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/* Kernel module to match IPComp parameters for IPv4 and IPv6
*
* Copyright (C) 2013 WindRiver
*
* Author:
* Fan Du <fan.du@windriver.com>
*
* Based on:
* net/netfilter/xt_esp.c
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/in.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/netfilter/xt_ipcomp.h>
#include <linux/netfilter/x_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
MODULE_ALIAS("ipt_ipcomp");
MODULE_ALIAS("ip6t_ipcomp");
/* 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;
pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
invert ? '!' : ' ', min, spi, max);
r = (spi >= min && spi <= max) ^ invert;
pr_debug(" result %s\n", r ? "PASS" : "FAILED");
return r;
}
static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
struct ip_comp_hdr _comphdr;
const struct ip_comp_hdr *chdr;
const struct xt_ipcomp *compinfo = par->matchinfo;
/* Must not be a fragment. */
if (par->fragoff != 0)
return false;
chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
if (chdr == NULL) {
/* We've been asked to examine this packet, and we
* can't. Hence, no choice but to drop.
*/
pr_debug("Dropping evil IPComp tinygram.\n");
par->hotdrop = true;
return false;
}
return spi_match(compinfo->spis[0], compinfo->spis[1],
ntohs(chdr->cpi),
!!(compinfo->invflags & XT_IPCOMP_INV_SPI));
}
static int comp_mt_check(const struct xt_mtchk_param *par)
{
const struct xt_ipcomp *compinfo = par->matchinfo;
/* Must specify no unknown invflags */
if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
pr_err("unknown flags %X\n", compinfo->invflags);
return -EINVAL;
}
return 0;
}
static struct xt_match comp_mt_reg[] __read_mostly = {
{
.name = "ipcomp",
.family = NFPROTO_IPV4,
.match = comp_mt,
.matchsize = sizeof(struct xt_ipcomp),
.proto = IPPROTO_COMP,
.checkentry = comp_mt_check,
.me = THIS_MODULE,
},
{
.name = "ipcomp",
.family = NFPROTO_IPV6,
.match = comp_mt,
.matchsize = sizeof(struct xt_ipcomp),
.proto = IPPROTO_COMP,
.checkentry = comp_mt_check,
.me = THIS_MODULE,
},
};
static int __init comp_mt_init(void)
{
return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
}
static void __exit comp_mt_exit(void)
{
xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
}
module_init(comp_mt_init);
module_exit(comp_mt_exit);
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