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/* Kernel module to match AH parameters. */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4/ipt_ah.h>
#include <linux/netfilter_ipv4/ip_tables.h>
EXPORT_NO_SYMBOLS;
MODULE_LICENSE("GPL");
#ifdef DEBUG_CONNTRACK
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif
struct ahhdr {
__u32 spi;
};
/* 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("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 int
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const void *matchinfo,
int offset,
const void *hdr,
u_int16_t datalen,
int *hotdrop)
{
const struct ahhdr *ah = hdr;
const struct ipt_ah *ahinfo = matchinfo;
if (offset == 0 && datalen < sizeof(struct ahhdr)) {
/* 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 = 1;
return 0;
}
/* Must not be a fragment. */
return !offset
&& 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 int
checkentry(const char *tablename,
const struct ipt_ip *ip,
void *matchinfo,
unsigned int matchinfosize,
unsigned int hook_mask)
{
const struct ipt_ah *ahinfo = matchinfo;
/* Must specify proto == AH, and no unknown invflags */
if (ip->proto != IPPROTO_AH || (ip->invflags & IPT_INV_PROTO)) {
duprintf("ipt_ah: Protocol %u != %u\n", ip->proto,
IPPROTO_AH);
return 0;
}
if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_ah))) {
duprintf("ipt_ah: matchsize %u != %u\n",
matchinfosize, IPT_ALIGN(sizeof(struct ipt_ah)));
return 0;
}
if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
duprintf("ipt_ah: unknown flags %X\n",
ahinfo->invflags);
return 0;
}
return 1;
}
static struct ipt_match ah_match
= { { NULL, NULL }, "ah", &match, &checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
return ipt_register_match(&ah_match);
}
static void __exit cleanup(void)
{
ipt_unregister_match(&ah_match);
}
module_init(init);
module_exit(cleanup);
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