match,
void *matchinfo,
unsigned int hook_mask)
{
const struct xt_esp *espinfo = matchinfo;
if (espinfo->invflags & ~XT_ESP_INV_MASK) {
duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
return false;
}
return true;
}
static struct xt_match xt_esp_match[] __read_mostly = {
{
.name = "esp",
.family = AF_INET,
.checkentry = checkentry,
.match = match,
.matchsize = sizeof(struct xt_esp),
.proto = IPPROTO_ESP,
.me = THIS_MODULE,
},
{
.name = "esp",
.family = AF_INET6,
.checkentry = checkentry,
.match = match,
.matchsize = sizeof(struct xt_esp),
.proto = IPPROTO_ESP,
.me = THIS_MODULE,
},
};
static int __init xt_esp_init(void)
{
return xt_register_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
}
static void __exit xt_esp_cleanup(void)
{
xt_unregister_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
}
module_init(xt_esp_init);
module_exit(xt_esp_cleanup);
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